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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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SPDX-License-Identifier: GPL-2.0/* * Generic ring buffer * * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> */#include <linux/ring_buffer_types.h>#include <linux/sched/isolation.h>#include <linux/trace_recursion.h>#include <linux/panic_notifier.h>#include <linux/trace_events.h>#include <linux/ring_buffer.h>#include <linux/trace_clock.h>#include <linux/sched/clock.h>#include <linux/cacheflush.h>#include <linux/trace_seq.h>#include <linux/spinlock.h>#include <linux/irq_work.h>#include <linux/security.h>#include <linux/uaccess.h>#include <linux/hardirq.h>#include <linux/kthread.h> /* for self test */#include <linux/module.h>#include <linux/percpu.h>#include <linux/mutex.h>#include <linux/delay.h>#include <linux/slab.h>#include <linux/init.h>#include <linux/hash.h>#include <linux/list.h>#include <linux/cpu.h>#include <linux/oom.h>#include <linux/mm.h>
#include <asm/ring_buffer.h>#include <asm/local64.h>#include <asm/local.h>#include <asm/setup.h>
#include "trace.h"
/* * The "absolute" timestamp in the buffer is only 59 bits. * If a clock has the 5 MSBs set, it needs to be saved and * reinserted. */#define TS_MSB (0xf8ULL << 56)#define ABS_TS_MASK (~TS_MSB)
static void update_pages_handler(struct work_struct *work);
#define RING_BUFFER_META_MAGIC 0xBADFEED
struct ring_buffer_meta { int magic; int struct_sizes; unsigned long total_size; unsigned long buffers_offset;};
struct ring_buffer_cpu_meta { unsigned long first_buffer; unsigned long head_buffer; unsigned long commit_buffer; __u32 subbuf_size; __u32 nr_subbufs;#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT __u32 nr_invalid; __u32 entry_bytes;#endif int buffers[];};
/* * The ring buffer header is special. We must manually up keep it. */int ring_buffer_print_entry_header(struct trace_seq *s){ trace_seq_puts(s, "# compressed entry header\n"); trace_seq_puts(s, "\ttype_len : 5 bits\n"); trace_seq_puts(s, "\ttime_delta : 27 bits\n"); trace_seq_puts(s, "\tarray : 32 bits\n"); trace_seq_putc(s, '\n'); trace_seq_printf(s, "\tpadding : type == %d\n", RINGBUF_TYPE_PADDING); trace_seq_printf(s, "\ttime_extend : type == %d\n", RINGBUF_TYPE_TIME_EXTEND); trace_seq_printf(s, "\ttime_stamp : type == %d\n", RINGBUF_TYPE_TIME_STAMP); trace_seq_printf(s, "\tdata max type_len == %d\n", RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
return !trace_seq_has_overflowed(s);}
/* * The ring buffer is made up of a list of pages. A separate list of pages is * allocated for each CPU. A writer may only write to a buffer that is * associated with the CPU it is currently executing on. A reader may read * from any per cpu buffer. * * The reader is special. For each per cpu buffer, the reader has its own * reader page. When a reader has read the entire reader page, this reader * page is swapped with another page in the ring buffer. * * Now, as long as the writer is off the reader page, the reader can do what * ever it wants with that page. The writer will never write to that page * again (as long as it is out of the ring buffer). * * Here's some silly ASCII art. * * +------+ * |reader| RING BUFFER * |page | * +------+ +---+ +---+ +---+ * | |-->| |-->| | * +---+ +---+ +---+ * ^ | * | | * +---------------+ * * * +------+ * |reader| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * | |-->| |-->| | * +---+ +---+ +---+ * ^ | * | | * +---------------+ * * * +------+ * |reader| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * ^ | |-->| |-->| | * | +---+ +---+ +---+ * | | * | | * +------------------------------+ * * * +------+ * |buffer| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * ^ | | | |-->| | * | New +---+ +---+ +---+ * | Reader------^ | * | page | * +------------------------------+ * * * After we make this swap, the reader can hand this page off to the splice * code and be done with it. It can even allocate a new page if it needs to * and swap that into the ring buffer. * * We will be using cmpxchg soon to make all this lockless. * */
/* Used for individual buffers (after the counter) */#define RB_BUFFER_OFF (1 << 20)
/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
enum { RB_LEN_TIME_EXTEND = 8, RB_LEN_TIME_STAMP = 8,};
#define skip_time_extend(event) \ ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
#define extended_time(event) \ (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
static inline bool rb_null_event(struct ring_buffer_event *event){ return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;}
static void rb_event_set_padding(struct ring_buffer_event *event){ /* padding has a NULL time_delta */ event->type_len = RINGBUF_TYPE_PADDING; event->time_delta = 0;}
static unsignedrb_event_data_length(struct ring_buffer_event *event){ unsigned length;
if (event->type_len) length = event->type_len * RB_ALIGNMENT; else length = event->array[0]; return length + RB_EVNT_HDR_SIZE;}
/* * Return the length of the given event. Will return * the length of the time extend if the event is a * time extend. */static inline unsignedrb_event_length(struct ring_buffer_event *event){ switch (event->type_len) { case RINGBUF_TYPE_PADDING: if (rb_null_event(event)) /* undefined */ return -1; return event->array[0] + RB_EVNT_HDR_SIZE;
case RINGBUF_TYPE_TIME_EXTEND: return RB_LEN_TIME_EXTEND;
case RINGBUF_TYPE_TIME_STAMP: return RB_LEN_TIME_STAMP;
case RINGBUF_TYPE_DATA: return rb_event_data_length(event); default: WARN_ON_ONCE(1); } /* not hit */ return 0;}
/* * Return total length of time extend and data, * or just the event length for all other events. */static inline unsignedrb_event_ts_length(struct ring_buffer_event *event){ unsigned len = 0;
if (extended_time(event)) { /* time extends include the data event after it */ len = RB_LEN_TIME_EXTEND; event = skip_time_extend(event); } return len + rb_event_length(event);}
/** * ring_buffer_event_length - return the length of the event * @event: the event to get the length of * * Returns the size of the data load of a data event. * If the event is something other than a data event, it * returns the size of the event itself. With the exception * of a TIME EXTEND, where it still returns the size of the * data load of the data event after it. */unsigned ring_buffer_event_length(struct ring_buffer_event *event){ unsigned length;
if (extended_time(event)) event = skip_time_extend(event);
length = rb_event_length(event); if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) return length; length -= RB_EVNT_HDR_SIZE; if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]) || RB_FORCE_8BYTE_ALIGNMENT) length -= sizeof(event->array[0]); return length;}EXPORT_SYMBOL_GPL(ring_buffer_event_length);
/* inline for ring buffer fast paths */static __always_inline void *rb_event_data(struct ring_buffer_event *event){ if (extended_time(event)) event = skip_time_extend(event); WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); /* If length is in len field, then array[0] has the data */ if (event->type_len) return (void *)&event->array[0]; /* Otherwise length is in array[0] and array[1] has the data */ return (void *)&event->array[1];}
/** * ring_buffer_event_data - return the data of the event * @event: the event to get the data from */void *ring_buffer_event_data(struct ring_buffer_event *event){ return rb_event_data(event);}EXPORT_SYMBOL_GPL(ring_buffer_event_data);
#define for_each_buffer_cpu(buffer, cpu) \ for_each_cpu(cpu, buffer->cpumask)
#define for_each_online_buffer_cpu(buffer, cpu) \ for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
static u64 rb_event_time_stamp(struct ring_buffer_event *event){ u64 ts;
ts = event->array[0]; ts <<= TS_SHIFT; ts += event->time_delta;
return ts;}
/* Flag when events were overwritten */#define RB_MISSED_EVENTS (1 << 31)/* Missed count stored at end */#define RB_MISSED_STORED (1 << 30)
#define RB_MISSED_MASK (3 << 30)
struct buffer_data_read_page { unsigned order; /* order of the page */ struct buffer_data_page *data; /* actual data, stored in this page */};
/* * Note, the buffer_page list must be first. The buffer pages * are allocated in cache lines, which means that each buffer * page will be at the beginning of a cache line, and thus * the least significant bits will be zero. We use this to * add flags in the list struct pointers, to make the ring buffer * lockless. */struct buffer_page { struct list_head list; /* list of buffer pages */ local_t write; /* index for next write */ unsigned read; /* index for next read */ local_t entries; /* entries on this page */ unsigned long real_end; /* real end of data */ unsigned order; /* order of the page */ u32 id:30; /* ID for external mapping */ u32 range:1; /* Mapped via a range */ struct buffer_data_page *page; /* Actual data page */};
/* * The buffer page counters, write and entries, must be reset * atomically when crossing page boundaries. To synchronize this * update, two counters are inserted into the number. One is * the actual counter for the write position or count on the page. * * The other is a counter of updaters. Before an update happens * the update partition of the counter is incremented. This will * allow the updater to update the counter atomically. * * The counter is 20 bits, and the state data is 12. */#define RB_WRITE_MASK 0xfffff#define RB_WRITE_INTCNT (1 << 20)
static void rb_init_data_page(struct buffer_data_page *bpage){ local_set(&bpage->commit, 0); bpage->time_stamp = 0;}
static __always_inline long rb_data_page_commit(struct buffer_data_page *dpage){ return local_read(&dpage->commit);}
static __always_inline long rb_data_page_size(struct buffer_data_page *dpage){ return rb_data_page_commit(dpage) & ~RB_MISSED_MASK;}
static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage){ return rb_data_page_commit(bpage->page);}
static __always_inline unsigned int rb_page_size(struct buffer_page *bpage){ return rb_data_page_size(bpage->page);}
static void free_buffer_page(struct buffer_page *bpage){ /* Range pages are not to be freed */ if (!bpage->range) free_pages((unsigned long)bpage->page, bpage->order); kfree(bpage);}
/* * For best performance, allocate cpu buffer data cache line sized * and per CPU. */#define alloc_cpu_buffer(cpu) (struct ring_buffer_per_cpu *) \ kzalloc_node(ALIGN(sizeof(struct ring_buffer_per_cpu), \ cache_line_size()), GFP_KERNEL, cpu_to_node(cpu));
#define alloc_cpu_page(cpu) (struct buffer_page *) \ kzalloc_node(ALIGN(sizeof(struct buffer_page), \ cache_line_size()), GFP_KERNEL, cpu_to_node(cpu));
static struct buffer_data_page *alloc_cpu_data(int cpu, int order){ struct buffer_data_page *dpage; struct page *page; gfp_t mflags;
/* * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails * gracefully without invoking oom-killer and the system is not * destabilized. */ mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_COMP | __GFP_ZERO;
page = alloc_pages_node(cpu_to_node(cpu), mflags, order); if (!page) return NULL;
dpage = page_address(page); rb_init_data_page(dpage);
return dpage;}
struct rb_irq_work { struct irq_work work; wait_queue_head_t waiters; wait_queue_head_t full_waiters; atomic_t seq; bool waiters_pending; bool full_waiters_pending; bool wakeup_full;};
/* * Structure to hold event state and handle nested events. */struct rb_event_info { u64 ts; u64 delta; u64 before; u64 after; unsigned long length; struct buffer_page *tail_page; int add_timestamp;};
/* * Used for the add_timestamp * NONE * EXTEND - wants a time extend * ABSOLUTE - the buffer requests all events to have absolute time stamps * FORCE - force a full time stamp. */enum { RB_ADD_STAMP_NONE = 0, RB_ADD_STAMP_EXTEND = BIT(1), RB_ADD_STAMP_ABSOLUTE = BIT(2), RB_ADD_STAMP_FORCE = BIT(3)};/* * Used for which event context the event is in. * TRANSITION = 0 * NMI = 1 * IRQ = 2 * SOFTIRQ = 3 * NORMAL = 4 * * See trace_recursive_lock() comment below for more details. */enum { RB_CTX_TRANSITION, RB_CTX_NMI, RB_CTX_IRQ, RB_CTX_SOFTIRQ, RB_CTX_NORMAL, RB_CTX_MAX};
struct rb_time_struct { local64_t time;};typedef struct rb_time_struct rb_time_t;
#define MAX_NEST 5
/* * head_page == tail_page && head == tail then buffer is empty. */struct ring_buffer_per_cpu { int cpu; atomic_t record_disabled; atomic_t resize_disabled; struct trace_buffer *buffer; raw_spinlock_t reader_lock; /* serialize readers */ arch_spinlock_t lock; struct lock_class_key lock_key; struct buffer_data_page *free_page; unsigned long nr_pages; unsigned int current_context; struct list_head *pages; /* pages generation counter, incremented when the list changes */ unsigned long cnt; struct buffer_page *head_page; /* read from head */ struct buffer_page *tail_page; /* write to tail */ struct buffer_page *commit_page; /* committed pages */ struct buffer_page *reader_page; unsigned long lost_events; unsigned long last_overrun; unsigned long nest; local_t entries_bytes; local_t entries; local_t overrun; local_t commit_overrun; local_t dropped_events; local_t committing; local_t commits; local_t pages_touched; local_t pages_lost; local_t pages_read; long last_pages_touch; size_t shortest_full; unsigned long read; unsigned long read_bytes; rb_time_t write_stamp; rb_time_t before_stamp; u64 event_stamp[MAX_NEST]; u64 read_stamp; /* pages removed since last reset */ unsigned long pages_removed;
unsigned int mapped; unsigned int user_mapped; /* user space mapping */ struct mutex mapping_lock; struct buffer_page **subbuf_ids; /* ID to subbuf VA */ struct trace_buffer_meta *meta_page; struct ring_buffer_cpu_meta *ring_meta;
struct ring_buffer_remote *remote;
/* ring buffer pages to update, > 0 to add, < 0 to remove */ long nr_pages_to_update; struct list_head new_pages; /* new pages to add */ struct work_struct update_pages_work; struct completion update_done;
struct rb_irq_work irq_work;};
struct trace_buffer { unsigned flags; int cpus; atomic_t record_disabled; atomic_t resizing; cpumask_var_t cpumask;
struct lock_class_key *reader_lock_key;
struct mutex mutex;
struct ring_buffer_per_cpu **buffers;
struct ring_buffer_remote *remote;
struct hlist_node node; u64 (*clock)(void);
struct rb_irq_work irq_work; bool time_stamp_abs;
unsigned long range_addr_start; unsigned long range_addr_end; struct notifier_block flush_nb;
struct ring_buffer_meta *meta;
unsigned int subbuf_size; unsigned int subbuf_order; unsigned int max_data_size;};
struct ring_buffer_iter { struct ring_buffer_per_cpu *cpu_buffer; unsigned long head; unsigned long next_event; struct buffer_page *head_page; struct buffer_page *cache_reader_page; unsigned long cache_read; unsigned long cache_pages_removed; u64 read_stamp; u64 page_stamp; struct ring_buffer_event *event; size_t event_size; int missed_events;};
int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s){ struct buffer_data_page field;
trace_seq_printf(s, "\tfield: u64 timestamp;\t" "offset:0;\tsize:%u;\tsigned:%u;\n", (unsigned int)sizeof(field.time_stamp), (unsigned int)is_signed_type(u64));
trace_seq_printf(s, "\tfield: local_t commit;\t" "offset:%u;\tsize:%u;\tsigned:%u;\n", (unsigned int)offsetof(typeof(field), commit), (unsigned int)sizeof(field.commit), (unsigned int)is_signed_type(long));
trace_seq_printf(s, "\tfield: char overwrite;\t" "offset:%u;\tsize:%u;\tsigned:%u;\n", (unsigned int)offsetof(typeof(field), commit), 1, (unsigned int)is_signed_type(char));
trace_seq_printf(s, "\tfield: char data;\t" "offset:%u;\tsize:%u;\tsigned:%u;\n", (unsigned int)offsetof(typeof(field), data), (unsigned int)(buffer ? buffer->subbuf_size : PAGE_SIZE - BUF_PAGE_HDR_SIZE), (unsigned int)is_signed_type(char));
return !trace_seq_has_overflowed(s);}
static inline void rb_time_read(rb_time_t *t, u64 *ret){ *ret = local64_read(&t->time);}static void rb_time_set(rb_time_t *t, u64 val){ local64_set(&t->time, val);}
/* * Enable this to make sure that the event passed to * ring_buffer_event_time_stamp() is not committed and also * is on the buffer that it passed in. *///#define RB_VERIFY_EVENT#ifdef RB_VERIFY_EVENTstatic struct list_head *rb_list_head(struct list_head *list);static void verify_event(struct ring_buffer_per_cpu *cpu_buffer, void *event){ struct buffer_page *page = cpu_buffer->commit_page; struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page); struct list_head *next; long commit, write; unsigned long addr = (unsigned long)event; bool done = false; int stop = 0;
/* Make sure the event exists and is not committed yet */ do { if (page == tail_page || WARN_ON_ONCE(stop++ > 100)) done = true; commit = rb_page_commit(page); write = local_read(&page->write); if (addr >= (unsigned long)&page->page->data[commit] && addr < (unsigned long)&page->page->data[write]) return;
next = rb_list_head(page->list.next); page = list_entry(next, struct buffer_page, list); } while (!done); WARN_ON_ONCE(1);}#elsestatic inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer, void *event){}#endif
/* * The absolute time stamp drops the 5 MSBs and some clocks may * require them. The rb_fix_abs_ts() will take a previous full * time stamp, and add the 5 MSB of that time stamp on to the * saved absolute time stamp. Then they are compared in case of * the unlikely event that the latest time stamp incremented * the 5 MSB. */static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts){ if (save_ts & TS_MSB) { abs |= save_ts & TS_MSB; /* Check for overflow */ if (unlikely(abs < save_ts)) abs += 1ULL << 59; } return abs;}
static inline u64 rb_time_stamp(struct trace_buffer *buffer);
/** * ring_buffer_event_time_stamp - return the event's current time stamp * @buffer: The buffer that the event is on * @event: the event to get the time stamp of * * Note, this must be called after @event is reserved, and before it is * committed to the ring buffer. And must be called from the same * context where the event was reserved (normal, softirq, irq, etc). * * Returns the time stamp associated with the current event. * If the event has an extended time stamp, then that is used as * the time stamp to return. * In the highly unlikely case that the event was nested more than * the max nesting, then the write_stamp of the buffer is returned, * otherwise current time is returned, but that really neither of * the last two cases should ever happen. */u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer, struct ring_buffer_event *event){ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()]; unsigned int nest; u64 ts;
/* If the event includes an absolute time, then just use that */ if (event->type_len == RINGBUF_TYPE_TIME_STAMP) { ts = rb_event_time_stamp(event); return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp); }
nest = local_read(&cpu_buffer->committing); verify_event(cpu_buffer, event); if (WARN_ON_ONCE(!nest)) goto fail;
/* Read the current saved nesting level time stamp */ if (likely(--nest < MAX_NEST)) return cpu_buffer->event_stamp[nest];
/* Shouldn't happen, warn if it does */ WARN_ONCE(1, "nest (%d) greater than max", nest);
fail: rb_time_read(&cpu_buffer->write_stamp, &ts);
return ts;}
/** * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer * @buffer: The ring_buffer to get the number of pages from * @cpu: The cpu of the ring_buffer to get the number of pages from * * Returns the number of pages that have content in the ring buffer. */size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu){ size_t read; size_t lost; size_t cnt;
read = local_read(&buffer->buffers[cpu]->pages_read); lost = local_read(&buffer->buffers[cpu]->pages_lost); cnt = local_read(&buffer->buffers[cpu]->pages_touched);
if (WARN_ON_ONCE(cnt < lost)) return 0;
cnt -= lost;
/* The reader can read an empty page, but not more than that */ if (cnt < read) { WARN_ON_ONCE(read > cnt + 1); return 0; }
return cnt - read;}
static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full){ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; size_t nr_pages; size_t dirty;
nr_pages = cpu_buffer->nr_pages; if (!nr_pages || !full) return true;
/* * Add one as dirty will never equal nr_pages, as the sub-buffer * that the writer is on is not counted as dirty. * This is needed if "buffer_percent" is set to 100. */ dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
return (dirty * 100) >= (full * nr_pages);}
/* * rb_wake_up_waiters - wake up tasks waiting for ring buffer input * * Schedules a delayed work to wake up any task that is blocked on the * ring buffer waiters queue. */static void rb_wake_up_waiters(struct irq_work *work){ struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
/* For waiters waiting for the first wake up */ (void)atomic_fetch_inc_release(&rbwork->seq);
wake_up_all(&rbwork->waiters); if (rbwork->full_waiters_pending || rbwork->wakeup_full) { /* Only cpu_buffer sets the above flags */ struct ring_buffer_per_cpu *cpu_buffer = container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
/* Called from interrupt context */ raw_spin_lock(&cpu_buffer->reader_lock); rbwork->wakeup_full = false; rbwork->full_waiters_pending = false;
/* Waking up all waiters, they will reset the shortest full */ cpu_buffer->shortest_full = 0; raw_spin_unlock(&cpu_buffer->reader_lock);
wake_up_all(&rbwork->full_waiters); }}
/** * ring_buffer_wake_waiters - wake up any waiters on this ring buffer * @buffer: The ring buffer to wake waiters on * @cpu: The CPU buffer to wake waiters on * * In the case of a file that represents a ring buffer is closing, * it is prudent to wake up any waiters that are on this. */void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; struct rb_irq_work *rbwork;
if (!buffer) return;
if (cpu == RING_BUFFER_ALL_CPUS) {
/* Wake up individual ones too. One level recursion */ for_each_buffer_cpu(buffer, cpu) ring_buffer_wake_waiters(buffer, cpu);
rbwork = &buffer->irq_work; } else { if (WARN_ON_ONCE(!buffer->buffers)) return; if (WARN_ON_ONCE(cpu >= nr_cpu_ids)) return;
cpu_buffer = buffer->buffers[cpu]; /* The CPU buffer may not have been initialized yet */ if (!cpu_buffer) return; rbwork = &cpu_buffer->irq_work; }
/* This can be called in any context */ irq_work_queue(&rbwork->work);}
static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full){ struct ring_buffer_per_cpu *cpu_buffer; bool ret = false;
/* Reads of all CPUs always waits for any data */ if (cpu == RING_BUFFER_ALL_CPUS) return !ring_buffer_empty(buffer);
cpu_buffer = buffer->buffers[cpu];
if (!ring_buffer_empty_cpu(buffer, cpu)) { unsigned long flags; bool pagebusy;
if (!full) return true;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; ret = !pagebusy && full_hit(buffer, cpu, full);
if (!ret && (!cpu_buffer->shortest_full || cpu_buffer->shortest_full > full)) { cpu_buffer->shortest_full = full; } raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } return ret;}
static inline boolrb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer, int cpu, int full, ring_buffer_cond_fn cond, void *data){ if (rb_watermark_hit(buffer, cpu, full)) return true;
if (cond(data)) return true;
/* * The events can happen in critical sections where * checking a work queue can cause deadlocks. * After adding a task to the queue, this flag is set * only to notify events to try to wake up the queue * using irq_work. * * We don't clear it even if the buffer is no longer * empty. The flag only causes the next event to run * irq_work to do the work queue wake up. The worse * that can happen if we race with !trace_empty() is that * an event will cause an irq_work to try to wake up * an empty queue. * * There's no reason to protect this flag either, as * the work queue and irq_work logic will do the necessary * synchronization for the wake ups. The only thing * that is necessary is that the wake up happens after * a task has been queued. It's OK for spurious wake ups. */ if (full) rbwork->full_waiters_pending = true; else rbwork->waiters_pending = true;
return false;}
struct rb_wait_data { struct rb_irq_work *irq_work; int seq;};
/* * The default wait condition for ring_buffer_wait() is to just to exit the * wait loop the first time it is woken up. */static bool rb_wait_once(void *data){ struct rb_wait_data *rdata = data; struct rb_irq_work *rbwork = rdata->irq_work;
return atomic_read_acquire(&rbwork->seq) != rdata->seq;}
/** * ring_buffer_wait - wait for input to the ring buffer * @buffer: buffer to wait on * @cpu: the cpu buffer to wait on * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS * @cond: condition function to break out of wait (NULL to run once) * @data: the data to pass to @cond. * * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon * as data is added to any of the @buffer's cpu buffers. Otherwise * it will wait for data to be added to a specific cpu buffer. */int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full, ring_buffer_cond_fn cond, void *data){ struct ring_buffer_per_cpu *cpu_buffer; struct wait_queue_head *waitq; struct rb_irq_work *rbwork; struct rb_wait_data rdata; int ret = 0;
/* * Depending on what the caller is waiting for, either any * data in any cpu buffer, or a specific buffer, put the * caller on the appropriate wait queue. */ if (cpu == RING_BUFFER_ALL_CPUS) { rbwork = &buffer->irq_work; /* Full only makes sense on per cpu reads */ full = 0; } else { if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -ENODEV; cpu_buffer = buffer->buffers[cpu]; rbwork = &cpu_buffer->irq_work; }
if (full) waitq = &rbwork->full_waiters; else waitq = &rbwork->waiters;
/* Set up to exit loop as soon as it is woken */ if (!cond) { cond = rb_wait_once; rdata.irq_work = rbwork; rdata.seq = atomic_read_acquire(&rbwork->seq); data = &rdata; }
ret = wait_event_interruptible((*waitq), rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
return ret;}
/** * ring_buffer_poll_wait - poll on buffer input * @buffer: buffer to wait on * @cpu: the cpu buffer to wait on * @filp: the file descriptor * @poll_table: The poll descriptor * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS * * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon * as data is added to any of the @buffer's cpu buffers. Otherwise * it will wait for data to be added to a specific cpu buffer. * * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, * zero otherwise. */__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu, struct file *filp, poll_table *poll_table, int full){ struct ring_buffer_per_cpu *cpu_buffer; struct rb_irq_work *rbwork;
if (cpu == RING_BUFFER_ALL_CPUS) { rbwork = &buffer->irq_work; full = 0; } else { if (!cpumask_test_cpu(cpu, buffer->cpumask)) return EPOLLERR;
cpu_buffer = buffer->buffers[cpu]; rbwork = &cpu_buffer->irq_work; }
if (full) { poll_wait(filp, &rbwork->full_waiters, poll_table);
if (rb_watermark_hit(buffer, cpu, full)) return EPOLLIN | EPOLLRDNORM; /* * Only allow full_waiters_pending update to be seen after * the shortest_full is set (in rb_watermark_hit). If the * writer sees the full_waiters_pending flag set, it will * compare the amount in the ring buffer to shortest_full. * If the amount in the ring buffer is greater than the * shortest_full percent, it will call the irq_work handler * to wake up this list. The irq_handler will reset shortest_full * back to zero. That's done under the reader_lock, but * the below smp_mb() makes sure that the update to * full_waiters_pending doesn't leak up into the above. */ smp_mb(); rbwork->full_waiters_pending = true; return 0; }
poll_wait(filp, &rbwork->waiters, poll_table); rbwork->waiters_pending = true;
/* * There's a tight race between setting the waiters_pending and * checking if the ring buffer is empty. Once the waiters_pending bit * is set, the next event will wake the task up, but we can get stuck * if there's only a single event in. * * FIXME: Ideally, we need a memory barrier on the writer side as well, * but adding a memory barrier to all events will cause too much of a * performance hit in the fast path. We only need a memory barrier when * the buffer goes from empty to having content. But as this race is * extremely small, and it's not a problem if another event comes in, we * will fix it later. */ smp_mb();
if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) return EPOLLIN | EPOLLRDNORM; return 0;}
/* buffer may be either ring_buffer or ring_buffer_per_cpu */#define RB_WARN_ON(b, cond) \ ({ \ int _____ret = unlikely(cond); \ if (_____ret) { \ if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ struct ring_buffer_per_cpu *__b = \ (void *)b; \ atomic_inc(&__b->buffer->record_disabled); \ } else \ atomic_inc(&b->record_disabled); \ WARN_ON(1); \ } \ _____ret; \ })
/* Up this if you want to test the TIME_EXTENTS and normalization */#define DEBUG_SHIFT 0
static inline u64 rb_time_stamp(struct trace_buffer *buffer){ u64 ts;
/* Skip retpolines :-( */ if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local)) ts = trace_clock_local(); else ts = buffer->clock();
/* shift to debug/test normalization and TIME_EXTENTS */ return ts << DEBUG_SHIFT;}
u64 ring_buffer_time_stamp(struct trace_buffer *buffer){ u64 time;
preempt_disable_notrace(); time = rb_time_stamp(buffer); preempt_enable_notrace();
return time;}EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer, int cpu, u64 *ts){ /* Just stupid testing the normalize function and deltas */ *ts >>= DEBUG_SHIFT;}EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
/* * Making the ring buffer lockless makes things tricky. * Although writes only happen on the CPU that they are on, * and they only need to worry about interrupts. Reads can * happen on any CPU. * * The reader page is always off the ring buffer, but when the * reader finishes with a page, it needs to swap its page with * a new one from the buffer. The reader needs to take from * the head (writes go to the tail). But if a writer is in overwrite * mode and wraps, it must push the head page forward. * * Here lies the problem. * * The reader must be careful to replace only the head page, and * not another one. As described at the top of the file in the * ASCII art, the reader sets its old page to point to the next * page after head. It then sets the page after head to point to * the old reader page. But if the writer moves the head page * during this operation, the reader could end up with the tail. * * We use cmpxchg to help prevent this race. We also do something * special with the page before head. We set the LSB to 1. * * When the writer must push the page forward, it will clear the * bit that points to the head page, move the head, and then set * the bit that points to the new head page. * * We also don't want an interrupt coming in and moving the head * page on another writer. Thus we use the second LSB to catch * that too. Thus: * * head->list->prev->next bit 1 bit 0 * ------- ------- * Normal page 0 0 * Points to head page 0 1 * New head page 1 0 * * Note we can not trust the prev pointer of the head page, because: * * +----+ +-----+ +-----+ * | |------>| T |---X--->| N | * | |<------| | | | * +----+ +-----+ +-----+ * ^ ^ | * | +-----+ | | * +----------| R |----------+ | * | |<-----------+ * +-----+ * * Key: ---X--> HEAD flag set in pointer * T Tail page * R Reader page * N Next page * * (see __rb_reserve_next() to see where this happens) * * What the above shows is that the reader just swapped out * the reader page with a page in the buffer, but before it * could make the new header point back to the new page added * it was preempted by a writer. The writer moved forward onto * the new page added by the reader and is about to move forward * again. * * You can see, it is legitimate for the previous pointer of * the head (or any page) not to point back to itself. But only * temporarily. */
#define RB_PAGE_NORMAL 0UL#define RB_PAGE_HEAD 1UL#define RB_PAGE_UPDATE 2UL
#define RB_FLAG_MASK 3UL
/* PAGE_MOVED is not part of the mask */#define RB_PAGE_MOVED 4UL
/* * rb_list_head - remove any bit */static struct list_head *rb_list_head(struct list_head *list){ unsigned long val = (unsigned long)list;
return (struct list_head *)(val & ~RB_FLAG_MASK);}
/* * rb_is_head_page - test if the given page is the head page * * Because the reader may move the head_page pointer, we can * not trust what the head page is (it may be pointing to * the reader page). But if the next page is a header page, * its flags will be non zero. */static inline intrb_is_head_page(struct buffer_page *page, struct list_head *list){ unsigned long val;
val = (unsigned long)list->next;
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) return RB_PAGE_MOVED;
return val & RB_FLAG_MASK;}
/* * rb_is_reader_page * * The unique thing about the reader page, is that, if the * writer is ever on it, the previous pointer never points * back to the reader page. */static bool rb_is_reader_page(struct buffer_page *page){ struct list_head *list = page->list.prev;
return rb_list_head(list->next) != &page->list;}
/* * rb_set_list_to_head - set a list_head to be pointing to head. */static void rb_set_list_to_head(struct list_head *list){ unsigned long *ptr;
ptr = (unsigned long *)&list->next; *ptr |= RB_PAGE_HEAD; *ptr &= ~RB_PAGE_UPDATE;}
/* * rb_head_page_activate - sets up head page */static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer){ struct buffer_page *head;
head = cpu_buffer->head_page; if (!head) return;
/* * Set the previous list pointer to have the HEAD flag. */ rb_set_list_to_head(head->list.prev);
if (cpu_buffer->ring_meta) { struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; meta->head_buffer = (unsigned long)head->page; }}
static void rb_list_head_clear(struct list_head *list){ unsigned long *ptr = (unsigned long *)&list->next;
*ptr &= ~RB_FLAG_MASK;}
/* * rb_head_page_deactivate - clears head page ptr (for free list) */static voidrb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer){ struct list_head *hd;
/* Go through the whole list and clear any pointers found. */ rb_list_head_clear(cpu_buffer->pages);
list_for_each(hd, cpu_buffer->pages) rb_list_head_clear(hd);}
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag, int new_flag){ struct list_head *list; unsigned long val = (unsigned long)&head->list; unsigned long ret;
list = &prev->list;
val &= ~RB_FLAG_MASK;
ret = cmpxchg((unsigned long *)&list->next, val | old_flag, val | new_flag);
/* check if the reader took the page */ if ((ret & ~RB_FLAG_MASK) != val) return RB_PAGE_MOVED;
return ret & RB_FLAG_MASK;}
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag){ return rb_head_page_set(cpu_buffer, head, prev, old_flag, RB_PAGE_UPDATE);}
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag){ return rb_head_page_set(cpu_buffer, head, prev, old_flag, RB_PAGE_HEAD);}
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *head, struct buffer_page *prev, int old_flag){ return rb_head_page_set(cpu_buffer, head, prev, old_flag, RB_PAGE_NORMAL);}
static inline void rb_inc_page(struct buffer_page **bpage){ struct list_head *p = rb_list_head((*bpage)->list.next);
*bpage = list_entry(p, struct buffer_page, list);}
static inline void rb_dec_page(struct buffer_page **bpage){ struct list_head *p = rb_list_head((*bpage)->list.prev);
*bpage = list_entry(p, struct buffer_page, list);}
static struct buffer_page *rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer){ struct buffer_page *head; struct buffer_page *page; struct list_head *list; int i;
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) return NULL;
/* sanity check */ list = cpu_buffer->pages; if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) return NULL;
page = head = cpu_buffer->head_page; /* * It is possible that the writer moves the header behind * where we started, and we miss in one loop. * A second loop should grab the header, but we'll do * three loops just because I'm paranoid. */ for (i = 0; i < 3; i++) { do { if (rb_is_head_page(page, page->list.prev)) { cpu_buffer->head_page = page; return page; } rb_inc_page(&page); } while (page != head); }
RB_WARN_ON(cpu_buffer, 1);
return NULL;}
static bool rb_head_page_replace(struct buffer_page *old, struct buffer_page *new){ unsigned long *ptr = (unsigned long *)&old->list.prev->next; unsigned long val;
val = *ptr & ~RB_FLAG_MASK; val |= RB_PAGE_HEAD;
return try_cmpxchg(ptr, &val, (unsigned long)&new->list);}
/* * rb_tail_page_update - move the tail page forward */static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *tail_page, struct buffer_page *next_page){ unsigned long old_entries; unsigned long old_write;
/* * The tail page now needs to be moved forward. * * We need to reset the tail page, but without messing * with possible erasing of data brought in by interrupts * that have moved the tail page and are currently on it. * * We add a counter to the write field to denote this. */ old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
/* * Just make sure we have seen our old_write and synchronize * with any interrupts that come in. */ barrier();
/* * If the tail page is still the same as what we think * it is, then it is up to us to update the tail * pointer. */ if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { /* Zero the write counter */ unsigned long val = old_write & ~RB_WRITE_MASK; unsigned long eval = old_entries & ~RB_WRITE_MASK;
/* * This will only succeed if an interrupt did * not come in and change it. In which case, we * do not want to modify it. * * We add (void) to let the compiler know that we do not care * about the return value of these functions. We use the * cmpxchg to only update if an interrupt did not already * do it for us. If the cmpxchg fails, we don't care. */ (void)local_cmpxchg(&next_page->write, old_write, val); (void)local_cmpxchg(&next_page->entries, old_entries, eval);
/* * No need to worry about races with clearing out the commit. * it only can increment when a commit takes place. But that * only happens in the outer most nested commit. */ local_set(&next_page->page->commit, 0);
/* Either we update tail_page or an interrupt does */ if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page)) local_inc(&cpu_buffer->pages_touched); }}
static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *bpage){ unsigned long val = (unsigned long)bpage;
RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);}
static bool rb_check_links(struct ring_buffer_per_cpu *cpu_buffer, struct list_head *list){ if (RB_WARN_ON(cpu_buffer, rb_list_head(rb_list_head(list->next)->prev) != list)) return false;
if (RB_WARN_ON(cpu_buffer, rb_list_head(rb_list_head(list->prev)->next) != list)) return false;
return true;}
/** * rb_check_pages - integrity check of buffer pages * @cpu_buffer: CPU buffer with pages to test * * As a safety measure we check to make sure the data pages have not * been corrupted. */static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer){ struct list_head *head, *tmp; unsigned long buffer_cnt; unsigned long flags; int nr_loops = 0;
/* * Walk the linked list underpinning the ring buffer and validate all * its next and prev links. * * The check acquires the reader_lock to avoid concurrent processing * with code that could be modifying the list. However, the lock cannot * be held for the entire duration of the walk, as this would make the * time when interrupts are disabled non-deterministic, dependent on the * ring buffer size. Therefore, the code releases and re-acquires the * lock after checking each page. The ring_buffer_per_cpu.cnt variable * is then used to detect if the list was modified while the lock was * not held, in which case the check needs to be restarted. * * The code attempts to perform the check at most three times before * giving up. This is acceptable because this is only a self-validation * to detect problems early on. In practice, the list modification * operations are fairly spaced, and so this check typically succeeds at * most on the second try. */again: if (++nr_loops > 3) return;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); head = rb_list_head(cpu_buffer->pages); if (!rb_check_links(cpu_buffer, head)) goto out_locked; buffer_cnt = cpu_buffer->cnt; tmp = head; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
while (true) { raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
if (buffer_cnt != cpu_buffer->cnt) { /* The list was updated, try again. */ raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); goto again; }
tmp = rb_list_head(tmp->next); if (tmp == head) /* The iteration circled back, all is done. */ goto out_locked;
if (!rb_check_links(cpu_buffer, tmp)) goto out_locked;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); }
out_locked: raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);}
/* * Take an address, add the meta data size as well as the array of * array subbuffer indexes, then align it to a subbuffer size. * * This is used to help find the next per cpu subbuffer within a mapped range. */static unsigned longrb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs){ addr += sizeof(struct ring_buffer_cpu_meta) + sizeof(int) * nr_subbufs; return ALIGN(addr, subbuf_size);}
/* * Return the ring_buffer_meta for a given @cpu. */static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu){ int subbuf_size = buffer->subbuf_size + BUF_PAGE_HDR_SIZE; struct ring_buffer_cpu_meta *meta; struct ring_buffer_meta *bmeta; unsigned long ptr; int nr_subbufs;
bmeta = buffer->meta; if (!bmeta) return NULL;
ptr = (unsigned long)bmeta + bmeta->buffers_offset; meta = (struct ring_buffer_cpu_meta *)ptr;
/* When nr_pages passed in is zero, the first meta has already been initialized */ if (!nr_pages) { nr_subbufs = meta->nr_subbufs; } else { /* Include the reader page */ nr_subbufs = nr_pages + 1; }
/* * The first chunk may not be subbuffer aligned, where as * the rest of the chunks are. */ if (cpu) { ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs); ptr += subbuf_size * nr_subbufs;
/* We can use multiplication to find chunks greater than 1 */ if (cpu > 1) { unsigned long size; unsigned long p;
/* Save the beginning of this CPU chunk */ p = ptr; ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs); ptr += subbuf_size * nr_subbufs;
/* Now all chunks after this are the same size */ size = ptr - p; ptr += size * (cpu - 2); } } return (void *)ptr;}
/* Return the start of subbufs given the meta pointer */static void *rb_subbufs_from_meta(struct ring_buffer_cpu_meta *meta){ int subbuf_size = meta->subbuf_size; unsigned long ptr;
ptr = (unsigned long)meta; ptr = rb_range_align_subbuf(ptr, subbuf_size, meta->nr_subbufs);
return (void *)ptr;}
/* * Return a specific sub-buffer for a given @cpu defined by @idx. */static void *rb_range_buffer(struct ring_buffer_per_cpu *cpu_buffer, int idx){ struct ring_buffer_cpu_meta *meta; unsigned long ptr; int subbuf_size;
meta = rb_range_meta(cpu_buffer->buffer, 0, cpu_buffer->cpu); if (!meta) return NULL;
if (WARN_ON_ONCE(idx >= meta->nr_subbufs)) return NULL;
subbuf_size = meta->subbuf_size;
/* Map this buffer to the order that's in meta->buffers[] */ idx = meta->buffers[idx];
ptr = (unsigned long)rb_subbufs_from_meta(meta);
ptr += subbuf_size * idx; if (ptr + subbuf_size > cpu_buffer->buffer->range_addr_end) return NULL;
return (void *)ptr;}
/* * See if the existing memory contains a valid meta section. * if so, use that, otherwise initialize it. */static bool rb_meta_init(struct trace_buffer *buffer, int scratch_size){ unsigned long ptr = buffer->range_addr_start; struct ring_buffer_meta *bmeta; unsigned long total_size; int struct_sizes;
bmeta = (struct ring_buffer_meta *)ptr; buffer->meta = bmeta;
total_size = buffer->range_addr_end - buffer->range_addr_start;
struct_sizes = sizeof(struct ring_buffer_cpu_meta); struct_sizes |= sizeof(*bmeta) << 16;
/* The first buffer will start word size after the meta page */ ptr += sizeof(*bmeta); ptr = ALIGN(ptr, sizeof(long)); ptr += scratch_size;
if (bmeta->magic != RING_BUFFER_META_MAGIC) { pr_info("Ring buffer boot meta mismatch of magic\n"); goto init; }
if (bmeta->struct_sizes != struct_sizes) { pr_info("Ring buffer boot meta mismatch of struct size\n"); goto init; }
if (bmeta->total_size != total_size) { pr_info("Ring buffer boot meta mismatch of total size\n"); goto init; }
if (bmeta->buffers_offset > bmeta->total_size) { pr_info("Ring buffer boot meta mismatch of offset outside of total size\n"); goto init; }
if (bmeta->buffers_offset != (void *)ptr - (void *)bmeta) { pr_info("Ring buffer boot meta mismatch of first buffer offset\n"); goto init; }
return true;
init: bmeta->magic = RING_BUFFER_META_MAGIC; bmeta->struct_sizes = struct_sizes; bmeta->total_size = total_size; bmeta->buffers_offset = (void *)ptr - (void *)bmeta;
/* Zero out the scratch pad */ memset((void *)bmeta + sizeof(*bmeta), 0, bmeta->buffers_offset - sizeof(*bmeta));
return false;}
/* * See if the existing memory contains valid ring buffer data. * As the previous kernel must be the same as this kernel, all * the calculations (size of buffers and number of buffers) * must be the same. */static bool rb_cpu_meta_valid(struct ring_buffer_cpu_meta *meta, int cpu, struct trace_buffer *buffer, int nr_pages, unsigned long *subbuf_mask){ int subbuf_size = PAGE_SIZE; unsigned long buffers_start; unsigned long buffers_end; int i;
if (!subbuf_mask) return false;
if (meta->subbuf_size != PAGE_SIZE) { pr_info("Ring buffer boot meta [%d] invalid subbuf_size\n", cpu); return false; }
buffers_start = meta->first_buffer; buffers_end = meta->first_buffer + (subbuf_size * meta->nr_subbufs);
/* Is the head and commit buffers within the range of buffers? */ if (meta->head_buffer < buffers_start || meta->head_buffer >= buffers_end) { pr_info("Ring buffer boot meta [%d] head buffer out of range\n", cpu); return false; }
if (meta->commit_buffer < buffers_start || meta->commit_buffer >= buffers_end) { pr_info("Ring buffer boot meta [%d] commit buffer out of range\n", cpu); return false; }
bitmap_clear(subbuf_mask, 0, meta->nr_subbufs);
/* * Ensure the meta::buffers array has correct data. The data in each subbufs * are checked later in rb_meta_validate_events(). */ for (i = 0; i < meta->nr_subbufs; i++) { if (meta->buffers[i] < 0 || meta->buffers[i] >= meta->nr_subbufs) { pr_info("Ring buffer boot meta [%d] array out of range\n", cpu); return false; }
if (test_bit(meta->buffers[i], subbuf_mask)) { pr_info("Ring buffer boot meta [%d] array has duplicates\n", cpu); return false; }
set_bit(meta->buffers[i], subbuf_mask); }
return true;}
static int rb_meta_subbuf_idx(struct ring_buffer_cpu_meta *meta, void *subbuf);
static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu, unsigned long long *timestamp, u64 *delta_ptr){ struct ring_buffer_event *event; u64 ts, delta; int events = 0; int len; int e;
*delta_ptr = 0; *timestamp = 0;
ts = dpage->time_stamp;
for (e = 0; e < tail; e += len) {
event = (struct ring_buffer_event *)(dpage->data + e); len = rb_event_length(event); if (len <= 0 || len > tail - e) return -1;
switch (event->type_len) {
case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); ts += delta; break;
case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); delta = rb_fix_abs_ts(delta, ts); if (delta < ts) { *delta_ptr = delta; *timestamp = ts; return -1; } ts = delta; break;
case RINGBUF_TYPE_PADDING: if (event->time_delta == 1) break; fallthrough; case RINGBUF_TYPE_DATA: events++; ts += event->time_delta; break;
default: return -1; } } *timestamp = ts; return events;}
struct rb_validation_state { unsigned long entries; unsigned long entry_bytes; int discarded; u64 ts;};
static int __rb_validate_buffer(struct buffer_page *bpage, int cpu, struct ring_buffer_cpu_meta *meta, u64 prev_ts, u64 next_ts){ struct buffer_data_page *dpage = bpage->page; unsigned long long ts; unsigned long tail; u64 delta; int ret;
/* * When a sub-buffer is recovered from a read, the commit value may * have RB_MISSED_* bits set, as these bits are reset on reuse. * Even after clearing these bits, a commit value greater than the * subbuf_size is considered invalid. */ tail = rb_data_page_commit(dpage); if (tail <= meta->subbuf_size - BUF_PAGE_HDR_SIZE) ret = rb_read_data_buffer(dpage, tail, cpu, &ts, &delta); else ret = -1;
/* * The timestamp must be greater than @prev_ts and smaller than @next_ts. * Since this function works in both forward (verify) and reverse (unwind) * loop, we don't know both @prev_ts and @next_ts at the same time. * So use the known boundary as the boundary. */ if (ret < 0 || (prev_ts && prev_ts > ts) || (next_ts && ts > next_ts)) { local_set(&bpage->entries, 0); /* * Note, the RB_MISSED_EVENTS is only set inside the main write * buffer by this verification logic. The normal ring buffer * has this bit set when the page is read and passed to the * consumers. */ local_set(&dpage->commit, RB_MISSED_EVENTS); dpage->time_stamp = prev_ts ? prev_ts : next_ts; ret = -1; } else { local_set(&bpage->entries, ret); }
return ret;}
/** * rb_validate_buffer - validates a single buffer page and updates the state. * @bpage: buffer page to validate * @cpu_buffer: cpu_buffer this page belongs to * @meta: meta of the cpu_buffer * @state: validation state * @prev_ts: previous buffer's timestamp (optional) * @next_ts: next buffer's timestamp (optional) * * If the page is invalid (wrong event length or timestamp), it increments the * discarded counter and warns it. Otherwise, it updates the validation state. */static void rb_validate_buffer(struct buffer_page *bpage, struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_cpu_meta *meta, struct rb_validation_state *state, u64 prev_ts, u64 next_ts){ int ret;
ret = __rb_validate_buffer(bpage, cpu_buffer->cpu, meta, prev_ts, next_ts); if (ret < 0) { if (!state->discarded) pr_info("Ring buffer meta [%d] invalid buffer page detected\n", cpu_buffer->cpu); state->discarded++; } else { /* If the buffer has content, update pages_touched */ if (ret) local_inc(&cpu_buffer->pages_touched);
state->entries += ret; state->entry_bytes += rb_page_size(bpage); state->ts = bpage->page->time_stamp; }}
static void rb_meta_inject_reader_page(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_cpu_meta *meta, struct buffer_page *orig_head, struct buffer_page *head_page){ struct buffer_page *bpage = orig_head; int i;
rb_dec_page(&bpage); /* * Insert the reader_page before the original head page. * Since the list encode RB_PAGE flags, general list * operations should be avoided. */ cpu_buffer->reader_page->list.next = &orig_head->list; cpu_buffer->reader_page->list.prev = orig_head->list.prev; orig_head->list.prev = &cpu_buffer->reader_page->list; bpage->list.next = &cpu_buffer->reader_page->list;
/* Make the head_page the reader page */ cpu_buffer->reader_page = head_page; bpage = head_page; rb_inc_page(&head_page); head_page->list.prev = bpage->list.prev; rb_dec_page(&bpage); bpage->list.next = &head_page->list; rb_set_list_to_head(&bpage->list); cpu_buffer->pages = &head_page->list;
cpu_buffer->head_page = head_page; meta->head_buffer = (unsigned long)head_page->page;
/* Reset all the indexes */ bpage = cpu_buffer->reader_page; meta->buffers[0] = rb_meta_subbuf_idx(meta, bpage->page); bpage->id = 0;
for (i = 1, bpage = head_page; i < meta->nr_subbufs; i++, rb_inc_page(&bpage)) { meta->buffers[i] = rb_meta_subbuf_idx(meta, bpage->page); bpage->id = i; }}
/* If the meta data has been validated, now validate the events */static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer){ struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; struct buffer_page *head_page, *orig_head, *orig_reader; struct rb_validation_state state = { 0 }; bool skip = false; int ret; int i;
if (!meta || !meta->head_buffer) return;
orig_head = head_page = cpu_buffer->head_page; orig_reader = cpu_buffer->reader_page;
/* Do the head page first */ ret = __rb_validate_buffer(head_page, cpu_buffer->cpu, meta, 0, 0); if (ret < 0) { pr_info("Ring buffer meta [%d] invalid head page detected\n", cpu_buffer->cpu); /* Don't bother rewinding */ skip = true; state.ts = 0; } else { state.ts = head_page->page->time_stamp; }
/* Do the reader page - reader must be previous to head. */ rb_validate_buffer(orig_reader, cpu_buffer, meta, &state, 0, state.ts);
if (skip) goto skip_rewind;
/* * Try to rewind the head so that we can read the pages which are already * read in the previous boot. */ if (head_page == cpu_buffer->tail_page) goto skip_rewind;
rb_dec_page(&head_page); for (i = 0; i < meta->nr_subbufs + 1; i++, rb_dec_page(&head_page)) {
/* Rewind until tail (writer) page. */ if (head_page == cpu_buffer->tail_page) break;
/* Rewind until unused page (no timestamp, no commit). */ if (!head_page->page->time_stamp && rb_page_commit(head_page) == 0) break;
/* * Skip if the page is invalid, or its timestamp is newer than the * previous valid page. */ rb_validate_buffer(head_page, cpu_buffer, meta, &state, 0, state.ts); } if (i) pr_info("Ring buffer [%d] rewound %d pages\n", cpu_buffer->cpu, i);
/* The last rewound page must be skipped. */ if (head_page != orig_head) rb_inc_page(&head_page);
/* * If the ring buffer was rewound, then inject the reader page * into the location just before the original head page. */ if (head_page != orig_head) { rb_meta_inject_reader_page(cpu_buffer, meta, orig_head, head_page); /* We'll restart verifying from orig_head */ head_page = orig_head; }
skip_rewind: /* If the commit_buffer is the reader page, update the commit page */ if (meta->commit_buffer == (unsigned long)cpu_buffer->reader_page->page) { cpu_buffer->commit_page = cpu_buffer->reader_page; /* Nothing more to do, the only page is the reader page */ goto done; } state.ts = head_page->page->time_stamp;
/* Iterate until finding the commit page */ for (i = 0; i < meta->nr_subbufs + 1; i++, rb_inc_page(&head_page)) {
/* The original reader page has already been checked/counted. */ if (head_page == orig_reader) continue;
rb_validate_buffer(head_page, cpu_buffer, meta, &state, state.ts, 0);
if (head_page == cpu_buffer->commit_page) break; }
if (head_page != cpu_buffer->commit_page) { pr_info("Ring buffer meta [%d] commit page not found\n", cpu_buffer->cpu); goto invalid; } done: local_set(&cpu_buffer->entries, state.entries); local_set(&cpu_buffer->entries_bytes, state.entry_bytes);
pr_info("Ring buffer meta [%d] is from previous boot!", cpu_buffer->cpu); if (state.discarded) pr_cont(" (%d pages discarded)", state.discarded); pr_cont("\n");
#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT if (meta->nr_invalid) pr_warn("Ring buffer testing [%d] invalid pages: %s (%d/%d)\n", cpu_buffer->cpu, (state.discarded == meta->nr_invalid) ? "PASSED" : "FAILED", state.discarded, meta->nr_invalid); if (meta->entry_bytes) pr_warn("Ring buffer testing [%d] entry_bytes: %s (%ld/%ld)\n", cpu_buffer->cpu, (state.entry_bytes == meta->entry_bytes) ? "PASSED" : "FAILED", (long)state.entry_bytes, (long)meta->entry_bytes); meta->nr_invalid = 0; meta->entry_bytes = 0;#endif return;
invalid: /* The content of the buffers are invalid, reset the meta data */ meta->head_buffer = 0; meta->commit_buffer = 0;
/* Reset the reader page */ local_set(&cpu_buffer->reader_page->entries, 0); rb_init_data_page(cpu_buffer->reader_page->page);
/* Reset all the subbuffers */ for (i = 0; i < meta->nr_subbufs - 1; i++, rb_inc_page(&head_page)) { local_set(&head_page->entries, 0); rb_init_data_page(head_page->page); }}
static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages, int scratch_size){ struct ring_buffer_cpu_meta *meta; unsigned long *subbuf_mask; unsigned long delta; void *subbuf; bool valid = false; int cpu; int i;
/* Create a mask to test the subbuf array */ subbuf_mask = bitmap_alloc(nr_pages + 1, GFP_KERNEL); /* If subbuf_mask fails to allocate, then rb_meta_valid() will return false */
if (rb_meta_init(buffer, scratch_size)) valid = true;
for (cpu = 0; cpu < nr_cpu_ids; cpu++) { void *next_meta;
meta = rb_range_meta(buffer, nr_pages, cpu);
if (valid && rb_cpu_meta_valid(meta, cpu, buffer, nr_pages, subbuf_mask)) { /* Make the mappings match the current address */ subbuf = rb_subbufs_from_meta(meta); delta = (unsigned long)subbuf - meta->first_buffer; meta->first_buffer += delta; meta->head_buffer += delta; meta->commit_buffer += delta; continue; }
if (cpu < nr_cpu_ids - 1) next_meta = rb_range_meta(buffer, nr_pages, cpu + 1); else next_meta = (void *)buffer->range_addr_end;
memset(meta, 0, next_meta - (void *)meta);
meta->nr_subbufs = nr_pages + 1; meta->subbuf_size = PAGE_SIZE;
subbuf = rb_subbufs_from_meta(meta);
meta->first_buffer = (unsigned long)subbuf;
/* * The buffers[] array holds the order of the sub-buffers * that are after the meta data. The sub-buffers may * be swapped out when read and inserted into a different * location of the ring buffer. Although their addresses * remain the same, the buffers[] array contains the * index into the sub-buffers holding their actual order. */ for (i = 0; i < meta->nr_subbufs; i++) { meta->buffers[i] = i; rb_init_data_page(subbuf); subbuf += meta->subbuf_size; } } bitmap_free(subbuf_mask);}
static void *rbm_start(struct seq_file *m, loff_t *pos){ struct ring_buffer_per_cpu *cpu_buffer = m->private; struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; unsigned long val;
if (!meta) return NULL;
if (*pos > meta->nr_subbufs) return NULL;
val = *pos; val++;
return (void *)val;}
static void *rbm_next(struct seq_file *m, void *v, loff_t *pos){ (*pos)++;
return rbm_start(m, pos);}
static int rbm_show(struct seq_file *m, void *v){ struct ring_buffer_per_cpu *cpu_buffer = m->private; struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; unsigned long val = (unsigned long)v; struct buffer_data_page *dpage;
if (val == 1) { seq_printf(m, "head_buffer: %d\n", rb_meta_subbuf_idx(meta, (void *)meta->head_buffer)); seq_printf(m, "commit_buffer: %d\n", rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer)); seq_printf(m, "subbuf_size: %d\n", meta->subbuf_size); seq_printf(m, "nr_subbufs: %d\n", meta->nr_subbufs); return 0; }
val -= 2; dpage = rb_range_buffer(cpu_buffer, val); seq_printf(m, "buffer[%ld]: %d (commit: %ld)\n", val, meta->buffers[val], dpage ? rb_data_page_commit(dpage) : -1);
return 0;}
static void rbm_stop(struct seq_file *m, void *p){}
static const struct seq_operations rb_meta_seq_ops = { .start = rbm_start, .next = rbm_next, .show = rbm_show, .stop = rbm_stop,};
int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buffer, int cpu){ struct seq_file *m; int ret;
ret = seq_open(file, &rb_meta_seq_ops); if (ret) return ret;
m = file->private_data; m->private = buffer->buffers[cpu];
return 0;}
/* Map the buffer_pages to the previous head and commit pages */static void rb_meta_buffer_update(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *bpage){ struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta;
if (meta->head_buffer == (unsigned long)bpage->page) cpu_buffer->head_page = bpage;
if (meta->commit_buffer == (unsigned long)bpage->page) { cpu_buffer->commit_page = bpage; cpu_buffer->tail_page = bpage; }}
static struct ring_buffer_desc *ring_buffer_desc(struct trace_buffer_desc *trace_desc, int cpu){ struct ring_buffer_desc *desc, *end; size_t len; int i;
if (!trace_desc || !trace_desc->nr_cpus) return NULL;
end = (struct ring_buffer_desc *)((void *)trace_desc + trace_desc->struct_len); desc = __first_ring_buffer_desc(trace_desc); len = struct_size(desc, page_va, desc->nr_page_va); desc = (struct ring_buffer_desc *)((void *)desc + (len * cpu));
if (desc < end && desc->cpu == cpu) return desc;
/* Missing CPUs, need to linear search */ for_each_ring_buffer_desc(desc, i, trace_desc) { if (desc->cpu == cpu) return desc; }
return NULL;}
static void *ring_buffer_desc_page(struct ring_buffer_desc *desc, unsigned int page_id){ return page_id >= desc->nr_page_va ? NULL : (void *)desc->page_va[page_id];}
static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, long nr_pages, struct list_head *pages){ struct trace_buffer *buffer = cpu_buffer->buffer; struct ring_buffer_cpu_meta *meta = NULL; struct buffer_page *bpage, *tmp; bool user_thread = current->mm != NULL; struct ring_buffer_desc *desc = NULL; long i;
/* * Check if the available memory is there first. * Note, si_mem_available() only gives us a rough estimate of available * memory. It may not be accurate. But we don't care, we just want * to prevent doing any allocation when it is obvious that it is * not going to succeed. */ i = si_mem_available(); if (i < nr_pages) return -ENOMEM;
/* * If a user thread allocates too much, and si_mem_available() * reports there's enough memory, even though there is not. * Make sure the OOM killer kills this thread. This can happen * even with RETRY_MAYFAIL because another task may be doing * an allocation after this task has taken all memory. * This is the task the OOM killer needs to take out during this * loop, even if it was triggered by an allocation somewhere else. */ if (user_thread) set_current_oom_origin();
if (buffer->range_addr_start) meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
if (buffer->remote) { desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu); if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1))) return -EINVAL; }
for (i = 0; i < nr_pages; i++) {
bpage = alloc_cpu_page(cpu_buffer->cpu); if (!bpage) goto free_pages;
rb_check_bpage(cpu_buffer, bpage);
/* * Append the pages as for mapped buffers we want to keep * the order */ list_add_tail(&bpage->list, pages);
if (meta) { /* A range was given. Use that for the buffer page */ bpage->page = rb_range_buffer(cpu_buffer, i + 1); if (!bpage->page) goto free_pages; /* If this is valid from a previous boot */ if (meta->head_buffer) rb_meta_buffer_update(cpu_buffer, bpage); bpage->range = 1; bpage->id = i + 1; } else if (desc) { void *p = ring_buffer_desc_page(desc, i + 1);
if (WARN_ON(!p)) goto free_pages;
bpage->page = p; bpage->range = 1; /* bpage->page can't be freed */ bpage->id = i + 1; cpu_buffer->subbuf_ids[i + 1] = bpage; } else { int order = cpu_buffer->buffer->subbuf_order; bpage->page = alloc_cpu_data(cpu_buffer->cpu, order); if (!bpage->page) goto free_pages; } bpage->order = cpu_buffer->buffer->subbuf_order;
if (user_thread && fatal_signal_pending(current)) goto free_pages; } if (user_thread) clear_current_oom_origin();
return 0;
free_pages: list_for_each_entry_safe(bpage, tmp, pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } if (user_thread) clear_current_oom_origin();
return -ENOMEM;}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages){ LIST_HEAD(pages);
WARN_ON(!nr_pages);
if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages)) return -ENOMEM;
/* * The ring buffer page list is a circular list that does not * start and end with a list head. All page list items point to * other pages. */ cpu_buffer->pages = pages.next; list_del(&pages);
cpu_buffer->nr_pages = nr_pages;
rb_check_pages(cpu_buffer);
return 0;}
static struct ring_buffer_per_cpu *rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu){ struct ring_buffer_per_cpu *cpu_buffer __free(kfree) = alloc_cpu_buffer(cpu); struct ring_buffer_cpu_meta *meta; struct buffer_page *bpage; int ret;
if (!cpu_buffer) return NULL;
cpu_buffer->cpu = cpu; cpu_buffer->buffer = buffer; raw_spin_lock_init(&cpu_buffer->reader_lock); lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); init_completion(&cpu_buffer->update_done); init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); init_waitqueue_head(&cpu_buffer->irq_work.waiters); init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); mutex_init(&cpu_buffer->mapping_lock);
bpage = alloc_cpu_page(cpu); if (!bpage) return NULL;
rb_check_bpage(cpu_buffer, bpage);
cpu_buffer->reader_page = bpage;
if (buffer->range_addr_start) { /* * Range mapped buffers have the same restrictions as memory * mapped ones do. */ cpu_buffer->mapped = 1; cpu_buffer->ring_meta = rb_range_meta(buffer, nr_pages, cpu); bpage->page = rb_range_buffer(cpu_buffer, 0); if (!bpage->page) goto fail_free_reader; if (cpu_buffer->ring_meta->head_buffer) rb_meta_buffer_update(cpu_buffer, bpage); bpage->range = 1; } else if (buffer->remote) { struct ring_buffer_desc *desc = ring_buffer_desc(buffer->remote->desc, cpu);
if (!desc) goto fail_free_reader;
cpu_buffer->remote = buffer->remote; cpu_buffer->meta_page = (struct trace_buffer_meta *)(void *)desc->meta_va; cpu_buffer->nr_pages = nr_pages; cpu_buffer->subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*cpu_buffer->subbuf_ids), GFP_KERNEL); if (!cpu_buffer->subbuf_ids) goto fail_free_reader;
/* Remote buffers are read-only and immutable */ atomic_inc(&cpu_buffer->record_disabled); atomic_inc(&cpu_buffer->resize_disabled);
bpage->page = ring_buffer_desc_page(desc, cpu_buffer->meta_page->reader.id); if (!bpage->page) goto fail_free_reader;
bpage->range = 1; cpu_buffer->subbuf_ids[0] = bpage; } else { int order = cpu_buffer->buffer->subbuf_order; bpage->page = alloc_cpu_data(cpu, order); if (!bpage->page) goto fail_free_reader; }
INIT_LIST_HEAD(&cpu_buffer->reader_page->list); INIT_LIST_HEAD(&cpu_buffer->new_pages);
ret = rb_allocate_pages(cpu_buffer, nr_pages); if (ret < 0) goto fail_free_reader;
rb_meta_validate_events(cpu_buffer);
/* If the boot meta was valid then this has already been updated */ meta = cpu_buffer->ring_meta; if (!meta || !meta->head_buffer || !cpu_buffer->head_page || !cpu_buffer->commit_page || !cpu_buffer->tail_page) { if (meta && meta->head_buffer && (cpu_buffer->head_page || cpu_buffer->commit_page || cpu_buffer->tail_page)) { pr_warn("Ring buffer meta buffers not all mapped\n"); if (!cpu_buffer->head_page) pr_warn(" Missing head_page\n"); if (!cpu_buffer->commit_page) pr_warn(" Missing commit_page\n"); if (!cpu_buffer->tail_page) pr_warn(" Missing tail_page\n"); }
cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
rb_head_page_activate(cpu_buffer);
if (cpu_buffer->ring_meta) meta->commit_buffer = meta->head_buffer; } else { /* The valid meta buffer still needs to activate the head page */ rb_head_page_activate(cpu_buffer); }
return_ptr(cpu_buffer);
fail_free_reader: free_buffer_page(cpu_buffer->reader_page);
return NULL;}
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer){ struct list_head *head = cpu_buffer->pages; struct buffer_page *bpage, *tmp;
irq_work_sync(&cpu_buffer->irq_work.work);
if (cpu_buffer->remote) kfree(cpu_buffer->subbuf_ids);
free_buffer_page(cpu_buffer->reader_page);
if (head) { rb_head_page_deactivate(cpu_buffer);
list_for_each_entry_safe(bpage, tmp, head, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } bpage = list_entry(head, struct buffer_page, list); free_buffer_page(bpage); }
free_page((unsigned long)cpu_buffer->free_page);
kfree(cpu_buffer);}
#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECTstatic void rb_test_inject_invalid_pages(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_cpu_meta *meta; struct buffer_data_page *dpage; unsigned long entry_bytes = 0; unsigned long ptr; int subbuf_size; int invalid = 0; int cpu; int i;
if (!(buffer->flags & RB_FL_TESTING)) return;
guard(preempt)(); cpu = smp_processor_id();
cpu_buffer = buffer->buffers[cpu]; if (!cpu_buffer) return; meta = cpu_buffer->ring_meta; if (!meta) return;
ptr = (unsigned long)rb_subbufs_from_meta(meta); subbuf_size = meta->subbuf_size;
for (i = 0; i < meta->nr_subbufs; i++) { unsigned long idx = meta->buffers[i];
dpage = (void *)(ptr + idx * subbuf_size); /* Skip unused pages */ if (!rb_data_page_commit(dpage)) continue;
/* * Invalidate even pages or multiples of 5. This will cause 3 * contiguous invalidated(empty) pages. */ if (!(i & 0x1) || !(i % 5)) { local_add(subbuf_size + 1, &dpage->commit); invalid++; } else { /* Count total commit bytes. */ entry_bytes += rb_data_page_size(dpage); } }
pr_info("Inject invalidated %d pages on CPU%d, total size: %ld\n", invalid, cpu, (long)entry_bytes); meta->nr_invalid = invalid; meta->entry_bytes = entry_bytes;}#else /* !CONFIG_RING_BUFFER_PERSISTENT_INJECT */#define rb_test_inject_invalid_pages(buffer) do { } while (0)#endif
/* Stop recording on a persistent buffer and flush cache if needed. */static int rb_flush_buffer_cb(struct notifier_block *nb, unsigned long event, void *data){ struct trace_buffer *buffer = container_of(nb, struct trace_buffer, flush_nb);
ring_buffer_record_off(buffer); rb_test_inject_invalid_pages(buffer); arch_ring_buffer_flush_range(buffer->range_addr_start, buffer->range_addr_end); return NOTIFY_DONE;}
static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags, int order, unsigned long start, unsigned long end, unsigned long scratch_size, struct lock_class_key *key, struct ring_buffer_remote *remote){ struct trace_buffer *buffer __free(kfree) = NULL; long nr_pages; int subbuf_size; int bsize; int cpu; int ret;
/* keep it in its own cache line */ buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), GFP_KERNEL); if (!buffer) return NULL;
if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) return NULL;
buffer->subbuf_order = order; subbuf_size = (PAGE_SIZE << order); buffer->subbuf_size = subbuf_size - BUF_PAGE_HDR_SIZE;
/* Max payload is buffer page size - header (8bytes) */ buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
buffer->flags = flags; buffer->clock = trace_clock_local; buffer->reader_lock_key = key;
init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); init_waitqueue_head(&buffer->irq_work.waiters);
buffer->cpus = nr_cpu_ids;
bsize = sizeof(void *) * nr_cpu_ids; buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), GFP_KERNEL); if (!buffer->buffers) goto fail_free_cpumask;
cpu = raw_smp_processor_id();
/* If start/end are specified, then that overrides size */ if (start && end) { unsigned long buffers_start; unsigned long ptr; int n;
/* Make sure that start is word aligned */ start = ALIGN(start, sizeof(long));
/* scratch_size needs to be aligned too */ scratch_size = ALIGN(scratch_size, sizeof(long));
/* Subtract the buffer meta data and word aligned */ buffers_start = start + sizeof(struct ring_buffer_cpu_meta); buffers_start = ALIGN(buffers_start, sizeof(long)); buffers_start += scratch_size;
/* Calculate the size for the per CPU data */ size = end - buffers_start; size = size / nr_cpu_ids;
/* * The number of sub-buffers (nr_pages) is determined by the * total size allocated minus the meta data size. * Then that is divided by the number of per CPU buffers * needed, plus account for the integer array index that * will be appended to the meta data. */ nr_pages = (size - sizeof(struct ring_buffer_cpu_meta)) / (subbuf_size + sizeof(int)); /* Need at least two pages plus the reader page */ if (nr_pages < 3) goto fail_free_buffers;
again: /* Make sure that the size fits aligned */ for (n = 0, ptr = buffers_start; n < nr_cpu_ids; n++) { ptr += sizeof(struct ring_buffer_cpu_meta) + sizeof(int) * nr_pages; ptr = ALIGN(ptr, subbuf_size); ptr += subbuf_size * nr_pages; } if (ptr > end) { if (nr_pages <= 3) goto fail_free_buffers; nr_pages--; goto again; }
/* nr_pages should not count the reader page */ nr_pages--; buffer->range_addr_start = start; buffer->range_addr_end = end;
rb_range_meta_init(buffer, nr_pages, scratch_size); } else if (remote) { struct ring_buffer_desc *desc = ring_buffer_desc(remote->desc, cpu);
buffer->remote = remote; /* The writer is remote. This ring-buffer is read-only */ atomic_inc(&buffer->record_disabled); nr_pages = desc->nr_page_va - 1; if (nr_pages < 2) goto fail_free_buffers; } else {
/* need at least two pages */ nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size); if (nr_pages < 2) nr_pages = 2; }
cpumask_set_cpu(cpu, buffer->cpumask); buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); if (!buffer->buffers[cpu]) goto fail_free_buffers;
ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); if (ret < 0) goto fail_free_buffers;
mutex_init(&buffer->mutex);
/* Persistent ring buffer needs to flush cache before reboot. */ if (start && end) { buffer->flush_nb.notifier_call = rb_flush_buffer_cb; atomic_notifier_chain_register(&panic_notifier_list, &buffer->flush_nb); }
return_ptr(buffer);
fail_free_buffers: for_each_buffer_cpu(buffer, cpu) { if (buffer->buffers[cpu]) rb_free_cpu_buffer(buffer->buffers[cpu]); } kfree(buffer->buffers);
fail_free_cpumask: free_cpumask_var(buffer->cpumask);
return NULL;}
/** * __ring_buffer_alloc - allocate a new ring_buffer * @size: the size in bytes per cpu that is needed. * @flags: attributes to set for the ring buffer. * @key: ring buffer reader_lock_key. * * Currently the only flag that is available is the RB_FL_OVERWRITE * flag. This flag means that the buffer will overwrite old data * when the buffer wraps. If this flag is not set, the buffer will * drop data when the tail hits the head. */struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *key){ /* Default buffer page size - one system page */ return alloc_buffer(size, flags, 0, 0, 0, 0, key, NULL);
}EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
/** * __ring_buffer_alloc_range - allocate a new ring_buffer from existing memory * @size: the size in bytes per cpu that is needed. * @flags: attributes to set for the ring buffer. * @order: sub-buffer order * @start: start of allocated range * @range_size: size of allocated range * @scratch_size: size of scratch area (for preallocated memory buffers) * @key: ring buffer reader_lock_key. * * Currently the only flag that is available is the RB_FL_OVERWRITE * flag. This flag means that the buffer will overwrite old data * when the buffer wraps. If this flag is not set, the buffer will * drop data when the tail hits the head. */struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags, int order, unsigned long start, unsigned long range_size, unsigned long scratch_size, struct lock_class_key *key){ return alloc_buffer(size, flags, order, start, start + range_size, scratch_size, key, NULL);}
/** * __ring_buffer_alloc_remote - allocate a new ring_buffer from a remote * @remote: Contains a description of the ring-buffer pages and remote callbacks. * @key: ring buffer reader_lock_key. */struct trace_buffer *__ring_buffer_alloc_remote(struct ring_buffer_remote *remote, struct lock_class_key *key){ return alloc_buffer(0, 0, 0, 0, 0, 0, key, remote);}
void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int *size){ struct ring_buffer_meta *meta; void *ptr;
if (!buffer || !buffer->meta) return NULL;
meta = buffer->meta;
ptr = (void *)ALIGN((unsigned long)meta + sizeof(*meta), sizeof(long));
if (size) *size = (void *)meta + meta->buffers_offset - ptr;
return ptr;}
/** * ring_buffer_free - free a ring buffer. * @buffer: the buffer to free. */voidring_buffer_free(struct trace_buffer *buffer){ int cpu;
if (buffer->range_addr_start && buffer->range_addr_end) atomic_notifier_chain_unregister(&panic_notifier_list, &buffer->flush_nb);
cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
irq_work_sync(&buffer->irq_work.work);
for_each_buffer_cpu(buffer, cpu) rb_free_cpu_buffer(buffer->buffers[cpu]);
kfree(buffer->buffers); free_cpumask_var(buffer->cpumask);
kfree(buffer);}EXPORT_SYMBOL_GPL(ring_buffer_free);
void ring_buffer_set_clock(struct trace_buffer *buffer, u64 (*clock)(void)){ buffer->clock = clock;}
void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs){ buffer->time_stamp_abs = abs;}
bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer){ return buffer->time_stamp_abs;}
static inline unsigned long rb_page_entries(struct buffer_page *bpage){ return local_read(&bpage->entries) & RB_WRITE_MASK;}
static inline unsigned long rb_page_write(struct buffer_page *bpage){ return local_read(&bpage->write) & RB_WRITE_MASK;}
static boolrb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages){ struct list_head *tail_page, *to_remove, *next_page; struct buffer_page *to_remove_page, *tmp_iter_page; struct buffer_page *last_page, *first_page; unsigned long nr_removed; unsigned long head_bit; int page_entries;
head_bit = 0;
raw_spin_lock_irq(&cpu_buffer->reader_lock); atomic_inc(&cpu_buffer->record_disabled); /* * We don't race with the readers since we have acquired the reader * lock. We also don't race with writers after disabling recording. * This makes it easy to figure out the first and the last page to be * removed from the list. We unlink all the pages in between including * the first and last pages. This is done in a busy loop so that we * lose the least number of traces. * The pages are freed after we restart recording and unlock readers. */ tail_page = &cpu_buffer->tail_page->list;
/* * tail page might be on reader page, we remove the next page * from the ring buffer */ if (cpu_buffer->tail_page == cpu_buffer->reader_page) tail_page = rb_list_head(tail_page->next); to_remove = tail_page;
/* start of pages to remove */ first_page = list_entry(rb_list_head(to_remove->next), struct buffer_page, list);
for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { to_remove = rb_list_head(to_remove)->next; head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; } /* Read iterators need to reset themselves when some pages removed */ cpu_buffer->pages_removed += nr_removed;
next_page = rb_list_head(to_remove)->next;
/* * Now we remove all pages between tail_page and next_page. * Make sure that we have head_bit value preserved for the * next page */ tail_page->next = (struct list_head *)((unsigned long)next_page | head_bit); next_page = rb_list_head(next_page); next_page->prev = tail_page;
/* make sure pages points to a valid page in the ring buffer */ cpu_buffer->pages = next_page; cpu_buffer->cnt++;
/* update head page */ if (head_bit) cpu_buffer->head_page = list_entry(next_page, struct buffer_page, list);
/* pages are removed, resume tracing and then free the pages */ atomic_dec(&cpu_buffer->record_disabled); raw_spin_unlock_irq(&cpu_buffer->reader_lock);
RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
/* last buffer page to remove */ last_page = list_entry(rb_list_head(to_remove), struct buffer_page, list); tmp_iter_page = first_page;
do { cond_resched();
to_remove_page = tmp_iter_page; rb_inc_page(&tmp_iter_page);
/* update the counters */ page_entries = rb_page_entries(to_remove_page); if (page_entries) { /* * If something was added to this page, it was full * since it is not the tail page. So we deduct the * bytes consumed in ring buffer from here. * Increment overrun to account for the lost events. */ local_add(page_entries, &cpu_buffer->overrun); local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes); local_inc(&cpu_buffer->pages_lost); }
/* * We have already removed references to this list item, just * free up the buffer_page and its page */ free_buffer_page(to_remove_page); nr_removed--;
} while (to_remove_page != last_page);
RB_WARN_ON(cpu_buffer, nr_removed);
return nr_removed == 0;}
static boolrb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer){ struct list_head *pages = &cpu_buffer->new_pages; unsigned long flags; bool success; int retries;
/* Can be called at early boot up, where interrupts must not been enabled */ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); /* * We are holding the reader lock, so the reader page won't be swapped * in the ring buffer. Now we are racing with the writer trying to * move head page and the tail page. * We are going to adapt the reader page update process where: * 1. We first splice the start and end of list of new pages between * the head page and its previous page. * 2. We cmpxchg the prev_page->next to point from head page to the * start of new pages list. * 3. Finally, we update the head->prev to the end of new list. * * We will try this process 10 times, to make sure that we don't keep * spinning. */ retries = 10; success = false; while (retries--) { struct list_head *head_page, *prev_page; struct list_head *last_page, *first_page; struct list_head *head_page_with_bit; struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
if (!hpage) break; head_page = &hpage->list; prev_page = head_page->prev;
first_page = pages->next; last_page = pages->prev;
head_page_with_bit = (struct list_head *) ((unsigned long)head_page | RB_PAGE_HEAD);
last_page->next = head_page_with_bit; first_page->prev = prev_page;
/* caution: head_page_with_bit gets updated on cmpxchg failure */ if (try_cmpxchg(&prev_page->next, &head_page_with_bit, first_page)) { /* * yay, we replaced the page pointer to our new list, * now, we just have to update to head page's prev * pointer to point to end of list */ head_page->prev = last_page; cpu_buffer->cnt++; success = true; break; } }
if (success) INIT_LIST_HEAD(pages); /* * If we weren't successful in adding in new pages, warn and stop * tracing */ RB_WARN_ON(cpu_buffer, !success); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
/* free pages if they weren't inserted */ if (!success) { struct buffer_page *bpage, *tmp; list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } } return success;}
static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer){ bool success;
if (cpu_buffer->nr_pages_to_update > 0) success = rb_insert_pages(cpu_buffer); else success = rb_remove_pages(cpu_buffer, -cpu_buffer->nr_pages_to_update);
if (success) cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;}
static void update_pages_handler(struct work_struct *work){ struct ring_buffer_per_cpu *cpu_buffer = container_of(work, struct ring_buffer_per_cpu, update_pages_work); rb_update_pages(cpu_buffer); complete(&cpu_buffer->update_done);}
/** * ring_buffer_resize - resize the ring buffer * @buffer: the buffer to resize. * @size: the new size. * @cpu_id: the cpu buffer to resize * * Minimum size is 2 * buffer->subbuf_size. * * Returns 0 on success and < 0 on failure. */int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, int cpu_id){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long nr_pages; int cpu, err;
/* * Always succeed at resizing a non-existent buffer: */ if (!buffer) return 0;
/* Make sure the requested buffer exists */ if (cpu_id != RING_BUFFER_ALL_CPUS && !cpumask_test_cpu(cpu_id, buffer->cpumask)) return 0;
nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
/* we need a minimum of two pages */ if (nr_pages < 2) nr_pages = 2;
/* * Keep CPUs from coming online while resizing to synchronize * with new per CPU buffers being created. */ guard(cpus_read_lock)();
/* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex); atomic_inc(&buffer->resizing);
if (cpu_id == RING_BUFFER_ALL_CPUS) { /* * Don't succeed if resizing is disabled, as a reader might be * manipulating the ring buffer and is expecting a sane state while * this is true. */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (atomic_read(&cpu_buffer->resize_disabled)) { err = -EBUSY; goto out_err_unlock; } }
/* calculate the pages to update */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
cpu_buffer->nr_pages_to_update = nr_pages - cpu_buffer->nr_pages; /* * nothing more to do for removing pages or no update */ if (cpu_buffer->nr_pages_to_update <= 0) continue; /* * to add pages, make sure all new pages can be * allocated without receiving ENOMEM */ INIT_LIST_HEAD(&cpu_buffer->new_pages); if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update, &cpu_buffer->new_pages)) { /* not enough memory for new pages */ err = -ENOMEM; goto out_err; }
cond_resched(); }
/* * Fire off all the required work handlers * We can't schedule on offline CPUs, but it's not necessary * since we can change their buffer sizes without any race. */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (!cpu_buffer->nr_pages_to_update) continue;
/* Can't run something on an offline CPU. */ if (!cpu_online(cpu)) { rb_update_pages(cpu_buffer); cpu_buffer->nr_pages_to_update = 0; } else { /* Run directly if possible. */ migrate_disable(); if (cpu != smp_processor_id()) { migrate_enable(); schedule_work_on(cpu, &cpu_buffer->update_pages_work); } else { update_pages_handler(&cpu_buffer->update_pages_work); migrate_enable(); } } }
/* wait for all the updates to complete */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (!cpu_buffer->nr_pages_to_update) continue;
if (cpu_online(cpu)) wait_for_completion(&cpu_buffer->update_done); cpu_buffer->nr_pages_to_update = 0; }
} else { cpu_buffer = buffer->buffers[cpu_id];
if (nr_pages == cpu_buffer->nr_pages) goto out;
/* * Don't succeed if resizing is disabled, as a reader might be * manipulating the ring buffer and is expecting a sane state while * this is true. */ if (atomic_read(&cpu_buffer->resize_disabled)) { err = -EBUSY; goto out_err_unlock; }
cpu_buffer->nr_pages_to_update = nr_pages - cpu_buffer->nr_pages;
INIT_LIST_HEAD(&cpu_buffer->new_pages); if (cpu_buffer->nr_pages_to_update > 0 && __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update, &cpu_buffer->new_pages)) { err = -ENOMEM; goto out_err; }
/* Can't run something on an offline CPU. */ if (!cpu_online(cpu_id)) rb_update_pages(cpu_buffer); else { /* Run directly if possible. */ migrate_disable(); if (cpu_id == smp_processor_id()) { rb_update_pages(cpu_buffer); migrate_enable(); } else { migrate_enable(); schedule_work_on(cpu_id, &cpu_buffer->update_pages_work); wait_for_completion(&cpu_buffer->update_done); } }
cpu_buffer->nr_pages_to_update = 0; }
out: /* * The ring buffer resize can happen with the ring buffer * enabled, so that the update disturbs the tracing as little * as possible. But if the buffer is disabled, we do not need * to worry about that, and we can take the time to verify * that the buffer is not corrupt. */ if (atomic_read(&buffer->record_disabled)) { atomic_inc(&buffer->record_disabled); /* * Even though the buffer was disabled, we must make sure * that it is truly disabled before calling rb_check_pages. * There could have been a race between checking * record_disable and incrementing it. */ synchronize_rcu(); for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; rb_check_pages(cpu_buffer); } atomic_dec(&buffer->record_disabled); }
atomic_dec(&buffer->resizing); mutex_unlock(&buffer->mutex); return 0;
out_err: for_each_buffer_cpu(buffer, cpu) { struct buffer_page *bpage, *tmp;
cpu_buffer = buffer->buffers[cpu]; cpu_buffer->nr_pages_to_update = 0;
if (list_empty(&cpu_buffer->new_pages)) continue;
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage);
cond_resched(); } } out_err_unlock: atomic_dec(&buffer->resizing); mutex_unlock(&buffer->mutex); return err;}EXPORT_SYMBOL_GPL(ring_buffer_resize);
void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val){ mutex_lock(&buffer->mutex); if (val) buffer->flags |= RB_FL_OVERWRITE; else buffer->flags &= ~RB_FL_OVERWRITE; mutex_unlock(&buffer->mutex);}EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index){ return bpage->page->data + index;}
static __always_inline struct ring_buffer_event *rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer){ return __rb_page_index(cpu_buffer->reader_page, cpu_buffer->reader_page->read);}
static struct ring_buffer_event *rb_iter_head_event(struct ring_buffer_iter *iter){ struct ring_buffer_event *event; struct buffer_page *iter_head_page = iter->head_page; unsigned long commit; unsigned length;
if (iter->head != iter->next_event) return iter->event;
/* * When the writer goes across pages, it issues a cmpxchg which * is a mb(), which will synchronize with the rmb here. * (see rb_tail_page_update() and __rb_reserve_next()) */ commit = rb_page_size(iter_head_page); smp_rmb();
/* An event needs to be at least 8 bytes in size */ if (iter->head > commit - 8) goto reset;
event = __rb_page_index(iter_head_page, iter->head); length = rb_event_length(event);
/* * READ_ONCE() doesn't work on functions and we don't want the * compiler doing any crazy optimizations with length. */ barrier();
if ((iter->head + length) > commit || length > iter->event_size) /* Writer corrupted the read? */ goto reset;
memcpy(iter->event, event, length); /* * If the page stamp is still the same after this rmb() then the * event was safely copied without the writer entering the page. */ smp_rmb();
/* Make sure the page didn't change since we read this */ if (iter->page_stamp != iter_head_page->page->time_stamp || commit > rb_page_size(iter_head_page)) goto reset;
iter->next_event = iter->head + length; return iter->event; reset: /* Reset to the beginning */ iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; iter->head = 0; iter->next_event = 0; iter->missed_events = 1; return NULL;}
static __always_inline unsignedrb_commit_index(struct ring_buffer_per_cpu *cpu_buffer){ return rb_page_commit(cpu_buffer->commit_page);}
static __always_inline unsignedrb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event){ unsigned long addr = (unsigned long)event;
addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
return addr - BUF_PAGE_HDR_SIZE;}
static void rb_inc_iter(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
/* * The iterator could be on the reader page (it starts there). * But the head could have moved, since the reader was * found. Check for this case and assign the iterator * to the head page instead of next. */ if (iter->head_page == cpu_buffer->reader_page) iter->head_page = rb_set_head_page(cpu_buffer); else rb_inc_page(&iter->head_page);
if (rb_page_commit(iter->head_page) & RB_MISSED_EVENTS) iter->missed_events = -1;
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; iter->head = 0; iter->next_event = 0;}
/* Return the index into the sub-buffers for a given sub-buffer */static int rb_meta_subbuf_idx(struct ring_buffer_cpu_meta *meta, void *subbuf){ void *subbuf_array;
subbuf_array = (void *)meta + sizeof(int) * meta->nr_subbufs; subbuf_array = (void *)ALIGN((unsigned long)subbuf_array, meta->subbuf_size); return (subbuf - subbuf_array) / meta->subbuf_size;}
static void rb_update_meta_head(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *next_page){ struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; unsigned long old_head = (unsigned long)next_page->page; unsigned long new_head;
rb_inc_page(&next_page); new_head = (unsigned long)next_page->page;
/* * Only move it forward once, if something else came in and * moved it forward, then we don't want to touch it. */ (void)cmpxchg(&meta->head_buffer, old_head, new_head);}
static void rb_update_meta_reader(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *reader){ struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; void *old_reader = cpu_buffer->reader_page->page; void *new_reader = reader->page; int id;
id = reader->id; cpu_buffer->reader_page->id = id; reader->id = 0;
meta->buffers[0] = rb_meta_subbuf_idx(meta, new_reader); meta->buffers[id] = rb_meta_subbuf_idx(meta, old_reader);
/* The head pointer is the one after the reader */ rb_update_meta_head(cpu_buffer, reader);}
/* * rb_handle_head_page - writer hit the head page * * Returns: +1 to retry page * 0 to continue * -1 on error */static intrb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *tail_page, struct buffer_page *next_page){ struct buffer_page *new_head; int entries; int type; int ret;
entries = rb_page_entries(next_page);
/* * The hard part is here. We need to move the head * forward, and protect against both readers on * other CPUs and writers coming in via interrupts. */ type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, RB_PAGE_HEAD);
/* * type can be one of four: * NORMAL - an interrupt already moved it for us * HEAD - we are the first to get here. * UPDATE - we are the interrupt interrupting * a current move. * MOVED - a reader on another CPU moved the next * pointer to its reader page. Give up * and try again. */
switch (type) { case RB_PAGE_HEAD: /* * We changed the head to UPDATE, thus * it is our responsibility to update * the counters. */ local_add(entries, &cpu_buffer->overrun); local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes); local_inc(&cpu_buffer->pages_lost);
if (cpu_buffer->ring_meta) rb_update_meta_head(cpu_buffer, next_page); /* * The entries will be zeroed out when we move the * tail page. */
/* still more to do */ break;
case RB_PAGE_UPDATE: /* * This is an interrupt that interrupt the * previous update. Still more to do. */ break; case RB_PAGE_NORMAL: /* * An interrupt came in before the update * and processed this for us. * Nothing left to do. */ return 1; case RB_PAGE_MOVED: /* * The reader is on another CPU and just did * a swap with our next_page. * Try again. */ return 1; default: RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ return -1; }
/* * Now that we are here, the old head pointer is * set to UPDATE. This will keep the reader from * swapping the head page with the reader page. * The reader (on another CPU) will spin till * we are finished. * * We just need to protect against interrupts * doing the job. We will set the next pointer * to HEAD. After that, we set the old pointer * to NORMAL, but only if it was HEAD before. * otherwise we are an interrupt, and only * want the outer most commit to reset it. */ new_head = next_page; rb_inc_page(&new_head);
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, RB_PAGE_NORMAL);
/* * Valid returns are: * HEAD - an interrupt came in and already set it. * NORMAL - One of two things: * 1) We really set it. * 2) A bunch of interrupts came in and moved * the page forward again. */ switch (ret) { case RB_PAGE_HEAD: case RB_PAGE_NORMAL: /* OK */ break; default: RB_WARN_ON(cpu_buffer, 1); return -1; }
/* * It is possible that an interrupt came in, * set the head up, then more interrupts came in * and moved it again. When we get back here, * the page would have been set to NORMAL but we * just set it back to HEAD. * * How do you detect this? Well, if that happened * the tail page would have moved. */ if (ret == RB_PAGE_NORMAL) { struct buffer_page *buffer_tail_page;
buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); /* * If the tail had moved passed next, then we need * to reset the pointer. */ if (buffer_tail_page != tail_page && buffer_tail_page != next_page) rb_head_page_set_normal(cpu_buffer, new_head, next_page, RB_PAGE_HEAD); }
/* * If this was the outer most commit (the one that * changed the original pointer from HEAD to UPDATE), * then it is up to us to reset it to NORMAL. */ if (type == RB_PAGE_HEAD) { ret = rb_head_page_set_normal(cpu_buffer, next_page, tail_page, RB_PAGE_UPDATE); if (RB_WARN_ON(cpu_buffer, ret != RB_PAGE_UPDATE)) return -1; }
return 0;}
static inline voidrb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, unsigned long tail, struct rb_event_info *info){ unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size); struct buffer_page *tail_page = info->tail_page; struct ring_buffer_event *event; unsigned long length = info->length;
/* * Only the event that crossed the page boundary * must fill the old tail_page with padding. */ if (tail >= bsize) { /* * If the page was filled, then we still need * to update the real_end. Reset it to zero * and the reader will ignore it. */ if (tail == bsize) tail_page->real_end = 0;
local_sub(length, &tail_page->write); return; }
event = __rb_page_index(tail_page, tail);
/* * Save the original length to the meta data. * This will be used by the reader to add lost event * counter. */ tail_page->real_end = tail;
/* * If this event is bigger than the minimum size, then * we need to be careful that we don't subtract the * write counter enough to allow another writer to slip * in on this page. * We put in a discarded commit instead, to make sure * that this space is not used again, and this space will * not be accounted into 'entries_bytes'. * * If we are less than the minimum size, we don't need to * worry about it. */ if (tail > (bsize - RB_EVNT_MIN_SIZE)) { /* No room for any events */
/* Mark the rest of the page with padding */ rb_event_set_padding(event);
/* Make sure the padding is visible before the write update */ smp_wmb();
/* Set the write back to the previous setting */ local_sub(length, &tail_page->write); return; }
/* Put in a discarded event */ event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE; event->type_len = RINGBUF_TYPE_PADDING; /* time delta must be non zero */ event->time_delta = 1;
/* account for padding bytes */ local_add(bsize - tail, &cpu_buffer->entries_bytes);
/* Make sure the padding is visible before the tail_page->write update */ smp_wmb();
/* Set write to end of buffer */ length = (tail + length) - bsize; local_sub(length, &tail_page->write);}
static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
/* * This is the slow path, force gcc not to inline it. */static noinline struct ring_buffer_event *rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, unsigned long tail, struct rb_event_info *info){ struct buffer_page *tail_page = info->tail_page; struct buffer_page *commit_page = cpu_buffer->commit_page; struct trace_buffer *buffer = cpu_buffer->buffer; struct buffer_page *next_page; int ret;
next_page = tail_page;
rb_inc_page(&next_page);
/* * If for some reason, we had an interrupt storm that made * it all the way around the buffer, bail, and warn * about it. */ if (unlikely(next_page == commit_page)) { local_inc(&cpu_buffer->commit_overrun); goto out_reset; }
/* * This is where the fun begins! * * We are fighting against races between a reader that * could be on another CPU trying to swap its reader * page with the buffer head. * * We are also fighting against interrupts coming in and * moving the head or tail on us as well. * * If the next page is the head page then we have filled * the buffer, unless the commit page is still on the * reader page. */ if (rb_is_head_page(next_page, &tail_page->list)) {
/* * If the commit is not on the reader page, then * move the header page. */ if (!rb_is_reader_page(cpu_buffer->commit_page)) { /* * If we are not in overwrite mode, * this is easy, just stop here. */ if (!(buffer->flags & RB_FL_OVERWRITE)) { local_inc(&cpu_buffer->dropped_events); goto out_reset; }
ret = rb_handle_head_page(cpu_buffer, tail_page, next_page); if (ret < 0) goto out_reset; if (ret) goto out_again; } else { /* * We need to be careful here too. The * commit page could still be on the reader * page. We could have a small buffer, and * have filled up the buffer with events * from interrupts and such, and wrapped. * * Note, if the tail page is also on the * reader_page, we let it move out. */ if (unlikely((cpu_buffer->commit_page != cpu_buffer->tail_page) && (cpu_buffer->commit_page == cpu_buffer->reader_page))) { local_inc(&cpu_buffer->commit_overrun); goto out_reset; } } }
rb_tail_page_update(cpu_buffer, tail_page, next_page);
out_again:
rb_reset_tail(cpu_buffer, tail, info);
/* Commit what we have for now. */ rb_end_commit(cpu_buffer); /* rb_end_commit() decs committing */ local_inc(&cpu_buffer->committing);
/* fail and let the caller try again */ return ERR_PTR(-EAGAIN);
out_reset: /* reset write */ rb_reset_tail(cpu_buffer, tail, info);
return NULL;}
/* Slow path */static struct ring_buffer_event *rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event, u64 delta, bool abs){ if (abs) event->type_len = RINGBUF_TYPE_TIME_STAMP; else event->type_len = RINGBUF_TYPE_TIME_EXTEND;
/* Not the first event on the page, or not delta? */ if (abs || rb_event_index(cpu_buffer, event)) { event->time_delta = delta & TS_MASK; event->array[0] = delta >> TS_SHIFT; } else { /* nope, just zero it */ event->time_delta = 0; event->array[0] = 0; }
return skip_time_extend(event);}
static voidrb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info){ u64 write_stamp;
WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s", (unsigned long long)info->delta, (unsigned long long)info->ts, (unsigned long long)info->before, (unsigned long long)info->after, (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}), sched_clock_stable() ? "" : "If you just came from a suspend/resume,\n" "please switch to the trace global clock:\n" " echo global > /sys/kernel/tracing/trace_clock\n" "or add trace_clock=global to the kernel command line\n");}
static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event **event, struct rb_event_info *info, u64 *delta, unsigned int *length){ bool abs = info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
if (unlikely(info->delta > (1ULL << 59))) { /* * Some timers can use more than 59 bits, and when a timestamp * is added to the buffer, it will lose those bits. */ if (abs && (info->ts & TS_MSB)) { info->delta &= ABS_TS_MASK;
/* did the clock go backwards */ } else if (info->before == info->after && info->before > info->ts) { /* not interrupted */ static int once;
/* * This is possible with a recalibrating of the TSC. * Do not produce a call stack, but just report it. */ if (!once) { once++; pr_warn("Ring buffer clock went backwards: %llu -> %llu\n", info->before, info->ts); } } else rb_check_timestamp(cpu_buffer, info); if (!abs) info->delta = 0; } *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs); *length -= RB_LEN_TIME_EXTEND; *delta = 0;}
/** * rb_update_event - update event type and data * @cpu_buffer: The per cpu buffer of the @event * @event: the event to update * @info: The info to update the @event with (contains length and delta) * * Update the type and data fields of the @event. The length * is the actual size that is written to the ring buffer, * and with this, we can determine what to place into the * data field. */static voidrb_update_event(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event, struct rb_event_info *info){ unsigned length = info->length; u64 delta = info->delta; unsigned int nest = local_read(&cpu_buffer->committing) - 1;
if (!WARN_ON_ONCE(nest >= MAX_NEST)) cpu_buffer->event_stamp[nest] = info->ts;
/* * If we need to add a timestamp, then we * add it to the start of the reserved space. */ if (unlikely(info->add_timestamp)) rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
event->time_delta = delta; length -= RB_EVNT_HDR_SIZE; if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { event->type_len = 0; event->array[0] = length; } else event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);}
static unsigned rb_calculate_event_length(unsigned length){ struct ring_buffer_event event; /* Used only for sizeof array */
/* zero length can cause confusions */ if (!length) length++;
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) length += sizeof(event.array[0]);
length += RB_EVNT_HDR_SIZE; length = ALIGN(length, RB_ARCH_ALIGNMENT);
/* * In case the time delta is larger than the 27 bits for it * in the header, we need to add a timestamp. If another * event comes in when trying to discard this one to increase * the length, then the timestamp will be added in the allocated * space of this event. If length is bigger than the size needed * for the TIME_EXTEND, then padding has to be used. The events * length must be either RB_LEN_TIME_EXTEND, or greater than or equal * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. * As length is a multiple of 4, we only need to worry if it * is 12 (RB_LEN_TIME_EXTEND + 4). */ if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) length += RB_ALIGNMENT;
return length;}
static inline boolrb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event){ unsigned long new_index, old_index; struct buffer_page *bpage; unsigned long addr;
new_index = rb_event_index(cpu_buffer, event); old_index = new_index + rb_event_ts_length(event); addr = (unsigned long)event; addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
bpage = READ_ONCE(cpu_buffer->tail_page);
/* * Make sure the tail_page is still the same and * the next write location is the end of this event */ if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { unsigned long write_mask = local_read(&bpage->write) & ~RB_WRITE_MASK; unsigned long event_length = rb_event_length(event);
/* * For the before_stamp to be different than the write_stamp * to make sure that the next event adds an absolute * value and does not rely on the saved write stamp, which * is now going to be bogus. * * By setting the before_stamp to zero, the next event * is not going to use the write_stamp and will instead * create an absolute timestamp. This means there's no * reason to update the wirte_stamp! */ rb_time_set(&cpu_buffer->before_stamp, 0);
/* * If an event were to come in now, it would see that the * write_stamp and the before_stamp are different, and assume * that this event just added itself before updating * the write stamp. The interrupting event will fix the * write stamp for us, and use an absolute timestamp. */
/* * This is on the tail page. It is possible that * a write could come in and move the tail page * and write to the next page. That is fine * because we just shorten what is on this page. */ old_index += write_mask; new_index += write_mask;
/* caution: old_index gets updated on cmpxchg failure */ if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) { /* update counters */ local_sub(event_length, &cpu_buffer->entries_bytes); return true; } }
/* could not discard */ return false;}
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer){ local_inc(&cpu_buffer->committing); local_inc(&cpu_buffer->commits);}
static __always_inline voidrb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer){ unsigned long max_count;
/* * We only race with interrupts and NMIs on this CPU. * If we own the commit event, then we can commit * all others that interrupted us, since the interruptions * are in stack format (they finish before they come * back to us). This allows us to do a simple loop to * assign the commit to the tail. */ again: max_count = cpu_buffer->nr_pages * 100;
while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { if (RB_WARN_ON(cpu_buffer, !(--max_count))) return; if (RB_WARN_ON(cpu_buffer, rb_is_reader_page(cpu_buffer->tail_page))) return; /* * No need for a memory barrier here, as the update * of the tail_page did it for this page. */ local_set(&cpu_buffer->commit_page->page->commit, rb_page_write(cpu_buffer->commit_page)); rb_inc_page(&cpu_buffer->commit_page); if (cpu_buffer->ring_meta) { struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; meta->commit_buffer = (unsigned long)cpu_buffer->commit_page->page; } /* add barrier to keep gcc from optimizing too much */ barrier(); } while (rb_commit_index(cpu_buffer) != rb_page_write(cpu_buffer->commit_page)) {
/* Make sure the readers see the content of what is committed. */ smp_wmb(); local_set(&cpu_buffer->commit_page->page->commit, rb_page_write(cpu_buffer->commit_page)); RB_WARN_ON(cpu_buffer, rb_page_commit(cpu_buffer->commit_page) & ~RB_WRITE_MASK); barrier(); }
/* again, keep gcc from optimizing */ barrier();
/* * If an interrupt came in just after the first while loop * and pushed the tail page forward, we will be left with * a dangling commit that will never go forward. */ if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) goto again;}
static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer){ unsigned long commits;
if (RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))) return;
again: commits = local_read(&cpu_buffer->commits); /* synchronize with interrupts */ barrier(); if (local_read(&cpu_buffer->committing) == 1) rb_set_commit_to_write(cpu_buffer);
local_dec(&cpu_buffer->committing);
/* synchronize with interrupts */ barrier();
/* * Need to account for interrupts coming in between the * updating of the commit page and the clearing of the * committing counter. */ if (unlikely(local_read(&cpu_buffer->commits) != commits) && !local_read(&cpu_buffer->committing)) { local_inc(&cpu_buffer->committing); goto again; }}
static inline void rb_event_discard(struct ring_buffer_event *event){ if (extended_time(event)) event = skip_time_extend(event);
/* array[0] holds the actual length for the discarded event */ event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; event->type_len = RINGBUF_TYPE_PADDING; /* time delta must be non zero */ if (!event->time_delta) event->time_delta = 1;}
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer){ local_inc(&cpu_buffer->entries); rb_end_commit(cpu_buffer);}
static boolrb_irq_work_queue(struct rb_irq_work *irq_work){ int cpu;
/* irq_work_queue_on() is not NMI-safe */ if (unlikely(in_nmi())) return irq_work_queue(&irq_work->work);
/* * If CPU isolation is not active, cpu is always the current * CPU, and the following is equivallent to irq_work_queue(). */ cpu = housekeeping_any_cpu(HK_TYPE_KERNEL_NOISE); return irq_work_queue_on(&irq_work->work, cpu);}
static __always_inline voidrb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer){ if (buffer->irq_work.waiters_pending) { buffer->irq_work.waiters_pending = false; /* irq_work_queue() supplies it's own memory barriers */ rb_irq_work_queue(&buffer->irq_work); }
if (cpu_buffer->irq_work.waiters_pending) { cpu_buffer->irq_work.waiters_pending = false; /* irq_work_queue() supplies it's own memory barriers */ rb_irq_work_queue(&cpu_buffer->irq_work); }
if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) return;
if (cpu_buffer->reader_page == cpu_buffer->commit_page) return;
if (!cpu_buffer->irq_work.full_waiters_pending) return;
cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full)) return;
cpu_buffer->irq_work.wakeup_full = true; cpu_buffer->irq_work.full_waiters_pending = false; /* irq_work_queue() supplies it's own memory barriers */ rb_irq_work_queue(&cpu_buffer->irq_work);}
#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION# define do_ring_buffer_record_recursion() \ do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)#else# define do_ring_buffer_record_recursion() do { } while (0)#endif
/* * The lock and unlock are done within a preempt disable section. * The current_context per_cpu variable can only be modified * by the current task between lock and unlock. But it can * be modified more than once via an interrupt. To pass this * information from the lock to the unlock without having to * access the 'in_interrupt()' functions again (which do show * a bit of overhead in something as critical as function tracing, * we use a bitmask trick. * * bit 1 = NMI context * bit 2 = IRQ context * bit 3 = SoftIRQ context * bit 4 = normal context. * * This works because this is the order of contexts that can * preempt other contexts. A SoftIRQ never preempts an IRQ * context. * * When the context is determined, the corresponding bit is * checked and set (if it was set, then a recursion of that context * happened). * * On unlock, we need to clear this bit. To do so, just subtract * 1 from the current_context and AND it to itself. * * (binary) * 101 - 1 = 100 * 101 & 100 = 100 (clearing bit zero) * * 1010 - 1 = 1001 * 1010 & 1001 = 1000 (clearing bit 1) * * The least significant bit can be cleared this way, and it * just so happens that it is the same bit corresponding to * the current context. * * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit * is set when a recursion is detected at the current context, and if * the TRANSITION bit is already set, it will fail the recursion. * This is needed because there's a lag between the changing of * interrupt context and updating the preempt count. In this case, * a false positive will be found. To handle this, one extra recursion * is allowed, and this is done by the TRANSITION bit. If the TRANSITION * bit is already set, then it is considered a recursion and the function * ends. Otherwise, the TRANSITION bit is set, and that bit is returned. * * On the trace_recursive_unlock(), the TRANSITION bit will be the first * to be cleared. Even if it wasn't the context that set it. That is, * if an interrupt comes in while NORMAL bit is set and the ring buffer * is called before preempt_count() is updated, since the check will * be on the NORMAL bit, the TRANSITION bit will then be set. If an * NMI then comes in, it will set the NMI bit, but when the NMI code * does the trace_recursive_unlock() it will clear the TRANSITION bit * and leave the NMI bit set. But this is fine, because the interrupt * code that set the TRANSITION bit will then clear the NMI bit when it * calls trace_recursive_unlock(). If another NMI comes in, it will * set the TRANSITION bit and continue. * * Note: The TRANSITION bit only handles a single transition between context. */
static __always_inline booltrace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer){ unsigned int val = cpu_buffer->current_context; int bit = interrupt_context_level();
bit = RB_CTX_NORMAL - bit;
if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) { /* * It is possible that this was called by transitioning * between interrupt context, and preempt_count() has not * been updated yet. In this case, use the TRANSITION bit. */ bit = RB_CTX_TRANSITION; if (val & (1 << (bit + cpu_buffer->nest))) { do_ring_buffer_record_recursion(); return true; } }
val |= (1 << (bit + cpu_buffer->nest)); cpu_buffer->current_context = val;
return false;}
static __always_inline voidtrace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer){ cpu_buffer->current_context &= cpu_buffer->current_context - (1 << cpu_buffer->nest);}
/* The recursive locking above uses 5 bits */#define NESTED_BITS 5
/** * ring_buffer_nest_start - Allow to trace while nested * @buffer: The ring buffer to modify * * The ring buffer has a safety mechanism to prevent recursion. * But there may be a case where a trace needs to be done while * tracing something else. In this case, calling this function * will allow this function to nest within a currently active * ring_buffer_lock_reserve(). * * Call this function before calling another ring_buffer_lock_reserve() and * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). */void ring_buffer_nest_start(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; int cpu;
/* Enabled by ring_buffer_nest_end() */ preempt_disable_notrace(); cpu = raw_smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; /* This is the shift value for the above recursive locking */ cpu_buffer->nest += NESTED_BITS;}
/** * ring_buffer_nest_end - Allow to trace while nested * @buffer: The ring buffer to modify * * Must be called after ring_buffer_nest_start() and after the * ring_buffer_unlock_commit(). */void ring_buffer_nest_end(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; int cpu;
/* disabled by ring_buffer_nest_start() */ cpu = raw_smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; /* This is the shift value for the above recursive locking */ cpu_buffer->nest -= NESTED_BITS; preempt_enable_notrace();}
/** * ring_buffer_unlock_commit - commit a reserved * @buffer: The buffer to commit to * * This commits the data to the ring buffer, and releases any locks held. * * Must be paired with ring_buffer_lock_reserve. */int ring_buffer_unlock_commit(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; int cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
rb_commit(cpu_buffer);
rb_wakeups(buffer, cpu_buffer);
trace_recursive_unlock(cpu_buffer);
preempt_enable_notrace();
return 0;}EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
/* Special value to validate all deltas on a page. */#define CHECK_FULL_PAGE 1L
#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
static const char *show_irq_str(int bits){ static const char * type[] = { ".", // 0 "s", // 1 "h", // 2 "Hs", // 3 "n", // 4 "Ns", // 5 "Nh", // 6 "NHs", // 7 };
return type[bits];}
/* Assume this is a trace event */static const char *show_flags(struct ring_buffer_event *event){ struct trace_entry *entry; int bits = 0;
if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry)) return "X";
entry = ring_buffer_event_data(event);
if (entry->flags & TRACE_FLAG_SOFTIRQ) bits |= 1;
if (entry->flags & TRACE_FLAG_HARDIRQ) bits |= 2;
if (entry->flags & TRACE_FLAG_NMI) bits |= 4;
return show_irq_str(bits);}
static const char *show_irq(struct ring_buffer_event *event){ struct trace_entry *entry;
if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry)) return "";
entry = ring_buffer_event_data(event); if (entry->flags & TRACE_FLAG_IRQS_OFF) return "d"; return "";}
static const char *show_interrupt_level(void){ unsigned long pc = preempt_count(); unsigned char level = 0;
if (pc & SOFTIRQ_OFFSET) level |= 1;
if (pc & HARDIRQ_MASK) level |= 2;
if (pc & NMI_MASK) level |= 4;
return show_irq_str(level);}
static void dump_buffer_page(struct buffer_data_page *dpage, struct rb_event_info *info, unsigned long tail){ struct ring_buffer_event *event; u64 ts, delta; int e;
ts = dpage->time_stamp; pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
for (e = 0; e < tail; e += rb_event_length(event)) {
event = (struct ring_buffer_event *)(dpage->data + e);
switch (event->type_len) {
case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); ts += delta; pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n", e, ts, delta); break;
case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); ts = rb_fix_abs_ts(delta, ts); pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n", e, ts, delta); break;
case RINGBUF_TYPE_PADDING: ts += event->time_delta; pr_warn(" 0x%x: [%lld] delta:%d PADDING\n", e, ts, event->time_delta); break;
case RINGBUF_TYPE_DATA: ts += event->time_delta; pr_warn(" 0x%x: [%lld] delta:%d %s%s\n", e, ts, event->time_delta, show_flags(event), show_irq(event)); break;
default: break; } } pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);}
static DEFINE_PER_CPU(atomic_t, checking);static atomic_t ts_dump;
#define buffer_warn_return(fmt, ...) \ do { \ /* If another report is happening, ignore this one */ \ if (atomic_inc_return(&ts_dump) != 1) { \ atomic_dec(&ts_dump); \ goto out; \ } \ atomic_inc(&cpu_buffer->record_disabled); \ pr_warn(fmt, ##__VA_ARGS__); \ dump_buffer_page(dpage, info, tail); \ atomic_dec(&ts_dump); \ /* There's some cases in boot up that this can happen */ \ if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \ /* Do not re-enable checking */ \ return; \ } while (0)
/* * Check if the current event time stamp matches the deltas on * the buffer page. */static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info, unsigned long tail){ struct buffer_data_page *dpage; u64 ts, delta; bool full = false; int ret;
dpage = info->tail_page->page;
if (tail == CHECK_FULL_PAGE) { full = true; tail = rb_data_page_commit(dpage); } else if (info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) { /* Ignore events with absolute time stamps */ return; }
/* * Do not check the first event (skip possible extends too). * Also do not check if previous events have not been committed. */ if (tail <= 8 || tail > rb_data_page_commit(dpage)) return;
/* * If this interrupted another event, */ if (atomic_inc_return(this_cpu_ptr(&checking)) != 1) goto out;
ret = rb_read_data_buffer(dpage, tail, cpu_buffer->cpu, &ts, &delta); if (ret < 0) { if (delta < ts) { buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld clock:%pS\n", cpu_buffer->cpu, ts, delta, cpu_buffer->buffer->clock); goto out; } } if ((full && ts > info->ts) || (!full && ts + info->delta != info->ts)) { buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\ntrace clock:%pS", cpu_buffer->cpu, ts + info->delta, info->ts, info->delta, info->before, info->after, full ? " (full)" : "", show_interrupt_level(), cpu_buffer->buffer->clock); }out: atomic_dec(this_cpu_ptr(&checking));}#elsestatic inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info, unsigned long tail){}#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
static struct ring_buffer_event *__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, struct rb_event_info *info){ struct ring_buffer_event *event; struct buffer_page *tail_page; unsigned long tail, write, w;
/* Don't let the compiler play games with cpu_buffer->tail_page */ tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
/*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK; barrier(); rb_time_read(&cpu_buffer->before_stamp, &info->before); rb_time_read(&cpu_buffer->write_stamp, &info->after); barrier(); info->ts = rb_time_stamp(cpu_buffer->buffer);
if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) { info->delta = info->ts; } else { /* * If interrupting an event time update, we may need an * absolute timestamp. * Don't bother if this is the start of a new page (w == 0). */ if (!w) { /* Use the sub-buffer timestamp */ info->delta = 0; } else if (unlikely(info->before != info->after)) { info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND; info->length += RB_LEN_TIME_EXTEND; } else { info->delta = info->ts - info->after; if (unlikely(test_time_stamp(info->delta))) { info->add_timestamp |= RB_ADD_STAMP_EXTEND; info->length += RB_LEN_TIME_EXTEND; } } }
/*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
/*C*/ write = local_add_return(info->length, &tail_page->write);
/* set write to only the index of the write */ write &= RB_WRITE_MASK;
tail = write - info->length;
/* See if we shot pass the end of this buffer page */ if (unlikely(write > cpu_buffer->buffer->subbuf_size)) { check_buffer(cpu_buffer, info, CHECK_FULL_PAGE); return rb_move_tail(cpu_buffer, tail, info); }
if (likely(tail == w)) { /* Nothing interrupted us between A and C */ /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts); /* * If something came in between C and D, the write stamp * may now not be in sync. But that's fine as the before_stamp * will be different and then next event will just be forced * to use an absolute timestamp. */ if (likely(!(info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) /* This did not interrupt any time update */ info->delta = info->ts - info->after; else /* Just use full timestamp for interrupting event */ info->delta = info->ts; check_buffer(cpu_buffer, info, tail); } else { u64 ts; /* SLOW PATH - Interrupted between A and C */
/* Save the old before_stamp */ rb_time_read(&cpu_buffer->before_stamp, &info->before);
/* * Read a new timestamp and update the before_stamp to make * the next event after this one force using an absolute * timestamp. This is in case an interrupt were to come in * between E and F. */ ts = rb_time_stamp(cpu_buffer->buffer); rb_time_set(&cpu_buffer->before_stamp, ts);
barrier(); /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after); barrier(); /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) && info->after == info->before && info->after < ts) { /* * Nothing came after this event between C and F, it is * safe to use info->after for the delta as it * matched info->before and is still valid. */ info->delta = ts - info->after; } else { /* * Interrupted between C and F: * Lost the previous events time stamp. Just set the * delta to zero, and this will be the same time as * the event this event interrupted. And the events that * came after this will still be correct (as they would * have built their delta on the previous event. */ info->delta = 0; } info->ts = ts; info->add_timestamp &= ~RB_ADD_STAMP_FORCE; }
/* * If this is the first commit on the page, then it has the same * timestamp as the page itself. */ if (unlikely(!tail && !(info->add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) info->delta = 0;
/* We reserved something on the buffer */
event = __rb_page_index(tail_page, tail); rb_update_event(cpu_buffer, event, info);
local_inc(&tail_page->entries);
/* * If this is the first commit on the page, then update * its timestamp. */ if (unlikely(!tail)) tail_page->page->time_stamp = info->ts;
/* account for these added bytes */ local_add(info->length, &cpu_buffer->entries_bytes);
return event;}
static __always_inline struct ring_buffer_event *rb_reserve_next_event(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer, unsigned long length){ struct ring_buffer_event *event; struct rb_event_info info; int nr_loops = 0; int add_ts_default;
/* * ring buffer does cmpxchg as well as atomic64 operations * (which some archs use locking for atomic64), make sure this * is safe in NMI context */ if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) || IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) && (unlikely(in_nmi()))) { return NULL; }
rb_start_commit(cpu_buffer); /* The commit page can not change after this */
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP /* * Due to the ability to swap a cpu buffer from a buffer * it is possible it was swapped before we committed. * (committing stops a swap). We check for it here and * if it happened, we have to fail the write. */ barrier(); if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { local_dec(&cpu_buffer->committing); local_dec(&cpu_buffer->commits); return NULL; }#endif
info.length = rb_calculate_event_length(length);
if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) { add_ts_default = RB_ADD_STAMP_ABSOLUTE; info.length += RB_LEN_TIME_EXTEND; if (info.length > cpu_buffer->buffer->max_data_size) goto out_fail; } else { add_ts_default = RB_ADD_STAMP_NONE; }
again: info.add_timestamp = add_ts_default; info.delta = 0;
/* * We allow for interrupts to reenter here and do a trace. * If one does, it will cause this original code to loop * back here. Even with heavy interrupts happening, this * should only happen a few times in a row. If this happens * 1000 times in a row, there must be either an interrupt * storm or we have something buggy. * Bail! */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) goto out_fail;
event = __rb_reserve_next(cpu_buffer, &info);
if (unlikely(PTR_ERR(event) == -EAGAIN)) { if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND)) info.length -= RB_LEN_TIME_EXTEND; goto again; }
if (likely(event)) return event; out_fail: rb_end_commit(cpu_buffer); return NULL;}
/** * ring_buffer_lock_reserve - reserve a part of the buffer * @buffer: the ring buffer to reserve from * @length: the length of the data to reserve (excluding event header) * * Returns a reserved event on the ring buffer to copy directly to. * The user of this interface will need to get the body to write into * and can use the ring_buffer_event_data() interface. * * The length is the length of the data needed, not the event length * which also includes the event header. * * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. * If NULL is returned, then nothing has been allocated or locked. */struct ring_buffer_event *ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length){ struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; int cpu;
/* If we are tracing schedule, we don't want to recurse */ preempt_disable_notrace();
if (unlikely(atomic_read(&buffer->record_disabled))) goto out;
cpu = raw_smp_processor_id();
if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) goto out;
cpu_buffer = buffer->buffers[cpu];
if (unlikely(atomic_read(&cpu_buffer->record_disabled))) goto out;
if (unlikely(length > buffer->max_data_size)) goto out;
if (unlikely(trace_recursive_lock(cpu_buffer))) goto out;
event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) goto out_unlock;
return event;
out_unlock: trace_recursive_unlock(cpu_buffer); out: preempt_enable_notrace(); return NULL;}EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
/* * Decrement the entries to the page that an event is on. * The event does not even need to exist, only the pointer * to the page it is on. This may only be called before the commit * takes place. */static inline voidrb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event){ unsigned long addr = (unsigned long)event; struct buffer_page *bpage = cpu_buffer->commit_page; struct buffer_page *start;
addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
/* Do the likely case first */ if (likely(bpage->page == (void *)addr)) { local_dec(&bpage->entries); return; }
/* * Because the commit page may be on the reader page we * start with the next page and check the end loop there. */ rb_inc_page(&bpage); start = bpage; do { if (bpage->page == (void *)addr) { local_dec(&bpage->entries); return; } rb_inc_page(&bpage); } while (bpage != start);
/* commit not part of this buffer?? */ RB_WARN_ON(cpu_buffer, 1);}
/** * ring_buffer_discard_commit - discard an event that has not been committed * @buffer: the ring buffer * @event: non committed event to discard * * Sometimes an event that is in the ring buffer needs to be ignored. * This function lets the user discard an event in the ring buffer * and then that event will not be read later. * * This function only works if it is called before the item has been * committed. It will try to free the event from the ring buffer * if another event has not been added behind it. * * If another event has been added behind it, it will set the event * up as discarded, and perform the commit. * * If this function is called, do not call ring_buffer_unlock_commit on * the event. */void ring_buffer_discard_commit(struct trace_buffer *buffer, struct ring_buffer_event *event){ struct ring_buffer_per_cpu *cpu_buffer; int cpu;
/* The event is discarded regardless */ rb_event_discard(event);
cpu = smp_processor_id(); cpu_buffer = buffer->buffers[cpu];
/* * This must only be called if the event has not been * committed yet. Thus we can assume that preemption * is still disabled. */ RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
rb_decrement_entry(cpu_buffer, event); rb_try_to_discard(cpu_buffer, event); rb_end_commit(cpu_buffer);
trace_recursive_unlock(cpu_buffer);
preempt_enable_notrace();
}EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
/** * ring_buffer_write - write data to the buffer without reserving * @buffer: The ring buffer to write to. * @length: The length of the data being written (excluding the event header) * @data: The data to write to the buffer. * * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as * one function. If you already have the data to write to the buffer, it * may be easier to simply call this function. * * Note, like ring_buffer_lock_reserve, the length is the length of the data * and not the length of the event which would hold the header. */int ring_buffer_write(struct trace_buffer *buffer, unsigned long length, void *data){ struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; void *body; int ret = -EBUSY; int cpu;
guard(preempt_notrace)();
if (atomic_read(&buffer->record_disabled)) return -EBUSY;
cpu = raw_smp_processor_id();
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -EBUSY;
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->record_disabled)) return -EBUSY;
if (length > buffer->max_data_size) return -EBUSY;
if (unlikely(trace_recursive_lock(cpu_buffer))) return -EBUSY;
event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) goto out_unlock;
body = rb_event_data(event);
memcpy(body, data, length);
rb_commit(cpu_buffer);
rb_wakeups(buffer, cpu_buffer);
ret = 0;
out_unlock: trace_recursive_unlock(cpu_buffer); return ret;}EXPORT_SYMBOL_GPL(ring_buffer_write);
/* * The total entries in the ring buffer is the running counter * of entries entered into the ring buffer, minus the sum of * the entries read from the ring buffer and the number of * entries that were overwritten. */static inline unsigned longrb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer){ return local_read(&cpu_buffer->entries) - (local_read(&cpu_buffer->overrun) + cpu_buffer->read);}
static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer){ return !rb_num_of_entries(cpu_buffer);}
/** * ring_buffer_record_disable - stop all writes into the buffer * @buffer: The ring buffer to stop writes to. * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * The caller should call synchronize_rcu() after this. */void ring_buffer_record_disable(struct trace_buffer *buffer){ atomic_inc(&buffer->record_disabled);}EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
/** * ring_buffer_record_enable - enable writes to the buffer * @buffer: The ring buffer to enable writes * * Note, multiple disables will need the same number of enables * to truly enable the writing (much like preempt_disable). */void ring_buffer_record_enable(struct trace_buffer *buffer){ atomic_dec(&buffer->record_disabled);}EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
/** * ring_buffer_record_off - stop all writes into the buffer * @buffer: The ring buffer to stop writes to. * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * This is different than ring_buffer_record_disable() as * it works like an on/off switch, where as the disable() version * must be paired with a enable(). */void ring_buffer_record_off(struct trace_buffer *buffer){ unsigned int rd; unsigned int new_rd;
rd = atomic_read(&buffer->record_disabled); do { new_rd = rd | RB_BUFFER_OFF; } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));}EXPORT_SYMBOL_GPL(ring_buffer_record_off);
/** * ring_buffer_record_on - restart writes into the buffer * @buffer: The ring buffer to start writes to. * * This enables all writes to the buffer that was disabled by * ring_buffer_record_off(). * * This is different than ring_buffer_record_enable() as * it works like an on/off switch, where as the enable() version * must be paired with a disable(). */void ring_buffer_record_on(struct trace_buffer *buffer){ unsigned int rd; unsigned int new_rd;
rd = atomic_read(&buffer->record_disabled); do { new_rd = rd & ~RB_BUFFER_OFF; } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));}EXPORT_SYMBOL_GPL(ring_buffer_record_on);
/** * ring_buffer_record_is_on - return true if the ring buffer can write * @buffer: The ring buffer to see if write is enabled * * Returns true if the ring buffer is in a state that it accepts writes. */bool ring_buffer_record_is_on(struct trace_buffer *buffer){ return !atomic_read(&buffer->record_disabled);}
/** * ring_buffer_record_is_set_on - return true if the ring buffer is set writable * @buffer: The ring buffer to see if write is set enabled * * Returns true if the ring buffer is set writable by ring_buffer_record_on(). * Note that this does NOT mean it is in a writable state. * * It may return true when the ring buffer has been disabled by * ring_buffer_record_disable(), as that is a temporary disabling of * the ring buffer. */bool ring_buffer_record_is_set_on(struct trace_buffer *buffer){ return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);}
/** * ring_buffer_record_is_on_cpu - return true if the ring buffer can write * @buffer: The ring buffer to see if write is enabled * @cpu: The CPU to test if the ring buffer can write too * * Returns true if the ring buffer is in a state that it accepts writes * for a particular CPU. */bool ring_buffer_record_is_on_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
cpu_buffer = buffer->buffers[cpu];
return ring_buffer_record_is_set_on(buffer) && !atomic_read(&cpu_buffer->record_disabled);}
/** * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer * @buffer: The ring buffer to stop writes to. * @cpu: The CPU buffer to stop * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * The caller should call synchronize_rcu() after this. */void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return;
cpu_buffer = buffer->buffers[cpu]; atomic_inc(&cpu_buffer->record_disabled);}EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
/** * ring_buffer_record_enable_cpu - enable writes to the buffer * @buffer: The ring buffer to enable writes * @cpu: The CPU to enable. * * Note, multiple disables will need the same number of enables * to truly enable the writing (much like preempt_disable). */void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return;
cpu_buffer = buffer->buffers[cpu]; atomic_dec(&cpu_buffer->record_disabled);}EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
/** * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to read from. */u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu){ unsigned long flags; struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; u64 ret = 0;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu]; raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); /* * if the tail is on reader_page, oldest time stamp is on the reader * page */ if (cpu_buffer->tail_page == cpu_buffer->reader_page) bpage = cpu_buffer->reader_page; else bpage = rb_set_head_page(cpu_buffer); if (bpage) ret = bpage->page->time_stamp; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
return ret;}EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
/** * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to read from. */unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
return ret;}EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
/** * ring_buffer_entries_cpu - get the number of entries in a cpu buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to get the entries from. */unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu];
return rb_num_of_entries(cpu_buffer);}EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
/** * ring_buffer_overrun_cpu - get the number of overruns caused by the ring * buffer wrapping around (only if RB_FL_OVERWRITE is on). * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->overrun);
return ret;}EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
/** * ring_buffer_commit_overrun_cpu - get the number of overruns caused by * commits failing due to the buffer wrapping around while there are uncommitted * events, such as during an interrupt storm. * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */unsigned longring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->commit_overrun);
return ret;}EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
/** * ring_buffer_dropped_events_cpu - get the number of dropped events caused by * the ring buffer filling up (only if RB_FL_OVERWRITE is off). * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */unsigned longring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu]; ret = local_read(&cpu_buffer->dropped_events);
return ret;}EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
/** * ring_buffer_read_events_cpu - get the number of events successfully read * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of events read */unsigned longring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
cpu_buffer = buffer->buffers[cpu]; return cpu_buffer->read;}EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
/** * ring_buffer_entries - get the number of entries in a buffer * @buffer: The ring buffer * * Returns the total number of entries in the ring buffer * (all CPU entries) */unsigned long ring_buffer_entries(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long entries = 0; int cpu;
/* if you care about this being correct, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; entries += rb_num_of_entries(cpu_buffer); }
return entries;}EXPORT_SYMBOL_GPL(ring_buffer_entries);
/** * ring_buffer_overruns - get the number of overruns in buffer * @buffer: The ring buffer * * Returns the total number of overruns in the ring buffer * (all CPU entries) */unsigned long ring_buffer_overruns(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long overruns = 0; int cpu;
/* if you care about this being correct, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; overruns += local_read(&cpu_buffer->overrun); }
return overruns;}EXPORT_SYMBOL_GPL(ring_buffer_overruns);
static bool rb_read_remote_meta_page(struct ring_buffer_per_cpu *cpu_buffer){ local_set(&cpu_buffer->entries, READ_ONCE(cpu_buffer->meta_page->entries)); local_set(&cpu_buffer->overrun, READ_ONCE(cpu_buffer->meta_page->overrun)); local_set(&cpu_buffer->pages_touched, READ_ONCE(cpu_buffer->meta_page->pages_touched)); local_set(&cpu_buffer->pages_lost, READ_ONCE(cpu_buffer->meta_page->pages_lost));
return rb_num_of_entries(cpu_buffer);}
static void rb_update_remote_head(struct ring_buffer_per_cpu *cpu_buffer){ struct buffer_page *next, *orig; int retry = 3;
orig = next = cpu_buffer->head_page; rb_inc_page(&next);
/* Run after the writer */ while (cpu_buffer->head_page->page->time_stamp > next->page->time_stamp) { rb_inc_page(&next);
rb_list_head_clear(cpu_buffer->head_page->list.prev); rb_inc_page(&cpu_buffer->head_page); rb_set_list_to_head(cpu_buffer->head_page->list.prev);
if (cpu_buffer->head_page == orig) { if (WARN_ON_ONCE(!(--retry))) return; } }
orig = cpu_buffer->commit_page = cpu_buffer->head_page; retry = 3;
while (cpu_buffer->commit_page->page->time_stamp < next->page->time_stamp) { rb_inc_page(&next); rb_inc_page(&cpu_buffer->commit_page);
if (cpu_buffer->commit_page == orig) { if (WARN_ON_ONCE(!(--retry))) return; } }}
static void rb_iter_reset(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
if (cpu_buffer->remote) { rb_read_remote_meta_page(cpu_buffer); rb_update_remote_head(cpu_buffer); }
/* Iterator usage is expected to have record disabled */ iter->head_page = cpu_buffer->reader_page; iter->head = cpu_buffer->reader_page->read; iter->next_event = iter->head; iter->missed_events = 0;
iter->cache_reader_page = iter->head_page; iter->cache_read = cpu_buffer->read; iter->cache_pages_removed = cpu_buffer->pages_removed;
if (iter->head) { iter->read_stamp = cpu_buffer->read_stamp; iter->page_stamp = cpu_buffer->reader_page->page->time_stamp; } else { iter->read_stamp = iter->head_page->page->time_stamp; iter->page_stamp = iter->read_stamp; }}
/** * ring_buffer_iter_reset - reset an iterator * @iter: The iterator to reset * * Resets the iterator, so that it will start from the beginning * again. */void ring_buffer_iter_reset(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags;
if (!iter) return;
cpu_buffer = iter->cpu_buffer;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_iter_reset(iter); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);}EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
/** * ring_buffer_iter_empty - check if an iterator has no more to read * @iter: The iterator to check */int ring_buffer_iter_empty(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *reader; struct buffer_page *head_page; struct buffer_page *commit_page; struct buffer_page *curr_commit_page; unsigned commit; u64 curr_commit_ts; u64 commit_ts;
cpu_buffer = iter->cpu_buffer; reader = cpu_buffer->reader_page; head_page = cpu_buffer->head_page; commit_page = READ_ONCE(cpu_buffer->commit_page); commit_ts = commit_page->page->time_stamp;
/* * When the writer goes across pages, it issues a cmpxchg which * is a mb(), which will synchronize with the rmb here. * (see rb_tail_page_update()) */ smp_rmb(); commit = rb_page_size(commit_page); /* We want to make sure that the commit page doesn't change */ smp_rmb();
/* Make sure commit page didn't change */ curr_commit_page = READ_ONCE(cpu_buffer->commit_page); curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
/* If the commit page changed, then there's more data */ if (curr_commit_page != commit_page || curr_commit_ts != commit_ts) return 0;
/* Still racy, as it may return a false positive, but that's OK */ return ((iter->head_page == commit_page && iter->head >= commit) || (iter->head_page == reader && commit_page == head_page && head_page->read == commit && iter->head == rb_page_size(cpu_buffer->reader_page)));}EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
static voidrb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event){ u64 delta;
switch (event->type_len) { case RINGBUF_TYPE_PADDING: return;
case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); cpu_buffer->read_stamp += delta; return;
case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp); cpu_buffer->read_stamp = delta; return;
case RINGBUF_TYPE_DATA: cpu_buffer->read_stamp += event->time_delta; return;
default: RB_WARN_ON(cpu_buffer, 1); }}
static voidrb_update_iter_read_stamp(struct ring_buffer_iter *iter, struct ring_buffer_event *event){ u64 delta;
switch (event->type_len) { case RINGBUF_TYPE_PADDING: return;
case RINGBUF_TYPE_TIME_EXTEND: delta = rb_event_time_stamp(event); iter->read_stamp += delta; return;
case RINGBUF_TYPE_TIME_STAMP: delta = rb_event_time_stamp(event); delta = rb_fix_abs_ts(delta, iter->read_stamp); iter->read_stamp = delta; return;
case RINGBUF_TYPE_DATA: iter->read_stamp += event->time_delta; return;
default: RB_WARN_ON(iter->cpu_buffer, 1); }}
static struct buffer_page *__rb_get_reader_page_from_remote(struct ring_buffer_per_cpu *cpu_buffer){ struct buffer_page *new_reader, *prev_reader, *prev_head, *new_head, *last;
if (!rb_read_remote_meta_page(cpu_buffer)) return NULL;
/* More to read on the reader page */ if (cpu_buffer->reader_page->read < rb_page_size(cpu_buffer->reader_page)) { if (!cpu_buffer->reader_page->read) cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp; return cpu_buffer->reader_page; }
prev_reader = cpu_buffer->subbuf_ids[cpu_buffer->meta_page->reader.id];
WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, cpu_buffer->remote->priv)); /* nr_pages doesn't include the reader page */ if (WARN_ON_ONCE(cpu_buffer->meta_page->reader.id > cpu_buffer->nr_pages)) return NULL;
new_reader = cpu_buffer->subbuf_ids[cpu_buffer->meta_page->reader.id];
WARN_ON_ONCE(prev_reader == new_reader);
prev_head = new_reader; /* New reader was also the previous head */ new_head = prev_head; rb_inc_page(&new_head); last = prev_head; rb_dec_page(&last);
/* Clear the old HEAD flag */ rb_list_head_clear(cpu_buffer->head_page->list.prev);
prev_reader->list.next = prev_head->list.next; prev_reader->list.prev = prev_head->list.prev;
/* Swap prev_reader with new_reader */ last->list.next = &prev_reader->list; new_head->list.prev = &prev_reader->list;
new_reader->list.prev = &new_reader->list; new_reader->list.next = &new_head->list;
/* Reactivate the HEAD flag */ rb_set_list_to_head(&last->list);
cpu_buffer->head_page = new_head; cpu_buffer->reader_page = new_reader; cpu_buffer->pages = &new_head->list; cpu_buffer->read_stamp = new_reader->page->time_stamp; cpu_buffer->lost_events = cpu_buffer->meta_page->reader.lost_events;
return rb_page_size(cpu_buffer->reader_page) ? cpu_buffer->reader_page : NULL;}
static struct buffer_page *__rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer){ int max_loops = cpu_buffer->ring_meta ? cpu_buffer->nr_pages : 3; unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size); struct buffer_page *reader = NULL; unsigned long overwrite; unsigned long flags; int missed_events = 0; int nr_loops = 0; bool ret;
local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock);
again: /* * This should normally only loop twice. But because the * start of the reader inserts an empty page, it causes a * case where we will loop three times. There should be no * reason to loop four times unless the ring buffer is a * recovered persistent ring buffer. For persistent ring buffers, * invalid pages are reset during recovery, so there may be more * than 3 contiguous pages can be empty, but less than nr_pages. */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > max_loops)) { reader = NULL; goto out; }
reader = cpu_buffer->reader_page;
/* If there's more to read, return this page */ if (cpu_buffer->reader_page->read < rb_page_size(reader)) goto out;
/* Never should we have an index greater than the size */ if (RB_WARN_ON(cpu_buffer, cpu_buffer->reader_page->read > rb_page_size(reader))) goto out;
/* check if we caught up to the tail */ reader = NULL; if (cpu_buffer->commit_page == cpu_buffer->reader_page) goto out;
/* Don't bother swapping if the ring buffer is empty */ if (rb_num_of_entries(cpu_buffer) == 0) goto out;
/* * Reset the reader page to size zero. */ local_set(&cpu_buffer->reader_page->write, 0); local_set(&cpu_buffer->reader_page->entries, 0); rb_init_data_page(cpu_buffer->reader_page->page); cpu_buffer->reader_page->real_end = 0;
spin: /* * Splice the empty reader page into the list around the head. */ reader = rb_set_head_page(cpu_buffer); if (!reader) goto out; cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); cpu_buffer->reader_page->list.prev = reader->list.prev;
/* * cpu_buffer->pages just needs to point to the buffer, it * has no specific buffer page to point to. Lets move it out * of our way so we don't accidentally swap it. */ cpu_buffer->pages = reader->list.prev;
/* The reader page will be pointing to the new head */ rb_set_list_to_head(&cpu_buffer->reader_page->list);
/* * We want to make sure we read the overruns after we set up our * pointers to the next object. The writer side does a * cmpxchg to cross pages which acts as the mb on the writer * side. Note, the reader will constantly fail the swap * while the writer is updating the pointers, so this * guarantees that the overwrite recorded here is the one we * want to compare with the last_overrun. */ smp_mb(); overwrite = local_read(&(cpu_buffer->overrun));
/* * Here's the tricky part. * * We need to move the pointer past the header page. * But we can only do that if a writer is not currently * moving it. The page before the header page has the * flag bit '1' set if it is pointing to the page we want. * but if the writer is in the process of moving it * then it will be '2' or already moved '0'. */
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
/* * If we did not convert it, then we must try again. */ if (!ret) goto spin;
if (rb_page_commit(reader) & RB_MISSED_EVENTS) missed_events = -1;
if (cpu_buffer->ring_meta) rb_update_meta_reader(cpu_buffer, reader);
/* * Yay! We succeeded in replacing the page. * * Now make the new head point back to the reader page. */ rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; rb_inc_page(&cpu_buffer->head_page);
cpu_buffer->cnt++; local_inc(&cpu_buffer->pages_read);
/* Finally update the reader page to the new head */ cpu_buffer->reader_page = reader; cpu_buffer->reader_page->read = 0;
if (overwrite != cpu_buffer->last_overrun) { cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; cpu_buffer->last_overrun = overwrite; }
goto again;
out: /* Update the read_stamp on the first event */ if (reader && reader->read == 0) cpu_buffer->read_stamp = reader->page->time_stamp;
arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags);
/* * The writer has preempt disable, wait for it. But not forever * Although, 1 second is pretty much "forever" */#define USECS_WAIT 1000000 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) { /* If the write is past the end of page, a writer is still updating it */ if (likely(!reader || rb_page_write(reader) <= bsize)) break;
udelay(1);
/* Get the latest version of the reader write value */ smp_rmb(); }
/* The writer is not moving forward? Something is wrong */ if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT)) reader = NULL;
/* * Make sure we see any padding after the write update * (see rb_reset_tail()). * * In addition, a writer may be writing on the reader page * if the page has not been fully filled, so the read barrier * is also needed to make sure we see the content of what is * committed by the writer (see rb_set_commit_to_write()). */ smp_rmb();
if (!cpu_buffer->lost_events) cpu_buffer->lost_events = missed_events;
return reader;}
static struct buffer_page *rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer){ return cpu_buffer->remote ? __rb_get_reader_page_from_remote(cpu_buffer) : __rb_get_reader_page(cpu_buffer);}
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer){ struct ring_buffer_event *event; struct buffer_page *reader; unsigned length;
reader = rb_get_reader_page(cpu_buffer);
/* This function should not be called when buffer is empty */ if (RB_WARN_ON(cpu_buffer, !reader)) return;
event = rb_reader_event(cpu_buffer);
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) cpu_buffer->read++;
rb_update_read_stamp(cpu_buffer, event);
length = rb_event_length(event); cpu_buffer->reader_page->read += length; cpu_buffer->read_bytes += length;}
static void rb_advance_iter(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer;
cpu_buffer = iter->cpu_buffer;
/* If head == next_event then we need to jump to the next event */ if (iter->head == iter->next_event) { /* If the event gets overwritten again, there's nothing to do */ if (rb_iter_head_event(iter) == NULL) return; }
iter->head = iter->next_event;
/* * Check if we are at the end of the buffer. */ if (iter->next_event >= rb_page_size(iter->head_page)) { /* discarded commits can make the page empty */ if (iter->head_page == cpu_buffer->commit_page) return; rb_inc_iter(iter); return; }
rb_update_iter_read_stamp(iter, iter->event);}
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer){ return cpu_buffer->lost_events;}
static struct ring_buffer_event *rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, unsigned long *lost_events){ struct ring_buffer_event *event; struct buffer_page *reader; int nr_loops = 0;
if (ts) *ts = 0; again: /* * We repeat when a time extend is encountered. * Since the time extend is always attached to a data event, * we should never loop more than once. * (We never hit the following condition more than twice). */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) return NULL;
reader = rb_get_reader_page(cpu_buffer); if (!reader) return NULL;
event = rb_reader_event(cpu_buffer);
switch (event->type_len) { case RINGBUF_TYPE_PADDING: if (rb_null_event(event)) RB_WARN_ON(cpu_buffer, 1); /* * Because the writer could be discarding every * event it creates (which would probably be bad) * if we were to go back to "again" then we may never * catch up, and will trigger the warn on, or lock * the box. Return the padding, and we will release * the current locks, and try again. */ return event;
case RINGBUF_TYPE_TIME_EXTEND: /* Internal data, OK to advance */ rb_advance_reader(cpu_buffer); goto again;
case RINGBUF_TYPE_TIME_STAMP: if (ts) { *ts = rb_event_time_stamp(event); *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp); ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); } /* Internal data, OK to advance */ rb_advance_reader(cpu_buffer); goto again;
case RINGBUF_TYPE_DATA: if (ts && !(*ts)) { *ts = cpu_buffer->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); } if (lost_events) *lost_events = rb_lost_events(cpu_buffer); return event;
default: RB_WARN_ON(cpu_buffer, 1); }
return NULL;}EXPORT_SYMBOL_GPL(ring_buffer_peek);
static struct ring_buffer_event *rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts){ struct trace_buffer *buffer; struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; int nr_loops = 0; int max_loops;
if (ts) *ts = 0;
cpu_buffer = iter->cpu_buffer; buffer = cpu_buffer->buffer; max_loops = cpu_buffer->ring_meta ? cpu_buffer->nr_pages : 3;
/* * Check if someone performed a consuming read to the buffer * or removed some pages from the buffer. In these cases, * iterator was invalidated and we need to reset it. */ if (unlikely(iter->cache_read != cpu_buffer->read || iter->cache_reader_page != cpu_buffer->reader_page || iter->cache_pages_removed != cpu_buffer->pages_removed)) rb_iter_reset(iter);
again: if (ring_buffer_iter_empty(iter)) return NULL;
/* * As the writer can mess with what the iterator is trying * to read, just give up if we fail to get an event after * three tries. The iterator is not as reliable when reading * the ring buffer with an active write as the consumer is. * Do not warn if the three failures is reached. */ if (++nr_loops > max_loops) return NULL;
if (rb_per_cpu_empty(cpu_buffer)) return NULL;
if (iter->head >= rb_page_size(iter->head_page)) { rb_inc_iter(iter); goto again; }
event = rb_iter_head_event(iter); if (!event) goto again;
switch (event->type_len) { case RINGBUF_TYPE_PADDING: if (rb_null_event(event)) { rb_inc_iter(iter); goto again; } rb_advance_iter(iter); return event;
case RINGBUF_TYPE_TIME_EXTEND: /* Internal data, OK to advance */ rb_advance_iter(iter); goto again;
case RINGBUF_TYPE_TIME_STAMP: if (ts) { *ts = rb_event_time_stamp(event); *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp); ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); } /* Internal data, OK to advance */ rb_advance_iter(iter); goto again;
case RINGBUF_TYPE_DATA: if (ts && !(*ts)) { *ts = iter->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(buffer, cpu_buffer->cpu, ts); } return event;
default: RB_WARN_ON(cpu_buffer, 1); }
return NULL;}EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer){ if (likely(!in_nmi())) { raw_spin_lock(&cpu_buffer->reader_lock); return true; }
/* * If an NMI die dumps out the content of the ring buffer * trylock must be used to prevent a deadlock if the NMI * preempted a task that holds the ring buffer locks. If * we get the lock then all is fine, if not, then continue * to do the read, but this can corrupt the ring buffer, * so it must be permanently disabled from future writes. * Reading from NMI is a oneshot deal. */ if (raw_spin_trylock(&cpu_buffer->reader_lock)) return true;
/* Continue without locking, but disable the ring buffer */ atomic_inc(&cpu_buffer->record_disabled); return false;}
static inline voidrb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked){ if (likely(locked)) raw_spin_unlock(&cpu_buffer->reader_lock);}
/** * ring_buffer_peek - peek at the next event to be read * @buffer: The ring buffer to read * @cpu: The cpu to peak at * @ts: The timestamp counter of this event. * @lost_events: a variable to store if events were lost (may be NULL) * * This will return the event that will be read next, but does * not consume the data. */struct ring_buffer_event *ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts, unsigned long *lost_events){ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; unsigned long flags; bool dolock;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL;
again: local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); event = rb_buffer_peek(cpu_buffer, ts, lost_events); if (event && event->type_len == RINGBUF_TYPE_PADDING) rb_advance_reader(cpu_buffer); rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags);
if (event && event->type_len == RINGBUF_TYPE_PADDING) goto again;
return event;}
/** ring_buffer_iter_dropped - report if there are dropped events * @iter: The ring buffer iterator * * Returns true if there was dropped events since the last peek. */bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter){ return iter->missed_events != 0;}EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
/** * ring_buffer_iter_peek - peek at the next event to be read * @iter: The ring buffer iterator * @ts: The timestamp counter of this event. * * This will return the event that will be read next, but does * not increment the iterator. */struct ring_buffer_event *ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts){ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; struct ring_buffer_event *event; unsigned long flags;
again: raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); event = rb_iter_peek(iter, ts); raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
if (event && event->type_len == RINGBUF_TYPE_PADDING) goto again;
return event;}
/** * ring_buffer_consume - return an event and consume it * @buffer: The ring buffer to get the next event from * @cpu: the cpu to read the buffer from * @ts: a variable to store the timestamp (may be NULL) * @lost_events: a variable to store if events were lost (may be NULL) * * Returns the next event in the ring buffer, and that event is consumed. * Meaning, that sequential reads will keep returning a different event, * and eventually empty the ring buffer if the producer is slower. */struct ring_buffer_event *ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts, unsigned long *lost_events){ struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event = NULL; unsigned long flags; bool dolock;
again: /* might be called in atomic */ preempt_disable();
if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out;
cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer);
event = rb_buffer_peek(cpu_buffer, ts, lost_events); if (event) { cpu_buffer->lost_events = 0; rb_advance_reader(cpu_buffer); }
rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags);
out: preempt_enable();
if (event && event->type_len == RINGBUF_TYPE_PADDING) goto again;
return event;}EXPORT_SYMBOL_GPL(ring_buffer_consume);
/** * ring_buffer_read_start - start a non consuming read of the buffer * @buffer: The ring buffer to read from * @cpu: The cpu buffer to iterate over * @flags: gfp flags to use for memory allocation * * This creates an iterator to allow non-consuming iteration through * the buffer. If the buffer is disabled for writing, it will produce * the same information each time, but if the buffer is still writing * then the first hit of a write will cause the iteration to stop. * * Must be paired with ring_buffer_read_finish. */struct ring_buffer_iter *ring_buffer_read_start(struct trace_buffer *buffer, int cpu, gfp_t flags){ struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_iter *iter;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL;
iter = kzalloc_obj(*iter, flags); if (!iter) return NULL;
/* Holds the entire event: data and meta data */ iter->event_size = buffer->subbuf_size; iter->event = kmalloc(iter->event_size, flags); if (!iter->event) { kfree(iter); return NULL; }
cpu_buffer = buffer->buffers[cpu];
iter->cpu_buffer = cpu_buffer;
atomic_inc(&cpu_buffer->resize_disabled);
guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock); arch_spin_lock(&cpu_buffer->lock); rb_iter_reset(iter); arch_spin_unlock(&cpu_buffer->lock);
return iter;}EXPORT_SYMBOL_GPL(ring_buffer_read_start);
/** * ring_buffer_read_finish - finish reading the iterator of the buffer * @iter: The iterator retrieved by ring_buffer_start * * This re-enables resizing of the buffer, and frees the iterator. */voidring_buffer_read_finish(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
/* Use this opportunity to check the integrity of the ring buffer. */ rb_check_pages(cpu_buffer);
atomic_dec(&cpu_buffer->resize_disabled); kfree(iter->event); kfree(iter);}EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
/** * ring_buffer_iter_advance - advance the iterator to the next location * @iter: The ring buffer iterator * * Move the location of the iterator such that the next read will * be the next location of the iterator. */void ring_buffer_iter_advance(struct ring_buffer_iter *iter){ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; unsigned long flags;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); iter->missed_events = 0; rb_advance_iter(iter);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);}EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
/** * ring_buffer_size - return the size of the ring buffer (in bytes) * @buffer: The ring buffer. * @cpu: The CPU to get ring buffer size from. */unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu){ if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;}EXPORT_SYMBOL_GPL(ring_buffer_size);
/** * ring_buffer_max_event_size - return the max data size of an event * @buffer: The ring buffer. * * Returns the maximum size an event can be. */unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer){ /* If abs timestamp is requested, events have a timestamp too */ if (ring_buffer_time_stamp_abs(buffer)) return buffer->max_data_size - RB_LEN_TIME_EXTEND; return buffer->max_data_size;}EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
static void rb_clear_buffer_page(struct buffer_page *page){ local_set(&page->write, 0); local_set(&page->entries, 0); rb_init_data_page(page->page); page->read = 0;}
/* * When the buffer is memory mapped to user space, each sub buffer * has a unique id that is used by the meta data to tell the user * where the current reader page is. * * For a normal allocated ring buffer, the id is saved in the buffer page * id field, and updated via this function. * * But for a fixed memory mapped buffer, the id is already assigned for * fixed memory ordering in the memory layout and can not be used. Instead * the index of where the page lies in the memory layout is used. * * For the normal pages, set the buffer page id with the passed in @id * value and return that. * * For fixed memory mapped pages, get the page index in the memory layout * and return that as the id. */static int rb_page_id(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *bpage, int id){ /* * For boot buffers, the id is the index, * otherwise, set the buffer page with this id */ if (cpu_buffer->ring_meta) id = rb_meta_subbuf_idx(cpu_buffer->ring_meta, bpage->page); else bpage->id = id;
return id;}
static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer){ struct trace_buffer_meta *meta = cpu_buffer->meta_page;
if (!meta) return;
meta->reader.read = cpu_buffer->reader_page->read; meta->reader.id = rb_page_id(cpu_buffer, cpu_buffer->reader_page, cpu_buffer->reader_page->id);
meta->reader.lost_events = cpu_buffer->lost_events;
meta->entries = local_read(&cpu_buffer->entries); meta->overrun = local_read(&cpu_buffer->overrun); meta->read = cpu_buffer->read; meta->pages_lost = local_read(&cpu_buffer->pages_lost); meta->pages_touched = local_read(&cpu_buffer->pages_touched);
/* Some archs do not have data cache coherency between kernel and user-space */ flush_kernel_vmap_range(cpu_buffer->meta_page, PAGE_SIZE);}
static voidrb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer){ struct buffer_page *page;
if (cpu_buffer->remote) { if (!cpu_buffer->remote->reset) return;
cpu_buffer->remote->reset(cpu_buffer->cpu, cpu_buffer->remote->priv); rb_read_remote_meta_page(cpu_buffer);
/* Read related values, not covered by the meta-page */ local_set(&cpu_buffer->pages_read, 0); cpu_buffer->read = 0; cpu_buffer->read_bytes = 0; cpu_buffer->last_overrun = 0; cpu_buffer->reader_page->read = 0;
return; }
rb_head_page_deactivate(cpu_buffer);
cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); rb_clear_buffer_page(cpu_buffer->head_page); list_for_each_entry(page, cpu_buffer->pages, list) { rb_clear_buffer_page(page); }
cpu_buffer->tail_page = cpu_buffer->head_page; cpu_buffer->commit_page = cpu_buffer->head_page;
INIT_LIST_HEAD(&cpu_buffer->reader_page->list); INIT_LIST_HEAD(&cpu_buffer->new_pages); rb_clear_buffer_page(cpu_buffer->reader_page);
local_set(&cpu_buffer->entries_bytes, 0); local_set(&cpu_buffer->overrun, 0); local_set(&cpu_buffer->commit_overrun, 0); local_set(&cpu_buffer->dropped_events, 0); local_set(&cpu_buffer->entries, 0); local_set(&cpu_buffer->committing, 0); local_set(&cpu_buffer->commits, 0); local_set(&cpu_buffer->pages_touched, 0); local_set(&cpu_buffer->pages_lost, 0); local_set(&cpu_buffer->pages_read, 0); cpu_buffer->last_pages_touch = 0; cpu_buffer->shortest_full = 0; cpu_buffer->read = 0; cpu_buffer->read_bytes = 0;
rb_time_set(&cpu_buffer->write_stamp, 0); rb_time_set(&cpu_buffer->before_stamp, 0);
memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
cpu_buffer->lost_events = 0; cpu_buffer->last_overrun = 0;
rb_head_page_activate(cpu_buffer); cpu_buffer->pages_removed = 0;
if (cpu_buffer->mapped) { rb_update_meta_page(cpu_buffer); if (cpu_buffer->ring_meta) { struct ring_buffer_cpu_meta *meta = cpu_buffer->ring_meta; meta->commit_buffer = meta->head_buffer; } }}
/* Must have disabled the cpu buffer then done a synchronize_rcu */static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer){ guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock);
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) return;
arch_spin_lock(&cpu_buffer->lock);
rb_reset_cpu(cpu_buffer);
arch_spin_unlock(&cpu_buffer->lock);}
/** * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer * @buffer: The ring buffer to reset a per cpu buffer of * @cpu: The CPU buffer to be reset */void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return;
/* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex);
atomic_inc(&cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled);
/* Make sure all commits have finished */ synchronize_rcu();
reset_disabled_cpu_buffer(cpu_buffer);
atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&cpu_buffer->resize_disabled);
mutex_unlock(&buffer->mutex);}EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
/* Flag to ensure proper resetting of atomic variables */#define RESET_BIT (1 << 30)
/** * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer * @buffer: The ring buffer to reset a per cpu buffer of */void ring_buffer_reset_online_cpus(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; int cpu;
/* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex);
for_each_online_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
atomic_add(RESET_BIT, &cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); }
/* Make sure all commits have finished */ synchronize_rcu();
for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
/* * If a CPU came online during the synchronize_rcu(), then * ignore it. */ if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT)) continue;
reset_disabled_cpu_buffer(cpu_buffer);
atomic_dec(&cpu_buffer->record_disabled); atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled); }
mutex_unlock(&buffer->mutex);}
/** * ring_buffer_reset - reset a ring buffer * @buffer: The ring buffer to reset all cpu buffers */void ring_buffer_reset(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; int cpu;
/* prevent another thread from changing buffer sizes */ mutex_lock(&buffer->mutex);
for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
atomic_inc(&cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); }
/* Make sure all commits have finished */ synchronize_rcu();
for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
reset_disabled_cpu_buffer(cpu_buffer);
atomic_dec(&cpu_buffer->record_disabled); atomic_dec(&cpu_buffer->resize_disabled); }
mutex_unlock(&buffer->mutex);}EXPORT_SYMBOL_GPL(ring_buffer_reset);
/** * ring_buffer_empty - is the ring buffer empty? * @buffer: The ring buffer to test */bool ring_buffer_empty(struct trace_buffer *buffer){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; bool dolock; bool ret; int cpu;
/* yes this is racy, but if you don't like the race, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); ret = rb_per_cpu_empty(cpu_buffer); rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags);
if (!ret) return false; }
return true;}EXPORT_SYMBOL_GPL(ring_buffer_empty);
/** * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? * @buffer: The ring buffer * @cpu: The CPU buffer to test */bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; bool dolock; bool ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return true;
cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); dolock = rb_reader_lock(cpu_buffer); ret = rb_per_cpu_empty(cpu_buffer); rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags);
return ret;}EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
int ring_buffer_poll_remote(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (cpu != RING_BUFFER_ALL_CPUS) { if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -EINVAL;
cpu_buffer = buffer->buffers[cpu];
guard(raw_spinlock)(&cpu_buffer->reader_lock); if (rb_read_remote_meta_page(cpu_buffer)) rb_wakeups(buffer, cpu_buffer);
return 0; }
guard(cpus_read_lock)();
/* * Make sure all the ring buffers are up to date before we start reading * them. */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
guard(raw_spinlock)(&cpu_buffer->reader_lock); rb_read_remote_meta_page(cpu_buffer); }
for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
if (rb_num_of_entries(cpu_buffer)) rb_wakeups(buffer, cpu_buffer); }
return 0;}
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP/** * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers * @buffer_a: One buffer to swap with * @buffer_b: The other buffer to swap with * @cpu: the CPU of the buffers to swap * * This function is useful for tracers that want to take a "snapshot" * of a CPU buffer and has another back up buffer lying around. * it is expected that the tracer handles the cpu buffer not being * used at the moment. */int ring_buffer_swap_cpu(struct trace_buffer *buffer_a, struct trace_buffer *buffer_b, int cpu){ struct ring_buffer_per_cpu *cpu_buffer_a; struct ring_buffer_per_cpu *cpu_buffer_b; int ret = -EINVAL;
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || !cpumask_test_cpu(cpu, buffer_b->cpumask)) return -EINVAL;
cpu_buffer_a = buffer_a->buffers[cpu]; cpu_buffer_b = buffer_b->buffers[cpu];
/* It's up to the callers to not try to swap mapped buffers */ if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) return -EBUSY;
/* At least make sure the two buffers are somewhat the same */ if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) return -EINVAL;
if (buffer_a->subbuf_order != buffer_b->subbuf_order) return -EINVAL;
if (atomic_read(&buffer_a->record_disabled)) return -EAGAIN;
if (atomic_read(&buffer_b->record_disabled)) return -EAGAIN;
if (atomic_read(&cpu_buffer_a->record_disabled)) return -EAGAIN;
if (atomic_read(&cpu_buffer_b->record_disabled)) return -EAGAIN;
/* * We can't do a synchronize_rcu here because this * function can be called in atomic context. * Normally this will be called from the same CPU as cpu. * If not it's up to the caller to protect this. */ atomic_inc(&cpu_buffer_a->record_disabled); atomic_inc(&cpu_buffer_b->record_disabled);
ret = -EBUSY; if (local_read(&cpu_buffer_a->committing)) goto out_dec; if (local_read(&cpu_buffer_b->committing)) goto out_dec;
/* * When resize is in progress, we cannot swap it because * it will mess the state of the cpu buffer. */ if (atomic_read(&buffer_a->resizing)) goto out_dec; if (atomic_read(&buffer_b->resizing)) goto out_dec;
buffer_a->buffers[cpu] = cpu_buffer_b; buffer_b->buffers[cpu] = cpu_buffer_a;
cpu_buffer_b->buffer = buffer_a; cpu_buffer_a->buffer = buffer_b;
ret = 0;
out_dec: atomic_dec(&cpu_buffer_a->record_disabled); atomic_dec(&cpu_buffer_b->record_disabled); return ret;}EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
/** * ring_buffer_alloc_read_page - allocate a page to read from buffer * @buffer: the buffer to allocate for. * @cpu: the cpu buffer to allocate. * * This function is used in conjunction with ring_buffer_read_page. * When reading a full page from the ring buffer, these functions * can be used to speed up the process. The calling function should * allocate a few pages first with this function. Then when it * needs to get pages from the ring buffer, it passes the result * of this function into ring_buffer_read_page, which will swap * the page that was allocated, with the read page of the buffer. * * Returns: * The page allocated, or ERR_PTR */struct buffer_data_read_page *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; struct buffer_data_read_page *bpage = NULL; unsigned long flags;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return ERR_PTR(-ENODEV);
bpage = kzalloc_obj(*bpage); if (!bpage) return ERR_PTR(-ENOMEM);
bpage->order = buffer->subbuf_order; cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock);
if (cpu_buffer->free_page) { bpage->data = cpu_buffer->free_page; cpu_buffer->free_page = NULL; }
arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags);
if (bpage->data) { rb_init_data_page(bpage->data); } else { bpage->data = alloc_cpu_data(cpu, cpu_buffer->buffer->subbuf_order); if (!bpage->data) { kfree(bpage); return ERR_PTR(-ENOMEM); } }
return bpage;}EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
/** * ring_buffer_free_read_page - free an allocated read page * @buffer: the buffer the page was allocate for * @cpu: the cpu buffer the page came from * @data_page: the page to free * * Free a page allocated from ring_buffer_alloc_read_page. */void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, struct buffer_data_read_page *data_page){ struct ring_buffer_per_cpu *cpu_buffer; struct buffer_data_page *dpage = data_page->data; struct page *page = virt_to_page(dpage); unsigned long flags;
if (!buffer || !buffer->buffers || !buffer->buffers[cpu]) return;
cpu_buffer = buffer->buffers[cpu];
/* * If the page is still in use someplace else, or order of the page * is different from the subbuffer order of the buffer - * we can't reuse it */ if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order) goto out;
local_irq_save(flags); arch_spin_lock(&cpu_buffer->lock);
if (!cpu_buffer->free_page) { cpu_buffer->free_page = dpage; dpage = NULL; }
arch_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags);
out: free_pages((unsigned long)dpage, data_page->order); kfree(data_page);}EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
/** * ring_buffer_read_page - extract a page from the ring buffer * @buffer: buffer to extract from * @data_page: the page to use allocated from ring_buffer_alloc_read_page * @len: amount to extract * @cpu: the cpu of the buffer to extract * @full: should the extraction only happen when the page is full. * * This function will pull out a page from the ring buffer and consume it. * @data_page must be the address of the variable that was returned * from ring_buffer_alloc_read_page. This is because the page might be used * to swap with a page in the ring buffer. * * for example: * rpage = ring_buffer_alloc_read_page(buffer, cpu); * if (IS_ERR(rpage)) * return PTR_ERR(rpage); * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0); * if (ret >= 0) * process_page(ring_buffer_read_page_data(rpage), ret); * ring_buffer_free_read_page(buffer, cpu, rpage); * * When @full is set, the function will not return true unless * the writer is off the reader page. * * Note: it is up to the calling functions to handle sleeps and wakeups. * The ring buffer can be used anywhere in the kernel and can not * blindly call wake_up. The layer that uses the ring buffer must be * responsible for that. * * Returns: * >=0 if data has been transferred, returns the offset of consumed data. * <0 if no data has been transferred. */int ring_buffer_read_page(struct trace_buffer *buffer, struct buffer_data_read_page *data_page, size_t len, int cpu, int full){ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; struct buffer_data_page *dpage; struct buffer_page *reader; long missed_events; unsigned int commit; unsigned int size; unsigned int read; u64 save_timestamp; bool force_memcpy;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -1;
/* * If len is not big enough to hold the page header, then * we can not copy anything. */ if (len <= BUF_PAGE_HDR_SIZE) return -1;
len -= BUF_PAGE_HDR_SIZE;
if (!data_page || !data_page->data) return -1;
if (data_page->order != buffer->subbuf_order) return -1;
dpage = data_page->data; if (!dpage) return -1;
guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock);
reader = rb_get_reader_page(cpu_buffer); if (!reader) return -1;
event = rb_reader_event(cpu_buffer);
read = reader->read; commit = rb_page_commit(reader); size = rb_page_size(reader);
/* Check if any events were dropped */ missed_events = cpu_buffer->lost_events;
force_memcpy = cpu_buffer->mapped || cpu_buffer->remote;
/* * If this page has been partially read or * if len is not big enough to read the rest of the page or * a writer is still on the page, then * we must copy the data from the page to the buffer. * Otherwise, we can simply swap the page with the one passed in. */ if (read || (len < (size - read)) || cpu_buffer->reader_page == cpu_buffer->commit_page || force_memcpy) { struct buffer_data_page *rpage = cpu_buffer->reader_page->page; unsigned int rpos = read; unsigned int pos = 0; unsigned int event_size; unsigned int flags = 0;
/* * If a full page is expected, this can still be returned * if there's been a previous partial read and the * rest of the page can be read and the commit page is off * the reader page. */ if (full && (!read || (len < (size - read)) || cpu_buffer->reader_page == cpu_buffer->commit_page)) return -1;
if (len > (size - read)) len = (size - read);
/* Always keep the time extend and data together */ event_size = rb_event_ts_length(event);
if (len < event_size) return -1;
if (commit & RB_MISSED_EVENTS) flags = RB_MISSED_EVENTS;
/* save the current timestamp, since the user will need it */ save_timestamp = cpu_buffer->read_stamp;
/* Need to copy one event at a time */ do { /* We need the size of one event, because * rb_advance_reader only advances by one event, * whereas rb_event_ts_length may include the size of * one or two events. * We have already ensured there's enough space if this * is a time extend. */ event_size = rb_event_length(event); memcpy(dpage->data + pos, rpage->data + rpos, event_size);
len -= event_size;
rb_advance_reader(cpu_buffer); rpos = reader->read; pos += event_size;
if (rpos >= size) break;
event = rb_reader_event(cpu_buffer); /* Always keep the time extend and data together */ event_size = rb_event_ts_length(event); } while (len >= event_size);
/* update dpage */ local_set(&dpage->commit, pos | flags); dpage->time_stamp = save_timestamp;
/* we copied everything to the beginning */ read = 0; } else { /* update the entry counter */ cpu_buffer->read += rb_page_entries(reader); cpu_buffer->read_bytes += rb_page_size(reader);
/* swap the pages */ rb_init_data_page(dpage); dpage = reader->page; reader->page = data_page->data; local_set(&reader->write, 0); local_set(&reader->entries, 0); reader->read = 0; data_page->data = dpage; if (!missed_events && rb_data_page_commit(dpage) & RB_MISSED_EVENTS) missed_events = -1;
/* * Use the real_end for the data size, * This gives us a chance to store the lost events * on the page. */ if (reader->real_end) local_set(&dpage->commit, reader->real_end); }
cpu_buffer->lost_events = 0;
size = rb_data_page_size(dpage); /* * Set a flag in the commit field if we lost events */ if (missed_events) { /* * If there is room at the end of the page to save the * missed events, then record it there. */ if (missed_events > 0 && buffer->subbuf_size - size >= sizeof(missed_events)) { memcpy(&dpage->data[size], &missed_events, sizeof(missed_events)); local_add(RB_MISSED_STORED, &dpage->commit); size += sizeof(missed_events); } /* * Note, for the persistent ring buffer, the RB_MISSED_EVENTS * may have been set in the main buffer via the verification code. * But here, dpage is a copy of that page and has not yet had * the RB_MISSED_EVENTS set. As for the normal buffers, * the main write buffer does not set these bits and it needs * to be set here. */ local_add(RB_MISSED_EVENTS, &dpage->commit); }
/* * This page may be off to user land. Zero it out here. */ if (size < buffer->subbuf_size) memset(&dpage->data[size], 0, buffer->subbuf_size - size);
return read;}EXPORT_SYMBOL_GPL(ring_buffer_read_page);
/** * ring_buffer_read_page_data - get pointer to the data in the page. * @page: the page to get the data from * * Returns pointer to the actual data in this page. */void *ring_buffer_read_page_data(struct buffer_data_read_page *page){ return page->data;}EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
/** * ring_buffer_subbuf_size_get - get size of the sub buffer. * @buffer: the buffer to get the sub buffer size from * * Returns size of the sub buffer, in bytes. */int ring_buffer_subbuf_size_get(struct trace_buffer *buffer){ return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;}EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
/** * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page. * @buffer: The ring_buffer to get the system sub page order from * * By default, one ring buffer sub page equals to one system page. This parameter * is configurable, per ring buffer. The size of the ring buffer sub page can be * extended, but must be an order of system page size. * * Returns the order of buffer sub page size, in system pages: * 0 means the sub buffer size is 1 system page and so forth. * In case of an error < 0 is returned. */int ring_buffer_subbuf_order_get(struct trace_buffer *buffer){ if (!buffer) return -EINVAL;
return buffer->subbuf_order;}EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
/** * ring_buffer_subbuf_order_set - set the size of ring buffer sub page. * @buffer: The ring_buffer to set the new page size. * @order: Order of the system pages in one sub buffer page * * By default, one ring buffer pages equals to one system page. This API can be * used to set new size of the ring buffer page. The size must be order of * system page size, that's why the input parameter @order is the order of * system pages that are allocated for one ring buffer page: * 0 - 1 system page * 1 - 2 system pages * 3 - 4 system pages * ... * * Returns 0 on success or < 0 in case of an error. */int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order){ struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage, *tmp; int old_order, old_size; int nr_pages; int psize; int err; int cpu;
if (!buffer || order < 0) return -EINVAL;
if (buffer->subbuf_order == order) return 0;
psize = (1 << order) * PAGE_SIZE; if (psize <= BUF_PAGE_HDR_SIZE) return -EINVAL;
/* Size of a subbuf cannot be greater than the write counter */ if (psize > RB_WRITE_MASK + 1) return -EINVAL;
old_order = buffer->subbuf_order; old_size = buffer->subbuf_size;
/* prevent another thread from changing buffer sizes */ guard(mutex)(&buffer->mutex); atomic_inc(&buffer->record_disabled);
/* Make sure all commits have finished */ synchronize_rcu();
buffer->subbuf_order = order; buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
/* Make sure all new buffers are allocated, before deleting the old ones */ for_each_buffer_cpu(buffer, cpu) {
if (!cpumask_test_cpu(cpu, buffer->cpumask)) continue;
cpu_buffer = buffer->buffers[cpu];
if (cpu_buffer->mapped) { err = -EBUSY; goto error; }
/* Update the number of pages to match the new size */ nr_pages = old_size * buffer->buffers[cpu]->nr_pages; nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
/* we need a minimum of two pages */ if (nr_pages < 2) nr_pages = 2;
cpu_buffer->nr_pages_to_update = nr_pages;
/* Include the reader page */ nr_pages++;
/* Allocate the new size buffer */ INIT_LIST_HEAD(&cpu_buffer->new_pages); if (__rb_allocate_pages(cpu_buffer, nr_pages, &cpu_buffer->new_pages)) { /* not enough memory for new pages */ err = -ENOMEM; goto error; } }
for_each_buffer_cpu(buffer, cpu) { struct buffer_data_page *old_free_data_page; struct list_head old_pages; unsigned long flags;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) continue;
cpu_buffer = buffer->buffers[cpu];
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* Clear the head bit to make the link list normal to read */ rb_head_page_deactivate(cpu_buffer);
/* * Collect buffers from the cpu_buffer pages list and the * reader_page on old_pages, so they can be freed later when not * under a spinlock. The pages list is a linked list with no * head, adding old_pages turns it into a regular list with * old_pages being the head. */ list_add(&old_pages, cpu_buffer->pages); list_add(&cpu_buffer->reader_page->list, &old_pages);
/* One page was allocated for the reader page */ cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next, struct buffer_page, list); list_del_init(&cpu_buffer->reader_page->list);
/* Install the new pages, remove the head from the list */ cpu_buffer->pages = cpu_buffer->new_pages.next; list_del_init(&cpu_buffer->new_pages); cpu_buffer->cnt++;
cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update; cpu_buffer->nr_pages_to_update = 0;
old_free_data_page = cpu_buffer->free_page; cpu_buffer->free_page = NULL;
rb_head_page_activate(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
/* Free old sub buffers */ list_for_each_entry_safe(bpage, tmp, &old_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } free_pages((unsigned long)old_free_data_page, old_order);
rb_check_pages(cpu_buffer); }
atomic_dec(&buffer->record_disabled);
return 0;
error: buffer->subbuf_order = old_order; buffer->subbuf_size = old_size;
atomic_dec(&buffer->record_disabled);
for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu];
if (!cpu_buffer->nr_pages_to_update) continue;
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } }
return err;}EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer){ struct page *page;
if (cpu_buffer->meta_page) return 0;
page = alloc_page(GFP_USER | __GFP_ZERO); if (!page) return -ENOMEM;
cpu_buffer->meta_page = page_to_virt(page);
return 0;}
static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer){ unsigned long addr = (unsigned long)cpu_buffer->meta_page;
free_page(addr); cpu_buffer->meta_page = NULL;}
static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page **subbuf_ids){ struct trace_buffer_meta *meta = cpu_buffer->meta_page; unsigned int nr_subbufs = cpu_buffer->nr_pages + 1; struct buffer_page *first_subbuf, *subbuf; int cnt = 0; int id = 0;
id = rb_page_id(cpu_buffer, cpu_buffer->reader_page, id); subbuf_ids[id++] = cpu_buffer->reader_page; cnt++;
first_subbuf = subbuf = rb_set_head_page(cpu_buffer); do { id = rb_page_id(cpu_buffer, subbuf, id);
if (WARN_ON(id >= nr_subbufs)) break;
subbuf_ids[id] = subbuf;
rb_inc_page(&subbuf); id++; cnt++; } while (subbuf != first_subbuf);
WARN_ON(cnt != nr_subbufs);
/* install subbuf ID to bpage translation */ cpu_buffer->subbuf_ids = subbuf_ids;
meta->meta_struct_len = sizeof(*meta); meta->nr_subbufs = nr_subbufs; meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE; meta->meta_page_size = meta->subbuf_size;
rb_update_meta_page(cpu_buffer);}
static struct ring_buffer_per_cpu *rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return ERR_PTR(-EINVAL);
cpu_buffer = buffer->buffers[cpu];
mutex_lock(&cpu_buffer->mapping_lock);
if (!cpu_buffer->user_mapped) { mutex_unlock(&cpu_buffer->mapping_lock); return ERR_PTR(-ENODEV); }
return cpu_buffer;}
static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer){ mutex_unlock(&cpu_buffer->mapping_lock);}
/* * Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need * to be set-up or torn-down. */static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer, bool inc){ unsigned long flags;
lockdep_assert_held(&cpu_buffer->mapping_lock);
/* mapped is always greater or equal to user_mapped */ if (WARN_ON(cpu_buffer->mapped < cpu_buffer->user_mapped)) return -EINVAL;
if (inc && cpu_buffer->mapped == UINT_MAX) return -EBUSY;
if (WARN_ON(!inc && cpu_buffer->user_mapped == 0)) return -EINVAL;
mutex_lock(&cpu_buffer->buffer->mutex); raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
if (inc) { cpu_buffer->user_mapped++; cpu_buffer->mapped++; } else { cpu_buffer->user_mapped--; cpu_buffer->mapped--; }
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); mutex_unlock(&cpu_buffer->buffer->mutex);
return 0;}
/* * +--------------+ pgoff == 0 * | meta page | * +--------------+ pgoff == 1 * | subbuffer 0 | * | | * +--------------+ pgoff == (1 + (1 << subbuf_order)) * | subbuffer 1 | * | | * ... */#ifdef CONFIG_MMUstatic int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, struct vm_area_struct *vma){ unsigned long nr_subbufs, nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff; unsigned int subbuf_pages, subbuf_order; struct page **pages __free(kfree) = NULL; int p = 0, s = 0; int err;
/* Refuse MP_PRIVATE or writable mappings */ if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC || !(vma->vm_flags & VM_MAYSHARE)) return -EPERM;
subbuf_order = cpu_buffer->buffer->subbuf_order; subbuf_pages = 1 << subbuf_order;
if (subbuf_order && pgoff % subbuf_pages) return -EINVAL;
/* * Make sure the mapping cannot become writable later. Also tell the VM * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND). */ vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP, VM_MAYWRITE);
lockdep_assert_held(&cpu_buffer->mapping_lock);
nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */ nr_pages = ((nr_subbufs + 1) << subbuf_order); /* + meta-page */ if (nr_pages <= pgoff) return -EINVAL;
nr_pages -= pgoff;
nr_vma_pages = vma_pages(vma); if (!nr_vma_pages || nr_vma_pages > nr_pages) return -EINVAL;
nr_pages = nr_vma_pages;
pages = kzalloc_objs(*pages, nr_pages); if (!pages) return -ENOMEM;
if (!pgoff) { unsigned long meta_page_padding;
pages[p++] = virt_to_page(cpu_buffer->meta_page);
/* * Pad with the zero-page to align the meta-page with the * sub-buffers. */ meta_page_padding = subbuf_pages - 1; while (meta_page_padding-- && p < nr_pages) { unsigned long __maybe_unused zero_addr = vma->vm_start + (PAGE_SIZE * p);
pages[p++] = ZERO_PAGE(zero_addr); } } else { /* Skip the meta-page */ pgoff -= subbuf_pages;
s += pgoff / subbuf_pages; }
while (p < nr_pages) { struct buffer_page *subbuf; struct page *page; int off = 0;
if (WARN_ON_ONCE(s >= nr_subbufs)) return -EINVAL;
subbuf = cpu_buffer->subbuf_ids[s]; page = virt_to_page((void *)subbuf->page);
for (; off < (1 << (subbuf_order)); off++, page++) { if (p >= nr_pages) break;
pages[p++] = page; } s++; }
err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
return err;}#elsestatic int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, struct vm_area_struct *vma){ return -EOPNOTSUPP;}#endif
int ring_buffer_map(struct trace_buffer *buffer, int cpu, struct vm_area_struct *vma){ struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page **subbuf_ids; unsigned long flags; int err;
if (!cpumask_test_cpu(cpu, buffer->cpumask) || buffer->remote) return -EINVAL;
cpu_buffer = buffer->buffers[cpu];
guard(mutex)(&cpu_buffer->mapping_lock);
if (cpu_buffer->user_mapped) { err = __rb_map_vma(cpu_buffer, vma); if (!err) err = __rb_inc_dec_mapped(cpu_buffer, true); return err; }
/* prevent another thread from changing buffer/sub-buffer sizes */ guard(mutex)(&buffer->mutex);
err = rb_alloc_meta_page(cpu_buffer); if (err) return err;
/* subbuf_ids includes the reader while nr_pages does not */ subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL); if (!subbuf_ids) { rb_free_meta_page(cpu_buffer); return -ENOMEM; }
atomic_inc(&cpu_buffer->resize_disabled);
/* * Lock all readers to block any subbuf swap until the subbuf IDs are * assigned. */ raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
err = __rb_map_vma(cpu_buffer, vma); if (!err) { raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); /* This is the first time it is mapped by user */ cpu_buffer->mapped++; cpu_buffer->user_mapped = 1; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } else { kfree(cpu_buffer->subbuf_ids); cpu_buffer->subbuf_ids = NULL; rb_free_meta_page(cpu_buffer); atomic_dec(&cpu_buffer->resize_disabled); }
return err;}
/* * This is called when a VMA is duplicated (e.g., on fork()) to increment * the user_mapped counter without remapping pages. */void ring_buffer_map_dup(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer;
if (WARN_ON(!cpumask_test_cpu(cpu, buffer->cpumask))) return;
cpu_buffer = buffer->buffers[cpu];
guard(mutex)(&cpu_buffer->mapping_lock);
if (cpu_buffer->user_mapped) __rb_inc_dec_mapped(cpu_buffer, true); else WARN(1, "Unexpected buffer stat, it should be mapped");}
int ring_buffer_unmap(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags;
if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -EINVAL;
cpu_buffer = buffer->buffers[cpu];
guard(mutex)(&cpu_buffer->mapping_lock);
if (!cpu_buffer->user_mapped) { return -ENODEV; } else if (cpu_buffer->user_mapped > 1) { __rb_inc_dec_mapped(cpu_buffer, false); return 0; }
guard(mutex)(&buffer->mutex); raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* This is the last user space mapping */ if (!WARN_ON_ONCE(cpu_buffer->mapped < cpu_buffer->user_mapped)) cpu_buffer->mapped--; cpu_buffer->user_mapped = 0;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
kfree(cpu_buffer->subbuf_ids); cpu_buffer->subbuf_ids = NULL; rb_free_meta_page(cpu_buffer); atomic_dec(&cpu_buffer->resize_disabled);
return 0;}
int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu){ struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *reader; unsigned long missed_events; unsigned long reader_size; unsigned long flags;
cpu_buffer = rb_get_mapped_buffer(buffer, cpu); if (IS_ERR(cpu_buffer)) return (int)PTR_ERR(cpu_buffer);
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
consume: if (rb_per_cpu_empty(cpu_buffer)) goto out;
reader_size = rb_page_size(cpu_buffer->reader_page);
/* * There are data to be read on the current reader page, we can * return to the caller. But before that, we assume the latter will read * everything. Let's update the kernel reader accordingly. */ if (cpu_buffer->reader_page->read < reader_size) { while (cpu_buffer->reader_page->read < reader_size) rb_advance_reader(cpu_buffer); goto out; }
/* Did the reader catch up with the writer? */ if (cpu_buffer->reader_page == cpu_buffer->commit_page) goto out;
reader = rb_get_reader_page(cpu_buffer); if (WARN_ON(!reader)) goto out;
/* Check if any events were dropped */ missed_events = cpu_buffer->lost_events;
if (missed_events) { if (cpu_buffer->reader_page != cpu_buffer->commit_page) { struct buffer_data_page *dpage = reader->page; unsigned int commit; /* * Use the real_end for the data size, * This gives us a chance to store the lost events * on the page. */ if (reader->real_end) local_set(&dpage->commit, reader->real_end); /* * If there is room at the end of the page to save the * missed events, then record it there. */ commit = rb_page_size(reader); if (buffer->subbuf_size - commit >= sizeof(missed_events)) { memcpy(&dpage->data[commit], &missed_events, sizeof(missed_events)); local_add(RB_MISSED_STORED, &dpage->commit); } local_add(RB_MISSED_EVENTS, &dpage->commit); } else if (!WARN_ONCE(cpu_buffer->reader_page == cpu_buffer->tail_page, "Reader on commit with %ld missed events", missed_events)) { /* * There shouldn't be any missed events if the tail_page * is on the reader page. But if the tail page is not on the * reader page and the commit_page is, that would mean that * there's a commit_overrun (an interrupt preempted an * addition of an event and then filled the buffer * with new events). In this case it's not an * error, but it should still be reported. * * TODO: Add missed events to the page for user space to know. */ pr_info("Ring buffer [%d] commit overrun lost %ld events at timestamp:%lld\n", cpu, missed_events, cpu_buffer->reader_page->page->time_stamp); } }
cpu_buffer->lost_events = 0;
goto consume;
out: /* Some archs do not have data cache coherency between kernel and user-space */ flush_kernel_vmap_range(cpu_buffer->reader_page->page, buffer->subbuf_size + BUF_PAGE_HDR_SIZE);
rb_update_meta_page(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); rb_put_mapped_buffer(cpu_buffer);
return 0;}
static void rb_cpu_sync(void *data){ /* Not really needed, but documents what is happening */ smp_rmb();}
/* * We only allocate new buffers, never free them if the CPU goes down. * If we were to free the buffer, then the user would lose any trace that was in * the buffer. */int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node){ struct trace_buffer *buffer; long nr_pages_same; int cpu_i; unsigned long nr_pages;
buffer = container_of(node, struct trace_buffer, node); if (cpumask_test_cpu(cpu, buffer->cpumask)) return 0;
nr_pages = 0; nr_pages_same = 1; /* check if all cpu sizes are same */ for_each_buffer_cpu(buffer, cpu_i) { /* fill in the size from first enabled cpu */ if (nr_pages == 0) nr_pages = buffer->buffers[cpu_i]->nr_pages; if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { nr_pages_same = 0; break; } } /* allocate minimum pages, user can later expand it */ if (!nr_pages_same) nr_pages = 2; buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); if (!buffer->buffers[cpu]) { WARN(1, "failed to allocate ring buffer on CPU %u\n", cpu); return -ENOMEM; }
/* * Ensure trace_buffer readers observe the newly allocated * ring_buffer_per_cpu before they check the cpumask. Instead of using a * read barrier for all readers, send an IPI. */ if (unlikely(system_state == SYSTEM_RUNNING)) { on_each_cpu(rb_cpu_sync, NULL, 1); /* Not really needed, but documents what is happening */ smp_wmb(); }
cpumask_set_cpu(cpu, buffer->cpumask); return 0;}
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST/* * This is a basic integrity check of the ring buffer. * Late in the boot cycle this test will run when configured in. * It will kick off a thread per CPU that will go into a loop * writing to the per cpu ring buffer various sizes of data. * Some of the data will be large items, some small. * * Another thread is created that goes into a spin, sending out * IPIs to the other CPUs to also write into the ring buffer. * this is to test the nesting ability of the buffer. * * Basic stats are recorded and reported. If something in the * ring buffer should happen that's not expected, a big warning * is displayed and all ring buffers are disabled. */static struct task_struct *rb_threads[NR_CPUS] __initdata;
struct rb_test_data { struct trace_buffer *buffer; unsigned long events; unsigned long bytes_written; unsigned long bytes_alloc; unsigned long bytes_dropped; unsigned long events_nested; unsigned long bytes_written_nested; unsigned long bytes_alloc_nested; unsigned long bytes_dropped_nested; int min_size_nested; int max_size_nested; int max_size; int min_size; int cpu; int cnt;};
static struct rb_test_data rb_data[NR_CPUS] __initdata;
/* 1 meg per cpu */#define RB_TEST_BUFFER_SIZE 1048576
static char rb_string[] __initdata = "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
static bool rb_test_started __initdata;
struct rb_item { int size; char str[];};
static __init int rb_write_something(struct rb_test_data *data, bool nested){ struct ring_buffer_event *event; struct rb_item *item; bool started; int event_len; int size; int len; int cnt;
/* Have nested writes different that what is written */ cnt = data->cnt + (nested ? 27 : 0);
/* Multiply cnt by ~e, to make some unique increment */ size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
len = size + sizeof(struct rb_item);
started = rb_test_started; /* read rb_test_started before checking buffer enabled */ smp_rmb();
event = ring_buffer_lock_reserve(data->buffer, len); if (!event) { /* Ignore dropped events before test starts. */ if (started) { if (nested) data->bytes_dropped_nested += len; else data->bytes_dropped += len; } return len; }
event_len = ring_buffer_event_length(event);
if (RB_WARN_ON(data->buffer, event_len < len)) goto out;
item = ring_buffer_event_data(event); item->size = size; memcpy(item->str, rb_string, size);
if (nested) { data->bytes_alloc_nested += event_len; data->bytes_written_nested += len; data->events_nested++; if (!data->min_size_nested || len < data->min_size_nested) data->min_size_nested = len; if (len > data->max_size_nested) data->max_size_nested = len; } else { data->bytes_alloc += event_len; data->bytes_written += len; data->events++; if (!data->min_size || len < data->min_size) data->max_size = len; if (len > data->max_size) data->max_size = len; }
out: ring_buffer_unlock_commit(data->buffer);
return 0;}
static __init int rb_test(void *arg){ struct rb_test_data *data = arg;
while (!kthread_should_stop()) { rb_write_something(data, false); data->cnt++;
set_current_state(TASK_INTERRUPTIBLE); /* Now sleep between a min of 100-300us and a max of 1ms */ usleep_range(((data->cnt % 3) + 1) * 100, 1000); }
return 0;}
static __init void rb_ipi(void *ignore){ struct rb_test_data *data; int cpu = smp_processor_id();
data = &rb_data[cpu]; rb_write_something(data, true);}
static __init int rb_hammer_test(void *arg){ while (!kthread_should_stop()) {
/* Send an IPI to all cpus to write data! */ smp_call_function(rb_ipi, NULL, 1); /* No sleep, but for non preempt, let others run */ schedule(); }
return 0;}
static __init int test_ringbuffer(void){ struct task_struct *rb_hammer; struct trace_buffer *buffer; int cpu; int ret = 0;
if (security_locked_down(LOCKDOWN_TRACEFS)) { pr_warn("Lockdown is enabled, skipping ring buffer tests\n"); return 0; }
pr_info("Running ring buffer tests...\n");
buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); if (WARN_ON(!buffer)) return 0;
/* Disable buffer so that threads can't write to it yet */ ring_buffer_record_off(buffer);
for_each_online_cpu(cpu) { rb_data[cpu].buffer = buffer; rb_data[cpu].cpu = cpu; rb_data[cpu].cnt = cpu; rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu], cpu, "rbtester/%u"); if (WARN_ON(IS_ERR(rb_threads[cpu]))) { pr_cont("FAILED\n"); ret = PTR_ERR(rb_threads[cpu]); goto out_free; } }
/* Now create the rb hammer! */ rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); if (WARN_ON(IS_ERR(rb_hammer))) { pr_cont("FAILED\n"); ret = PTR_ERR(rb_hammer); goto out_free; }
ring_buffer_record_on(buffer); /* * Show buffer is enabled before setting rb_test_started. * Yes there's a small race window where events could be * dropped and the thread won't catch it. But when a ring * buffer gets enabled, there will always be some kind of * delay before other CPUs see it. Thus, we don't care about * those dropped events. We care about events dropped after * the threads see that the buffer is active. */ smp_wmb(); rb_test_started = true;
set_current_state(TASK_INTERRUPTIBLE); /* Just run for 10 seconds */ schedule_timeout(10 * HZ);
kthread_stop(rb_hammer);
out_free: for_each_online_cpu(cpu) { if (!rb_threads[cpu]) break; kthread_stop(rb_threads[cpu]); } if (ret) { ring_buffer_free(buffer); return ret; }
/* Report! */ pr_info("finished\n"); for_each_online_cpu(cpu) { struct ring_buffer_event *event; struct rb_test_data *data = &rb_data[cpu]; struct rb_item *item; unsigned long total_events; unsigned long total_dropped; unsigned long total_written; unsigned long total_alloc; unsigned long total_read = 0; unsigned long total_size = 0; unsigned long total_len = 0; unsigned long total_lost = 0; unsigned long lost; int big_event_size; int small_event_size;
ret = -1;
total_events = data->events + data->events_nested; total_written = data->bytes_written + data->bytes_written_nested; total_alloc = data->bytes_alloc + data->bytes_alloc_nested; total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
big_event_size = data->max_size + data->max_size_nested; small_event_size = data->min_size + data->min_size_nested;
pr_info("CPU %d:\n", cpu); pr_info(" events: %ld\n", total_events); pr_info(" dropped bytes: %ld\n", total_dropped); pr_info(" alloced bytes: %ld\n", total_alloc); pr_info(" written bytes: %ld\n", total_written); pr_info(" biggest event: %d\n", big_event_size); pr_info(" smallest event: %d\n", small_event_size);
if (RB_WARN_ON(buffer, total_dropped)) break;
ret = 0;
while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { total_lost += lost; item = ring_buffer_event_data(event); total_len += ring_buffer_event_length(event); total_size += item->size + sizeof(struct rb_item); if (memcmp(&item->str[0], rb_string, item->size) != 0) { pr_info("FAILED!\n"); pr_info("buffer had: %.*s\n", item->size, item->str); pr_info("expected: %.*s\n", item->size, rb_string); RB_WARN_ON(buffer, 1); ret = -1; break; } total_read++; } if (ret) break;
ret = -1;
pr_info(" read events: %ld\n", total_read); pr_info(" lost events: %ld\n", total_lost); pr_info(" total events: %ld\n", total_lost + total_read); pr_info(" recorded len bytes: %ld\n", total_len); pr_info(" recorded size bytes: %ld\n", total_size); if (total_lost) { pr_info(" With dropped events, record len and size may not match\n" " alloced and written from above\n"); } else { if (RB_WARN_ON(buffer, total_len != total_alloc || total_size != total_written)) break; } if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) break;
ret = 0; } if (!ret) pr_info("Ring buffer PASSED!\n");
ring_buffer_free(buffer); return 0;}
late_initcall(test_ringbuffer);#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */