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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#define pr_fmt(fmt) "kcsan: " fmt
#include <linux/atomic.h>#include <linux/bsearch.h>#include <linux/bug.h>#include <linux/debugfs.h>#include <linux/init.h>#include <linux/kallsyms.h>#include <linux/sched.h>#include <linux/seq_file.h>#include <linux/slab.h>#include <linux/sort.h>#include <linux/string.h>#include <linux/uaccess.h>
#include "kcsan.h"
atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT];static const char *const counter_names[] = { [KCSAN_COUNTER_USED_WATCHPOINTS] = "used_watchpoints", [KCSAN_COUNTER_SETUP_WATCHPOINTS] = "setup_watchpoints", [KCSAN_COUNTER_DATA_RACES] = "data_races", [KCSAN_COUNTER_ASSERT_FAILURES] = "assert_failures", [KCSAN_COUNTER_NO_CAPACITY] = "no_capacity", [KCSAN_COUNTER_REPORT_RACES] = "report_races", [KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN] = "races_unknown_origin", [KCSAN_COUNTER_UNENCODABLE_ACCESSES] = "unencodable_accesses", [KCSAN_COUNTER_ENCODING_FALSE_POSITIVES] = "encoding_false_positives",};static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT);
/* * Addresses for filtering functions from reporting. This list can be used as a * whitelist or blacklist. */static struct { unsigned long *addrs; /* array of addresses */ size_t size; /* current size */ int used; /* number of elements used */ bool sorted; /* if elements are sorted */ bool whitelist; /* if list is a blacklist or whitelist */} report_filterlist;static DEFINE_RAW_SPINLOCK(report_filterlist_lock);
/* * The microbenchmark allows benchmarking KCSAN core runtime only. To run * multiple threads, pipe 'microbench=<iters>' from multiple tasks into the * debugfs file. This will not generate any conflicts, and tests fast-path only. */static noinline void microbenchmark(unsigned long iters){ const struct kcsan_ctx ctx_save = current->kcsan_ctx; const bool was_enabled = READ_ONCE(kcsan_enabled); u64 cycles;
/* We may have been called from an atomic region; reset context. */ memset(¤t->kcsan_ctx, 0, sizeof(current->kcsan_ctx)); /* * Disable to benchmark fast-path for all accesses, and (expected * negligible) call into slow-path, but never set up watchpoints. */ WRITE_ONCE(kcsan_enabled, false);
pr_info("%s begin | iters: %lu\n", __func__, iters);
cycles = get_cycles(); while (iters--) { unsigned long addr = iters & ((PAGE_SIZE << 8) - 1); int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC : (!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0); __kcsan_check_access((void *)addr, sizeof(long), type); } cycles = get_cycles() - cycles;
pr_info("%s end | cycles: %llu\n", __func__, cycles);
WRITE_ONCE(kcsan_enabled, was_enabled); /* restore context */ current->kcsan_ctx = ctx_save;}
static int cmp_filterlist_addrs(const void *rhs, const void *lhs){ const unsigned long a = *(const unsigned long *)rhs; const unsigned long b = *(const unsigned long *)lhs;
return a < b ? -1 : a == b ? 0 : 1;}
bool kcsan_skip_report_debugfs(unsigned long func_addr){ unsigned long symbolsize, offset; unsigned long flags; bool ret = false;
if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset)) return false; func_addr -= offset; /* Get function start */
raw_spin_lock_irqsave(&report_filterlist_lock, flags); if (report_filterlist.used == 0) goto out;
/* Sort array if it is unsorted, and then do a binary search. */ if (!report_filterlist.sorted) { sort(report_filterlist.addrs, report_filterlist.used, sizeof(unsigned long), cmp_filterlist_addrs, NULL); report_filterlist.sorted = true; } ret = !!bsearch(&func_addr, report_filterlist.addrs, report_filterlist.used, sizeof(unsigned long), cmp_filterlist_addrs); if (report_filterlist.whitelist) ret = !ret;
out: raw_spin_unlock_irqrestore(&report_filterlist_lock, flags); return ret;}
static void set_report_filterlist_whitelist(bool whitelist){ unsigned long flags;
raw_spin_lock_irqsave(&report_filterlist_lock, flags); report_filterlist.whitelist = whitelist; raw_spin_unlock_irqrestore(&report_filterlist_lock, flags);}
/* Returns 0 on success, error-code otherwise. */static ssize_t insert_report_filterlist(const char *func){ unsigned long flags; unsigned long addr = kallsyms_lookup_name(func); unsigned long *delay_free = NULL; unsigned long *new_addrs = NULL; size_t new_size = 0; ssize_t ret = 0;
if (!addr) { pr_err("could not find function: '%s'\n", func); return -ENOENT; }
retry_alloc: /* * Check if we need an allocation, and re-validate under the lock. Since * the report_filterlist_lock is a raw, cannot allocate under the lock. */ if (data_race(report_filterlist.used == report_filterlist.size)) { new_size = (report_filterlist.size ?: 4) * 2; delay_free = new_addrs = kmalloc_array(new_size, sizeof(unsigned long), GFP_KERNEL); if (!new_addrs) return -ENOMEM; }
raw_spin_lock_irqsave(&report_filterlist_lock, flags); if (report_filterlist.used == report_filterlist.size) { /* Check we pre-allocated enough, and retry if not. */ if (report_filterlist.used >= new_size) { raw_spin_unlock_irqrestore(&report_filterlist_lock, flags); kfree(new_addrs); /* kfree(NULL) is safe */ delay_free = new_addrs = NULL; goto retry_alloc; }
if (report_filterlist.used) memcpy(new_addrs, report_filterlist.addrs, report_filterlist.used * sizeof(unsigned long)); delay_free = report_filterlist.addrs; /* free the old list */ report_filterlist.addrs = new_addrs; /* switch to the new list */ report_filterlist.size = new_size; }
/* Note: deduplicating should be done in userspace. */ report_filterlist.addrs[report_filterlist.used++] = addr; report_filterlist.sorted = false;
raw_spin_unlock_irqrestore(&report_filterlist_lock, flags);
kfree(delay_free); return ret;}
static int show_info(struct seq_file *file, void *v){ int i; unsigned long flags;
/* show stats */ seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled)); for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) { seq_printf(file, "%s: %ld\n", counter_names[i], atomic_long_read(&kcsan_counters[i])); }
/* show filter functions, and filter type */ raw_spin_lock_irqsave(&report_filterlist_lock, flags); seq_printf(file, "\n%s functions: %s\n", report_filterlist.whitelist ? "whitelisted" : "blacklisted", report_filterlist.used == 0 ? "none" : ""); for (i = 0; i < report_filterlist.used; ++i) seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]); raw_spin_unlock_irqrestore(&report_filterlist_lock, flags);
return 0;}
static int debugfs_open(struct inode *inode, struct file *file){ return single_open(file, show_info, NULL);}
static ssize_tdebugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off){ char kbuf[KSYM_NAME_LEN]; char *arg; const size_t read_len = min(count, sizeof(kbuf) - 1);
if (copy_from_user(kbuf, buf, read_len)) return -EFAULT; kbuf[read_len] = '\0'; arg = strstrip(kbuf);
if (!strcmp(arg, "on")) { WRITE_ONCE(kcsan_enabled, true); } else if (!strcmp(arg, "off")) { WRITE_ONCE(kcsan_enabled, false); } else if (str_has_prefix(arg, "microbench=")) { unsigned long iters;
if (kstrtoul(&arg[strlen("microbench=")], 0, &iters)) return -EINVAL; microbenchmark(iters); } else if (!strcmp(arg, "whitelist")) { set_report_filterlist_whitelist(true); } else if (!strcmp(arg, "blacklist")) { set_report_filterlist_whitelist(false); } else if (arg[0] == '!') { ssize_t ret = insert_report_filterlist(&arg[1]);
if (ret < 0) return ret; } else { return -EINVAL; }
return count;}
static const struct file_operations debugfs_ops ={ .read = seq_read, .open = debugfs_open, .write = debugfs_write, .release = single_release};
static int __init kcsan_debugfs_init(void){ debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops); return 0;}
late_initcall(kcsan_debugfs_init);