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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144// SPDX-License-Identifier: GPL-2.0-only#include <linux/module.h>#include <linux/kthread.h>#include <linux/trace.h>#include <linux/trace_events.h>#include <linux/timer.h>#include <linux/err.h>#include <linux/jiffies.h>#include <linux/workqueue.h>
/* * Any file that uses trace points, must include the header. * But only one file, must include the header by defining * CREATE_TRACE_POINTS first. This will make the C code that * creates the handles for the trace points. */#define CREATE_TRACE_POINTS#include "sample-trace-array.h"
struct trace_array *tr;static void mytimer_handler(struct timer_list *unused);static struct task_struct *simple_tsk;
static void trace_work_fn(struct work_struct *work){ /* * Disable tracing for event "sample_event". */ trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", false);}static DECLARE_WORK(trace_work, trace_work_fn);
/* * mytimer: Timer setup to disable tracing for event "sample_event". This * timer is only for the purposes of the sample module to demonstrate access of * Ftrace instances from within kernel. */static DEFINE_TIMER(mytimer, mytimer_handler);
static void mytimer_handler(struct timer_list *unused){ schedule_work(&trace_work);}
static void simple_thread_func(int count){ set_current_state(TASK_INTERRUPTIBLE); schedule_timeout(HZ);
/* * Printing count value using trace_array_printk() - trace_printk() * equivalent for the instance buffers. */ trace_array_printk(tr, _THIS_IP_, "trace_array_printk: count=%d\n", count); /* * Tracepoint for event "sample_event". This will print the * current value of count and current jiffies. */ trace_sample_event(count, jiffies);}
static int simple_thread(void *arg){ int count = 0; unsigned long delay = msecs_to_jiffies(5000);
/* * Enable tracing for "sample_event". */ trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", true);
/* * Adding timer - mytimer. This timer will disable tracing after * delay seconds. * */ add_timer(&mytimer); mod_timer(&mytimer, jiffies+delay);
while (!kthread_should_stop()) simple_thread_func(count++);
timer_delete(&mytimer); cancel_work_sync(&trace_work);
/* * trace_array_put() decrements the reference counter associated with * the trace array - "tr". We are done using the trace array, hence * decrement the reference counter so that it can be destroyed using * trace_array_destroy(). */ trace_array_put(tr);
return 0;}
static int __init sample_trace_array_init(void){ /* * Return a pointer to the trace array with name "sample-instance" if it * exists, else create a new trace array. * * NOTE: This function increments the reference counter * associated with the trace array - "tr". */ tr = trace_array_get_by_name("sample-instance", "sched,timer,kprobes");
if (!tr) return -1; /* * If context specific per-cpu buffers havent already been allocated. */ trace_array_init_printk(tr);
simple_tsk = kthread_run(simple_thread, NULL, "sample-instance"); if (IS_ERR(simple_tsk)) { trace_array_put(tr); trace_array_destroy(tr); return -1; }
return 0;}
static void __exit sample_trace_array_exit(void){ kthread_stop(simple_tsk);
/* * We are unloading our module and no longer require the trace array. * Remove/destroy "tr" using trace_array_destroy() */ trace_array_destroy(tr);}
module_init(sample_trace_array_init);module_exit(sample_trace_array_exit);
MODULE_AUTHOR("Divya Indi");MODULE_DESCRIPTION("Sample module for kernel access to Ftrace instances");MODULE_LICENSE("GPL");