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