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143 lines
3.5 KiB
143 lines
3.5 KiB
// 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"); |
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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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