165 lines
3.3 KiB
C
165 lines
3.3 KiB
C
/*
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* trace event based perf counter profiling
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*
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* Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
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*
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*/
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#include "trace.h"
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static char *perf_trace_buf;
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static char *perf_trace_buf_nmi;
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typedef typeof(char [FTRACE_MAX_PROFILE_SIZE]) perf_trace_t ;
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/* Count the events in use (per event id, not per instance) */
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static int total_profile_count;
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static int ftrace_profile_enable_event(struct ftrace_event_call *event)
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{
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char *buf;
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int ret = -ENOMEM;
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if (event->profile_count++ > 0)
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return 0;
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if (!total_profile_count) {
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail_buf;
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rcu_assign_pointer(perf_trace_buf, buf);
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buf = (char *)alloc_percpu(perf_trace_t);
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if (!buf)
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goto fail_buf_nmi;
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rcu_assign_pointer(perf_trace_buf_nmi, buf);
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}
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ret = event->profile_enable(event);
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if (!ret) {
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total_profile_count++;
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return 0;
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}
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fail_buf_nmi:
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if (!total_profile_count) {
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free_percpu(perf_trace_buf_nmi);
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free_percpu(perf_trace_buf);
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perf_trace_buf_nmi = NULL;
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perf_trace_buf = NULL;
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}
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fail_buf:
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event->profile_count--;
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return ret;
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}
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int ftrace_profile_enable(int event_id)
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{
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struct ftrace_event_call *event;
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int ret = -EINVAL;
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mutex_lock(&event_mutex);
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list_for_each_entry(event, &ftrace_events, list) {
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if (event->id == event_id && event->profile_enable &&
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try_module_get(event->mod)) {
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ret = ftrace_profile_enable_event(event);
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break;
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}
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}
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mutex_unlock(&event_mutex);
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return ret;
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}
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static void ftrace_profile_disable_event(struct ftrace_event_call *event)
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{
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char *buf, *nmi_buf;
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if (--event->profile_count > 0)
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return;
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event->profile_disable(event);
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if (!--total_profile_count) {
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buf = perf_trace_buf;
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rcu_assign_pointer(perf_trace_buf, NULL);
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nmi_buf = perf_trace_buf_nmi;
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rcu_assign_pointer(perf_trace_buf_nmi, NULL);
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/*
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* Ensure every events in profiling have finished before
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* releasing the buffers
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*/
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synchronize_sched();
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free_percpu(buf);
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free_percpu(nmi_buf);
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}
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}
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void ftrace_profile_disable(int event_id)
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{
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struct ftrace_event_call *event;
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mutex_lock(&event_mutex);
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list_for_each_entry(event, &ftrace_events, list) {
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if (event->id == event_id) {
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ftrace_profile_disable_event(event);
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module_put(event->mod);
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break;
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}
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}
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mutex_unlock(&event_mutex);
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}
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__kprobes void *ftrace_perf_buf_prepare(int size, unsigned short type,
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int *rctxp, unsigned long *irq_flags)
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{
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struct trace_entry *entry;
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char *trace_buf, *raw_data;
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int pc, cpu;
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pc = preempt_count();
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/* Protect the per cpu buffer, begin the rcu read side */
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local_irq_save(*irq_flags);
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*rctxp = perf_swevent_get_recursion_context();
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if (*rctxp < 0)
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goto err_recursion;
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cpu = smp_processor_id();
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if (in_nmi())
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trace_buf = rcu_dereference(perf_trace_buf_nmi);
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else
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trace_buf = rcu_dereference(perf_trace_buf);
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if (!trace_buf)
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goto err;
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raw_data = per_cpu_ptr(trace_buf, cpu);
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/* zero the dead bytes from align to not leak stack to user */
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*(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
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entry = (struct trace_entry *)raw_data;
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tracing_generic_entry_update(entry, *irq_flags, pc);
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entry->type = type;
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return raw_data;
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err:
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perf_swevent_put_recursion_context(*rctxp);
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err_recursion:
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local_irq_restore(*irq_flags);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(ftrace_perf_buf_prepare);
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