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/*
* trace event based perf event profiling/tracing
*
* Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
* Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
*/
#include <linux/module.h>
#include <linux/kprobes.h>
#include "trace.h"
DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
static char *perf_trace_buf;
static char *perf_trace_buf_nmi;
typedef typeof(char [PERF_MAX_TRACE_SIZE]) perf_trace_t ;
/* Count the events in use (per event id, not per instance) */
static int total_ref_count;
static int perf_trace_event_enable(struct ftrace_event_call *event)
{
char *buf;
int ret = -ENOMEM;
if (event->perf_refcount++ > 0)
return 0;
if (!total_ref_count) {
buf = (char *)alloc_percpu(perf_trace_t);
if (!buf)
goto fail_buf;
rcu_assign_pointer(perf_trace_buf, buf);
buf = (char *)alloc_percpu(perf_trace_t);
if (!buf)
goto fail_buf_nmi;
rcu_assign_pointer(perf_trace_buf_nmi, buf);
}
ret = event->perf_event_enable(event);
if (!ret) {
total_ref_count++;
return 0;
}
fail_buf_nmi:
if (!total_ref_count) {
free_percpu(perf_trace_buf_nmi);
free_percpu(perf_trace_buf);
perf_trace_buf_nmi = NULL;
perf_trace_buf = NULL;
}
fail_buf:
event->perf_refcount--;
return ret;
}
int perf_trace_enable(int event_id)
{
struct ftrace_event_call *event;
int ret = -EINVAL;
mutex_lock(&event_mutex);
list_for_each_entry(event, &ftrace_events, list) {
if (event->id == event_id && event->perf_event_enable &&
try_module_get(event->mod)) {
ret = perf_trace_event_enable(event);
break;
}
}
mutex_unlock(&event_mutex);
return ret;
}
static void perf_trace_event_disable(struct ftrace_event_call *event)
{
char *buf, *nmi_buf;
if (--event->perf_refcount > 0)
return;
event->perf_event_disable(event);
if (!--total_ref_count) {
buf = perf_trace_buf;
rcu_assign_pointer(perf_trace_buf, NULL);
nmi_buf = perf_trace_buf_nmi;
rcu_assign_pointer(perf_trace_buf_nmi, NULL);
/*
* Ensure every events in profiling have finished before
* releasing the buffers
*/
synchronize_sched();
free_percpu(buf);
free_percpu(nmi_buf);
}
}
void perf_trace_disable(int event_id)
{
struct ftrace_event_call *event;
mutex_lock(&event_mutex);
list_for_each_entry(event, &ftrace_events, list) {
if (event->id == event_id) {
perf_trace_event_disable(event);
module_put(event->mod);
break;
}
}
mutex_unlock(&event_mutex);
}
__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
int *rctxp, unsigned long *irq_flags)
{
struct trace_entry *entry;
char *trace_buf, *raw_data;
int pc, cpu;
pc = preempt_count();
/* Protect the per cpu buffer, begin the rcu read side */
local_irq_save(*irq_flags);
*rctxp = perf_swevent_get_recursion_context();
if (*rctxp < 0)
goto err_recursion;
cpu = smp_processor_id();
if (in_nmi())
trace_buf = rcu_dereference(perf_trace_buf_nmi);
else
trace_buf = rcu_dereference(perf_trace_buf);
if (!trace_buf)
goto err;
raw_data = per_cpu_ptr(trace_buf, cpu);
/* zero the dead bytes from align to not leak stack to user */
*(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
entry = (struct trace_entry *)raw_data;
tracing_generic_entry_update(entry, *irq_flags, pc);
entry->type = type;
return raw_data;
err:
perf_swevent_put_recursion_context(*rctxp);
err_recursion:
local_irq_restore(*irq_flags);
return NULL;
}
EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
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