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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"
EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
static char *perf_trace_buf[4];
/*
* Force it to be aligned to unsigned long to avoid misaligned accesses
* suprises
*/
typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
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, void *data)
{
int ret = -ENOMEM;
if (event->perf_refcount++ > 0) {
event->perf_data = NULL;
return 0;
}
if (!total_ref_count) {
char *buf;
int i;
for (i = 0; i < 4; i++) {
buf = (char *)alloc_percpu(perf_trace_t);
if (!buf)
goto fail_buf;
rcu_assign_pointer(perf_trace_buf[i], buf);
}
}
ret = event->perf_event_enable(event);
if (!ret) {
event->perf_data = data;
total_ref_count++;
return 0;
}
fail_buf:
if (!total_ref_count) {
int i;
for (i = 0; i < 4; i++) {
free_percpu(perf_trace_buf[i]);
perf_trace_buf[i] = NULL;
}
}
event->perf_refcount--;
return ret;
}
int perf_trace_enable(int event_id, void *data)
{
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, data);
break;
}
}
mutex_unlock(&event_mutex);
return ret;
}
static void perf_trace_event_disable(struct ftrace_event_call *event)
{
if (--event->perf_refcount > 0)
return;
event->perf_event_disable(event);
if (!--total_ref_count) {
char *buf[4];
int i;
for (i = 0; i < 4; i++) {
buf[i] = perf_trace_buf[i];
rcu_assign_pointer(perf_trace_buf[i], NULL);
}
/*
* Ensure every events in profiling have finished before
* releasing the buffers
*/
synchronize_sched();
for (i = 0; i < 4; i++)
free_percpu(buf[i]);
}
}
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,
struct pt_regs *regs, int *rctxp)
{
struct trace_entry *entry;
char *trace_buf, *raw_data;
int pc;
BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
pc = preempt_count();
*rctxp = perf_swevent_get_recursion_context();
if (*rctxp < 0)
goto err_recursion;
trace_buf = rcu_dereference_sched(perf_trace_buf[*rctxp]);
if (!trace_buf)
goto err;
raw_data = per_cpu_ptr(trace_buf, smp_processor_id());
/* zero the dead bytes from align to not leak stack to user */
memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
entry = (struct trace_entry *)raw_data;
tracing_generic_entry_update(entry, regs->flags, pc);
entry->type = type;
return raw_data;
err:
perf_swevent_put_recursion_context(*rctxp);
err_recursion:
return NULL;
}
EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
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