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/*
* trace stack traces
*
* Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
* Copyright (C) 2004, 2005, Soeren Sandmann
*/
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/hrtimer.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/irq.h>
#include <linux/fs.h>
#include "trace.h"
static struct trace_array *sysprof_trace;
static int __read_mostly tracer_enabled;
/*
* 10 msecs for now:
*/
static const unsigned long sample_period = 1000000;
static const unsigned int sample_max_depth = 512;
/*
* Per CPU hrtimers that do the profiling:
*/
static DEFINE_PER_CPU(struct hrtimer, stack_trace_hrtimer);
struct stack_frame {
const void __user *next_fp;
unsigned long return_address;
};
static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
{
int ret;
if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
return 0;
ret = 1;
pagefault_disable();
if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
ret = 0;
pagefault_enable();
return ret;
}
static void timer_notify(struct pt_regs *regs, int cpu)
{
struct trace_array_cpu *data;
struct stack_frame frame;
struct trace_array *tr;
const void __user *fp;
int is_user;
int i;
if (!regs)
return;
tr = sysprof_trace;
data = tr->data[cpu];
is_user = user_mode(regs);
if (!current || current->pid == 0)
return;
if (is_user && current->state != TASK_RUNNING)
return;
if (!is_user) {
/* kernel */
ftrace(tr, data, current->pid, 1, 0);
return;
}
trace_special(tr, data, 0, current->pid, regs->ip);
fp = (void __user *)regs->bp;
for (i = 0; i < sample_max_depth; i++) {
frame.next_fp = 0;
frame.return_address = 0;
if (!copy_stack_frame(fp, &frame))
break;
if ((unsigned long)fp < regs->sp)
break;
trace_special(tr, data, 1, frame.return_address,
(unsigned long)fp);
fp = frame.next_fp;
}
trace_special(tr, data, 2, current->pid, i);
/*
* Special trace entry if we overflow the max depth:
*/
if (i == sample_max_depth)
trace_special(tr, data, -1, -1, -1);
}
static enum hrtimer_restart stack_trace_timer_fn(struct hrtimer *hrtimer)
{
/* trace here */
timer_notify(get_irq_regs(), smp_processor_id());
hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
return HRTIMER_RESTART;
}
static void start_stack_timer(int cpu)
{
struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);
hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hrtimer->function = stack_trace_timer_fn;
hrtimer->cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL);
}
static void start_stack_timers(void)
{
cpumask_t saved_mask = current->cpus_allowed;
int cpu;
for_each_online_cpu(cpu) {
set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
start_stack_timer(cpu);
}
set_cpus_allowed_ptr(current, &saved_mask);
}
static void stop_stack_timer(int cpu)
{
struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);
hrtimer_cancel(hrtimer);
}
static void stop_stack_timers(void)
{
int cpu;
for_each_online_cpu(cpu)
stop_stack_timer(cpu);
}
static notrace void stack_reset(struct trace_array *tr)
{
int cpu;
tr->time_start = ftrace_now(tr->cpu);
for_each_online_cpu(cpu)
tracing_reset(tr->data[cpu]);
}
static notrace void start_stack_trace(struct trace_array *tr)
{
stack_reset(tr);
start_stack_timers();
tracer_enabled = 1;
}
static notrace void stop_stack_trace(struct trace_array *tr)
{
stop_stack_timers();
tracer_enabled = 0;
}
static notrace void stack_trace_init(struct trace_array *tr)
{
sysprof_trace = tr;
if (tr->ctrl)
start_stack_trace(tr);
}
static notrace void stack_trace_reset(struct trace_array *tr)
{
if (tr->ctrl)
stop_stack_trace(tr);
}
static void stack_trace_ctrl_update(struct trace_array *tr)
{
/* When starting a new trace, reset the buffers */
if (tr->ctrl)
start_stack_trace(tr);
else
stop_stack_trace(tr);
}
static struct tracer stack_trace __read_mostly =
{
.name = "sysprof",
.init = stack_trace_init,
.reset = stack_trace_reset,
.ctrl_update = stack_trace_ctrl_update,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_sysprof,
#endif
};
__init static int init_stack_trace(void)
{
return register_tracer(&stack_trace);
}
device_initcall(init_stack_trace);
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