kernel-ark/kernel/trace/trace_stack.c
Steven Rostedt 81520a1b06 ftrace: stack tracer only record when on stack
The stack trace API does not record if the stack is not on the current
task's stack. That is, if the stack is the interrupt stack or NMI stack,
the output does not show. Also, the size of those stacks are not
consistent with the size of the thread stack, this makes the calculation
of the stack size usually bogus.

This all confuses the stack tracer. I unfortunately do not have time to
fix all these problems, but this patch does record the worst stack when
the stack pointer is on the tasks stack (instead of bogus numbers).

The patch simply returns if the stack pointer is not on the task's stack.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-20 18:31:37 +02:00

315 lines
6.5 KiB
C

/*
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*
*/
#include <linux/stacktrace.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include "trace.h"
#define STACK_TRACE_ENTRIES 500
static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
{ [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
static struct stack_trace max_stack_trace = {
.max_entries = STACK_TRACE_ENTRIES,
.entries = stack_dump_trace,
};
static unsigned long max_stack_size;
static raw_spinlock_t max_stack_lock =
(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
static int stack_trace_disabled __read_mostly;
static DEFINE_PER_CPU(int, trace_active);
static inline void check_stack(void)
{
unsigned long this_size, flags;
unsigned long *p, *top, *start;
int i;
this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
this_size = THREAD_SIZE - this_size;
if (this_size <= max_stack_size)
return;
/* we do not handle interrupt stacks yet */
if (!object_is_on_stack(&this_size))
return;
raw_local_irq_save(flags);
__raw_spin_lock(&max_stack_lock);
/* a race could have already updated it */
if (this_size <= max_stack_size)
goto out;
max_stack_size = this_size;
max_stack_trace.nr_entries = 0;
max_stack_trace.skip = 3;
save_stack_trace(&max_stack_trace);
/*
* Now find where in the stack these are.
*/
i = 0;
start = &this_size;
top = (unsigned long *)
(((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
/*
* Loop through all the entries. One of the entries may
* for some reason be missed on the stack, so we may
* have to account for them. If they are all there, this
* loop will only happen once. This code only takes place
* on a new max, so it is far from a fast path.
*/
while (i < max_stack_trace.nr_entries) {
stack_dump_index[i] = this_size;
p = start;
for (; p < top && i < max_stack_trace.nr_entries; p++) {
if (*p == stack_dump_trace[i]) {
this_size = stack_dump_index[i++] =
(top - p) * sizeof(unsigned long);
/* Start the search from here */
start = p + 1;
}
}
i++;
}
out:
__raw_spin_unlock(&max_stack_lock);
raw_local_irq_restore(flags);
}
static void
stack_trace_call(unsigned long ip, unsigned long parent_ip)
{
int cpu, resched;
if (unlikely(!ftrace_enabled || stack_trace_disabled))
return;
resched = need_resched();
preempt_disable_notrace();
cpu = raw_smp_processor_id();
/* no atomic needed, we only modify this variable by this cpu */
if (per_cpu(trace_active, cpu)++ != 0)
goto out;
check_stack();
out:
per_cpu(trace_active, cpu)--;
/* prevent recursion in schedule */
if (resched)
preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
}
static struct ftrace_ops trace_ops __read_mostly =
{
.func = stack_trace_call,
};
static ssize_t
stack_max_size_read(struct file *filp, char __user *ubuf,
size_t count, loff_t *ppos)
{
unsigned long *ptr = filp->private_data;
char buf[64];
int r;
r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
if (r > sizeof(buf))
r = sizeof(buf);
return simple_read_from_buffer(ubuf, count, ppos, buf, r);
}
static ssize_t
stack_max_size_write(struct file *filp, const char __user *ubuf,
size_t count, loff_t *ppos)
{
long *ptr = filp->private_data;
unsigned long val, flags;
char buf[64];
int ret;
if (count >= sizeof(buf))
return -EINVAL;
if (copy_from_user(&buf, ubuf, count))
return -EFAULT;
buf[count] = 0;
ret = strict_strtoul(buf, 10, &val);
if (ret < 0)
return ret;
raw_local_irq_save(flags);
__raw_spin_lock(&max_stack_lock);
*ptr = val;
__raw_spin_unlock(&max_stack_lock);
raw_local_irq_restore(flags);
return count;
}
static struct file_operations stack_max_size_fops = {
.open = tracing_open_generic,
.read = stack_max_size_read,
.write = stack_max_size_write,
};
static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
long i = (long)m->private;
(*pos)++;
i++;
if (i >= max_stack_trace.nr_entries ||
stack_dump_trace[i] == ULONG_MAX)
return NULL;
m->private = (void *)i;
return &m->private;
}
static void *t_start(struct seq_file *m, loff_t *pos)
{
void *t = &m->private;
loff_t l = 0;
local_irq_disable();
__raw_spin_lock(&max_stack_lock);
for (; t && l < *pos; t = t_next(m, t, &l))
;
return t;
}
static void t_stop(struct seq_file *m, void *p)
{
__raw_spin_unlock(&max_stack_lock);
local_irq_enable();
}
static int trace_lookup_stack(struct seq_file *m, long i)
{
unsigned long addr = stack_dump_trace[i];
#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
sprint_symbol(str, addr);
return seq_printf(m, "%s\n", str);
#else
return seq_printf(m, "%p\n", (void*)addr);
#endif
}
static int t_show(struct seq_file *m, void *v)
{
long i = *(long *)v;
int size;
if (i < 0) {
seq_printf(m, " Depth Size Location"
" (%d entries)\n"
" ----- ---- --------\n",
max_stack_trace.nr_entries);
return 0;
}
if (i >= max_stack_trace.nr_entries ||
stack_dump_trace[i] == ULONG_MAX)
return 0;
if (i+1 == max_stack_trace.nr_entries ||
stack_dump_trace[i+1] == ULONG_MAX)
size = stack_dump_index[i];
else
size = stack_dump_index[i] - stack_dump_index[i+1];
seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
trace_lookup_stack(m, i);
return 0;
}
static struct seq_operations stack_trace_seq_ops = {
.start = t_start,
.next = t_next,
.stop = t_stop,
.show = t_show,
};
static int stack_trace_open(struct inode *inode, struct file *file)
{
int ret;
ret = seq_open(file, &stack_trace_seq_ops);
if (!ret) {
struct seq_file *m = file->private_data;
m->private = (void *)-1;
}
return ret;
}
static struct file_operations stack_trace_fops = {
.open = stack_trace_open,
.read = seq_read,
.llseek = seq_lseek,
};
static __init int stack_trace_init(void)
{
struct dentry *d_tracer;
struct dentry *entry;
d_tracer = tracing_init_dentry();
entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
&max_stack_size, &stack_max_size_fops);
if (!entry)
pr_warning("Could not create debugfs 'stack_max_size' entry\n");
entry = debugfs_create_file("stack_trace", 0444, d_tracer,
NULL, &stack_trace_fops);
if (!entry)
pr_warning("Could not create debugfs 'stack_trace' entry\n");
register_ftrace_function(&trace_ops);
return 0;
}
device_initcall(stack_trace_init);