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tracing: Allow arch-specific stack tracer 

A stack frame may be used in a different way depending on cpu architecture.
Thus it is not always appropriate to slurp the stack contents, as current
check_stack() does, in order to calcurate a stack index (height) at a given
function call. At least not on arm64.
In addition, there is a possibility that we will mistakenly detect a stale
stack frame which has not been overwritten.

This patch makes check_stack() a weak function so as to later implement
arch-specific version.

Link: http://lkml.kernel.org/r/1446182741-31019-5-git-send-email-takahiro.akashi@linaro.org

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
AKASHI Takahiro 2015-10-30 14:25:39 +09:00 committed by Steven Rostedt
parent 2ee8a74f2a
commit bb99d8ccec
2 changed files with 54 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/ftrace.h
View File

@ -263,7 +263,18 @@ static inline void ftrace_kill(void) { }
#endif /* CONFIG_FUNCTION_TRACER */
#ifdef CONFIG_STACK_TRACER
#define STACK_TRACE_ENTRIES 500
struct stack_trace;
extern unsigned stack_trace_index[];
extern struct stack_trace stack_trace_max;
extern unsigned long stack_trace_max_size;
extern arch_spinlock_t max_stack_lock;
extern int stack_tracer_enabled;
void stack_trace_print(void);
int
stack_trace_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,

80
kernel/trace/trace_stack.c
View File

@ -16,24 +16,22 @@
#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];
unsigned stack_trace_index[STACK_TRACE_ENTRIES];
/*
* Reserve one entry for the passed in ip. This will allow
* us to remove most or all of the stack size overhead
* added by the stack tracer itself.
*/
static struct stack_trace max_stack_trace = {
struct stack_trace stack_trace_max = {
.max_entries = STACK_TRACE_ENTRIES - 1,
.entries = &stack_dump_trace[0],
};
static unsigned long max_stack_size;
static arch_spinlock_t max_stack_lock =
unsigned long stack_trace_max_size;
arch_spinlock_t max_stack_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
static DEFINE_PER_CPU(int, trace_active);
@ -42,30 +40,38 @@ static DEFINE_MUTEX(stack_sysctl_mutex);
int stack_tracer_enabled;
static int last_stack_tracer_enabled;
static inline void print_max_stack(void)
void stack_trace_print(void)
{
long i;
int size;
pr_emerg(" Depth Size Location (%d entries)\n"
" ----- ---- --------\n",
max_stack_trace.nr_entries);
stack_trace_max.nr_entries);
for (i = 0; i < max_stack_trace.nr_entries; i++) {
for (i = 0; i < stack_trace_max.nr_entries; i++) {
if (stack_dump_trace[i] == ULONG_MAX)
break;
if (i+1 == max_stack_trace.nr_entries ||
if (i+1 == stack_trace_max.nr_entries ||
stack_dump_trace[i+1] == ULONG_MAX)
size = stack_dump_index[i];
size = stack_trace_index[i];
else
size = stack_dump_index[i] - stack_dump_index[i+1];
size = stack_trace_index[i] - stack_trace_index[i+1];
pr_emerg("%3ld) %8d %5d %pS\n", i, stack_dump_index[i],
pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
size, (void *)stack_dump_trace[i]);
}
}
static inline void
/*
* When arch-specific code overides this function, the following
* data should be filled up, assuming max_stack_lock is held to
* prevent concurrent updates.
* stack_trace_index[]
* stack_trace_max
* stack_trace_max_size
*/
void __weak
check_stack(unsigned long ip, unsigned long *stack)
{
unsigned long this_size, flags; unsigned long *p, *top, *start;
@ -78,7 +84,7 @@ check_stack(unsigned long ip, unsigned long *stack)
/* Remove the frame of the tracer */
this_size -= frame_size;
if (this_size <= max_stack_size)
if (this_size <= stack_trace_max_size)
return;
/* we do not handle interrupt stacks yet */
@ -93,18 +99,18 @@ check_stack(unsigned long ip, unsigned long *stack)
this_size -= tracer_frame;
/* a race could have already updated it */
if (this_size <= max_stack_size)
if (this_size <= stack_trace_max_size)
goto out;
max_stack_size = this_size;
stack_trace_max_size = this_size;
max_stack_trace.nr_entries = 0;
max_stack_trace.skip = 3;
stack_trace_max.nr_entries = 0;
stack_trace_max.skip = 3;
save_stack_trace(&max_stack_trace);
save_stack_trace(&stack_trace_max);
/* Skip over the overhead of the stack tracer itself */
for (i = 0; i < max_stack_trace.nr_entries; i++) {
for (i = 0; i < stack_trace_max.nr_entries; i++) {
if (stack_dump_trace[i] == ip)
break;
}
@ -124,18 +130,18 @@ check_stack(unsigned long ip, unsigned long *stack)
* 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) {
while (i < stack_trace_max.nr_entries) {
int found = 0;
stack_dump_index[x] = this_size;
stack_trace_index[x] = this_size;
p = start;
for (; p < top && i < max_stack_trace.nr_entries; p++) {
for (; p < top && i < stack_trace_max.nr_entries; p++) {
if (stack_dump_trace[i] == ULONG_MAX)
break;
if (*p == stack_dump_trace[i]) {
stack_dump_trace[x] = stack_dump_trace[i++];
this_size = stack_dump_index[x++] =
this_size = stack_trace_index[x++] =
(top - p) * sizeof(unsigned long);
found = 1;
/* Start the search from here */
@ -150,7 +156,7 @@ check_stack(unsigned long ip, unsigned long *stack)
if (unlikely(!tracer_frame)) {
tracer_frame = (p - stack) *
sizeof(unsigned long);
max_stack_size -= tracer_frame;
stack_trace_max_size -= tracer_frame;
}
}
}
@ -159,12 +165,12 @@ check_stack(unsigned long ip, unsigned long *stack)
i++;
}
max_stack_trace.nr_entries = x;
stack_trace_max.nr_entries = x;
for (; x < i; x++)
stack_dump_trace[x] = ULONG_MAX;
if (task_stack_end_corrupted(current)) {
print_max_stack();
stack_trace_print();
BUG();
}
@ -262,7 +268,7 @@ __next(struct seq_file *m, loff_t *pos)
{
long n = *pos - 1;
if (n > max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
return NULL;
m->private = (void *)n;
@ -332,9 +338,9 @@ static int t_show(struct seq_file *m, void *v)
seq_printf(m, " Depth Size Location"
" (%d entries)\n"
" ----- ---- --------\n",
max_stack_trace.nr_entries);
stack_trace_max.nr_entries);
if (!stack_tracer_enabled && !max_stack_size)
if (!stack_tracer_enabled && !stack_trace_max_size)
print_disabled(m);
return 0;
@ -342,17 +348,17 @@ static int t_show(struct seq_file *m, void *v)
i = *(long *)v;
if (i >= max_stack_trace.nr_entries ||
if (i >= stack_trace_max.nr_entries ||
stack_dump_trace[i] == ULONG_MAX)
return 0;
if (i+1 == max_stack_trace.nr_entries ||
if (i+1 == stack_trace_max.nr_entries ||
stack_dump_trace[i+1] == ULONG_MAX)
size = stack_dump_index[i];
size = stack_trace_index[i];
else
size = stack_dump_index[i] - stack_dump_index[i+1];
size = stack_trace_index[i] - stack_trace_index[i+1];
seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
trace_lookup_stack(m, i);
@ -442,7 +448,7 @@ static __init int stack_trace_init(void)
return 0;
trace_create_file("stack_max_size", 0644, d_tracer,
&max_stack_size, &stack_max_size_fops);
&stack_trace_max_size, &stack_max_size_fops);
trace_create_file("stack_trace", 0444, d_tracer,
NULL, &stack_trace_fops);