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488 lines (386 loc) · 11 KB
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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*
*/
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/init.h>
#include <asm/setup.h>
#include "trace.h"
static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
{ [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
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.
*/
struct stack_trace stack_trace_max = {
.max_entries = STACK_TRACE_ENTRIES - 1,
.entries = &stack_dump_trace[0],
};
unsigned long stack_trace_max_size;
arch_spinlock_t stack_trace_max_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
DEFINE_PER_CPU(int, disable_stack_tracer);
static DEFINE_MUTEX(stack_sysctl_mutex);
int stack_tracer_enabled;
static int last_stack_tracer_enabled;
void stack_trace_print(void)
{
long i;
int size;
pr_emerg(" Depth Size Location (%d entries)\n"
" ----- ---- --------\n",
stack_trace_max.nr_entries);
for (i = 0; i < stack_trace_max.nr_entries; i++) {
if (stack_dump_trace[i] == ULONG_MAX)
break;
if (i+1 == stack_trace_max.nr_entries ||
stack_dump_trace[i+1] == ULONG_MAX)
size = stack_trace_index[i];
else
size = stack_trace_index[i] - stack_trace_index[i+1];
pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
size, (void *)stack_dump_trace[i]);
}
}
/*
* When arch-specific code overrides this function, the following
* data should be filled up, assuming stack_trace_max_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;
static int tracer_frame;
int frame_size = READ_ONCE(tracer_frame);
int i, x;
this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
this_size = THREAD_SIZE - this_size;
/* Remove the frame of the tracer */
this_size -= frame_size;
if (this_size <= stack_trace_max_size)
return;
/* we do not handle interrupt stacks yet */
if (!object_is_on_stack(stack))
return;
/* Can't do this from NMI context (can cause deadlocks) */
if (in_nmi())
return;
local_irq_save(flags);
arch_spin_lock(&stack_trace_max_lock);
/* In case another CPU set the tracer_frame on us */
if (unlikely(!frame_size))
this_size -= tracer_frame;
/* a race could have already updated it */
if (this_size <= stack_trace_max_size)
goto out;
stack_trace_max_size = this_size;
stack_trace_max.nr_entries = 0;
stack_trace_max.skip = 3;
save_stack_trace(&stack_trace_max);
/* Skip over the overhead of the stack tracer itself */
for (i = 0; i < stack_trace_max.nr_entries; i++) {
if (stack_dump_trace[i] == ip)
break;
}
/*
* Some archs may not have the passed in ip in the dump.
* If that happens, we need to show everything.
*/
if (i == stack_trace_max.nr_entries)
i = 0;
/*
* Now find where in the stack these are.
*/
x = 0;
start = stack;
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 < stack_trace_max.nr_entries) {
int found = 0;
stack_trace_index[x] = this_size;
p = start;
for (; p < top && i < stack_trace_max.nr_entries; p++) {
if (stack_dump_trace[i] == ULONG_MAX)
break;
/*
* The READ_ONCE_NOCHECK is used to let KASAN know that
* this is not a stack-out-of-bounds error.
*/
if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
stack_dump_trace[x] = stack_dump_trace[i++];
this_size = stack_trace_index[x++] =
(top - p) * sizeof(unsigned long);
found = 1;
/* Start the search from here */
start = p + 1;
/*
* We do not want to show the overhead
* of the stack tracer stack in the
* max stack. If we haven't figured
* out what that is, then figure it out
* now.
*/
if (unlikely(!tracer_frame)) {
tracer_frame = (p - stack) *
sizeof(unsigned long);
stack_trace_max_size -= tracer_frame;
}
}
}
if (!found)
i++;
}
stack_trace_max.nr_entries = x;
for (; x < i; x++)
stack_dump_trace[x] = ULONG_MAX;
if (task_stack_end_corrupted(current)) {
stack_trace_print();
BUG();
}
out:
arch_spin_unlock(&stack_trace_max_lock);
local_irq_restore(flags);
}
static void
stack_trace_call(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *pt_regs)
{
unsigned long stack;
preempt_disable_notrace();
/* no atomic needed, we only modify this variable by this cpu */
__this_cpu_inc(disable_stack_tracer);
if (__this_cpu_read(disable_stack_tracer) != 1)
goto out;
/* If rcu is not watching, then save stack trace can fail */
if (!rcu_is_watching())
goto out;
ip += MCOUNT_INSN_SIZE;
check_stack(ip, &stack);
out:
__this_cpu_dec(disable_stack_tracer);
/* prevent recursion in schedule */
preempt_enable_notrace();
}
static struct ftrace_ops trace_ops __read_mostly =
{
.func = stack_trace_call,
.flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
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;
int ret;
ret = kstrtoul_from_user(ubuf, count, 10, &val);
if (ret)
return ret;
local_irq_save(flags);
/*
* In case we trace inside arch_spin_lock() or after (NMI),
* we will cause circular lock, so we also need to increase
* the percpu disable_stack_tracer here.
*/
__this_cpu_inc(disable_stack_tracer);
arch_spin_lock(&stack_trace_max_lock);
*ptr = val;
arch_spin_unlock(&stack_trace_max_lock);
__this_cpu_dec(disable_stack_tracer);
local_irq_restore(flags);
return count;
}
static const struct file_operations stack_max_size_fops = {
.open = tracing_open_generic,
.read = stack_max_size_read,
.write = stack_max_size_write,
.llseek = default_llseek,
};
static void *
__next(struct seq_file *m, loff_t *pos)
{
long n = *pos - 1;
if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
return NULL;
m->private = (void *)n;
return &m->private;
}
static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
(*pos)++;
return __next(m, pos);
}
static void *t_start(struct seq_file *m, loff_t *pos)
{
local_irq_disable();
__this_cpu_inc(disable_stack_tracer);
arch_spin_lock(&stack_trace_max_lock);
if (*pos == 0)
return SEQ_START_TOKEN;
return __next(m, pos);
}
static void t_stop(struct seq_file *m, void *p)
{
arch_spin_unlock(&stack_trace_max_lock);
__this_cpu_dec(disable_stack_tracer);
local_irq_enable();
}
static void trace_lookup_stack(struct seq_file *m, long i)
{
unsigned long addr = stack_dump_trace[i];
seq_printf(m, "%pS\n", (void *)addr);
}
static void print_disabled(struct seq_file *m)
{
seq_puts(m, "#\n"
"# Stack tracer disabled\n"
"#\n"
"# To enable the stack tracer, either add 'stacktrace' to the\n"
"# kernel command line\n"
"# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
"#\n");
}
static int t_show(struct seq_file *m, void *v)
{
long i;
int size;
if (v == SEQ_START_TOKEN) {
seq_printf(m, " Depth Size Location"
" (%d entries)\n"
" ----- ---- --------\n",
stack_trace_max.nr_entries);
if (!stack_tracer_enabled && !stack_trace_max_size)
print_disabled(m);
return 0;
}
i = *(long *)v;
if (i >= stack_trace_max.nr_entries ||
stack_dump_trace[i] == ULONG_MAX)
return 0;
if (i+1 == stack_trace_max.nr_entries ||
stack_dump_trace[i+1] == ULONG_MAX)
size = stack_trace_index[i];
else
size = stack_trace_index[i] - stack_trace_index[i+1];
seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
trace_lookup_stack(m, i);
return 0;
}
static const 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)
{
return seq_open(file, &stack_trace_seq_ops);
}
static const struct file_operations stack_trace_fops = {
.open = stack_trace_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
#ifdef CONFIG_DYNAMIC_FTRACE
static int
stack_trace_filter_open(struct inode *inode, struct file *file)
{
struct ftrace_ops *ops = inode->i_private;
return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
inode, file);
}
static const struct file_operations stack_trace_filter_fops = {
.open = stack_trace_filter_open,
.read = seq_read,
.write = ftrace_filter_write,
.llseek = tracing_lseek,
.release = ftrace_regex_release,
};
#endif /* CONFIG_DYNAMIC_FTRACE */
int
stack_trace_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
int ret;
mutex_lock(&stack_sysctl_mutex);
ret = proc_dointvec(table, write, buffer, lenp, ppos);
if (ret || !write ||
(last_stack_tracer_enabled == !!stack_tracer_enabled))
goto out;
last_stack_tracer_enabled = !!stack_tracer_enabled;
if (stack_tracer_enabled)
register_ftrace_function(&trace_ops);
else
unregister_ftrace_function(&trace_ops);
out:
mutex_unlock(&stack_sysctl_mutex);
return ret;
}
static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
static __init int enable_stacktrace(char *str)
{
if (strncmp(str, "_filter=", 8) == 0)
strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
stack_tracer_enabled = 1;
last_stack_tracer_enabled = 1;
return 1;
}
__setup("stacktrace", enable_stacktrace);
static __init int stack_trace_init(void)
{
struct dentry *d_tracer;
d_tracer = tracing_init_dentry();
if (IS_ERR(d_tracer))
return 0;
trace_create_file("stack_max_size", 0644, d_tracer,
&stack_trace_max_size, &stack_max_size_fops);
trace_create_file("stack_trace", 0444, d_tracer,
NULL, &stack_trace_fops);
#ifdef CONFIG_DYNAMIC_FTRACE
trace_create_file("stack_trace_filter", 0644, d_tracer,
&trace_ops, &stack_trace_filter_fops);
#endif
if (stack_trace_filter_buf[0])
ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
if (stack_tracer_enabled)
register_ftrace_function(&trace_ops);
return 0;
}
device_initcall(stack_trace_init);
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