Release 4.15 kernel/trace/trace_stack.c

// 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]);
	}
}

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/*
 * 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);
}

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2.07%
1
5.26%
Yang Shi
6
1.38%
1
5.26%
Aaron Tomlin
5
1.15%
2
10.53%
Thomas Gleixner
2
0.46%
1
5.26%
Mark Rutland
1
0.23%
1
5.26%
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435
100.00%
19
100.00%


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();
}

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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);
}

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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;
}

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3
2.91%
1
12.50%
Thomas Gleixner
2
1.94%
1
12.50%
Total
103
100.00%
8
100.00%


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;
}

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1
1.72%
1
20.00%
Total
58
100.00%
5
100.00%


static void *

t_next(struct seq_file *m, void *v, loff_t *pos)
{
	(*pos)++;
	return __next(m, pos);
}

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34
100.00%
2
100.00%



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);
}

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31.25%
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11.11%
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10
20.83%
1
11.11%
Lai Jiangshan
3
6.25%
1
11.11%
Thomas Gleixner
1
2.08%
1
11.11%
Total
48
100.00%
9
100.00%



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();
}

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1
3.45%
1
16.67%
Total
29
100.00%
6
100.00%



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);
}

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1
2.78%
1
25.00%
Total
36
100.00%
4
100.00%



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");
}

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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;
}

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8
5.26%
1
16.67%
Total
152
100.00%
6
100.00%


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);
}

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2
100.00%


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);
}

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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;
}

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100.00%
2
100.00%


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;
}
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__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", 0444, 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;
}

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72.73%
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6.48%
1
9.09%
Frédéric Weisbecker
2
1.85%
1
9.09%
AKASHI Takahiro
1
0.93%
1
9.09%
Total
108
100.00%
11
100.00%


device_initcall(stack_trace_init);
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55.77%
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6.37%
1
1.92%
Li Zefan
54
2.99%
3
5.77%
AKASHI Takahiro
36
1.99%
1
1.92%
Liming Wang
22
1.22%
1
1.92%
Lai Jiangshan
12
0.66%
1
1.92%
Thomas Gleixner
9
0.50%
3
5.77%
Namhyung Kim
7
0.39%
1
1.92%
Yang Shi
6
0.33%
1
1.92%
Aaron Tomlin
5
0.28%
2
3.85%
Arnd Bergmann
5
0.28%
1
1.92%
Peter Hüwe
3
0.17%
1
1.92%
Ingo Molnar
3
0.17%
1
1.92%
Joe Perches
2
0.11%
1
1.92%
Frédéric Weisbecker
2
0.11%
1
1.92%
Anton Blanchard
1
0.06%
1
1.92%
Greg Kroah-Hartman
1
0.06%
1
1.92%
Masahiro Yamada
1
0.06%
1
1.92%
Mark Rutland
1
0.06%
1
1.92%
Total
1806
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52
100.00%
Directory: kernel/trace

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