/*

* 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/sysctl.h>

#include <linux/init.h>

#include <linux/fs.h>

#include <asm/setup.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 arch_spinlock_t max_stack_lock =

(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

static int stack_trace_disabled __read_mostly;

static DEFINE_PER_CPU(int, trace_active);

static DEFINE_MUTEX(stack_sysctl_mutex);

int stack_tracer_enabled;

static int last_stack_tracer_enabled;

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;

local_irq_save(flags);

arch_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) {

int found = 0;

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);

found = 1;

/* Start the search from here */

start = p + 1;

}

}

if (!found)

i++;

}

out:

arch_spin_unlock(&max_stack_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)

{

int cpu;

if (unlikely(!ftrace_enabled || stack_trace_disabled))

return;

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 */

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;

int cpu;

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 trace_active here.

*/

cpu = smp_processor_id();

per_cpu(trace_active, cpu)++;

arch_spin_lock(&max_stack_lock);

*ptr = val;

arch_spin_unlock(&max_stack_lock);

per_cpu(trace_active, cpu)--;

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 >= max_stack_trace.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)

{

int cpu;

local_irq_disable();

cpu = smp_processor_id();

per_cpu(trace_active, cpu)++;

arch_spin_lock(&max_stack_lock);

if (*pos == 0)

return SEQ_START_TOKEN;

return __next(m, pos);

}

static void t_stop(struct seq_file *m, void *p)

{

int cpu;

arch_spin_unlock(&max_stack_lock);

cpu = smp_processor_id();

per_cpu(trace_active, cpu)--;

local_irq_enable();

}

static int trace_lookup_stack(struct seq_file *m, long i)

{

unsigned long addr = stack_dump_trace[i];

return 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",

max_stack_trace.nr_entries - 1);

if (!stack_tracer_enabled && !max_stack_size)

print_disabled(m);

return 0;

}

i = *(long *)v;

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 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,

};

static int

stack_trace_filter_open(struct inode *inode, struct file *file)

{

return ftrace_regex_open(&trace_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 = ftrace_regex_lseek,

.release = ftrace_regex_release,

};

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();

trace_create_file("stack_max_size", 0644, d_tracer,

&max_stack_size, &stack_max_size_fops);

trace_create_file("stack_trace", 0444, d_tracer,

NULL, &stack_trace_fops);

trace_create_file("stack_trace_filter", 0444, d_tracer,

NULL, &stack_trace_filter_fops);

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);