/*
   * 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 "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)
  {

  	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_GLOBAL,

  };
  
  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
  ", *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
  ", (void *)addr);

  }

  static void print_disabled(struct seq_file *m)
  {
  	seq_puts(m, "#
  "
  		 "#  Stack tracer disabled
  "
  		 "#
  "
  		 "# To enable the stack tracer, either add 'stacktrace' to the
  "
  		 "# kernel command line
  "
  		 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'
  "
  		 "#
  ");
  }

  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)
  "

  			   "        -----    ----   --------
  ",

  			   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,

  };

  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 __init int enable_stacktrace(char *str)
  {

  	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);

  	if (stack_tracer_enabled)

  		register_ftrace_function(&trace_ops);

  
  	return 0;
  }
  
  device_initcall(stack_trace_init);