trace_stack.c 6.5 KB
Newer Older
Steven Rostedt's avatar
Steven Rostedt committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 * 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/init.h>
#include <linux/fs.h>
#include "trace.h"

#define STACK_TRACE_ENTRIES 500

19 20 21 22
static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
	 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
static unsigned stack_dump_index[STACK_TRACE_ENTRIES];

Steven Rostedt's avatar
Steven Rostedt committed
23 24 25 26 27 28 29 30 31 32 33 34 35 36
static struct stack_trace max_stack_trace = {
	.max_entries		= STACK_TRACE_ENTRIES,
	.entries		= stack_dump_trace,
};

static unsigned long max_stack_size;
static raw_spinlock_t max_stack_lock =
	(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;

static int stack_trace_disabled __read_mostly;
static DEFINE_PER_CPU(int, trace_active);

static inline void check_stack(void)
{
37 38 39
	unsigned long this_size, flags;
	unsigned long *p, *top, *start;
	int i;
Steven Rostedt's avatar
Steven Rostedt committed
40 41 42 43 44 45 46

	this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
	this_size = THREAD_SIZE - this_size;

	if (this_size <= max_stack_size)
		return;

47 48 49 50
	/* we do not handle interrupt stacks yet */
	if (!object_is_on_stack(&this_size))
		return;

Steven Rostedt's avatar
Steven Rostedt committed
51 52 53 54 55 56 57 58 59 60
	raw_local_irq_save(flags);
	__raw_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;
61
	max_stack_trace.skip		= 3;
Steven Rostedt's avatar
Steven Rostedt committed
62 63 64

	save_stack_trace(&max_stack_trace);

65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96
	/*
	 * 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) {

		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);
				/* Start the search from here */
				start = p + 1;
			}
		}

		i++;
	}

Steven Rostedt's avatar
Steven Rostedt committed
97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186
 out:
	__raw_spin_unlock(&max_stack_lock);
	raw_local_irq_restore(flags);
}

static void
stack_trace_call(unsigned long ip, unsigned long parent_ip)
{
	int cpu, resched;

	if (unlikely(!ftrace_enabled || stack_trace_disabled))
		return;

	resched = need_resched();
	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 */
	if (resched)
		preempt_enable_no_resched_notrace();
	else
		preempt_enable_notrace();
}

static struct ftrace_ops trace_ops __read_mostly =
{
	.func = stack_trace_call,
};

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;
	char buf[64];
	int ret;

	if (count >= sizeof(buf))
		return -EINVAL;

	if (copy_from_user(&buf, ubuf, count))
		return -EFAULT;

	buf[count] = 0;

	ret = strict_strtoul(buf, 10, &val);
	if (ret < 0)
		return ret;

	raw_local_irq_save(flags);
	__raw_spin_lock(&max_stack_lock);
	*ptr = val;
	__raw_spin_unlock(&max_stack_lock);
	raw_local_irq_restore(flags);

	return count;
}

static struct file_operations stack_max_size_fops = {
	.open		= tracing_open_generic,
	.read		= stack_max_size_read,
	.write		= stack_max_size_write,
};

static void *
t_next(struct seq_file *m, void *v, loff_t *pos)
{
187
	long i = (long)m->private;
Steven Rostedt's avatar
Steven Rostedt committed
188 189 190

	(*pos)++;

191 192 193 194
	i++;

	if (i >= max_stack_trace.nr_entries ||
	    stack_dump_trace[i] == ULONG_MAX)
Steven Rostedt's avatar
Steven Rostedt committed
195 196
		return NULL;

197
	m->private = (void *)i;
Steven Rostedt's avatar
Steven Rostedt committed
198

199
	return &m->private;
Steven Rostedt's avatar
Steven Rostedt committed
200 201 202 203
}

static void *t_start(struct seq_file *m, loff_t *pos)
{
204
	void *t = &m->private;
Steven Rostedt's avatar
Steven Rostedt committed
205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221
	loff_t l = 0;

	local_irq_disable();
	__raw_spin_lock(&max_stack_lock);

	for (; t && l < *pos; t = t_next(m, t, &l))
		;

	return t;
}

static void t_stop(struct seq_file *m, void *p)
{
	__raw_spin_unlock(&max_stack_lock);
	local_irq_enable();
}

222
static int trace_lookup_stack(struct seq_file *m, long i)
Steven Rostedt's avatar
Steven Rostedt committed
223
{
224
	unsigned long addr = stack_dump_trace[i];
Steven Rostedt's avatar
Steven Rostedt committed
225 226 227 228 229
#ifdef CONFIG_KALLSYMS
	char str[KSYM_SYMBOL_LEN];

	sprint_symbol(str, addr);

230
	return seq_printf(m, "%s\n", str);
Steven Rostedt's avatar
Steven Rostedt committed
231 232 233 234 235 236 237
#else
	return seq_printf(m, "%p\n", (void*)addr);
#endif
}

static int t_show(struct seq_file *m, void *v)
{
238 239 240 241 242 243 244 245 246 247
	long i = *(long *)v;
	int size;

	if (i < 0) {
		seq_printf(m, "        Depth   Size      Location"
			   "    (%d entries)\n"
			   "        -----   ----      --------\n",
			   max_stack_trace.nr_entries);
		return 0;
	}
Steven Rostedt's avatar
Steven Rostedt committed
248

249 250
	if (i >= max_stack_trace.nr_entries ||
	    stack_dump_trace[i] == ULONG_MAX)
Steven Rostedt's avatar
Steven Rostedt committed
251 252
		return 0;

253 254 255 256 257 258 259 260 261
	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);
Steven Rostedt's avatar
Steven Rostedt committed
262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279

	return 0;
}

static 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)
{
	int ret;

	ret = seq_open(file, &stack_trace_seq_ops);
	if (!ret) {
		struct seq_file *m = file->private_data;
280
		m->private = (void *)-1;
Steven Rostedt's avatar
Steven Rostedt committed
281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314
	}

	return ret;
}

static struct file_operations stack_trace_fops = {
	.open		= stack_trace_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
};

static __init int stack_trace_init(void)
{
	struct dentry *d_tracer;
	struct dentry *entry;

	d_tracer = tracing_init_dentry();

	entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
				    &max_stack_size, &stack_max_size_fops);
	if (!entry)
		pr_warning("Could not create debugfs 'stack_max_size' entry\n");

	entry = debugfs_create_file("stack_trace", 0444, d_tracer,
				    NULL, &stack_trace_fops);
	if (!entry)
		pr_warning("Could not create debugfs 'stack_trace' entry\n");

	register_ftrace_function(&trace_ops);

	return 0;
}

device_initcall(stack_trace_init);