2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 #include <linux/stacktrace.h>
6 #include <linux/kallsyms.h>
7 #include <linux/seq_file.h>
8 #include <linux/spinlock.h>
9 #include <linux/uaccess.h>
10 #include <linux/debugfs.h>
11 #include <linux/ftrace.h>
12 #include <linux/module.h>
13 #include <linux/sysctl.h>
14 #include <linux/init.h>
17 #include <asm/setup.h>
21 #define STACK_TRACE_ENTRIES 500
23 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
24 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
25 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
27 static struct stack_trace max_stack_trace = {
28 .max_entries = STACK_TRACE_ENTRIES,
29 .entries = stack_dump_trace,
32 static unsigned long max_stack_size;
33 static arch_spinlock_t max_stack_lock =
34 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
36 static int stack_trace_disabled __read_mostly;
37 static DEFINE_PER_CPU(int, trace_active);
38 static DEFINE_MUTEX(stack_sysctl_mutex);
40 int stack_tracer_enabled;
41 static int last_stack_tracer_enabled;
43 static inline void check_stack(void)
45 unsigned long this_size, flags;
46 unsigned long *p, *top, *start;
49 this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
50 this_size = THREAD_SIZE - this_size;
52 if (this_size <= max_stack_size)
55 /* we do not handle interrupt stacks yet */
56 if (!object_is_on_stack(&this_size))
59 local_irq_save(flags);
60 arch_spin_lock(&max_stack_lock);
62 /* a race could have already updated it */
63 if (this_size <= max_stack_size)
66 max_stack_size = this_size;
68 max_stack_trace.nr_entries = 0;
69 max_stack_trace.skip = 3;
71 save_stack_trace(&max_stack_trace);
74 * Now find where in the stack these are.
78 top = (unsigned long *)
79 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
82 * Loop through all the entries. One of the entries may
83 * for some reason be missed on the stack, so we may
84 * have to account for them. If they are all there, this
85 * loop will only happen once. This code only takes place
86 * on a new max, so it is far from a fast path.
88 while (i < max_stack_trace.nr_entries) {
91 stack_dump_index[i] = this_size;
94 for (; p < top && i < max_stack_trace.nr_entries; p++) {
95 if (*p == stack_dump_trace[i]) {
96 this_size = stack_dump_index[i++] =
97 (top - p) * sizeof(unsigned long);
99 /* Start the search from here */
109 arch_spin_unlock(&max_stack_lock);
110 local_irq_restore(flags);
114 stack_trace_call(unsigned long ip, unsigned long parent_ip,
115 struct ftrace_ops *op, struct pt_regs *pt_regs)
119 if (unlikely(!ftrace_enabled || stack_trace_disabled))
122 preempt_disable_notrace();
124 cpu = raw_smp_processor_id();
125 /* no atomic needed, we only modify this variable by this cpu */
126 if (per_cpu(trace_active, cpu)++ != 0)
132 per_cpu(trace_active, cpu)--;
133 /* prevent recursion in schedule */
134 preempt_enable_notrace();
137 static struct ftrace_ops trace_ops __read_mostly =
139 .func = stack_trace_call,
140 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
144 stack_max_size_read(struct file *filp, char __user *ubuf,
145 size_t count, loff_t *ppos)
147 unsigned long *ptr = filp->private_data;
151 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
154 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
158 stack_max_size_write(struct file *filp, const char __user *ubuf,
159 size_t count, loff_t *ppos)
161 long *ptr = filp->private_data;
162 unsigned long val, flags;
166 ret = kstrtoul_from_user(ubuf, count, 10, &val);
170 local_irq_save(flags);
173 * In case we trace inside arch_spin_lock() or after (NMI),
174 * we will cause circular lock, so we also need to increase
175 * the percpu trace_active here.
177 cpu = smp_processor_id();
178 per_cpu(trace_active, cpu)++;
180 arch_spin_lock(&max_stack_lock);
182 arch_spin_unlock(&max_stack_lock);
184 per_cpu(trace_active, cpu)--;
185 local_irq_restore(flags);
190 static const struct file_operations stack_max_size_fops = {
191 .open = tracing_open_generic,
192 .read = stack_max_size_read,
193 .write = stack_max_size_write,
194 .llseek = default_llseek,
198 __next(struct seq_file *m, loff_t *pos)
202 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
205 m->private = (void *)n;
210 t_next(struct seq_file *m, void *v, loff_t *pos)
213 return __next(m, pos);
216 static void *t_start(struct seq_file *m, loff_t *pos)
222 cpu = smp_processor_id();
223 per_cpu(trace_active, cpu)++;
225 arch_spin_lock(&max_stack_lock);
228 return SEQ_START_TOKEN;
230 return __next(m, pos);
233 static void t_stop(struct seq_file *m, void *p)
237 arch_spin_unlock(&max_stack_lock);
239 cpu = smp_processor_id();
240 per_cpu(trace_active, cpu)--;
245 static int trace_lookup_stack(struct seq_file *m, long i)
247 unsigned long addr = stack_dump_trace[i];
249 return seq_printf(m, "%pS\n", (void *)addr);
252 static void print_disabled(struct seq_file *m)
255 "# Stack tracer disabled\n"
257 "# To enable the stack tracer, either add 'stacktrace' to the\n"
258 "# kernel command line\n"
259 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
263 static int t_show(struct seq_file *m, void *v)
268 if (v == SEQ_START_TOKEN) {
269 seq_printf(m, " Depth Size Location"
271 " ----- ---- --------\n",
272 max_stack_trace.nr_entries - 1);
274 if (!stack_tracer_enabled && !max_stack_size)
282 if (i >= max_stack_trace.nr_entries ||
283 stack_dump_trace[i] == ULONG_MAX)
286 if (i+1 == max_stack_trace.nr_entries ||
287 stack_dump_trace[i+1] == ULONG_MAX)
288 size = stack_dump_index[i];
290 size = stack_dump_index[i] - stack_dump_index[i+1];
292 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
294 trace_lookup_stack(m, i);
299 static const struct seq_operations stack_trace_seq_ops = {
306 static int stack_trace_open(struct inode *inode, struct file *file)
308 return seq_open(file, &stack_trace_seq_ops);
311 static const struct file_operations stack_trace_fops = {
312 .open = stack_trace_open,
315 .release = seq_release,
319 stack_trace_filter_open(struct inode *inode, struct file *file)
321 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
325 static const struct file_operations stack_trace_filter_fops = {
326 .open = stack_trace_filter_open,
328 .write = ftrace_filter_write,
329 .llseek = ftrace_regex_lseek,
330 .release = ftrace_regex_release,
334 stack_trace_sysctl(struct ctl_table *table, int write,
335 void __user *buffer, size_t *lenp,
340 mutex_lock(&stack_sysctl_mutex);
342 ret = proc_dointvec(table, write, buffer, lenp, ppos);
345 (last_stack_tracer_enabled == !!stack_tracer_enabled))
348 last_stack_tracer_enabled = !!stack_tracer_enabled;
350 if (stack_tracer_enabled)
351 register_ftrace_function(&trace_ops);
353 unregister_ftrace_function(&trace_ops);
356 mutex_unlock(&stack_sysctl_mutex);
360 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
362 static __init int enable_stacktrace(char *str)
364 if (strncmp(str, "_filter=", 8) == 0)
365 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
367 stack_tracer_enabled = 1;
368 last_stack_tracer_enabled = 1;
371 __setup("stacktrace", enable_stacktrace);
373 static __init int stack_trace_init(void)
375 struct dentry *d_tracer;
377 d_tracer = tracing_init_dentry();
379 trace_create_file("stack_max_size", 0644, d_tracer,
380 &max_stack_size, &stack_max_size_fops);
382 trace_create_file("stack_trace", 0444, d_tracer,
383 NULL, &stack_trace_fops);
385 trace_create_file("stack_trace_filter", 0444, d_tracer,
386 NULL, &stack_trace_filter_fops);
388 if (stack_trace_filter_buf[0])
389 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
391 if (stack_tracer_enabled)
392 register_ftrace_function(&trace_ops);
397 device_initcall(stack_trace_init);