projects/linux·blob da89fb16 · refs

395 lines · 8.3 KiB

1/*
2 * Copyright (C) 2008 Steven Rostedt <[email protected]>
3 *
4 */
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>
15#include <linux/fs.h>
16
17#include <asm/setup.h>
18
19#include "trace.h"
20
21#define STACK_TRACE_ENTRIES 500
22
23static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
24 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
25static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
26
27static struct stack_trace max_stack_trace = {
28 .max_entries = STACK_TRACE_ENTRIES,
29 .entries = stack_dump_trace,
30};
31
32static unsigned long max_stack_size;
33static arch_spinlock_t max_stack_lock =
34 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
35
36static int stack_trace_disabled __read_mostly;
37static DEFINE_PER_CPU(int, trace_active);
38static DEFINE_MUTEX(stack_sysctl_mutex);
39
40int stack_tracer_enabled;
41static int last_stack_tracer_enabled;
42
43static inline void check_stack(void)
44{
45 unsigned long this_size, flags;
46 unsigned long *p, *top, *start;
47 int i;
48
49 this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
50 this_size = THREAD_SIZE - this_size;
51
52 if (this_size <= max_stack_size)
53 return;
54
55 /* we do not handle interrupt stacks yet */
56 if (!object_is_on_stack(&this_size))
57 return;
58
59 local_irq_save(flags);
60 arch_spin_lock(&max_stack_lock);
61
62 /* a race could have already updated it */
63 if (this_size <= max_stack_size)
64 goto out;
65
66 max_stack_size = this_size;
67
68 max_stack_trace.nr_entries = 0;
69 max_stack_trace.skip = 3;
70
71 save_stack_trace(&max_stack_trace);
72
73 /*
74 * Now find where in the stack these are.
75 */
76 i = 0;
77 start = &this_size;
78 top = (unsigned long *)
79 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
80
81 /*
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.
87 */
88 while (i < max_stack_trace.nr_entries) {
89 int found = 0;
90
91 stack_dump_index[i] = this_size;
92 p = start;
93
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);
98 found = 1;
99 /* Start the search from here */
100 start = p + 1;
101 }
102 }
103
104 if (!found)
105 i++;
106 }
107
108 out:
109 arch_spin_unlock(&max_stack_lock);
110 local_irq_restore(flags);
111}
112
113static void
114stack_trace_call(unsigned long ip, unsigned long parent_ip)
115{
116 int cpu;
117
118 if (unlikely(!ftrace_enabled || stack_trace_disabled))
119 return;
120
121 preempt_disable_notrace();
122
123 cpu = raw_smp_processor_id();
124 /* no atomic needed, we only modify this variable by this cpu */
125 if (per_cpu(trace_active, cpu)++ != 0)
126 goto out;
127
128 check_stack();
129
130 out:
131 per_cpu(trace_active, cpu)--;
132 /* prevent recursion in schedule */
133 preempt_enable_notrace();
134}
135
136static struct ftrace_ops trace_ops __read_mostly =
137{
138 .func = stack_trace_call,
139};
140
141static ssize_t
142stack_max_size_read(struct file *filp, char __user *ubuf,
143 size_t count, loff_t *ppos)
144{
145 unsigned long *ptr = filp->private_data;
146 char buf[64];
147 int r;
148
149 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
150 if (r > sizeof(buf))
151 r = sizeof(buf);
152 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
153}
154
155static ssize_t
156stack_max_size_write(struct file *filp, const char __user *ubuf,
157 size_t count, loff_t *ppos)
158{
159 long *ptr = filp->private_data;
160 unsigned long val, flags;
161 int ret;
162 int cpu;
163
164 ret = kstrtoul_from_user(ubuf, count, 10, &val);
165 if (ret)
166 return ret;
167
168 local_irq_save(flags);
169
170 /*
171 * In case we trace inside arch_spin_lock() or after (NMI),
172 * we will cause circular lock, so we also need to increase
173 * the percpu trace_active here.
174 */
175 cpu = smp_processor_id();
176 per_cpu(trace_active, cpu)++;
177
178 arch_spin_lock(&max_stack_lock);
179 *ptr = val;
180 arch_spin_unlock(&max_stack_lock);
181
182 per_cpu(trace_active, cpu)--;
183 local_irq_restore(flags);
184
185 return count;
186}
187
188static const struct file_operations stack_max_size_fops = {
189 .open = tracing_open_generic,
190 .read = stack_max_size_read,
191 .write = stack_max_size_write,
192 .llseek = default_llseek,
193};
194
195static void *
196__next(struct seq_file *m, loff_t *pos)
197{
198 long n = *pos - 1;
199
200 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
201 return NULL;
202
203 m->private = (void *)n;
204 return &m->private;
205}
206
207static void *
208t_next(struct seq_file *m, void *v, loff_t *pos)
209{
210 (*pos)++;
211 return __next(m, pos);
212}
213
214static void *t_start(struct seq_file *m, loff_t *pos)
215{
216 int cpu;
217
218 local_irq_disable();
219
220 cpu = smp_processor_id();
221 per_cpu(trace_active, cpu)++;
222
223 arch_spin_lock(&max_stack_lock);
224
225 if (*pos == 0)
226 return SEQ_START_TOKEN;
227
228 return __next(m, pos);
229}
230
231static void t_stop(struct seq_file *m, void *p)
232{
233 int cpu;
234
235 arch_spin_unlock(&max_stack_lock);
236
237 cpu = smp_processor_id();
238 per_cpu(trace_active, cpu)--;
239
240 local_irq_enable();
241}
242
243static int trace_lookup_stack(struct seq_file *m, long i)
244{
245 unsigned long addr = stack_dump_trace[i];
246
247 return seq_printf(m, "%pS\n", (void *)addr);
248}
249
250static void print_disabled(struct seq_file *m)
251{
252 seq_puts(m, "#\n"
253 "# Stack tracer disabled\n"
254 "#\n"
255 "# To enable the stack tracer, either add 'stacktrace' to the\n"
256 "# kernel command line\n"
257 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
258 "#\n");
259}
260
261static int t_show(struct seq_file *m, void *v)
262{
263 long i;
264 int size;
265
266 if (v == SEQ_START_TOKEN) {
267 seq_printf(m, " Depth Size Location"
268 " (%d entries)\n"
269 " ----- ---- --------\n",
270 max_stack_trace.nr_entries - 1);
271
272 if (!stack_tracer_enabled && !max_stack_size)
273 print_disabled(m);
274
275 return 0;
276 }
277
278 i = *(long *)v;
279
280 if (i >= max_stack_trace.nr_entries ||
281 stack_dump_trace[i] == ULONG_MAX)
282 return 0;
283
284 if (i+1 == max_stack_trace.nr_entries ||
285 stack_dump_trace[i+1] == ULONG_MAX)
286 size = stack_dump_index[i];
287 else
288 size = stack_dump_index[i] - stack_dump_index[i+1];
289
290 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
291
292 trace_lookup_stack(m, i);
293
294 return 0;
295}
296
297static const struct seq_operations stack_trace_seq_ops = {
298 .start = t_start,
299 .next = t_next,
300 .stop = t_stop,
301 .show = t_show,
302};
303
304static int stack_trace_open(struct inode *inode, struct file *file)
305{
306 return seq_open(file, &stack_trace_seq_ops);
307}
308
309static const struct file_operations stack_trace_fops = {
310 .open = stack_trace_open,
311 .read = seq_read,
312 .llseek = seq_lseek,
313 .release = seq_release,
314};
315
316static int
317stack_trace_filter_open(struct inode *inode, struct file *file)
318{
319 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
320 inode, file);
321}
322
323static const struct file_operations stack_trace_filter_fops = {
324 .open = stack_trace_filter_open,
325 .read = seq_read,
326 .write = ftrace_filter_write,
327 .llseek = ftrace_regex_lseek,
328 .release = ftrace_regex_release,
329};
330
331int
332stack_trace_sysctl(struct ctl_table *table, int write,
333 void __user *buffer, size_t *lenp,
334 loff_t *ppos)
335{
336 int ret;
337
338 mutex_lock(&stack_sysctl_mutex);
339
340 ret = proc_dointvec(table, write, buffer, lenp, ppos);
341
342 if (ret || !write ||
343 (last_stack_tracer_enabled == !!stack_tracer_enabled))
344 goto out;
345
346 last_stack_tracer_enabled = !!stack_tracer_enabled;
347
348 if (stack_tracer_enabled)
349 register_ftrace_function(&trace_ops);
350 else
351 unregister_ftrace_function(&trace_ops);
352
353 out:
354 mutex_unlock(&stack_sysctl_mutex);
355 return ret;
356}
357
358static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
359
360static __init int enable_stacktrace(char *str)
361{
362 if (strncmp(str, "_filter=", 8) == 0)
363 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
364
365 stack_tracer_enabled = 1;
366 last_stack_tracer_enabled = 1;
367 return 1;
368}
369__setup("stacktrace", enable_stacktrace);
370
371static __init int stack_trace_init(void)
372{
373 struct dentry *d_tracer;
374
375 d_tracer = tracing_init_dentry();
376
377 trace_create_file("stack_max_size", 0644, d_tracer,
378 &max_stack_size, &stack_max_size_fops);
379
380 trace_create_file("stack_trace", 0444, d_tracer,
381 NULL, &stack_trace_fops);
382
383 trace_create_file("stack_trace_filter", 0444, d_tracer,
384 NULL, &stack_trace_filter_fops);
385
386 if (stack_trace_filter_buf[0])
387 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
388
389 if (stack_tracer_enabled)
390 register_ftrace_function(&trace_ops);
391
392 return 0;
393}
394
395device_initcall(stack_trace_init);