projects/linux·blob 243bfd2c · refs

490 lines · 11.0 KiB

1/*
2 * Copyright (C) 2008 Steven Rostedt <[email protected]>
3 *
4 */
5#include <linux/sched/task_stack.h>
6#include <linux/stacktrace.h>
7#include <linux/kallsyms.h>
8#include <linux/seq_file.h>
9#include <linux/spinlock.h>
10#include <linux/uaccess.h>
11#include <linux/ftrace.h>
12#include <linux/module.h>
13#include <linux/sysctl.h>
14#include <linux/init.h>
15
16#include <asm/setup.h>
17
18#include "trace.h"
19
20static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
21 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
22unsigned stack_trace_index[STACK_TRACE_ENTRIES];
23
24/*
25 * Reserve one entry for the passed in ip. This will allow
26 * us to remove most or all of the stack size overhead
27 * added by the stack tracer itself.
28 */
29struct stack_trace stack_trace_max = {
30 .max_entries = STACK_TRACE_ENTRIES - 1,
31 .entries = &stack_dump_trace[0],
32};
33
34unsigned long stack_trace_max_size;
35arch_spinlock_t stack_trace_max_lock =
36 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
37
38DEFINE_PER_CPU(int, disable_stack_tracer);
39static DEFINE_MUTEX(stack_sysctl_mutex);
40
41int stack_tracer_enabled;
42static int last_stack_tracer_enabled;
43
44void stack_trace_print(void)
45{
46 long i;
47 int size;
48
49 pr_emerg(" Depth Size Location (%d entries)\n"
50 " ----- ---- --------\n",
51 stack_trace_max.nr_entries);
52
53 for (i = 0; i < stack_trace_max.nr_entries; i++) {
54 if (stack_dump_trace[i] == ULONG_MAX)
55 break;
56 if (i+1 == stack_trace_max.nr_entries ||
57 stack_dump_trace[i+1] == ULONG_MAX)
58 size = stack_trace_index[i];
59 else
60 size = stack_trace_index[i] - stack_trace_index[i+1];
61
62 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
63 size, (void *)stack_dump_trace[i]);
64 }
65}
66
67/*
68 * When arch-specific code overrides this function, the following
69 * data should be filled up, assuming stack_trace_max_lock is held to
70 * prevent concurrent updates.
71 * stack_trace_index[]
72 * stack_trace_max
73 * stack_trace_max_size
74 */
75void __weak
76check_stack(unsigned long ip, unsigned long *stack)
77{
78 unsigned long this_size, flags; unsigned long *p, *top, *start;
79 static int tracer_frame;
80 int frame_size = ACCESS_ONCE(tracer_frame);
81 int i, x;
82
83 this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
84 this_size = THREAD_SIZE - this_size;
85 /* Remove the frame of the tracer */
86 this_size -= frame_size;
87
88 if (this_size <= stack_trace_max_size)
89 return;
90
91 /* we do not handle interrupt stacks yet */
92 if (!object_is_on_stack(stack))
93 return;
94
95 /* Can't do this from NMI context (can cause deadlocks) */
96 if (in_nmi())
97 return;
98
99 /*
100 * There's a slight chance that we are tracing inside the
101 * RCU infrastructure, and rcu_irq_enter() will not work
102 * as expected.
103 */
104 if (unlikely(rcu_irq_enter_disabled()))
105 return;
106
107 local_irq_save(flags);
108 arch_spin_lock(&stack_trace_max_lock);
109
110 /*
111 * RCU may not be watching, make it see us.
112 * The stack trace code uses rcu_sched.
113 */
114 rcu_irq_enter();
115
116 /* In case another CPU set the tracer_frame on us */
117 if (unlikely(!frame_size))
118 this_size -= tracer_frame;
119
120 /* a race could have already updated it */
121 if (this_size <= stack_trace_max_size)
122 goto out;
123
124 stack_trace_max_size = this_size;
125
126 stack_trace_max.nr_entries = 0;
127 stack_trace_max.skip = 3;
128
129 save_stack_trace(&stack_trace_max);
130
131 /* Skip over the overhead of the stack tracer itself */
132 for (i = 0; i < stack_trace_max.nr_entries; i++) {
133 if (stack_dump_trace[i] == ip)
134 break;
135 }
136
137 /*
138 * Some archs may not have the passed in ip in the dump.
139 * If that happens, we need to show everything.
140 */
141 if (i == stack_trace_max.nr_entries)
142 i = 0;
143
144 /*
145 * Now find where in the stack these are.
146 */
147 x = 0;
148 start = stack;
149 top = (unsigned long *)
150 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
151
152 /*
153 * Loop through all the entries. One of the entries may
154 * for some reason be missed on the stack, so we may
155 * have to account for them. If they are all there, this
156 * loop will only happen once. This code only takes place
157 * on a new max, so it is far from a fast path.
158 */
159 while (i < stack_trace_max.nr_entries) {
160 int found = 0;
161
162 stack_trace_index[x] = this_size;
163 p = start;
164
165 for (; p < top && i < stack_trace_max.nr_entries; p++) {
166 if (stack_dump_trace[i] == ULONG_MAX)
167 break;
168 /*
169 * The READ_ONCE_NOCHECK is used to let KASAN know that
170 * this is not a stack-out-of-bounds error.
171 */
172 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
173 stack_dump_trace[x] = stack_dump_trace[i++];
174 this_size = stack_trace_index[x++] =
175 (top - p) * sizeof(unsigned long);
176 found = 1;
177 /* Start the search from here */
178 start = p + 1;
179 /*
180 * We do not want to show the overhead
181 * of the stack tracer stack in the
182 * max stack. If we haven't figured
183 * out what that is, then figure it out
184 * now.
185 */
186 if (unlikely(!tracer_frame)) {
187 tracer_frame = (p - stack) *
188 sizeof(unsigned long);
189 stack_trace_max_size -= tracer_frame;
190 }
191 }
192 }
193
194 if (!found)
195 i++;
196 }
197
198 stack_trace_max.nr_entries = x;
199 for (; x < i; x++)
200 stack_dump_trace[x] = ULONG_MAX;
201
202 if (task_stack_end_corrupted(current)) {
203 stack_trace_print();
204 BUG();
205 }
206
207 out:
208 rcu_irq_exit();
209 arch_spin_unlock(&stack_trace_max_lock);
210 local_irq_restore(flags);
211}
212
213static void
214stack_trace_call(unsigned long ip, unsigned long parent_ip,
215 struct ftrace_ops *op, struct pt_regs *pt_regs)
216{
217 unsigned long stack;
218
219 preempt_disable_notrace();
220
221 /* no atomic needed, we only modify this variable by this cpu */
222 __this_cpu_inc(disable_stack_tracer);
223 if (__this_cpu_read(disable_stack_tracer) != 1)
224 goto out;
225
226 ip += MCOUNT_INSN_SIZE;
227
228 check_stack(ip, &stack);
229
230 out:
231 __this_cpu_dec(disable_stack_tracer);
232 /* prevent recursion in schedule */
233 preempt_enable_notrace();
234}
235
236static struct ftrace_ops trace_ops __read_mostly =
237{
238 .func = stack_trace_call,
239 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
240};
241
242static ssize_t
243stack_max_size_read(struct file *filp, char __user *ubuf,
244 size_t count, loff_t *ppos)
245{
246 unsigned long *ptr = filp->private_data;
247 char buf[64];
248 int r;
249
250 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
251 if (r > sizeof(buf))
252 r = sizeof(buf);
253 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
254}
255
256static ssize_t
257stack_max_size_write(struct file *filp, const char __user *ubuf,
258 size_t count, loff_t *ppos)
259{
260 long *ptr = filp->private_data;
261 unsigned long val, flags;
262 int ret;
263
264 ret = kstrtoul_from_user(ubuf, count, 10, &val);
265 if (ret)
266 return ret;
267
268 local_irq_save(flags);
269
270 /*
271 * In case we trace inside arch_spin_lock() or after (NMI),
272 * we will cause circular lock, so we also need to increase
273 * the percpu disable_stack_tracer here.
274 */
275 __this_cpu_inc(disable_stack_tracer);
276
277 arch_spin_lock(&stack_trace_max_lock);
278 *ptr = val;
279 arch_spin_unlock(&stack_trace_max_lock);
280
281 __this_cpu_dec(disable_stack_tracer);
282 local_irq_restore(flags);
283
284 return count;
285}
286
287static const struct file_operations stack_max_size_fops = {
288 .open = tracing_open_generic,
289 .read = stack_max_size_read,
290 .write = stack_max_size_write,
291 .llseek = default_llseek,
292};
293
294static void *
295__next(struct seq_file *m, loff_t *pos)
296{
297 long n = *pos - 1;
298
299 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
300 return NULL;
301
302 m->private = (void *)n;
303 return &m->private;
304}
305
306static void *
307t_next(struct seq_file *m, void *v, loff_t *pos)
308{
309 (*pos)++;
310 return __next(m, pos);
311}
312
313static void *t_start(struct seq_file *m, loff_t *pos)
314{
315 local_irq_disable();
316
317 __this_cpu_inc(disable_stack_tracer);
318
319 arch_spin_lock(&stack_trace_max_lock);
320
321 if (*pos == 0)
322 return SEQ_START_TOKEN;
323
324 return __next(m, pos);
325}
326
327static void t_stop(struct seq_file *m, void *p)
328{
329 arch_spin_unlock(&stack_trace_max_lock);
330
331 __this_cpu_dec(disable_stack_tracer);
332
333 local_irq_enable();
334}
335
336static void trace_lookup_stack(struct seq_file *m, long i)
337{
338 unsigned long addr = stack_dump_trace[i];
339
340 seq_printf(m, "%pS\n", (void *)addr);
341}
342
343static void print_disabled(struct seq_file *m)
344{
345 seq_puts(m, "#\n"
346 "# Stack tracer disabled\n"
347 "#\n"
348 "# To enable the stack tracer, either add 'stacktrace' to the\n"
349 "# kernel command line\n"
350 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
351 "#\n");
352}
353
354static int t_show(struct seq_file *m, void *v)
355{
356 long i;
357 int size;
358
359 if (v == SEQ_START_TOKEN) {
360 seq_printf(m, " Depth Size Location"
361 " (%d entries)\n"
362 " ----- ---- --------\n",
363 stack_trace_max.nr_entries);
364
365 if (!stack_tracer_enabled && !stack_trace_max_size)
366 print_disabled(m);
367
368 return 0;
369 }
370
371 i = *(long *)v;
372
373 if (i >= stack_trace_max.nr_entries ||
374 stack_dump_trace[i] == ULONG_MAX)
375 return 0;
376
377 if (i+1 == stack_trace_max.nr_entries ||
378 stack_dump_trace[i+1] == ULONG_MAX)
379 size = stack_trace_index[i];
380 else
381 size = stack_trace_index[i] - stack_trace_index[i+1];
382
383 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
384
385 trace_lookup_stack(m, i);
386
387 return 0;
388}
389
390static const struct seq_operations stack_trace_seq_ops = {
391 .start = t_start,
392 .next = t_next,
393 .stop = t_stop,
394 .show = t_show,
395};
396
397static int stack_trace_open(struct inode *inode, struct file *file)
398{
399 return seq_open(file, &stack_trace_seq_ops);
400}
401
402static const struct file_operations stack_trace_fops = {
403 .open = stack_trace_open,
404 .read = seq_read,
405 .llseek = seq_lseek,
406 .release = seq_release,
407};
408
409static int
410stack_trace_filter_open(struct inode *inode, struct file *file)
411{
412 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
413 inode, file);
414}
415
416static const struct file_operations stack_trace_filter_fops = {
417 .open = stack_trace_filter_open,
418 .read = seq_read,
419 .write = ftrace_filter_write,
420 .llseek = tracing_lseek,
421 .release = ftrace_regex_release,
422};
423
424int
425stack_trace_sysctl(struct ctl_table *table, int write,
426 void __user *buffer, size_t *lenp,
427 loff_t *ppos)
428{
429 int ret;
430
431 mutex_lock(&stack_sysctl_mutex);
432
433 ret = proc_dointvec(table, write, buffer, lenp, ppos);
434
435 if (ret || !write ||
436 (last_stack_tracer_enabled == !!stack_tracer_enabled))
437 goto out;
438
439 last_stack_tracer_enabled = !!stack_tracer_enabled;
440
441 if (stack_tracer_enabled)
442 register_ftrace_function(&trace_ops);
443 else
444 unregister_ftrace_function(&trace_ops);
445
446 out:
447 mutex_unlock(&stack_sysctl_mutex);
448 return ret;
449}
450
451static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
452
453static __init int enable_stacktrace(char *str)
454{
455 if (strncmp(str, "_filter=", 8) == 0)
456 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
457
458 stack_tracer_enabled = 1;
459 last_stack_tracer_enabled = 1;
460 return 1;
461}
462__setup("stacktrace", enable_stacktrace);
463
464static __init int stack_trace_init(void)
465{
466 struct dentry *d_tracer;
467
468 d_tracer = tracing_init_dentry();
469 if (IS_ERR(d_tracer))
470 return 0;
471
472 trace_create_file("stack_max_size", 0644, d_tracer,
473 &stack_trace_max_size, &stack_max_size_fops);
474
475 trace_create_file("stack_trace", 0444, d_tracer,
476 NULL, &stack_trace_fops);
477
478 trace_create_file("stack_trace_filter", 0444, d_tracer,
479 NULL, &stack_trace_filter_fops);
480
481 if (stack_trace_filter_buf[0])
482 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
483
484 if (stack_tracer_enabled)
485 register_ftrace_function(&trace_ops);
486
487 return 0;
488}
489
490device_initcall(stack_trace_init);