projects/linux·blob 8fe3ccae · refs

491 lines · 10.9 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
38static DEFINE_PER_CPU(int, trace_active);
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 local_irq_save(flags);
100 arch_spin_lock(&stack_trace_max_lock);
101
102 /*
103 * RCU may not be watching, make it see us.
104 * The stack trace code uses rcu_sched.
105 */
106 rcu_irq_enter();
107
108 /* In case another CPU set the tracer_frame on us */
109 if (unlikely(!frame_size))
110 this_size -= tracer_frame;
111
112 /* a race could have already updated it */
113 if (this_size <= stack_trace_max_size)
114 goto out;
115
116 stack_trace_max_size = this_size;
117
118 stack_trace_max.nr_entries = 0;
119 stack_trace_max.skip = 3;
120
121 save_stack_trace(&stack_trace_max);
122
123 /* Skip over the overhead of the stack tracer itself */
124 for (i = 0; i < stack_trace_max.nr_entries; i++) {
125 if (stack_dump_trace[i] == ip)
126 break;
127 }
128
129 /*
130 * Some archs may not have the passed in ip in the dump.
131 * If that happens, we need to show everything.
132 */
133 if (i == stack_trace_max.nr_entries)
134 i = 0;
135
136 /*
137 * Now find where in the stack these are.
138 */
139 x = 0;
140 start = stack;
141 top = (unsigned long *)
142 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
143
144 /*
145 * Loop through all the entries. One of the entries may
146 * for some reason be missed on the stack, so we may
147 * have to account for them. If they are all there, this
148 * loop will only happen once. This code only takes place
149 * on a new max, so it is far from a fast path.
150 */
151 while (i < stack_trace_max.nr_entries) {
152 int found = 0;
153
154 stack_trace_index[x] = this_size;
155 p = start;
156
157 for (; p < top && i < stack_trace_max.nr_entries; p++) {
158 if (stack_dump_trace[i] == ULONG_MAX)
159 break;
160 /*
161 * The READ_ONCE_NOCHECK is used to let KASAN know that
162 * this is not a stack-out-of-bounds error.
163 */
164 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
165 stack_dump_trace[x] = stack_dump_trace[i++];
166 this_size = stack_trace_index[x++] =
167 (top - p) * sizeof(unsigned long);
168 found = 1;
169 /* Start the search from here */
170 start = p + 1;
171 /*
172 * We do not want to show the overhead
173 * of the stack tracer stack in the
174 * max stack. If we haven't figured
175 * out what that is, then figure it out
176 * now.
177 */
178 if (unlikely(!tracer_frame)) {
179 tracer_frame = (p - stack) *
180 sizeof(unsigned long);
181 stack_trace_max_size -= tracer_frame;
182 }
183 }
184 }
185
186 if (!found)
187 i++;
188 }
189
190 stack_trace_max.nr_entries = x;
191 for (; x < i; x++)
192 stack_dump_trace[x] = ULONG_MAX;
193
194 if (task_stack_end_corrupted(current)) {
195 stack_trace_print();
196 BUG();
197 }
198
199 out:
200 rcu_irq_exit();
201 arch_spin_unlock(&stack_trace_max_lock);
202 local_irq_restore(flags);
203}
204
205static void
206stack_trace_call(unsigned long ip, unsigned long parent_ip,
207 struct ftrace_ops *op, struct pt_regs *pt_regs)
208{
209 unsigned long stack;
210 int cpu;
211
212 preempt_disable_notrace();
213
214 cpu = raw_smp_processor_id();
215 /* no atomic needed, we only modify this variable by this cpu */
216 if (per_cpu(trace_active, cpu)++ != 0)
217 goto out;
218
219 ip += MCOUNT_INSN_SIZE;
220
221 check_stack(ip, &stack);
222
223 out:
224 per_cpu(trace_active, cpu)--;
225 /* prevent recursion in schedule */
226 preempt_enable_notrace();
227}
228
229static struct ftrace_ops trace_ops __read_mostly =
230{
231 .func = stack_trace_call,
232 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
233};
234
235static ssize_t
236stack_max_size_read(struct file *filp, char __user *ubuf,
237 size_t count, loff_t *ppos)
238{
239 unsigned long *ptr = filp->private_data;
240 char buf[64];
241 int r;
242
243 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
244 if (r > sizeof(buf))
245 r = sizeof(buf);
246 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
247}
248
249static ssize_t
250stack_max_size_write(struct file *filp, const char __user *ubuf,
251 size_t count, loff_t *ppos)
252{
253 long *ptr = filp->private_data;
254 unsigned long val, flags;
255 int ret;
256 int cpu;
257
258 ret = kstrtoul_from_user(ubuf, count, 10, &val);
259 if (ret)
260 return ret;
261
262 local_irq_save(flags);
263
264 /*
265 * In case we trace inside arch_spin_lock() or after (NMI),
266 * we will cause circular lock, so we also need to increase
267 * the percpu trace_active here.
268 */
269 cpu = smp_processor_id();
270 per_cpu(trace_active, cpu)++;
271
272 arch_spin_lock(&stack_trace_max_lock);
273 *ptr = val;
274 arch_spin_unlock(&stack_trace_max_lock);
275
276 per_cpu(trace_active, cpu)--;
277 local_irq_restore(flags);
278
279 return count;
280}
281
282static const struct file_operations stack_max_size_fops = {
283 .open = tracing_open_generic,
284 .read = stack_max_size_read,
285 .write = stack_max_size_write,
286 .llseek = default_llseek,
287};
288
289static void *
290__next(struct seq_file *m, loff_t *pos)
291{
292 long n = *pos - 1;
293
294 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
295 return NULL;
296
297 m->private = (void *)n;
298 return &m->private;
299}
300
301static void *
302t_next(struct seq_file *m, void *v, loff_t *pos)
303{
304 (*pos)++;
305 return __next(m, pos);
306}
307
308static void *t_start(struct seq_file *m, loff_t *pos)
309{
310 int cpu;
311
312 local_irq_disable();
313
314 cpu = smp_processor_id();
315 per_cpu(trace_active, cpu)++;
316
317 arch_spin_lock(&stack_trace_max_lock);
318
319 if (*pos == 0)
320 return SEQ_START_TOKEN;
321
322 return __next(m, pos);
323}
324
325static void t_stop(struct seq_file *m, void *p)
326{
327 int cpu;
328
329 arch_spin_unlock(&stack_trace_max_lock);
330
331 cpu = smp_processor_id();
332 per_cpu(trace_active, cpu)--;
333
334 local_irq_enable();
335}
336
337static void trace_lookup_stack(struct seq_file *m, long i)
338{
339 unsigned long addr = stack_dump_trace[i];
340
341 seq_printf(m, "%pS\n", (void *)addr);
342}
343
344static void print_disabled(struct seq_file *m)
345{
346 seq_puts(m, "#\n"
347 "# Stack tracer disabled\n"
348 "#\n"
349 "# To enable the stack tracer, either add 'stacktrace' to the\n"
350 "# kernel command line\n"
351 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
352 "#\n");
353}
354
355static int t_show(struct seq_file *m, void *v)
356{
357 long i;
358 int size;
359
360 if (v == SEQ_START_TOKEN) {
361 seq_printf(m, " Depth Size Location"
362 " (%d entries)\n"
363 " ----- ---- --------\n",
364 stack_trace_max.nr_entries);
365
366 if (!stack_tracer_enabled && !stack_trace_max_size)
367 print_disabled(m);
368
369 return 0;
370 }
371
372 i = *(long *)v;
373
374 if (i >= stack_trace_max.nr_entries ||
375 stack_dump_trace[i] == ULONG_MAX)
376 return 0;
377
378 if (i+1 == stack_trace_max.nr_entries ||
379 stack_dump_trace[i+1] == ULONG_MAX)
380 size = stack_trace_index[i];
381 else
382 size = stack_trace_index[i] - stack_trace_index[i+1];
383
384 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
385
386 trace_lookup_stack(m, i);
387
388 return 0;
389}
390
391static const struct seq_operations stack_trace_seq_ops = {
392 .start = t_start,
393 .next = t_next,
394 .stop = t_stop,
395 .show = t_show,
396};
397
398static int stack_trace_open(struct inode *inode, struct file *file)
399{
400 return seq_open(file, &stack_trace_seq_ops);
401}
402
403static const struct file_operations stack_trace_fops = {
404 .open = stack_trace_open,
405 .read = seq_read,
406 .llseek = seq_lseek,
407 .release = seq_release,
408};
409
410static int
411stack_trace_filter_open(struct inode *inode, struct file *file)
412{
413 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
414 inode, file);
415}
416
417static const struct file_operations stack_trace_filter_fops = {
418 .open = stack_trace_filter_open,
419 .read = seq_read,
420 .write = ftrace_filter_write,
421 .llseek = tracing_lseek,
422 .release = ftrace_regex_release,
423};
424
425int
426stack_trace_sysctl(struct ctl_table *table, int write,
427 void __user *buffer, size_t *lenp,
428 loff_t *ppos)
429{
430 int ret;
431
432 mutex_lock(&stack_sysctl_mutex);
433
434 ret = proc_dointvec(table, write, buffer, lenp, ppos);
435
436 if (ret || !write ||
437 (last_stack_tracer_enabled == !!stack_tracer_enabled))
438 goto out;
439
440 last_stack_tracer_enabled = !!stack_tracer_enabled;
441
442 if (stack_tracer_enabled)
443 register_ftrace_function(&trace_ops);
444 else
445 unregister_ftrace_function(&trace_ops);
446
447 out:
448 mutex_unlock(&stack_sysctl_mutex);
449 return ret;
450}
451
452static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
453
454static __init int enable_stacktrace(char *str)
455{
456 if (strncmp(str, "_filter=", 8) == 0)
457 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
458
459 stack_tracer_enabled = 1;
460 last_stack_tracer_enabled = 1;
461 return 1;
462}
463__setup("stacktrace", enable_stacktrace);
464
465static __init int stack_trace_init(void)
466{
467 struct dentry *d_tracer;
468
469 d_tracer = tracing_init_dentry();
470 if (IS_ERR(d_tracer))
471 return 0;
472
473 trace_create_file("stack_max_size", 0644, d_tracer,
474 &stack_trace_max_size, &stack_max_size_fops);
475
476 trace_create_file("stack_trace", 0444, d_tracer,
477 NULL, &stack_trace_fops);
478
479 trace_create_file("stack_trace_filter", 0444, d_tracer,
480 NULL, &stack_trace_filter_fops);
481
482 if (stack_trace_filter_buf[0])
483 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
484
485 if (stack_tracer_enabled)
486 register_ftrace_function(&trace_ops);
487
488 return 0;
489}
490
491device_initcall(stack_trace_init);