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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
4 *
5 */
6#include <linux/sched/task_stack.h>
7#include <linux/stacktrace.h>
8#include <linux/security.h>
9#include <linux/kallsyms.h>
10#include <linux/seq_file.h>
11#include <linux/spinlock.h>
12#include <linux/uaccess.h>
13#include <linux/ftrace.h>
14#include <linux/module.h>
15#include <linux/sysctl.h>
16#include <linux/init.h>
17
18#include <asm/setup.h>
19
20#include "trace.h"
21
22#define STACK_TRACE_ENTRIES 500
23
24static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];
25static unsigned stack_trace_index[STACK_TRACE_ENTRIES];
26
27static unsigned int stack_trace_nr_entries;
28static unsigned long stack_trace_max_size;
29static arch_spinlock_t stack_trace_max_lock =
30 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
31
32DEFINE_PER_CPU(int, disable_stack_tracer);
33static DEFINE_MUTEX(stack_sysctl_mutex);
34
35int stack_tracer_enabled;
36
37static void print_max_stack(void)
38{
39 long i;
40 int size;
41
42 pr_emerg(" Depth Size Location (%d entries)\n"
43 " ----- ---- --------\n",
44 stack_trace_nr_entries);
45
46 for (i = 0; i < stack_trace_nr_entries; i++) {
47 if (i + 1 == stack_trace_nr_entries)
48 size = stack_trace_index[i];
49 else
50 size = stack_trace_index[i] - stack_trace_index[i+1];
51
52 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
53 size, (void *)stack_dump_trace[i]);
54 }
55}
56
57/*
58 * The stack tracer looks for a maximum stack at each call from a function. It
59 * registers a callback from ftrace, and in that callback it examines the stack
60 * size. It determines the stack size from the variable passed in, which is the
61 * address of a local variable in the stack_trace_call() callback function.
62 * The stack size is calculated by the address of the local variable to the top
63 * of the current stack. If that size is smaller than the currently saved max
64 * stack size, nothing more is done.
65 *
66 * If the size of the stack is greater than the maximum recorded size, then the
67 * following algorithm takes place.
68 *
69 * For architectures (like x86) that store the function's return address before
70 * saving the function's local variables, the stack will look something like
71 * this:
72 *
73 * [ top of stack ]
74 * 0: sys call entry frame
75 * 10: return addr to entry code
76 * 11: start of sys_foo frame
77 * 20: return addr to sys_foo
78 * 21: start of kernel_func_bar frame
79 * 30: return addr to kernel_func_bar
80 * 31: [ do trace stack here ]
81 *
82 * The save_stack_trace() is called returning all the functions it finds in the
83 * current stack. Which would be (from the bottom of the stack to the top):
84 *
85 * return addr to kernel_func_bar
86 * return addr to sys_foo
87 * return addr to entry code
88 *
89 * Now to figure out how much each of these functions' local variable size is,
90 * a search of the stack is made to find these values. When a match is made, it
91 * is added to the stack_dump_trace[] array. The offset into the stack is saved
92 * in the stack_trace_index[] array. The above example would show:
93 *
94 * stack_dump_trace[] | stack_trace_index[]
95 * ------------------ + -------------------
96 * return addr to kernel_func_bar | 30
97 * return addr to sys_foo | 20
98 * return addr to entry | 10
99 *
100 * The print_max_stack() function above, uses these values to print the size of
101 * each function's portion of the stack.
102 *
103 * for (i = 0; i < nr_entries; i++) {
104 * size = i == nr_entries - 1 ? stack_trace_index[i] :
105 * stack_trace_index[i] - stack_trace_index[i+1]
106 * print "%d %d %d %s\n", i, stack_trace_index[i], size, stack_dump_trace[i]);
107 * }
108 *
109 * The above shows
110 *
111 * depth size location
112 * ----- ---- --------
113 * 0 30 10 kernel_func_bar
114 * 1 20 10 sys_foo
115 * 2 10 10 entry code
116 *
117 * Now for architectures that might save the return address after the functions
118 * local variables (saving the link register before calling nested functions),
119 * this will cause the stack to look a little different:
120 *
121 * [ top of stack ]
122 * 0: sys call entry frame
123 * 10: start of sys_foo_frame
124 * 19: return addr to entry code << lr saved before calling kernel_func_bar
125 * 20: start of kernel_func_bar frame
126 * 29: return addr to sys_foo_frame << lr saved before calling next function
127 * 30: [ do trace stack here ]
128 *
129 * Although the functions returned by save_stack_trace() may be the same, the
130 * placement in the stack will be different. Using the same algorithm as above
131 * would yield:
132 *
133 * stack_dump_trace[] | stack_trace_index[]
134 * ------------------ + -------------------
135 * return addr to kernel_func_bar | 30
136 * return addr to sys_foo | 29
137 * return addr to entry | 19
138 *
139 * Where the mapping is off by one:
140 *
141 * kernel_func_bar stack frame size is 29 - 19 not 30 - 29!
142 *
143 * To fix this, if the architecture sets ARCH_RET_ADDR_AFTER_LOCAL_VARS the
144 * values in stack_trace_index[] are shifted by one to and the number of
145 * stack trace entries is decremented by one.
146 *
147 * stack_dump_trace[] | stack_trace_index[]
148 * ------------------ + -------------------
149 * return addr to kernel_func_bar | 29
150 * return addr to sys_foo | 19
151 *
152 * Although the entry function is not displayed, the first function (sys_foo)
153 * will still include the stack size of it.
154 */
155static void check_stack(unsigned long ip, unsigned long *stack)
156{
157 unsigned long this_size, flags; unsigned long *p, *top, *start;
158 static int tracer_frame;
159 int frame_size = READ_ONCE(tracer_frame);
160 int i, x;
161
162 this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
163 this_size = THREAD_SIZE - this_size;
164 /* Remove the frame of the tracer */
165 this_size -= frame_size;
166
167 if (this_size <= stack_trace_max_size)
168 return;
169
170 /* we do not handle interrupt stacks yet */
171 if (!object_is_on_stack(stack))
172 return;
173
174 /* Can't do this from NMI context (can cause deadlocks) */
175 if (in_nmi())
176 return;
177
178 local_irq_save(flags);
179 arch_spin_lock(&stack_trace_max_lock);
180
181 /* In case another CPU set the tracer_frame on us */
182 if (unlikely(!frame_size))
183 this_size -= tracer_frame;
184
185 /* a race could have already updated it */
186 if (this_size <= stack_trace_max_size)
187 goto out;
188
189 stack_trace_max_size = this_size;
190
191 stack_trace_nr_entries = stack_trace_save(stack_dump_trace,
192 ARRAY_SIZE(stack_dump_trace) - 1,
193 0);
194
195 /* Skip over the overhead of the stack tracer itself */
196 for (i = 0; i < stack_trace_nr_entries; i++) {
197 if (stack_dump_trace[i] == ip)
198 break;
199 }
200
201 /*
202 * Some archs may not have the passed in ip in the dump.
203 * If that happens, we need to show everything.
204 */
205 if (i == stack_trace_nr_entries)
206 i = 0;
207
208 /*
209 * Now find where in the stack these are.
210 */
211 x = 0;
212 start = stack;
213 top = (unsigned long *)
214 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
215
216 /*
217 * Loop through all the entries. One of the entries may
218 * for some reason be missed on the stack, so we may
219 * have to account for them. If they are all there, this
220 * loop will only happen once. This code only takes place
221 * on a new max, so it is far from a fast path.
222 */
223 while (i < stack_trace_nr_entries) {
224 int found = 0;
225
226 stack_trace_index[x] = this_size;
227 p = start;
228
229 for (; p < top && i < stack_trace_nr_entries; p++) {
230 /*
231 * The READ_ONCE_NOCHECK is used to let KASAN know that
232 * this is not a stack-out-of-bounds error.
233 */
234 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
235 stack_dump_trace[x] = stack_dump_trace[i++];
236 this_size = stack_trace_index[x++] =
237 (top - p) * sizeof(unsigned long);
238 found = 1;
239 /* Start the search from here */
240 start = p + 1;
241 /*
242 * We do not want to show the overhead
243 * of the stack tracer stack in the
244 * max stack. If we haven't figured
245 * out what that is, then figure it out
246 * now.
247 */
248 if (unlikely(!tracer_frame)) {
249 tracer_frame = (p - stack) *
250 sizeof(unsigned long);
251 stack_trace_max_size -= tracer_frame;
252 }
253 }
254 }
255
256 if (!found)
257 i++;
258 }
259
260#ifdef ARCH_FTRACE_SHIFT_STACK_TRACER
261 /*
262 * Some archs will store the link register before calling
263 * nested functions. This means the saved return address
264 * comes after the local storage, and we need to shift
265 * for that.
266 */
267 if (x > 1) {
268 memmove(&stack_trace_index[0], &stack_trace_index[1],
269 sizeof(stack_trace_index[0]) * (x - 1));
270 x--;
271 }
272#endif
273
274 stack_trace_nr_entries = x;
275
276 if (task_stack_end_corrupted(current)) {
277 print_max_stack();
278 BUG();
279 }
280
281 out:
282 arch_spin_unlock(&stack_trace_max_lock);
283 local_irq_restore(flags);
284}
285
286/* Some archs may not define MCOUNT_INSN_SIZE */
287#ifndef MCOUNT_INSN_SIZE
288# define MCOUNT_INSN_SIZE 0
289#endif
290
291static void
292stack_trace_call(unsigned long ip, unsigned long parent_ip,
293 struct ftrace_ops *op, struct ftrace_regs *fregs)
294{
295 unsigned long stack;
296
297 preempt_disable_notrace();
298
299 /* no atomic needed, we only modify this variable by this cpu */
300 __this_cpu_inc(disable_stack_tracer);
301 if (__this_cpu_read(disable_stack_tracer) != 1)
302 goto out;
303
304 /* If rcu is not watching, then save stack trace can fail */
305 if (!rcu_is_watching())
306 goto out;
307
308 ip += MCOUNT_INSN_SIZE;
309
310 check_stack(ip, &stack);
311
312 out:
313 __this_cpu_dec(disable_stack_tracer);
314 /* prevent recursion in schedule */
315 preempt_enable_notrace();
316}
317
318static struct ftrace_ops trace_ops __read_mostly =
319{
320 .func = stack_trace_call,
321};
322
323static ssize_t
324stack_max_size_read(struct file *filp, char __user *ubuf,
325 size_t count, loff_t *ppos)
326{
327 unsigned long *ptr = filp->private_data;
328 char buf[64];
329 int r;
330
331 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
332 if (r > sizeof(buf))
333 r = sizeof(buf);
334 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
335}
336
337static ssize_t
338stack_max_size_write(struct file *filp, const char __user *ubuf,
339 size_t count, loff_t *ppos)
340{
341 long *ptr = filp->private_data;
342 unsigned long val, flags;
343 int ret;
344
345 ret = kstrtoul_from_user(ubuf, count, 10, &val);
346 if (ret)
347 return ret;
348
349 local_irq_save(flags);
350
351 /*
352 * In case we trace inside arch_spin_lock() or after (NMI),
353 * we will cause circular lock, so we also need to increase
354 * the percpu disable_stack_tracer here.
355 */
356 __this_cpu_inc(disable_stack_tracer);
357
358 arch_spin_lock(&stack_trace_max_lock);
359 *ptr = val;
360 arch_spin_unlock(&stack_trace_max_lock);
361
362 __this_cpu_dec(disable_stack_tracer);
363 local_irq_restore(flags);
364
365 return count;
366}
367
368static const struct file_operations stack_max_size_fops = {
369 .open = tracing_open_generic,
370 .read = stack_max_size_read,
371 .write = stack_max_size_write,
372 .llseek = default_llseek,
373};
374
375static void *
376__next(struct seq_file *m, loff_t *pos)
377{
378 long n = *pos - 1;
379
380 if (n >= stack_trace_nr_entries)
381 return NULL;
382
383 m->private = (void *)n;
384 return &m->private;
385}
386
387static void *
388t_next(struct seq_file *m, void *v, loff_t *pos)
389{
390 (*pos)++;
391 return __next(m, pos);
392}
393
394static void *t_start(struct seq_file *m, loff_t *pos)
395{
396 local_irq_disable();
397
398 __this_cpu_inc(disable_stack_tracer);
399
400 arch_spin_lock(&stack_trace_max_lock);
401
402 if (*pos == 0)
403 return SEQ_START_TOKEN;
404
405 return __next(m, pos);
406}
407
408static void t_stop(struct seq_file *m, void *p)
409{
410 arch_spin_unlock(&stack_trace_max_lock);
411
412 __this_cpu_dec(disable_stack_tracer);
413
414 local_irq_enable();
415}
416
417static void trace_lookup_stack(struct seq_file *m, long i)
418{
419 unsigned long addr = stack_dump_trace[i];
420
421 seq_printf(m, "%pS\n", (void *)addr);
422}
423
424static void print_disabled(struct seq_file *m)
425{
426 seq_puts(m, "#\n"
427 "# Stack tracer disabled\n"
428 "#\n"
429 "# To enable the stack tracer, either add 'stacktrace' to the\n"
430 "# kernel command line\n"
431 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
432 "#\n");
433}
434
435static int t_show(struct seq_file *m, void *v)
436{
437 long i;
438 int size;
439
440 if (v == SEQ_START_TOKEN) {
441 seq_printf(m, " Depth Size Location"
442 " (%d entries)\n"
443 " ----- ---- --------\n",
444 stack_trace_nr_entries);
445
446 if (!stack_tracer_enabled && !stack_trace_max_size)
447 print_disabled(m);
448
449 return 0;
450 }
451
452 i = *(long *)v;
453
454 if (i >= stack_trace_nr_entries)
455 return 0;
456
457 if (i + 1 == stack_trace_nr_entries)
458 size = stack_trace_index[i];
459 else
460 size = stack_trace_index[i] - stack_trace_index[i+1];
461
462 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
463
464 trace_lookup_stack(m, i);
465
466 return 0;
467}
468
469static const struct seq_operations stack_trace_seq_ops = {
470 .start = t_start,
471 .next = t_next,
472 .stop = t_stop,
473 .show = t_show,
474};
475
476static int stack_trace_open(struct inode *inode, struct file *file)
477{
478 int ret;
479
480 ret = security_locked_down(LOCKDOWN_TRACEFS);
481 if (ret)
482 return ret;
483
484 return seq_open(file, &stack_trace_seq_ops);
485}
486
487static const struct file_operations stack_trace_fops = {
488 .open = stack_trace_open,
489 .read = seq_read,
490 .llseek = seq_lseek,
491 .release = seq_release,
492};
493
494#ifdef CONFIG_DYNAMIC_FTRACE
495
496static int
497stack_trace_filter_open(struct inode *inode, struct file *file)
498{
499 struct ftrace_ops *ops = inode->i_private;
500
501 /* Checks for tracefs lockdown */
502 return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
503 inode, file);
504}
505
506static const struct file_operations stack_trace_filter_fops = {
507 .open = stack_trace_filter_open,
508 .read = seq_read,
509 .write = ftrace_filter_write,
510 .llseek = tracing_lseek,
511 .release = ftrace_regex_release,
512};
513
514#endif /* CONFIG_DYNAMIC_FTRACE */
515
516int
517stack_trace_sysctl(struct ctl_table *table, int write, void *buffer,
518 size_t *lenp, loff_t *ppos)
519{
520 int was_enabled;
521 int ret;
522
523 mutex_lock(&stack_sysctl_mutex);
524 was_enabled = !!stack_tracer_enabled;
525
526 ret = proc_dointvec(table, write, buffer, lenp, ppos);
527
528 if (ret || !write || (was_enabled == !!stack_tracer_enabled))
529 goto out;
530
531 if (stack_tracer_enabled)
532 register_ftrace_function(&trace_ops);
533 else
534 unregister_ftrace_function(&trace_ops);
535 out:
536 mutex_unlock(&stack_sysctl_mutex);
537 return ret;
538}
539
540static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
541
542static __init int enable_stacktrace(char *str)
543{
544 int len;
545
546 if ((len = str_has_prefix(str, "_filter=")))
547 strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
548
549 stack_tracer_enabled = 1;
550 return 1;
551}
552__setup("stacktrace", enable_stacktrace);
553
554static __init int stack_trace_init(void)
555{
556 int ret;
557
558 ret = tracing_init_dentry();
559 if (ret)
560 return 0;
561
562 trace_create_file("stack_max_size", TRACE_MODE_WRITE, NULL,
563 &stack_trace_max_size, &stack_max_size_fops);
564
565 trace_create_file("stack_trace", TRACE_MODE_READ, NULL,
566 NULL, &stack_trace_fops);
567
568#ifdef CONFIG_DYNAMIC_FTRACE
569 trace_create_file("stack_trace_filter", TRACE_MODE_WRITE, NULL,
570 &trace_ops, &stack_trace_filter_fops);
571#endif
572
573 if (stack_trace_filter_buf[0])
574 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
575
576 if (stack_tracer_enabled)
577 register_ftrace_function(&trace_ops);
578
579 return 0;
580}
581
582device_initcall(stack_trace_init);
1/*
2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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/ftrace.h>
11#include <linux/module.h>
12#include <linux/sysctl.h>
13#include <linux/init.h>
14
15#include <asm/setup.h>
16
17#include "trace.h"
18
19static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
20 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
21unsigned stack_trace_index[STACK_TRACE_ENTRIES];
22
23/*
24 * Reserve one entry for the passed in ip. This will allow
25 * us to remove most or all of the stack size overhead
26 * added by the stack tracer itself.
27 */
28struct stack_trace stack_trace_max = {
29 .max_entries = STACK_TRACE_ENTRIES - 1,
30 .entries = &stack_dump_trace[0],
31};
32
33unsigned long stack_trace_max_size;
34arch_spinlock_t stack_trace_max_lock =
35 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
36
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
43void stack_trace_print(void)
44{
45 long i;
46 int size;
47
48 pr_emerg(" Depth Size Location (%d entries)\n"
49 " ----- ---- --------\n",
50 stack_trace_max.nr_entries);
51
52 for (i = 0; i < stack_trace_max.nr_entries; i++) {
53 if (stack_dump_trace[i] == ULONG_MAX)
54 break;
55 if (i+1 == stack_trace_max.nr_entries ||
56 stack_dump_trace[i+1] == ULONG_MAX)
57 size = stack_trace_index[i];
58 else
59 size = stack_trace_index[i] - stack_trace_index[i+1];
60
61 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
62 size, (void *)stack_dump_trace[i]);
63 }
64}
65
66/*
67 * When arch-specific code overides this function, the following
68 * data should be filled up, assuming stack_trace_max_lock is held to
69 * prevent concurrent updates.
70 * stack_trace_index[]
71 * stack_trace_max
72 * stack_trace_max_size
73 */
74void __weak
75check_stack(unsigned long ip, unsigned long *stack)
76{
77 unsigned long this_size, flags; unsigned long *p, *top, *start;
78 static int tracer_frame;
79 int frame_size = ACCESS_ONCE(tracer_frame);
80 int i, x;
81
82 this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
83 this_size = THREAD_SIZE - this_size;
84 /* Remove the frame of the tracer */
85 this_size -= frame_size;
86
87 if (this_size <= stack_trace_max_size)
88 return;
89
90 /* we do not handle interrupt stacks yet */
91 if (!object_is_on_stack(stack))
92 return;
93
94 /* Can't do this from NMI context (can cause deadlocks) */
95 if (in_nmi())
96 return;
97
98 local_irq_save(flags);
99 arch_spin_lock(&stack_trace_max_lock);
100
101 /*
102 * RCU may not be watching, make it see us.
103 * The stack trace code uses rcu_sched.
104 */
105 rcu_irq_enter();
106
107 /* In case another CPU set the tracer_frame on us */
108 if (unlikely(!frame_size))
109 this_size -= tracer_frame;
110
111 /* a race could have already updated it */
112 if (this_size <= stack_trace_max_size)
113 goto out;
114
115 stack_trace_max_size = this_size;
116
117 stack_trace_max.nr_entries = 0;
118 stack_trace_max.skip = 3;
119
120 save_stack_trace(&stack_trace_max);
121
122 /* Skip over the overhead of the stack tracer itself */
123 for (i = 0; i < stack_trace_max.nr_entries; i++) {
124 if (stack_dump_trace[i] == ip)
125 break;
126 }
127
128 /*
129 * Some archs may not have the passed in ip in the dump.
130 * If that happens, we need to show everything.
131 */
132 if (i == stack_trace_max.nr_entries)
133 i = 0;
134
135 /*
136 * Now find where in the stack these are.
137 */
138 x = 0;
139 start = stack;
140 top = (unsigned long *)
141 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
142
143 /*
144 * Loop through all the entries. One of the entries may
145 * for some reason be missed on the stack, so we may
146 * have to account for them. If they are all there, this
147 * loop will only happen once. This code only takes place
148 * on a new max, so it is far from a fast path.
149 */
150 while (i < stack_trace_max.nr_entries) {
151 int found = 0;
152
153 stack_trace_index[x] = this_size;
154 p = start;
155
156 for (; p < top && i < stack_trace_max.nr_entries; p++) {
157 if (stack_dump_trace[i] == ULONG_MAX)
158 break;
159 /*
160 * The READ_ONCE_NOCHECK is used to let KASAN know that
161 * this is not a stack-out-of-bounds error.
162 */
163 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
164 stack_dump_trace[x] = stack_dump_trace[i++];
165 this_size = stack_trace_index[x++] =
166 (top - p) * sizeof(unsigned long);
167 found = 1;
168 /* Start the search from here */
169 start = p + 1;
170 /*
171 * We do not want to show the overhead
172 * of the stack tracer stack in the
173 * max stack. If we haven't figured
174 * out what that is, then figure it out
175 * now.
176 */
177 if (unlikely(!tracer_frame)) {
178 tracer_frame = (p - stack) *
179 sizeof(unsigned long);
180 stack_trace_max_size -= tracer_frame;
181 }
182 }
183 }
184
185 if (!found)
186 i++;
187 }
188
189 stack_trace_max.nr_entries = x;
190 for (; x < i; x++)
191 stack_dump_trace[x] = ULONG_MAX;
192
193 if (task_stack_end_corrupted(current)) {
194 stack_trace_print();
195 BUG();
196 }
197
198 out:
199 rcu_irq_exit();
200 arch_spin_unlock(&stack_trace_max_lock);
201 local_irq_restore(flags);
202}
203
204static void
205stack_trace_call(unsigned long ip, unsigned long parent_ip,
206 struct ftrace_ops *op, struct pt_regs *pt_regs)
207{
208 unsigned long stack;
209 int cpu;
210
211 preempt_disable_notrace();
212
213 cpu = raw_smp_processor_id();
214 /* no atomic needed, we only modify this variable by this cpu */
215 if (per_cpu(trace_active, cpu)++ != 0)
216 goto out;
217
218 ip += MCOUNT_INSN_SIZE;
219
220 check_stack(ip, &stack);
221
222 out:
223 per_cpu(trace_active, cpu)--;
224 /* prevent recursion in schedule */
225 preempt_enable_notrace();
226}
227
228static struct ftrace_ops trace_ops __read_mostly =
229{
230 .func = stack_trace_call,
231 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
232};
233
234static ssize_t
235stack_max_size_read(struct file *filp, char __user *ubuf,
236 size_t count, loff_t *ppos)
237{
238 unsigned long *ptr = filp->private_data;
239 char buf[64];
240 int r;
241
242 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
243 if (r > sizeof(buf))
244 r = sizeof(buf);
245 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
246}
247
248static ssize_t
249stack_max_size_write(struct file *filp, const char __user *ubuf,
250 size_t count, loff_t *ppos)
251{
252 long *ptr = filp->private_data;
253 unsigned long val, flags;
254 int ret;
255 int cpu;
256
257 ret = kstrtoul_from_user(ubuf, count, 10, &val);
258 if (ret)
259 return ret;
260
261 local_irq_save(flags);
262
263 /*
264 * In case we trace inside arch_spin_lock() or after (NMI),
265 * we will cause circular lock, so we also need to increase
266 * the percpu trace_active here.
267 */
268 cpu = smp_processor_id();
269 per_cpu(trace_active, cpu)++;
270
271 arch_spin_lock(&stack_trace_max_lock);
272 *ptr = val;
273 arch_spin_unlock(&stack_trace_max_lock);
274
275 per_cpu(trace_active, cpu)--;
276 local_irq_restore(flags);
277
278 return count;
279}
280
281static const struct file_operations stack_max_size_fops = {
282 .open = tracing_open_generic,
283 .read = stack_max_size_read,
284 .write = stack_max_size_write,
285 .llseek = default_llseek,
286};
287
288static void *
289__next(struct seq_file *m, loff_t *pos)
290{
291 long n = *pos - 1;
292
293 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
294 return NULL;
295
296 m->private = (void *)n;
297 return &m->private;
298}
299
300static void *
301t_next(struct seq_file *m, void *v, loff_t *pos)
302{
303 (*pos)++;
304 return __next(m, pos);
305}
306
307static void *t_start(struct seq_file *m, loff_t *pos)
308{
309 int cpu;
310
311 local_irq_disable();
312
313 cpu = smp_processor_id();
314 per_cpu(trace_active, cpu)++;
315
316 arch_spin_lock(&stack_trace_max_lock);
317
318 if (*pos == 0)
319 return SEQ_START_TOKEN;
320
321 return __next(m, pos);
322}
323
324static void t_stop(struct seq_file *m, void *p)
325{
326 int cpu;
327
328 arch_spin_unlock(&stack_trace_max_lock);
329
330 cpu = smp_processor_id();
331 per_cpu(trace_active, cpu)--;
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);