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