tracing: Remove RCU work arounds from stack tracer
[sfrench/cifs-2.6.git] / kernel / trace / trace_stack.c
1 /*
2  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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
20 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
21          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
22 unsigned 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  */
29 struct stack_trace stack_trace_max = {
30         .max_entries            = STACK_TRACE_ENTRIES - 1,
31         .entries                = &stack_dump_trace[0],
32 };
33
34 unsigned long stack_trace_max_size;
35 arch_spinlock_t stack_trace_max_lock =
36         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
37
38 DEFINE_PER_CPU(int, disable_stack_tracer);
39 static DEFINE_MUTEX(stack_sysctl_mutex);
40
41 int stack_tracer_enabled;
42 static int last_stack_tracer_enabled;
43
44 void 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  */
75 void __weak
76 check_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         /* In case another CPU set the tracer_frame on us */
103         if (unlikely(!frame_size))
104                 this_size -= tracer_frame;
105
106         /* a race could have already updated it */
107         if (this_size <= stack_trace_max_size)
108                 goto out;
109
110         stack_trace_max_size = this_size;
111
112         stack_trace_max.nr_entries = 0;
113         stack_trace_max.skip = 3;
114
115         save_stack_trace(&stack_trace_max);
116
117         /* Skip over the overhead of the stack tracer itself */
118         for (i = 0; i < stack_trace_max.nr_entries; i++) {
119                 if (stack_dump_trace[i] == ip)
120                         break;
121         }
122
123         /*
124          * Some archs may not have the passed in ip in the dump.
125          * If that happens, we need to show everything.
126          */
127         if (i == stack_trace_max.nr_entries)
128                 i = 0;
129
130         /*
131          * Now find where in the stack these are.
132          */
133         x = 0;
134         start = stack;
135         top = (unsigned long *)
136                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
137
138         /*
139          * Loop through all the entries. One of the entries may
140          * for some reason be missed on the stack, so we may
141          * have to account for them. If they are all there, this
142          * loop will only happen once. This code only takes place
143          * on a new max, so it is far from a fast path.
144          */
145         while (i < stack_trace_max.nr_entries) {
146                 int found = 0;
147
148                 stack_trace_index[x] = this_size;
149                 p = start;
150
151                 for (; p < top && i < stack_trace_max.nr_entries; p++) {
152                         if (stack_dump_trace[i] == ULONG_MAX)
153                                 break;
154                         /*
155                          * The READ_ONCE_NOCHECK is used to let KASAN know that
156                          * this is not a stack-out-of-bounds error.
157                          */
158                         if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
159                                 stack_dump_trace[x] = stack_dump_trace[i++];
160                                 this_size = stack_trace_index[x++] =
161                                         (top - p) * sizeof(unsigned long);
162                                 found = 1;
163                                 /* Start the search from here */
164                                 start = p + 1;
165                                 /*
166                                  * We do not want to show the overhead
167                                  * of the stack tracer stack in the
168                                  * max stack. If we haven't figured
169                                  * out what that is, then figure it out
170                                  * now.
171                                  */
172                                 if (unlikely(!tracer_frame)) {
173                                         tracer_frame = (p - stack) *
174                                                 sizeof(unsigned long);
175                                         stack_trace_max_size -= tracer_frame;
176                                 }
177                         }
178                 }
179
180                 if (!found)
181                         i++;
182         }
183
184         stack_trace_max.nr_entries = x;
185         for (; x < i; x++)
186                 stack_dump_trace[x] = ULONG_MAX;
187
188         if (task_stack_end_corrupted(current)) {
189                 stack_trace_print();
190                 BUG();
191         }
192
193  out:
194         arch_spin_unlock(&stack_trace_max_lock);
195         local_irq_restore(flags);
196 }
197
198 static void
199 stack_trace_call(unsigned long ip, unsigned long parent_ip,
200                  struct ftrace_ops *op, struct pt_regs *pt_regs)
201 {
202         unsigned long stack;
203
204         preempt_disable_notrace();
205
206         /* no atomic needed, we only modify this variable by this cpu */
207         __this_cpu_inc(disable_stack_tracer);
208         if (__this_cpu_read(disable_stack_tracer) != 1)
209                 goto out;
210
211         ip += MCOUNT_INSN_SIZE;
212
213         check_stack(ip, &stack);
214
215  out:
216         __this_cpu_dec(disable_stack_tracer);
217         /* prevent recursion in schedule */
218         preempt_enable_notrace();
219 }
220
221 static struct ftrace_ops trace_ops __read_mostly =
222 {
223         .func = stack_trace_call,
224         .flags = FTRACE_OPS_FL_RECURSION_SAFE,
225 };
226
227 static ssize_t
228 stack_max_size_read(struct file *filp, char __user *ubuf,
229                     size_t count, loff_t *ppos)
230 {
231         unsigned long *ptr = filp->private_data;
232         char buf[64];
233         int r;
234
235         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
236         if (r > sizeof(buf))
237                 r = sizeof(buf);
238         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
239 }
240
241 static ssize_t
242 stack_max_size_write(struct file *filp, const char __user *ubuf,
243                      size_t count, loff_t *ppos)
244 {
245         long *ptr = filp->private_data;
246         unsigned long val, flags;
247         int ret;
248
249         ret = kstrtoul_from_user(ubuf, count, 10, &val);
250         if (ret)
251                 return ret;
252
253         local_irq_save(flags);
254
255         /*
256          * In case we trace inside arch_spin_lock() or after (NMI),
257          * we will cause circular lock, so we also need to increase
258          * the percpu disable_stack_tracer here.
259          */
260         __this_cpu_inc(disable_stack_tracer);
261
262         arch_spin_lock(&stack_trace_max_lock);
263         *ptr = val;
264         arch_spin_unlock(&stack_trace_max_lock);
265
266         __this_cpu_dec(disable_stack_tracer);
267         local_irq_restore(flags);
268
269         return count;
270 }
271
272 static const struct file_operations stack_max_size_fops = {
273         .open           = tracing_open_generic,
274         .read           = stack_max_size_read,
275         .write          = stack_max_size_write,
276         .llseek         = default_llseek,
277 };
278
279 static void *
280 __next(struct seq_file *m, loff_t *pos)
281 {
282         long n = *pos - 1;
283
284         if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
285                 return NULL;
286
287         m->private = (void *)n;
288         return &m->private;
289 }
290
291 static void *
292 t_next(struct seq_file *m, void *v, loff_t *pos)
293 {
294         (*pos)++;
295         return __next(m, pos);
296 }
297
298 static void *t_start(struct seq_file *m, loff_t *pos)
299 {
300         local_irq_disable();
301
302         __this_cpu_inc(disable_stack_tracer);
303
304         arch_spin_lock(&stack_trace_max_lock);
305
306         if (*pos == 0)
307                 return SEQ_START_TOKEN;
308
309         return __next(m, pos);
310 }
311
312 static void t_stop(struct seq_file *m, void *p)
313 {
314         arch_spin_unlock(&stack_trace_max_lock);
315
316         __this_cpu_dec(disable_stack_tracer);
317
318         local_irq_enable();
319 }
320
321 static void trace_lookup_stack(struct seq_file *m, long i)
322 {
323         unsigned long addr = stack_dump_trace[i];
324
325         seq_printf(m, "%pS\n", (void *)addr);
326 }
327
328 static void print_disabled(struct seq_file *m)
329 {
330         seq_puts(m, "#\n"
331                  "#  Stack tracer disabled\n"
332                  "#\n"
333                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
334                  "# kernel command line\n"
335                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
336                  "#\n");
337 }
338
339 static int t_show(struct seq_file *m, void *v)
340 {
341         long i;
342         int size;
343
344         if (v == SEQ_START_TOKEN) {
345                 seq_printf(m, "        Depth    Size   Location"
346                            "    (%d entries)\n"
347                            "        -----    ----   --------\n",
348                            stack_trace_max.nr_entries);
349
350                 if (!stack_tracer_enabled && !stack_trace_max_size)
351                         print_disabled(m);
352
353                 return 0;
354         }
355
356         i = *(long *)v;
357
358         if (i >= stack_trace_max.nr_entries ||
359             stack_dump_trace[i] == ULONG_MAX)
360                 return 0;
361
362         if (i+1 == stack_trace_max.nr_entries ||
363             stack_dump_trace[i+1] == ULONG_MAX)
364                 size = stack_trace_index[i];
365         else
366                 size = stack_trace_index[i] - stack_trace_index[i+1];
367
368         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_trace_index[i], size);
369
370         trace_lookup_stack(m, i);
371
372         return 0;
373 }
374
375 static const struct seq_operations stack_trace_seq_ops = {
376         .start          = t_start,
377         .next           = t_next,
378         .stop           = t_stop,
379         .show           = t_show,
380 };
381
382 static int stack_trace_open(struct inode *inode, struct file *file)
383 {
384         return seq_open(file, &stack_trace_seq_ops);
385 }
386
387 static const struct file_operations stack_trace_fops = {
388         .open           = stack_trace_open,
389         .read           = seq_read,
390         .llseek         = seq_lseek,
391         .release        = seq_release,
392 };
393
394 #ifdef CONFIG_DYNAMIC_FTRACE
395
396 static int
397 stack_trace_filter_open(struct inode *inode, struct file *file)
398 {
399         struct ftrace_ops *ops = inode->i_private;
400
401         return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
402                                  inode, file);
403 }
404
405 static const struct file_operations stack_trace_filter_fops = {
406         .open = stack_trace_filter_open,
407         .read = seq_read,
408         .write = ftrace_filter_write,
409         .llseek = tracing_lseek,
410         .release = ftrace_regex_release,
411 };
412
413 #endif /* CONFIG_DYNAMIC_FTRACE */
414
415 int
416 stack_trace_sysctl(struct ctl_table *table, int write,
417                    void __user *buffer, size_t *lenp,
418                    loff_t *ppos)
419 {
420         int ret;
421
422         mutex_lock(&stack_sysctl_mutex);
423
424         ret = proc_dointvec(table, write, buffer, lenp, ppos);
425
426         if (ret || !write ||
427             (last_stack_tracer_enabled == !!stack_tracer_enabled))
428                 goto out;
429
430         last_stack_tracer_enabled = !!stack_tracer_enabled;
431
432         if (stack_tracer_enabled)
433                 register_ftrace_function(&trace_ops);
434         else
435                 unregister_ftrace_function(&trace_ops);
436
437  out:
438         mutex_unlock(&stack_sysctl_mutex);
439         return ret;
440 }
441
442 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
443
444 static __init int enable_stacktrace(char *str)
445 {
446         if (strncmp(str, "_filter=", 8) == 0)
447                 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
448
449         stack_tracer_enabled = 1;
450         last_stack_tracer_enabled = 1;
451         return 1;
452 }
453 __setup("stacktrace", enable_stacktrace);
454
455 static __init int stack_trace_init(void)
456 {
457         struct dentry *d_tracer;
458
459         d_tracer = tracing_init_dentry();
460         if (IS_ERR(d_tracer))
461                 return 0;
462
463         trace_create_file("stack_max_size", 0644, d_tracer,
464                         &stack_trace_max_size, &stack_max_size_fops);
465
466         trace_create_file("stack_trace", 0444, d_tracer,
467                         NULL, &stack_trace_fops);
468
469 #ifdef CONFIG_DYNAMIC_FTRACE
470         trace_create_file("stack_trace_filter", 0444, d_tracer,
471                           &trace_ops, &stack_trace_filter_fops);
472 #endif
473
474         if (stack_trace_filter_buf[0])
475                 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
476
477         if (stack_tracer_enabled)
478                 register_ftrace_function(&trace_ops);
479
480         return 0;
481 }
482
483 device_initcall(stack_trace_init);