projects/linux·blob 04480094 · refs

455 lines · 10.0 KiB

1/*
2 * Copyright (C) 2008 Steven Rostedt <[email protected]>
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/debugfs.h>
11#include <linux/ftrace.h>
12#include <linux/module.h>
13#include <linux/sysctl.h>
14#include <linux/init.h>
15#include <linux/fs.h>
16
17#include <asm/setup.h>
18
19#include "trace.h"
20
21#define STACK_TRACE_ENTRIES 500
22
23#ifdef CC_USING_FENTRY
24# define fentry 1
25#else
26# define fentry 0
27#endif
28
29static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
30 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
31static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
32
33/*
34 * Reserve one entry for the passed in ip. This will allow
35 * us to remove most or all of the stack size overhead
36 * added by the stack tracer itself.
37 */
38static struct stack_trace max_stack_trace = {
39 .max_entries = STACK_TRACE_ENTRIES - 1,
40 .entries = &stack_dump_trace[1],
41};
42
43static unsigned long max_stack_size;
44static arch_spinlock_t max_stack_lock =
45 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
46
47static DEFINE_PER_CPU(int, trace_active);
48static DEFINE_MUTEX(stack_sysctl_mutex);
49
50int stack_tracer_enabled;
51static int last_stack_tracer_enabled;
52
53static inline void
54check_stack(unsigned long ip, unsigned long *stack)
55{
56 unsigned long this_size, flags;
57 unsigned long *p, *top, *start;
58 static int tracer_frame;
59 int frame_size = ACCESS_ONCE(tracer_frame);
60 int i;
61
62 this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
63 this_size = THREAD_SIZE - this_size;
64 /* Remove the frame of the tracer */
65 this_size -= frame_size;
66
67 if (this_size <= max_stack_size)
68 return;
69
70 /* we do not handle interrupt stacks yet */
71 if (!object_is_on_stack(stack))
72 return;
73
74 local_irq_save(flags);
75 arch_spin_lock(&max_stack_lock);
76
77 /* In case another CPU set the tracer_frame on us */
78 if (unlikely(!frame_size))
79 this_size -= tracer_frame;
80
81 /* a race could have already updated it */
82 if (this_size <= max_stack_size)
83 goto out;
84
85 max_stack_size = this_size;
86
87 max_stack_trace.nr_entries = 0;
88 max_stack_trace.skip = 3;
89
90 save_stack_trace(&max_stack_trace);
91
92 /*
93 * Add the passed in ip from the function tracer.
94 * Searching for this on the stack will skip over
95 * most of the overhead from the stack tracer itself.
96 */
97 stack_dump_trace[0] = ip;
98 max_stack_trace.nr_entries++;
99
100 /*
101 * Now find where in the stack these are.
102 */
103 i = 0;
104 start = stack;
105 top = (unsigned long *)
106 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
107
108 /*
109 * Loop through all the entries. One of the entries may
110 * for some reason be missed on the stack, so we may
111 * have to account for them. If they are all there, this
112 * loop will only happen once. This code only takes place
113 * on a new max, so it is far from a fast path.
114 */
115 while (i < max_stack_trace.nr_entries) {
116 int found = 0;
117
118 stack_dump_index[i] = this_size;
119 p = start;
120
121 for (; p < top && i < max_stack_trace.nr_entries; p++) {
122 if (*p == stack_dump_trace[i]) {
123 this_size = stack_dump_index[i++] =
124 (top - p) * sizeof(unsigned long);
125 found = 1;
126 /* Start the search from here */
127 start = p + 1;
128 /*
129 * We do not want to show the overhead
130 * of the stack tracer stack in the
131 * max stack. If we haven't figured
132 * out what that is, then figure it out
133 * now.
134 */
135 if (unlikely(!tracer_frame) && i == 1) {
136 tracer_frame = (p - stack) *
137 sizeof(unsigned long);
138 max_stack_size -= tracer_frame;
139 }
140 }
141 }
142
143 if (!found)
144 i++;
145 }
146
147 out:
148 arch_spin_unlock(&max_stack_lock);
149 local_irq_restore(flags);
150}
151
152static void
153stack_trace_call(unsigned long ip, unsigned long parent_ip,
154 struct ftrace_ops *op, struct pt_regs *pt_regs)
155{
156 unsigned long stack;
157 int cpu;
158
159 preempt_disable_notrace();
160
161 cpu = raw_smp_processor_id();
162 /* no atomic needed, we only modify this variable by this cpu */
163 if (per_cpu(trace_active, cpu)++ != 0)
164 goto out;
165
166 /*
167 * When fentry is used, the traced function does not get
168 * its stack frame set up, and we lose the parent.
169 * The ip is pretty useless because the function tracer
170 * was called before that function set up its stack frame.
171 * In this case, we use the parent ip.
172 *
173 * By adding the return address of either the parent ip
174 * or the current ip we can disregard most of the stack usage
175 * caused by the stack tracer itself.
176 *
177 * The function tracer always reports the address of where the
178 * mcount call was, but the stack will hold the return address.
179 */
180 if (fentry)
181 ip = parent_ip;
182 else
183 ip += MCOUNT_INSN_SIZE;
184
185 check_stack(ip, &stack);
186
187 out:
188 per_cpu(trace_active, cpu)--;
189 /* prevent recursion in schedule */
190 preempt_enable_notrace();
191}
192
193static struct ftrace_ops trace_ops __read_mostly =
194{
195 .func = stack_trace_call,
196 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
197};
198
199static ssize_t
200stack_max_size_read(struct file *filp, char __user *ubuf,
201 size_t count, loff_t *ppos)
202{
203 unsigned long *ptr = filp->private_data;
204 char buf[64];
205 int r;
206
207 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
208 if (r > sizeof(buf))
209 r = sizeof(buf);
210 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
211}
212
213static ssize_t
214stack_max_size_write(struct file *filp, const char __user *ubuf,
215 size_t count, loff_t *ppos)
216{
217 long *ptr = filp->private_data;
218 unsigned long val, flags;
219 int ret;
220 int cpu;
221
222 ret = kstrtoul_from_user(ubuf, count, 10, &val);
223 if (ret)
224 return ret;
225
226 local_irq_save(flags);
227
228 /*
229 * In case we trace inside arch_spin_lock() or after (NMI),
230 * we will cause circular lock, so we also need to increase
231 * the percpu trace_active here.
232 */
233 cpu = smp_processor_id();
234 per_cpu(trace_active, cpu)++;
235
236 arch_spin_lock(&max_stack_lock);
237 *ptr = val;
238 arch_spin_unlock(&max_stack_lock);
239
240 per_cpu(trace_active, cpu)--;
241 local_irq_restore(flags);
242
243 return count;
244}
245
246static const struct file_operations stack_max_size_fops = {
247 .open = tracing_open_generic,
248 .read = stack_max_size_read,
249 .write = stack_max_size_write,
250 .llseek = default_llseek,
251};
252
253static void *
254__next(struct seq_file *m, loff_t *pos)
255{
256 long n = *pos - 1;
257
258 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
259 return NULL;
260
261 m->private = (void *)n;
262 return &m->private;
263}
264
265static void *
266t_next(struct seq_file *m, void *v, loff_t *pos)
267{
268 (*pos)++;
269 return __next(m, pos);
270}
271
272static void *t_start(struct seq_file *m, loff_t *pos)
273{
274 int cpu;
275
276 local_irq_disable();
277
278 cpu = smp_processor_id();
279 per_cpu(trace_active, cpu)++;
280
281 arch_spin_lock(&max_stack_lock);
282
283 if (*pos == 0)
284 return SEQ_START_TOKEN;
285
286 return __next(m, pos);
287}
288
289static void t_stop(struct seq_file *m, void *p)
290{
291 int cpu;
292
293 arch_spin_unlock(&max_stack_lock);
294
295 cpu = smp_processor_id();
296 per_cpu(trace_active, cpu)--;
297
298 local_irq_enable();
299}
300
301static int trace_lookup_stack(struct seq_file *m, long i)
302{
303 unsigned long addr = stack_dump_trace[i];
304
305 return seq_printf(m, "%pS\n", (void *)addr);
306}
307
308static void print_disabled(struct seq_file *m)
309{
310 seq_puts(m, "#\n"
311 "# Stack tracer disabled\n"
312 "#\n"
313 "# To enable the stack tracer, either add 'stacktrace' to the\n"
314 "# kernel command line\n"
315 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
316 "#\n");
317}
318
319static int t_show(struct seq_file *m, void *v)
320{
321 long i;
322 int size;
323
324 if (v == SEQ_START_TOKEN) {
325 seq_printf(m, " Depth Size Location"
326 " (%d entries)\n"
327 " ----- ---- --------\n",
328 max_stack_trace.nr_entries - 1);
329
330 if (!stack_tracer_enabled && !max_stack_size)
331 print_disabled(m);
332
333 return 0;
334 }
335
336 i = *(long *)v;
337
338 if (i >= max_stack_trace.nr_entries ||
339 stack_dump_trace[i] == ULONG_MAX)
340 return 0;
341
342 if (i+1 == max_stack_trace.nr_entries ||
343 stack_dump_trace[i+1] == ULONG_MAX)
344 size = stack_dump_index[i];
345 else
346 size = stack_dump_index[i] - stack_dump_index[i+1];
347
348 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
349
350 trace_lookup_stack(m, i);
351
352 return 0;
353}
354
355static const struct seq_operations stack_trace_seq_ops = {
356 .start = t_start,
357 .next = t_next,
358 .stop = t_stop,
359 .show = t_show,
360};
361
362static int stack_trace_open(struct inode *inode, struct file *file)
363{
364 return seq_open(file, &stack_trace_seq_ops);
365}
366
367static const struct file_operations stack_trace_fops = {
368 .open = stack_trace_open,
369 .read = seq_read,
370 .llseek = seq_lseek,
371 .release = seq_release,
372};
373
374static int
375stack_trace_filter_open(struct inode *inode, struct file *file)
376{
377 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
378 inode, file);
379}
380
381static const struct file_operations stack_trace_filter_fops = {
382 .open = stack_trace_filter_open,
383 .read = seq_read,
384 .write = ftrace_filter_write,
385 .llseek = tracing_lseek,
386 .release = ftrace_regex_release,
387};
388
389int
390stack_trace_sysctl(struct ctl_table *table, int write,
391 void __user *buffer, size_t *lenp,
392 loff_t *ppos)
393{
394 int ret;
395
396 mutex_lock(&stack_sysctl_mutex);
397
398 ret = proc_dointvec(table, write, buffer, lenp, ppos);
399
400 if (ret || !write ||
401 (last_stack_tracer_enabled == !!stack_tracer_enabled))
402 goto out;
403
404 last_stack_tracer_enabled = !!stack_tracer_enabled;
405
406 if (stack_tracer_enabled)
407 register_ftrace_function(&trace_ops);
408 else
409 unregister_ftrace_function(&trace_ops);
410
411 out:
412 mutex_unlock(&stack_sysctl_mutex);
413 return ret;
414}
415
416static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
417
418static __init int enable_stacktrace(char *str)
419{
420 if (strncmp(str, "_filter=", 8) == 0)
421 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
422
423 stack_tracer_enabled = 1;
424 last_stack_tracer_enabled = 1;
425 return 1;
426}
427__setup("stacktrace", enable_stacktrace);
428
429static __init int stack_trace_init(void)
430{
431 struct dentry *d_tracer;
432
433 d_tracer = tracing_init_dentry();
434 if (!d_tracer)
435 return 0;
436
437 trace_create_file("stack_max_size", 0644, d_tracer,
438 &max_stack_size, &stack_max_size_fops);
439
440 trace_create_file("stack_trace", 0444, d_tracer,
441 NULL, &stack_trace_fops);
442
443 trace_create_file("stack_trace_filter", 0444, d_tracer,
444 NULL, &stack_trace_filter_fops);
445
446 if (stack_trace_filter_buf[0])
447 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
448
449 if (stack_tracer_enabled)
450 register_ftrace_function(&trace_ops);
451
452 return 0;
453}
454
455device_initcall(stack_trace_init);