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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/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 | static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = |
24 | { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; |
25 | static unsigned stack_dump_index[STACK_TRACE_ENTRIES]; |
26 | |
27 | static struct stack_trace max_stack_trace = { |
28 | .max_entries = STACK_TRACE_ENTRIES, |
29 | .entries = stack_dump_trace, |
30 | }; |
31 | |
32 | static unsigned long max_stack_size; |
33 | static arch_spinlock_t max_stack_lock = |
34 | (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
35 | |
36 | static int stack_trace_disabled __read_mostly; |
37 | static DEFINE_PER_CPU(int, trace_active); |
38 | static DEFINE_MUTEX(stack_sysctl_mutex); |
39 | |
40 | int stack_tracer_enabled; |
41 | static int last_stack_tracer_enabled; |
42 | |
43 | static inline void check_stack(void) |
44 | { |
45 | unsigned long this_size, flags; |
46 | unsigned long *p, *top, *start; |
47 | int i; |
48 | |
49 | this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1); |
50 | this_size = THREAD_SIZE - this_size; |
51 | |
52 | if (this_size <= max_stack_size) |
53 | return; |
54 | |
55 | /* we do not handle interrupt stacks yet */ |
56 | if (!object_is_on_stack(&this_size)) |
57 | return; |
58 | |
59 | local_irq_save(flags); |
60 | arch_spin_lock(&max_stack_lock); |
61 | |
62 | /* a race could have already updated it */ |
63 | if (this_size <= max_stack_size) |
64 | goto out; |
65 | |
66 | max_stack_size = this_size; |
67 | |
68 | max_stack_trace.nr_entries = 0; |
69 | max_stack_trace.skip = 3; |
70 | |
71 | save_stack_trace(&max_stack_trace); |
72 | |
73 | /* |
74 | * Now find where in the stack these are. |
75 | */ |
76 | i = 0; |
77 | start = &this_size; |
78 | top = (unsigned long *) |
79 | (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); |
80 | |
81 | /* |
82 | * Loop through all the entries. One of the entries may |
83 | * for some reason be missed on the stack, so we may |
84 | * have to account for them. If they are all there, this |
85 | * loop will only happen once. This code only takes place |
86 | * on a new max, so it is far from a fast path. |
87 | */ |
88 | while (i < max_stack_trace.nr_entries) { |
89 | int found = 0; |
90 | |
91 | stack_dump_index[i] = this_size; |
92 | p = start; |
93 | |
94 | for (; p < top && i < max_stack_trace.nr_entries; p++) { |
95 | if (*p == stack_dump_trace[i]) { |
96 | this_size = stack_dump_index[i++] = |
97 | (top - p) * sizeof(unsigned long); |
98 | found = 1; |
99 | /* Start the search from here */ |
100 | start = p + 1; |
101 | } |
102 | } |
103 | |
104 | if (!found) |
105 | i++; |
106 | } |
107 | |
108 | out: |
109 | arch_spin_unlock(&max_stack_lock); |
110 | local_irq_restore(flags); |
111 | } |
112 | |
113 | static void |
114 | stack_trace_call(unsigned long ip, unsigned long parent_ip) |
115 | { |
116 | int cpu; |
117 | |
118 | if (unlikely(!ftrace_enabled || stack_trace_disabled)) |
119 | return; |
120 | |
121 | preempt_disable_notrace(); |
122 | |
123 | cpu = raw_smp_processor_id(); |
124 | /* no atomic needed, we only modify this variable by this cpu */ |
125 | if (per_cpu(trace_active, cpu)++ != 0) |
126 | goto out; |
127 | |
128 | check_stack(); |
129 | |
130 | out: |
131 | per_cpu(trace_active, cpu)--; |
132 | /* prevent recursion in schedule */ |
133 | preempt_enable_notrace(); |
134 | } |
135 | |
136 | static struct ftrace_ops trace_ops __read_mostly = |
137 | { |
138 | .func = stack_trace_call, |
139 | }; |
140 | |
141 | static ssize_t |
142 | stack_max_size_read(struct file *filp, char __user *ubuf, |
143 | size_t count, loff_t *ppos) |
144 | { |
145 | unsigned long *ptr = filp->private_data; |
146 | char buf[64]; |
147 | int r; |
148 | |
149 | r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); |
150 | if (r > sizeof(buf)) |
151 | r = sizeof(buf); |
152 | return simple_read_from_buffer(ubuf, count, ppos, buf, r); |
153 | } |
154 | |
155 | static ssize_t |
156 | stack_max_size_write(struct file *filp, const char __user *ubuf, |
157 | size_t count, loff_t *ppos) |
158 | { |
159 | long *ptr = filp->private_data; |
160 | unsigned long val, flags; |
161 | int ret; |
162 | int cpu; |
163 | |
164 | ret = kstrtoul_from_user(ubuf, count, 10, &val); |
165 | if (ret) |
166 | return ret; |
167 | |
168 | local_irq_save(flags); |
169 | |
170 | /* |
171 | * In case we trace inside arch_spin_lock() or after (NMI), |
172 | * we will cause circular lock, so we also need to increase |
173 | * the percpu trace_active here. |
174 | */ |
175 | cpu = smp_processor_id(); |
176 | per_cpu(trace_active, cpu)++; |
177 | |
178 | arch_spin_lock(&max_stack_lock); |
179 | *ptr = val; |
180 | arch_spin_unlock(&max_stack_lock); |
181 | |
182 | per_cpu(trace_active, cpu)--; |
183 | local_irq_restore(flags); |
184 | |
185 | return count; |
186 | } |
187 | |
188 | static const struct file_operations stack_max_size_fops = { |
189 | .open = tracing_open_generic, |
190 | .read = stack_max_size_read, |
191 | .write = stack_max_size_write, |
192 | .llseek = default_llseek, |
193 | }; |
194 | |
195 | static void * |
196 | __next(struct seq_file *m, loff_t *pos) |
197 | { |
198 | long n = *pos - 1; |
199 | |
200 | if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX) |
201 | return NULL; |
202 | |
203 | m->private = (void *)n; |
204 | return &m->private; |
205 | } |
206 | |
207 | static void * |
208 | t_next(struct seq_file *m, void *v, loff_t *pos) |
209 | { |
210 | (*pos)++; |
211 | return __next(m, pos); |
212 | } |
213 | |
214 | static void *t_start(struct seq_file *m, loff_t *pos) |
215 | { |
216 | int cpu; |
217 | |
218 | local_irq_disable(); |
219 | |
220 | cpu = smp_processor_id(); |
221 | per_cpu(trace_active, cpu)++; |
222 | |
223 | arch_spin_lock(&max_stack_lock); |
224 | |
225 | if (*pos == 0) |
226 | return SEQ_START_TOKEN; |
227 | |
228 | return __next(m, pos); |
229 | } |
230 | |
231 | static void t_stop(struct seq_file *m, void *p) |
232 | { |
233 | int cpu; |
234 | |
235 | arch_spin_unlock(&max_stack_lock); |
236 | |
237 | cpu = smp_processor_id(); |
238 | per_cpu(trace_active, cpu)--; |
239 | |
240 | local_irq_enable(); |
241 | } |
242 | |
243 | static int trace_lookup_stack(struct seq_file *m, long i) |
244 | { |
245 | unsigned long addr = stack_dump_trace[i]; |
246 | |
247 | return seq_printf(m, "%pS\n", (void *)addr); |
248 | } |
249 | |
250 | static void print_disabled(struct seq_file *m) |
251 | { |
252 | seq_puts(m, "#\n" |
253 | "# Stack tracer disabled\n" |
254 | "#\n" |
255 | "# To enable the stack tracer, either add 'stacktrace' to the\n" |
256 | "# kernel command line\n" |
257 | "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" |
258 | "#\n"); |
259 | } |
260 | |
261 | static int t_show(struct seq_file *m, void *v) |
262 | { |
263 | long i; |
264 | int size; |
265 | |
266 | if (v == SEQ_START_TOKEN) { |
267 | seq_printf(m, " Depth Size Location" |
268 | " (%d entries)\n" |
269 | " ----- ---- --------\n", |
270 | max_stack_trace.nr_entries - 1); |
271 | |
272 | if (!stack_tracer_enabled && !max_stack_size) |
273 | print_disabled(m); |
274 | |
275 | return 0; |
276 | } |
277 | |
278 | i = *(long *)v; |
279 | |
280 | if (i >= max_stack_trace.nr_entries || |
281 | stack_dump_trace[i] == ULONG_MAX) |
282 | return 0; |
283 | |
284 | if (i+1 == max_stack_trace.nr_entries || |
285 | stack_dump_trace[i+1] == ULONG_MAX) |
286 | size = stack_dump_index[i]; |
287 | else |
288 | size = stack_dump_index[i] - stack_dump_index[i+1]; |
289 | |
290 | seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); |
291 | |
292 | trace_lookup_stack(m, i); |
293 | |
294 | return 0; |
295 | } |
296 | |
297 | static const struct seq_operations stack_trace_seq_ops = { |
298 | .start = t_start, |
299 | .next = t_next, |
300 | .stop = t_stop, |
301 | .show = t_show, |
302 | }; |
303 | |
304 | static int stack_trace_open(struct inode *inode, struct file *file) |
305 | { |
306 | return seq_open(file, &stack_trace_seq_ops); |
307 | } |
308 | |
309 | static const struct file_operations stack_trace_fops = { |
310 | .open = stack_trace_open, |
311 | .read = seq_read, |
312 | .llseek = seq_lseek, |
313 | .release = seq_release, |
314 | }; |
315 | |
316 | static int |
317 | stack_trace_filter_open(struct inode *inode, struct file *file) |
318 | { |
319 | return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER, |
320 | inode, file); |
321 | } |
322 | |
323 | static const struct file_operations stack_trace_filter_fops = { |
324 | .open = stack_trace_filter_open, |
325 | .read = seq_read, |
326 | .write = ftrace_filter_write, |
327 | .llseek = ftrace_regex_lseek, |
328 | .release = ftrace_regex_release, |
329 | }; |
330 | |
331 | int |
332 | stack_trace_sysctl(struct ctl_table *table, int write, |
333 | void __user *buffer, size_t *lenp, |
334 | loff_t *ppos) |
335 | { |
336 | int ret; |
337 | |
338 | mutex_lock(&stack_sysctl_mutex); |
339 | |
340 | ret = proc_dointvec(table, write, buffer, lenp, ppos); |
341 | |
342 | if (ret || !write || |
343 | (last_stack_tracer_enabled == !!stack_tracer_enabled)) |
344 | goto out; |
345 | |
346 | last_stack_tracer_enabled = !!stack_tracer_enabled; |
347 | |
348 | if (stack_tracer_enabled) |
349 | register_ftrace_function(&trace_ops); |
350 | else |
351 | unregister_ftrace_function(&trace_ops); |
352 | |
353 | out: |
354 | mutex_unlock(&stack_sysctl_mutex); |
355 | return ret; |
356 | } |
357 | |
358 | static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; |
359 | |
360 | static __init int enable_stacktrace(char *str) |
361 | { |
362 | if (strncmp(str, "_filter=", 8) == 0) |
363 | strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); |
364 | |
365 | stack_tracer_enabled = 1; |
366 | last_stack_tracer_enabled = 1; |
367 | return 1; |
368 | } |
369 | __setup("stacktrace", enable_stacktrace); |
370 | |
371 | static __init int stack_trace_init(void) |
372 | { |
373 | struct dentry *d_tracer; |
374 | |
375 | d_tracer = tracing_init_dentry(); |
376 | |
377 | trace_create_file("stack_max_size", 0644, d_tracer, |
378 | &max_stack_size, &stack_max_size_fops); |
379 | |
380 | trace_create_file("stack_trace", 0444, d_tracer, |
381 | NULL, &stack_trace_fops); |
382 | |
383 | trace_create_file("stack_trace_filter", 0444, d_tracer, |
384 | NULL, &stack_trace_filter_fops); |
385 | |
386 | if (stack_trace_filter_buf[0]) |
387 | ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1); |
388 | |
389 | if (stack_tracer_enabled) |
390 | register_ftrace_function(&trace_ops); |
391 | |
392 | return 0; |
393 | } |
394 | |
395 | device_initcall(stack_trace_init); |
396 |
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