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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 | #include "trace.h" |
17 | |
18 | #define STACK_TRACE_ENTRIES 500 |
19 | |
20 | static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = |
21 | { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; |
22 | static unsigned stack_dump_index[STACK_TRACE_ENTRIES]; |
23 | |
24 | static struct stack_trace max_stack_trace = { |
25 | .max_entries = STACK_TRACE_ENTRIES, |
26 | .entries = stack_dump_trace, |
27 | }; |
28 | |
29 | static unsigned long max_stack_size; |
30 | static arch_spinlock_t max_stack_lock = |
31 | (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
32 | |
33 | static int stack_trace_disabled __read_mostly; |
34 | static DEFINE_PER_CPU(int, trace_active); |
35 | static DEFINE_MUTEX(stack_sysctl_mutex); |
36 | |
37 | int stack_tracer_enabled; |
38 | static int last_stack_tracer_enabled; |
39 | |
40 | static inline void check_stack(void) |
41 | { |
42 | unsigned long this_size, flags; |
43 | unsigned long *p, *top, *start; |
44 | int i; |
45 | |
46 | this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1); |
47 | this_size = THREAD_SIZE - this_size; |
48 | |
49 | if (this_size <= max_stack_size) |
50 | return; |
51 | |
52 | /* we do not handle interrupt stacks yet */ |
53 | if (!object_is_on_stack(&this_size)) |
54 | return; |
55 | |
56 | local_irq_save(flags); |
57 | arch_spin_lock(&max_stack_lock); |
58 | |
59 | /* a race could have already updated it */ |
60 | if (this_size <= max_stack_size) |
61 | goto out; |
62 | |
63 | max_stack_size = this_size; |
64 | |
65 | max_stack_trace.nr_entries = 0; |
66 | max_stack_trace.skip = 3; |
67 | |
68 | save_stack_trace(&max_stack_trace); |
69 | |
70 | /* |
71 | * Now find where in the stack these are. |
72 | */ |
73 | i = 0; |
74 | start = &this_size; |
75 | top = (unsigned long *) |
76 | (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); |
77 | |
78 | /* |
79 | * Loop through all the entries. One of the entries may |
80 | * for some reason be missed on the stack, so we may |
81 | * have to account for them. If they are all there, this |
82 | * loop will only happen once. This code only takes place |
83 | * on a new max, so it is far from a fast path. |
84 | */ |
85 | while (i < max_stack_trace.nr_entries) { |
86 | int found = 0; |
87 | |
88 | stack_dump_index[i] = this_size; |
89 | p = start; |
90 | |
91 | for (; p < top && i < max_stack_trace.nr_entries; p++) { |
92 | if (*p == stack_dump_trace[i]) { |
93 | this_size = stack_dump_index[i++] = |
94 | (top - p) * sizeof(unsigned long); |
95 | found = 1; |
96 | /* Start the search from here */ |
97 | start = p + 1; |
98 | } |
99 | } |
100 | |
101 | if (!found) |
102 | i++; |
103 | } |
104 | |
105 | out: |
106 | arch_spin_unlock(&max_stack_lock); |
107 | local_irq_restore(flags); |
108 | } |
109 | |
110 | static void |
111 | stack_trace_call(unsigned long ip, unsigned long parent_ip) |
112 | { |
113 | int cpu; |
114 | |
115 | if (unlikely(!ftrace_enabled || stack_trace_disabled)) |
116 | return; |
117 | |
118 | preempt_disable_notrace(); |
119 | |
120 | cpu = raw_smp_processor_id(); |
121 | /* no atomic needed, we only modify this variable by this cpu */ |
122 | if (per_cpu(trace_active, cpu)++ != 0) |
123 | goto out; |
124 | |
125 | check_stack(); |
126 | |
127 | out: |
128 | per_cpu(trace_active, cpu)--; |
129 | /* prevent recursion in schedule */ |
130 | preempt_enable_notrace(); |
131 | } |
132 | |
133 | static struct ftrace_ops trace_ops __read_mostly = |
134 | { |
135 | .func = stack_trace_call, |
136 | .flags = FTRACE_OPS_FL_GLOBAL, |
137 | }; |
138 | |
139 | static ssize_t |
140 | stack_max_size_read(struct file *filp, char __user *ubuf, |
141 | size_t count, loff_t *ppos) |
142 | { |
143 | unsigned long *ptr = filp->private_data; |
144 | char buf[64]; |
145 | int r; |
146 | |
147 | r = snprintf(buf, sizeof(buf), "%ld\n", *ptr); |
148 | if (r > sizeof(buf)) |
149 | r = sizeof(buf); |
150 | return simple_read_from_buffer(ubuf, count, ppos, buf, r); |
151 | } |
152 | |
153 | static ssize_t |
154 | stack_max_size_write(struct file *filp, const char __user *ubuf, |
155 | size_t count, loff_t *ppos) |
156 | { |
157 | long *ptr = filp->private_data; |
158 | unsigned long val, flags; |
159 | char buf[64]; |
160 | int ret; |
161 | int cpu; |
162 | |
163 | if (count >= sizeof(buf)) |
164 | return -EINVAL; |
165 | |
166 | if (copy_from_user(&buf, ubuf, count)) |
167 | return -EFAULT; |
168 | |
169 | buf[count] = 0; |
170 | |
171 | ret = strict_strtoul(buf, 10, &val); |
172 | if (ret < 0) |
173 | return ret; |
174 | |
175 | local_irq_save(flags); |
176 | |
177 | /* |
178 | * In case we trace inside arch_spin_lock() or after (NMI), |
179 | * we will cause circular lock, so we also need to increase |
180 | * the percpu trace_active here. |
181 | */ |
182 | cpu = smp_processor_id(); |
183 | per_cpu(trace_active, cpu)++; |
184 | |
185 | arch_spin_lock(&max_stack_lock); |
186 | *ptr = val; |
187 | arch_spin_unlock(&max_stack_lock); |
188 | |
189 | per_cpu(trace_active, cpu)--; |
190 | local_irq_restore(flags); |
191 | |
192 | return count; |
193 | } |
194 | |
195 | static const struct file_operations stack_max_size_fops = { |
196 | .open = tracing_open_generic, |
197 | .read = stack_max_size_read, |
198 | .write = stack_max_size_write, |
199 | .llseek = default_llseek, |
200 | }; |
201 | |
202 | static void * |
203 | __next(struct seq_file *m, loff_t *pos) |
204 | { |
205 | long n = *pos - 1; |
206 | |
207 | if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX) |
208 | return NULL; |
209 | |
210 | m->private = (void *)n; |
211 | return &m->private; |
212 | } |
213 | |
214 | static void * |
215 | t_next(struct seq_file *m, void *v, loff_t *pos) |
216 | { |
217 | (*pos)++; |
218 | return __next(m, pos); |
219 | } |
220 | |
221 | static void *t_start(struct seq_file *m, loff_t *pos) |
222 | { |
223 | int cpu; |
224 | |
225 | local_irq_disable(); |
226 | |
227 | cpu = smp_processor_id(); |
228 | per_cpu(trace_active, cpu)++; |
229 | |
230 | arch_spin_lock(&max_stack_lock); |
231 | |
232 | if (*pos == 0) |
233 | return SEQ_START_TOKEN; |
234 | |
235 | return __next(m, pos); |
236 | } |
237 | |
238 | static void t_stop(struct seq_file *m, void *p) |
239 | { |
240 | int cpu; |
241 | |
242 | arch_spin_unlock(&max_stack_lock); |
243 | |
244 | cpu = smp_processor_id(); |
245 | per_cpu(trace_active, cpu)--; |
246 | |
247 | local_irq_enable(); |
248 | } |
249 | |
250 | static int trace_lookup_stack(struct seq_file *m, long i) |
251 | { |
252 | unsigned long addr = stack_dump_trace[i]; |
253 | |
254 | return seq_printf(m, "%pS\n", (void *)addr); |
255 | } |
256 | |
257 | static void print_disabled(struct seq_file *m) |
258 | { |
259 | seq_puts(m, "#\n" |
260 | "# Stack tracer disabled\n" |
261 | "#\n" |
262 | "# To enable the stack tracer, either add 'stacktrace' to the\n" |
263 | "# kernel command line\n" |
264 | "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n" |
265 | "#\n"); |
266 | } |
267 | |
268 | static int t_show(struct seq_file *m, void *v) |
269 | { |
270 | long i; |
271 | int size; |
272 | |
273 | if (v == SEQ_START_TOKEN) { |
274 | seq_printf(m, " Depth Size Location" |
275 | " (%d entries)\n" |
276 | " ----- ---- --------\n", |
277 | max_stack_trace.nr_entries - 1); |
278 | |
279 | if (!stack_tracer_enabled && !max_stack_size) |
280 | print_disabled(m); |
281 | |
282 | return 0; |
283 | } |
284 | |
285 | i = *(long *)v; |
286 | |
287 | if (i >= max_stack_trace.nr_entries || |
288 | stack_dump_trace[i] == ULONG_MAX) |
289 | return 0; |
290 | |
291 | if (i+1 == max_stack_trace.nr_entries || |
292 | stack_dump_trace[i+1] == ULONG_MAX) |
293 | size = stack_dump_index[i]; |
294 | else |
295 | size = stack_dump_index[i] - stack_dump_index[i+1]; |
296 | |
297 | seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size); |
298 | |
299 | trace_lookup_stack(m, i); |
300 | |
301 | return 0; |
302 | } |
303 | |
304 | static const struct seq_operations stack_trace_seq_ops = { |
305 | .start = t_start, |
306 | .next = t_next, |
307 | .stop = t_stop, |
308 | .show = t_show, |
309 | }; |
310 | |
311 | static int stack_trace_open(struct inode *inode, struct file *file) |
312 | { |
313 | return seq_open(file, &stack_trace_seq_ops); |
314 | } |
315 | |
316 | static const struct file_operations stack_trace_fops = { |
317 | .open = stack_trace_open, |
318 | .read = seq_read, |
319 | .llseek = seq_lseek, |
320 | .release = seq_release, |
321 | }; |
322 | |
323 | int |
324 | stack_trace_sysctl(struct ctl_table *table, int write, |
325 | void __user *buffer, size_t *lenp, |
326 | loff_t *ppos) |
327 | { |
328 | int ret; |
329 | |
330 | mutex_lock(&stack_sysctl_mutex); |
331 | |
332 | ret = proc_dointvec(table, write, buffer, lenp, ppos); |
333 | |
334 | if (ret || !write || |
335 | (last_stack_tracer_enabled == !!stack_tracer_enabled)) |
336 | goto out; |
337 | |
338 | last_stack_tracer_enabled = !!stack_tracer_enabled; |
339 | |
340 | if (stack_tracer_enabled) |
341 | register_ftrace_function(&trace_ops); |
342 | else |
343 | unregister_ftrace_function(&trace_ops); |
344 | |
345 | out: |
346 | mutex_unlock(&stack_sysctl_mutex); |
347 | return ret; |
348 | } |
349 | |
350 | static __init int enable_stacktrace(char *str) |
351 | { |
352 | stack_tracer_enabled = 1; |
353 | last_stack_tracer_enabled = 1; |
354 | return 1; |
355 | } |
356 | __setup("stacktrace", enable_stacktrace); |
357 | |
358 | static __init int stack_trace_init(void) |
359 | { |
360 | struct dentry *d_tracer; |
361 | |
362 | d_tracer = tracing_init_dentry(); |
363 | |
364 | trace_create_file("stack_max_size", 0644, d_tracer, |
365 | &max_stack_size, &stack_max_size_fops); |
366 | |
367 | trace_create_file("stack_trace", 0444, d_tracer, |
368 | NULL, &stack_trace_fops); |
369 | |
370 | if (stack_tracer_enabled) |
371 | register_ftrace_function(&trace_ops); |
372 | |
373 | return 0; |
374 | } |
375 | |
376 | device_initcall(stack_trace_init); |
377 |
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