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2
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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
23static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
24 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
25static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
26
27static struct stack_trace max_stack_trace = {
28 .max_entries = STACK_TRACE_ENTRIES,
29 .entries = stack_dump_trace,
30};
31
32static unsigned long max_stack_size;
33static arch_spinlock_t max_stack_lock =
34 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
35
36static int stack_trace_disabled __read_mostly;
37static DEFINE_PER_CPU(int, trace_active);
38static DEFINE_MUTEX(stack_sysctl_mutex);
39
40int stack_tracer_enabled;
41static int last_stack_tracer_enabled;
42
43static 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
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
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
75
76 i = 0;
77 start = &this_size;
78 top = (unsigned long *)
79 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
80
81
82
83
84
85
86
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
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
113static void
114stack_trace_call(unsigned long ip, unsigned long parent_ip,
115 struct ftrace_ops *op, struct pt_regs *pt_regs)
116{
117 int cpu;
118
119 if (unlikely(!ftrace_enabled || stack_trace_disabled))
120 return;
121
122 preempt_disable_notrace();
123
124 cpu = raw_smp_processor_id();
125
126 if (per_cpu(trace_active, cpu)++ != 0)
127 goto out;
128
129 check_stack();
130
131 out:
132 per_cpu(trace_active, cpu)--;
133
134 preempt_enable_notrace();
135}
136
137static struct ftrace_ops trace_ops __read_mostly =
138{
139 .func = stack_trace_call,
140 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
141};
142
143static ssize_t
144stack_max_size_read(struct file *filp, char __user *ubuf,
145 size_t count, loff_t *ppos)
146{
147 unsigned long *ptr = filp->private_data;
148 char buf[64];
149 int r;
150
151 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
152 if (r > sizeof(buf))
153 r = sizeof(buf);
154 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
155}
156
157static ssize_t
158stack_max_size_write(struct file *filp, const char __user *ubuf,
159 size_t count, loff_t *ppos)
160{
161 long *ptr = filp->private_data;
162 unsigned long val, flags;
163 int ret;
164 int cpu;
165
166 ret = kstrtoul_from_user(ubuf, count, 10, &val);
167 if (ret)
168 return ret;
169
170 local_irq_save(flags);
171
172
173
174
175
176
177 cpu = smp_processor_id();
178 per_cpu(trace_active, cpu)++;
179
180 arch_spin_lock(&max_stack_lock);
181 *ptr = val;
182 arch_spin_unlock(&max_stack_lock);
183
184 per_cpu(trace_active, cpu)--;
185 local_irq_restore(flags);
186
187 return count;
188}
189
190static const struct file_operations stack_max_size_fops = {
191 .open = tracing_open_generic,
192 .read = stack_max_size_read,
193 .write = stack_max_size_write,
194 .llseek = default_llseek,
195};
196
197static void *
198__next(struct seq_file *m, loff_t *pos)
199{
200 long n = *pos - 1;
201
202 if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
203 return NULL;
204
205 m->private = (void *)n;
206 return &m->private;
207}
208
209static void *
210t_next(struct seq_file *m, void *v, loff_t *pos)
211{
212 (*pos)++;
213 return __next(m, pos);
214}
215
216static void *t_start(struct seq_file *m, loff_t *pos)
217{
218 int cpu;
219
220 local_irq_disable();
221
222 cpu = smp_processor_id();
223 per_cpu(trace_active, cpu)++;
224
225 arch_spin_lock(&max_stack_lock);
226
227 if (*pos == 0)
228 return SEQ_START_TOKEN;
229
230 return __next(m, pos);
231}
232
233static void t_stop(struct seq_file *m, void *p)
234{
235 int cpu;
236
237 arch_spin_unlock(&max_stack_lock);
238
239 cpu = smp_processor_id();
240 per_cpu(trace_active, cpu)--;
241
242 local_irq_enable();
243}
244
245static int trace_lookup_stack(struct seq_file *m, long i)
246{
247 unsigned long addr = stack_dump_trace[i];
248
249 return seq_printf(m, "%pS\n", (void *)addr);
250}
251
252static void print_disabled(struct seq_file *m)
253{
254 seq_puts(m, "#\n"
255 "# Stack tracer disabled\n"
256 "#\n"
257 "# To enable the stack tracer, either add 'stacktrace' to the\n"
258 "# kernel command line\n"
259 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
260 "#\n");
261}
262
263static int t_show(struct seq_file *m, void *v)
264{
265 long i;
266 int size;
267
268 if (v == SEQ_START_TOKEN) {
269 seq_printf(m, " Depth Size Location"
270 " (%d entries)\n"
271 " ----- ---- --------\n",
272 max_stack_trace.nr_entries - 1);
273
274 if (!stack_tracer_enabled && !max_stack_size)
275 print_disabled(m);
276
277 return 0;
278 }
279
280 i = *(long *)v;
281
282 if (i >= max_stack_trace.nr_entries ||
283 stack_dump_trace[i] == ULONG_MAX)
284 return 0;
285
286 if (i+1 == max_stack_trace.nr_entries ||
287 stack_dump_trace[i+1] == ULONG_MAX)
288 size = stack_dump_index[i];
289 else
290 size = stack_dump_index[i] - stack_dump_index[i+1];
291
292 seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_index[i], size);
293
294 trace_lookup_stack(m, i);
295
296 return 0;
297}
298
299static const struct seq_operations stack_trace_seq_ops = {
300 .start = t_start,
301 .next = t_next,
302 .stop = t_stop,
303 .show = t_show,
304};
305
306static int stack_trace_open(struct inode *inode, struct file *file)
307{
308 return seq_open(file, &stack_trace_seq_ops);
309}
310
311static const struct file_operations stack_trace_fops = {
312 .open = stack_trace_open,
313 .read = seq_read,
314 .llseek = seq_lseek,
315 .release = seq_release,
316};
317
318static int
319stack_trace_filter_open(struct inode *inode, struct file *file)
320{
321 return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
322 inode, file);
323}
324
325static const struct file_operations stack_trace_filter_fops = {
326 .open = stack_trace_filter_open,
327 .read = seq_read,
328 .write = ftrace_filter_write,
329 .llseek = ftrace_regex_lseek,
330 .release = ftrace_regex_release,
331};
332
333int
334stack_trace_sysctl(struct ctl_table *table, int write,
335 void __user *buffer, size_t *lenp,
336 loff_t *ppos)
337{
338 int ret;
339
340 mutex_lock(&stack_sysctl_mutex);
341
342 ret = proc_dointvec(table, write, buffer, lenp, ppos);
343
344 if (ret || !write ||
345 (last_stack_tracer_enabled == !!stack_tracer_enabled))
346 goto out;
347
348 last_stack_tracer_enabled = !!stack_tracer_enabled;
349
350 if (stack_tracer_enabled)
351 register_ftrace_function(&trace_ops);
352 else
353 unregister_ftrace_function(&trace_ops);
354
355 out:
356 mutex_unlock(&stack_sysctl_mutex);
357 return ret;
358}
359
360static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
361
362static __init int enable_stacktrace(char *str)
363{
364 if (strncmp(str, "_filter=", 8) == 0)
365 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
366
367 stack_tracer_enabled = 1;
368 last_stack_tracer_enabled = 1;
369 return 1;
370}
371__setup("stacktrace", enable_stacktrace);
372
373static __init int stack_trace_init(void)
374{
375 struct dentry *d_tracer;
376
377 d_tracer = tracing_init_dentry();
378
379 trace_create_file("stack_max_size", 0644, d_tracer,
380 &max_stack_size, &stack_max_size_fops);
381
382 trace_create_file("stack_trace", 0444, d_tracer,
383 NULL, &stack_trace_fops);
384
385 trace_create_file("stack_trace_filter", 0444, d_tracer,
386 NULL, &stack_trace_filter_fops);
387
388 if (stack_trace_filter_buf[0])
389 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
390
391 if (stack_tracer_enabled)
392 register_ftrace_function(&trace_ops);
393
394 return 0;
395}
396
397device_initcall(stack_trace_init);
398