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TOMOYO Linux Cross Reference
Linux/kernel/trace/trace_stack.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
  4  *
  5  */
  6 #include <linux/sched/task_stack.h>
  7 #include <linux/stacktrace.h>
  8 #include <linux/kallsyms.h>
  9 #include <linux/seq_file.h>
 10 #include <linux/spinlock.h>
 11 #include <linux/uaccess.h>
 12 #include <linux/ftrace.h>
 13 #include <linux/module.h>
 14 #include <linux/sysctl.h>
 15 #include <linux/init.h>
 16 
 17 #include <asm/setup.h>
 18 
 19 #include "trace.h"
 20 
 21 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
 22          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
 23 unsigned stack_trace_index[STACK_TRACE_ENTRIES];
 24 
 25 /*
 26  * Reserve one entry for the passed in ip. This will allow
 27  * us to remove most or all of the stack size overhead
 28  * added by the stack tracer itself.
 29  */
 30 struct stack_trace stack_trace_max = {
 31         .max_entries            = STACK_TRACE_ENTRIES - 1,
 32         .entries                = &stack_dump_trace[0],
 33 };
 34 
 35 unsigned long stack_trace_max_size;
 36 arch_spinlock_t stack_trace_max_lock =
 37         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 38 
 39 DEFINE_PER_CPU(int, disable_stack_tracer);
 40 static DEFINE_MUTEX(stack_sysctl_mutex);
 41 
 42 int stack_tracer_enabled;
 43 static int last_stack_tracer_enabled;
 44 
 45 void stack_trace_print(void)
 46 {
 47         long i;
 48         int size;
 49 
 50         pr_emerg("        Depth    Size   Location    (%d entries)\n"
 51                            "        -----    ----   --------\n",
 52                            stack_trace_max.nr_entries);
 53 
 54         for (i = 0; i < stack_trace_max.nr_entries; i++) {
 55                 if (stack_dump_trace[i] == ULONG_MAX)
 56                         break;
 57                 if (i+1 == stack_trace_max.nr_entries ||
 58                                 stack_dump_trace[i+1] == ULONG_MAX)
 59                         size = stack_trace_index[i];
 60                 else
 61                         size = stack_trace_index[i] - stack_trace_index[i+1];
 62 
 63                 pr_emerg("%3ld) %8d   %5d   %pS\n", i, stack_trace_index[i],
 64                                 size, (void *)stack_dump_trace[i]);
 65         }
 66 }
 67 
 68 /*
 69  * When arch-specific code overrides this function, the following
 70  * data should be filled up, assuming stack_trace_max_lock is held to
 71  * prevent concurrent updates.
 72  *     stack_trace_index[]
 73  *     stack_trace_max
 74  *     stack_trace_max_size
 75  */
 76 void __weak
 77 check_stack(unsigned long ip, unsigned long *stack)
 78 {
 79         unsigned long this_size, flags; unsigned long *p, *top, *start;
 80         static int tracer_frame;
 81         int frame_size = READ_ONCE(tracer_frame);
 82         int i, x;
 83 
 84         this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
 85         this_size = THREAD_SIZE - this_size;
 86         /* Remove the frame of the tracer */
 87         this_size -= frame_size;
 88 
 89         if (this_size <= stack_trace_max_size)
 90                 return;
 91 
 92         /* we do not handle interrupt stacks yet */
 93         if (!object_is_on_stack(stack))
 94                 return;
 95 
 96         /* Can't do this from NMI context (can cause deadlocks) */
 97         if (in_nmi())
 98                 return;
 99 
100         local_irq_save(flags);
101         arch_spin_lock(&stack_trace_max_lock);
102 
103         /* In case another CPU set the tracer_frame on us */
104         if (unlikely(!frame_size))
105                 this_size -= tracer_frame;
106 
107         /* a race could have already updated it */
108         if (this_size <= stack_trace_max_size)
109                 goto out;
110 
111         stack_trace_max_size = this_size;
112 
113         stack_trace_max.nr_entries = 0;
114         stack_trace_max.skip = 3;
115 
116         save_stack_trace(&stack_trace_max);
117 
118         /* Skip over the overhead of the stack tracer itself */
119         for (i = 0; i < stack_trace_max.nr_entries; i++) {
120                 if (stack_dump_trace[i] == ip)
121                         break;
122         }
123 
124         /*
125          * Some archs may not have the passed in ip in the dump.
126          * If that happens, we need to show everything.
127          */
128         if (i == stack_trace_max.nr_entries)
129                 i = 0;
130 
131         /*
132          * Now find where in the stack these are.
133          */
134         x = 0;
135         start = stack;
136         top = (unsigned long *)
137                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
138 
139         /*
140          * Loop through all the entries. One of the entries may
141          * for some reason be missed on the stack, so we may
142          * have to account for them. If they are all there, this
143          * loop will only happen once. This code only takes place
144          * on a new max, so it is far from a fast path.
145          */
146         while (i < stack_trace_max.nr_entries) {
147                 int found = 0;
148 
149                 stack_trace_index[x] = this_size;
150                 p = start;
151 
152                 for (; p < top && i < stack_trace_max.nr_entries; p++) {
153                         if (stack_dump_trace[i] == ULONG_MAX)
154                                 break;
155                         /*
156                          * The READ_ONCE_NOCHECK is used to let KASAN know that
157                          * this is not a stack-out-of-bounds error.
158                          */
159                         if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
160                                 stack_dump_trace[x] = stack_dump_trace[i++];
161                                 this_size = stack_trace_index[x++] =
162                                         (top - p) * sizeof(unsigned long);
163                                 found = 1;
164                                 /* Start the search from here */
165                                 start = p + 1;
166                                 /*
167                                  * We do not want to show the overhead
168                                  * of the stack tracer stack in the
169                                  * max stack. If we haven't figured
170                                  * out what that is, then figure it out
171                                  * now.
172                                  */
173                                 if (unlikely(!tracer_frame)) {
174                                         tracer_frame = (p - stack) *
175                                                 sizeof(unsigned long);
176                                         stack_trace_max_size -= tracer_frame;
177                                 }
178                         }
179                 }
180 
181                 if (!found)
182                         i++;
183         }
184 
185         stack_trace_max.nr_entries = x;
186         for (; x < i; x++)
187                 stack_dump_trace[x] = ULONG_MAX;
188 
189         if (task_stack_end_corrupted(current)) {
190                 stack_trace_print();
191                 BUG();
192         }
193 
194  out:
195         arch_spin_unlock(&stack_trace_max_lock);
196         local_irq_restore(flags);
197 }
198 
199 static void
200 stack_trace_call(unsigned long ip, unsigned long parent_ip,
201                  struct ftrace_ops *op, struct pt_regs *pt_regs)
202 {
203         unsigned long stack;
204 
205         preempt_disable_notrace();
206 
207         /* no atomic needed, we only modify this variable by this cpu */
208         __this_cpu_inc(disable_stack_tracer);
209         if (__this_cpu_read(disable_stack_tracer) != 1)
210                 goto out;
211 
212         /* If rcu is not watching, then save stack trace can fail */
213         if (!rcu_is_watching())
214                 goto out;
215 
216         ip += MCOUNT_INSN_SIZE;
217 
218         check_stack(ip, &stack);
219 
220  out:
221         __this_cpu_dec(disable_stack_tracer);
222         /* prevent recursion in schedule */
223         preempt_enable_notrace();
224 }
225 
226 static struct ftrace_ops trace_ops __read_mostly =
227 {
228         .func = stack_trace_call,
229         .flags = FTRACE_OPS_FL_RECURSION_SAFE,
230 };
231 
232 static ssize_t
233 stack_max_size_read(struct file *filp, char __user *ubuf,
234                     size_t count, loff_t *ppos)
235 {
236         unsigned long *ptr = filp->private_data;
237         char buf[64];
238         int r;
239 
240         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
241         if (r > sizeof(buf))
242                 r = sizeof(buf);
243         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
244 }
245 
246 static ssize_t
247 stack_max_size_write(struct file *filp, const char __user *ubuf,
248                      size_t count, loff_t *ppos)
249 {
250         long *ptr = filp->private_data;
251         unsigned long val, flags;
252         int ret;
253 
254         ret = kstrtoul_from_user(ubuf, count, 10, &val);
255         if (ret)
256                 return ret;
257 
258         local_irq_save(flags);
259 
260         /*
261          * In case we trace inside arch_spin_lock() or after (NMI),
262          * we will cause circular lock, so we also need to increase
263          * the percpu disable_stack_tracer here.
264          */
265         __this_cpu_inc(disable_stack_tracer);
266 
267         arch_spin_lock(&stack_trace_max_lock);
268         *ptr = val;
269         arch_spin_unlock(&stack_trace_max_lock);
270 
271         __this_cpu_dec(disable_stack_tracer);
272         local_irq_restore(flags);
273 
274         return count;
275 }
276 
277 static const struct file_operations stack_max_size_fops = {
278         .open           = tracing_open_generic,
279         .read           = stack_max_size_read,
280         .write          = stack_max_size_write,
281         .llseek         = default_llseek,
282 };
283 
284 static void *
285 __next(struct seq_file *m, loff_t *pos)
286 {
287         long n = *pos - 1;
288 
289         if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
290                 return NULL;
291 
292         m->private = (void *)n;
293         return &m->private;
294 }
295 
296 static void *
297 t_next(struct seq_file *m, void *v, loff_t *pos)
298 {
299         (*pos)++;
300         return __next(m, pos);
301 }
302 
303 static void *t_start(struct seq_file *m, loff_t *pos)
304 {
305         local_irq_disable();
306 
307         __this_cpu_inc(disable_stack_tracer);
308 
309         arch_spin_lock(&stack_trace_max_lock);
310 
311         if (*pos == 0)
312                 return SEQ_START_TOKEN;
313 
314         return __next(m, pos);
315 }
316 
317 static void t_stop(struct seq_file *m, void *p)
318 {
319         arch_spin_unlock(&stack_trace_max_lock);
320 
321         __this_cpu_dec(disable_stack_tracer);
322 
323         local_irq_enable();
324 }
325 
326 static void trace_lookup_stack(struct seq_file *m, long i)
327 {
328         unsigned long addr = stack_dump_trace[i];
329 
330         seq_printf(m, "%pS\n", (void *)addr);
331 }
332 
333 static void print_disabled(struct seq_file *m)
334 {
335         seq_puts(m, "#\n"
336                  "#  Stack tracer disabled\n"
337                  "#\n"
338                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
339                  "# kernel command line\n"
340                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
341                  "#\n");
342 }
343 
344 static int t_show(struct seq_file *m, void *v)
345 {
346         long i;
347         int size;
348 
349         if (v == SEQ_START_TOKEN) {
350                 seq_printf(m, "        Depth    Size   Location"
351                            "    (%d entries)\n"
352                            "        -----    ----   --------\n",
353                            stack_trace_max.nr_entries);
354 
355                 if (!stack_tracer_enabled && !stack_trace_max_size)
356                         print_disabled(m);
357 
358                 return 0;
359         }
360 
361         i = *(long *)v;
362 
363         if (i >= stack_trace_max.nr_entries ||
364             stack_dump_trace[i] == ULONG_MAX)
365                 return 0;
366 
367         if (i+1 == stack_trace_max.nr_entries ||
368             stack_dump_trace[i+1] == ULONG_MAX)
369                 size = stack_trace_index[i];
370         else
371                 size = stack_trace_index[i] - stack_trace_index[i+1];
372 
373         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_trace_index[i], size);
374 
375         trace_lookup_stack(m, i);
376 
377         return 0;
378 }
379 
380 static const struct seq_operations stack_trace_seq_ops = {
381         .start          = t_start,
382         .next           = t_next,
383         .stop           = t_stop,
384         .show           = t_show,
385 };
386 
387 static int stack_trace_open(struct inode *inode, struct file *file)
388 {
389         return seq_open(file, &stack_trace_seq_ops);
390 }
391 
392 static const struct file_operations stack_trace_fops = {
393         .open           = stack_trace_open,
394         .read           = seq_read,
395         .llseek         = seq_lseek,
396         .release        = seq_release,
397 };
398 
399 #ifdef CONFIG_DYNAMIC_FTRACE
400 
401 static int
402 stack_trace_filter_open(struct inode *inode, struct file *file)
403 {
404         struct ftrace_ops *ops = inode->i_private;
405 
406         return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
407                                  inode, file);
408 }
409 
410 static const struct file_operations stack_trace_filter_fops = {
411         .open = stack_trace_filter_open,
412         .read = seq_read,
413         .write = ftrace_filter_write,
414         .llseek = tracing_lseek,
415         .release = ftrace_regex_release,
416 };
417 
418 #endif /* CONFIG_DYNAMIC_FTRACE */
419 
420 int
421 stack_trace_sysctl(struct ctl_table *table, int write,
422                    void __user *buffer, size_t *lenp,
423                    loff_t *ppos)
424 {
425         int ret;
426 
427         mutex_lock(&stack_sysctl_mutex);
428 
429         ret = proc_dointvec(table, write, buffer, lenp, ppos);
430 
431         if (ret || !write ||
432             (last_stack_tracer_enabled == !!stack_tracer_enabled))
433                 goto out;
434 
435         last_stack_tracer_enabled = !!stack_tracer_enabled;
436 
437         if (stack_tracer_enabled)
438                 register_ftrace_function(&trace_ops);
439         else
440                 unregister_ftrace_function(&trace_ops);
441 
442  out:
443         mutex_unlock(&stack_sysctl_mutex);
444         return ret;
445 }
446 
447 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
448 
449 static __init int enable_stacktrace(char *str)
450 {
451         if (strncmp(str, "_filter=", 8) == 0)
452                 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
453 
454         stack_tracer_enabled = 1;
455         last_stack_tracer_enabled = 1;
456         return 1;
457 }
458 __setup("stacktrace", enable_stacktrace);
459 
460 static __init int stack_trace_init(void)
461 {
462         struct dentry *d_tracer;
463 
464         d_tracer = tracing_init_dentry();
465         if (IS_ERR(d_tracer))
466                 return 0;
467 
468         trace_create_file("stack_max_size", 0644, d_tracer,
469                         &stack_trace_max_size, &stack_max_size_fops);
470 
471         trace_create_file("stack_trace", 0444, d_tracer,
472                         NULL, &stack_trace_fops);
473 
474 #ifdef CONFIG_DYNAMIC_FTRACE
475         trace_create_file("stack_trace_filter", 0644, d_tracer,
476                           &trace_ops, &stack_trace_filter_fops);
477 #endif
478 
479         if (stack_trace_filter_buf[0])
480                 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
481 
482         if (stack_tracer_enabled)
483                 register_ftrace_function(&trace_ops);
484 
485         return 0;
486 }
487 
488 device_initcall(stack_trace_init);
489 

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