1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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>
17 #include <asm/setup.h>
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];
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.
30 struct stack_trace stack_trace_max = {
31 .max_entries = STACK_TRACE_ENTRIES - 1,
32 .entries = &stack_dump_trace[0],
35 unsigned long stack_trace_max_size;
36 arch_spinlock_t stack_trace_max_lock =
37 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
39 DEFINE_PER_CPU(int, disable_stack_tracer);
40 static DEFINE_MUTEX(stack_sysctl_mutex);
42 int stack_tracer_enabled;
43 static int last_stack_tracer_enabled;
45 void stack_trace_print(void)
50 pr_emerg(" Depth Size Location (%d entries)\n"
51 " ----- ---- --------\n",
52 stack_trace_max.nr_entries);
54 for (i = 0; i < stack_trace_max.nr_entries; i++) {
55 if (stack_dump_trace[i] == ULONG_MAX)
57 if (i+1 == stack_trace_max.nr_entries ||
58 stack_dump_trace[i+1] == ULONG_MAX)
59 size = stack_trace_index[i];
61 size = stack_trace_index[i] - stack_trace_index[i+1];
63 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
64 size, (void *)stack_dump_trace[i]);
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.
74 * stack_trace_max_size
77 check_stack(unsigned long ip, unsigned long *stack)
79 unsigned long this_size, flags; unsigned long *p, *top, *start;
80 static int tracer_frame;
81 int frame_size = READ_ONCE(tracer_frame);
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;
89 if (this_size <= stack_trace_max_size)
92 /* we do not handle interrupt stacks yet */
93 if (!object_is_on_stack(stack))
96 /* Can't do this from NMI context (can cause deadlocks) */
100 local_irq_save(flags);
101 arch_spin_lock(&stack_trace_max_lock);
103 /* In case another CPU set the tracer_frame on us */
104 if (unlikely(!frame_size))
105 this_size -= tracer_frame;
107 /* a race could have already updated it */
108 if (this_size <= stack_trace_max_size)
111 stack_trace_max_size = this_size;
113 stack_trace_max.nr_entries = 0;
114 stack_trace_max.skip = 3;
116 save_stack_trace(&stack_trace_max);
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)
125 * Some archs may not have the passed in ip in the dump.
126 * If that happens, we need to show everything.
128 if (i == stack_trace_max.nr_entries)
132 * Now find where in the stack these are.
136 top = (unsigned long *)
137 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
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.
146 while (i < stack_trace_max.nr_entries) {
149 stack_trace_index[x] = this_size;
152 for (; p < top && i < stack_trace_max.nr_entries; p++) {
153 if (stack_dump_trace[i] == ULONG_MAX)
156 * The READ_ONCE_NOCHECK is used to let KASAN know that
157 * this is not a stack-out-of-bounds error.
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);
164 /* Start the search from here */
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
173 if (unlikely(!tracer_frame)) {
174 tracer_frame = (p - stack) *
175 sizeof(unsigned long);
176 stack_trace_max_size -= tracer_frame;
185 stack_trace_max.nr_entries = x;
187 stack_dump_trace[x] = ULONG_MAX;
189 if (task_stack_end_corrupted(current)) {
195 arch_spin_unlock(&stack_trace_max_lock);
196 local_irq_restore(flags);
200 stack_trace_call(unsigned long ip, unsigned long parent_ip,
201 struct ftrace_ops *op, struct pt_regs *pt_regs)
205 preempt_disable_notrace();
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)
212 ip += MCOUNT_INSN_SIZE;
214 check_stack(ip, &stack);
217 __this_cpu_dec(disable_stack_tracer);
218 /* prevent recursion in schedule */
219 preempt_enable_notrace();
222 static struct ftrace_ops trace_ops __read_mostly =
224 .func = stack_trace_call,
225 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
229 stack_max_size_read(struct file *filp, char __user *ubuf,
230 size_t count, loff_t *ppos)
232 unsigned long *ptr = filp->private_data;
236 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
239 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
243 stack_max_size_write(struct file *filp, const char __user *ubuf,
244 size_t count, loff_t *ppos)
246 long *ptr = filp->private_data;
247 unsigned long val, flags;
250 ret = kstrtoul_from_user(ubuf, count, 10, &val);
254 local_irq_save(flags);
257 * In case we trace inside arch_spin_lock() or after (NMI),
258 * we will cause circular lock, so we also need to increase
259 * the percpu disable_stack_tracer here.
261 __this_cpu_inc(disable_stack_tracer);
263 arch_spin_lock(&stack_trace_max_lock);
265 arch_spin_unlock(&stack_trace_max_lock);
267 __this_cpu_dec(disable_stack_tracer);
268 local_irq_restore(flags);
273 static const struct file_operations stack_max_size_fops = {
274 .open = tracing_open_generic,
275 .read = stack_max_size_read,
276 .write = stack_max_size_write,
277 .llseek = default_llseek,
281 __next(struct seq_file *m, loff_t *pos)
285 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
288 m->private = (void *)n;
293 t_next(struct seq_file *m, void *v, loff_t *pos)
296 return __next(m, pos);
299 static void *t_start(struct seq_file *m, loff_t *pos)
303 __this_cpu_inc(disable_stack_tracer);
305 arch_spin_lock(&stack_trace_max_lock);
308 return SEQ_START_TOKEN;
310 return __next(m, pos);
313 static void t_stop(struct seq_file *m, void *p)
315 arch_spin_unlock(&stack_trace_max_lock);
317 __this_cpu_dec(disable_stack_tracer);
322 static void trace_lookup_stack(struct seq_file *m, long i)
324 unsigned long addr = stack_dump_trace[i];
326 seq_printf(m, "%pS\n", (void *)addr);
329 static void print_disabled(struct seq_file *m)
332 "# Stack tracer disabled\n"
334 "# To enable the stack tracer, either add 'stacktrace' to the\n"
335 "# kernel command line\n"
336 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
340 static int t_show(struct seq_file *m, void *v)
345 if (v == SEQ_START_TOKEN) {
346 seq_printf(m, " Depth Size Location"
348 " ----- ---- --------\n",
349 stack_trace_max.nr_entries);
351 if (!stack_tracer_enabled && !stack_trace_max_size)
359 if (i >= stack_trace_max.nr_entries ||
360 stack_dump_trace[i] == ULONG_MAX)
363 if (i+1 == stack_trace_max.nr_entries ||
364 stack_dump_trace[i+1] == ULONG_MAX)
365 size = stack_trace_index[i];
367 size = stack_trace_index[i] - stack_trace_index[i+1];
369 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
371 trace_lookup_stack(m, i);
376 static const struct seq_operations stack_trace_seq_ops = {
383 static int stack_trace_open(struct inode *inode, struct file *file)
385 return seq_open(file, &stack_trace_seq_ops);
388 static const struct file_operations stack_trace_fops = {
389 .open = stack_trace_open,
392 .release = seq_release,
395 #ifdef CONFIG_DYNAMIC_FTRACE
398 stack_trace_filter_open(struct inode *inode, struct file *file)
400 struct ftrace_ops *ops = inode->i_private;
402 return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
406 static const struct file_operations stack_trace_filter_fops = {
407 .open = stack_trace_filter_open,
409 .write = ftrace_filter_write,
410 .llseek = tracing_lseek,
411 .release = ftrace_regex_release,
414 #endif /* CONFIG_DYNAMIC_FTRACE */
417 stack_trace_sysctl(struct ctl_table *table, int write,
418 void __user *buffer, size_t *lenp,
423 mutex_lock(&stack_sysctl_mutex);
425 ret = proc_dointvec(table, write, buffer, lenp, ppos);
428 (last_stack_tracer_enabled == !!stack_tracer_enabled))
431 last_stack_tracer_enabled = !!stack_tracer_enabled;
433 if (stack_tracer_enabled)
434 register_ftrace_function(&trace_ops);
436 unregister_ftrace_function(&trace_ops);
439 mutex_unlock(&stack_sysctl_mutex);
443 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
445 static __init int enable_stacktrace(char *str)
447 if (strncmp(str, "_filter=", 8) == 0)
448 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
450 stack_tracer_enabled = 1;
451 last_stack_tracer_enabled = 1;
454 __setup("stacktrace", enable_stacktrace);
456 static __init int stack_trace_init(void)
458 struct dentry *d_tracer;
460 d_tracer = tracing_init_dentry();
461 if (IS_ERR(d_tracer))
464 trace_create_file("stack_max_size", 0644, d_tracer,
465 &stack_trace_max_size, &stack_max_size_fops);
467 trace_create_file("stack_trace", 0444, d_tracer,
468 NULL, &stack_trace_fops);
470 #ifdef CONFIG_DYNAMIC_FTRACE
471 trace_create_file("stack_trace_filter", 0444, d_tracer,
472 &trace_ops, &stack_trace_filter_fops);
475 if (stack_trace_filter_buf[0])
476 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
478 if (stack_tracer_enabled)
479 register_ftrace_function(&trace_ops);
484 device_initcall(stack_trace_init);