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 = ACCESS_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);
199 /* Some archs may not define MCOUNT_INSN_SIZE */
200 #ifndef MCOUNT_INSN_SIZE
201 # define MCOUNT_INSN_SIZE 0
205 stack_trace_call(unsigned long ip, unsigned long parent_ip,
206 struct ftrace_ops *op, struct pt_regs *pt_regs)
210 preempt_disable_notrace();
212 /* no atomic needed, we only modify this variable by this cpu */
213 __this_cpu_inc(disable_stack_tracer);
214 if (__this_cpu_read(disable_stack_tracer) != 1)
217 ip += MCOUNT_INSN_SIZE;
219 check_stack(ip, &stack);
222 __this_cpu_dec(disable_stack_tracer);
223 /* prevent recursion in schedule */
224 preempt_enable_notrace();
227 static struct ftrace_ops trace_ops __read_mostly =
229 .func = stack_trace_call,
230 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
234 stack_max_size_read(struct file *filp, char __user *ubuf,
235 size_t count, loff_t *ppos)
237 unsigned long *ptr = filp->private_data;
241 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
244 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
248 stack_max_size_write(struct file *filp, const char __user *ubuf,
249 size_t count, loff_t *ppos)
251 long *ptr = filp->private_data;
252 unsigned long val, flags;
255 ret = kstrtoul_from_user(ubuf, count, 10, &val);
259 local_irq_save(flags);
262 * In case we trace inside arch_spin_lock() or after (NMI),
263 * we will cause circular lock, so we also need to increase
264 * the percpu disable_stack_tracer here.
266 __this_cpu_inc(disable_stack_tracer);
268 arch_spin_lock(&stack_trace_max_lock);
270 arch_spin_unlock(&stack_trace_max_lock);
272 __this_cpu_dec(disable_stack_tracer);
273 local_irq_restore(flags);
278 static const struct file_operations stack_max_size_fops = {
279 .open = tracing_open_generic,
280 .read = stack_max_size_read,
281 .write = stack_max_size_write,
282 .llseek = default_llseek,
286 __next(struct seq_file *m, loff_t *pos)
290 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
293 m->private = (void *)n;
298 t_next(struct seq_file *m, void *v, loff_t *pos)
301 return __next(m, pos);
304 static void *t_start(struct seq_file *m, loff_t *pos)
308 __this_cpu_inc(disable_stack_tracer);
310 arch_spin_lock(&stack_trace_max_lock);
313 return SEQ_START_TOKEN;
315 return __next(m, pos);
318 static void t_stop(struct seq_file *m, void *p)
320 arch_spin_unlock(&stack_trace_max_lock);
322 __this_cpu_dec(disable_stack_tracer);
327 static void trace_lookup_stack(struct seq_file *m, long i)
329 unsigned long addr = stack_dump_trace[i];
331 seq_printf(m, "%pS\n", (void *)addr);
334 static void print_disabled(struct seq_file *m)
337 "# Stack tracer disabled\n"
339 "# To enable the stack tracer, either add 'stacktrace' to the\n"
340 "# kernel command line\n"
341 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
345 static int t_show(struct seq_file *m, void *v)
350 if (v == SEQ_START_TOKEN) {
351 seq_printf(m, " Depth Size Location"
353 " ----- ---- --------\n",
354 stack_trace_max.nr_entries);
356 if (!stack_tracer_enabled && !stack_trace_max_size)
364 if (i >= stack_trace_max.nr_entries ||
365 stack_dump_trace[i] == ULONG_MAX)
368 if (i+1 == stack_trace_max.nr_entries ||
369 stack_dump_trace[i+1] == ULONG_MAX)
370 size = stack_trace_index[i];
372 size = stack_trace_index[i] - stack_trace_index[i+1];
374 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
376 trace_lookup_stack(m, i);
381 static const struct seq_operations stack_trace_seq_ops = {
388 static int stack_trace_open(struct inode *inode, struct file *file)
390 return seq_open(file, &stack_trace_seq_ops);
393 static const struct file_operations stack_trace_fops = {
394 .open = stack_trace_open,
397 .release = seq_release,
400 #ifdef CONFIG_DYNAMIC_FTRACE
403 stack_trace_filter_open(struct inode *inode, struct file *file)
405 struct ftrace_ops *ops = inode->i_private;
407 return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
411 static const struct file_operations stack_trace_filter_fops = {
412 .open = stack_trace_filter_open,
414 .write = ftrace_filter_write,
415 .llseek = tracing_lseek,
416 .release = ftrace_regex_release,
419 #endif /* CONFIG_DYNAMIC_FTRACE */
422 stack_trace_sysctl(struct ctl_table *table, int write,
423 void __user *buffer, size_t *lenp,
428 mutex_lock(&stack_sysctl_mutex);
430 ret = proc_dointvec(table, write, buffer, lenp, ppos);
433 (last_stack_tracer_enabled == !!stack_tracer_enabled))
436 last_stack_tracer_enabled = !!stack_tracer_enabled;
438 if (stack_tracer_enabled)
439 register_ftrace_function(&trace_ops);
441 unregister_ftrace_function(&trace_ops);
444 mutex_unlock(&stack_sysctl_mutex);
448 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
450 static __init int enable_stacktrace(char *str)
452 if (strncmp(str, "_filter=", 8) == 0)
453 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
455 stack_tracer_enabled = 1;
456 last_stack_tracer_enabled = 1;
459 __setup("stacktrace", enable_stacktrace);
461 static __init int stack_trace_init(void)
463 struct dentry *d_tracer;
465 d_tracer = tracing_init_dentry();
466 if (IS_ERR(d_tracer))
469 trace_create_file("stack_max_size", 0644, d_tracer,
470 &stack_trace_max_size, &stack_max_size_fops);
472 trace_create_file("stack_trace", 0444, d_tracer,
473 NULL, &stack_trace_fops);
475 #ifdef CONFIG_DYNAMIC_FTRACE
476 trace_create_file("stack_trace_filter", 0444, d_tracer,
477 &trace_ops, &stack_trace_filter_fops);
480 if (stack_trace_filter_buf[0])
481 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
483 if (stack_tracer_enabled)
484 register_ftrace_function(&trace_ops);
489 device_initcall(stack_trace_init);