2 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 #include <linux/sched/task_stack.h>
6 #include <linux/stacktrace.h>
7 #include <linux/kallsyms.h>
8 #include <linux/seq_file.h>
9 #include <linux/spinlock.h>
10 #include <linux/uaccess.h>
11 #include <linux/ftrace.h>
12 #include <linux/module.h>
13 #include <linux/sysctl.h>
14 #include <linux/init.h>
16 #include <asm/setup.h>
20 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
21 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
22 unsigned stack_trace_index[STACK_TRACE_ENTRIES];
25 * Reserve one entry for the passed in ip. This will allow
26 * us to remove most or all of the stack size overhead
27 * added by the stack tracer itself.
29 struct stack_trace stack_trace_max = {
30 .max_entries = STACK_TRACE_ENTRIES - 1,
31 .entries = &stack_dump_trace[0],
34 unsigned long stack_trace_max_size;
35 arch_spinlock_t stack_trace_max_lock =
36 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
38 DEFINE_PER_CPU(int, disable_stack_tracer);
39 static DEFINE_MUTEX(stack_sysctl_mutex);
41 int stack_tracer_enabled;
42 static int last_stack_tracer_enabled;
44 void stack_trace_print(void)
49 pr_emerg(" Depth Size Location (%d entries)\n"
50 " ----- ---- --------\n",
51 stack_trace_max.nr_entries);
53 for (i = 0; i < stack_trace_max.nr_entries; i++) {
54 if (stack_dump_trace[i] == ULONG_MAX)
56 if (i+1 == stack_trace_max.nr_entries ||
57 stack_dump_trace[i+1] == ULONG_MAX)
58 size = stack_trace_index[i];
60 size = stack_trace_index[i] - stack_trace_index[i+1];
62 pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
63 size, (void *)stack_dump_trace[i]);
68 * When arch-specific code overrides this function, the following
69 * data should be filled up, assuming stack_trace_max_lock is held to
70 * prevent concurrent updates.
73 * stack_trace_max_size
76 check_stack(unsigned long ip, unsigned long *stack)
78 unsigned long this_size, flags; unsigned long *p, *top, *start;
79 static int tracer_frame;
80 int frame_size = ACCESS_ONCE(tracer_frame);
83 this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
84 this_size = THREAD_SIZE - this_size;
85 /* Remove the frame of the tracer */
86 this_size -= frame_size;
88 if (this_size <= stack_trace_max_size)
91 /* we do not handle interrupt stacks yet */
92 if (!object_is_on_stack(stack))
95 /* Can't do this from NMI context (can cause deadlocks) */
99 local_irq_save(flags);
100 arch_spin_lock(&stack_trace_max_lock);
102 /* In case another CPU set the tracer_frame on us */
103 if (unlikely(!frame_size))
104 this_size -= tracer_frame;
106 /* a race could have already updated it */
107 if (this_size <= stack_trace_max_size)
110 stack_trace_max_size = this_size;
112 stack_trace_max.nr_entries = 0;
113 stack_trace_max.skip = 3;
115 save_stack_trace(&stack_trace_max);
117 /* Skip over the overhead of the stack tracer itself */
118 for (i = 0; i < stack_trace_max.nr_entries; i++) {
119 if (stack_dump_trace[i] == ip)
124 * Some archs may not have the passed in ip in the dump.
125 * If that happens, we need to show everything.
127 if (i == stack_trace_max.nr_entries)
131 * Now find where in the stack these are.
135 top = (unsigned long *)
136 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
139 * Loop through all the entries. One of the entries may
140 * for some reason be missed on the stack, so we may
141 * have to account for them. If they are all there, this
142 * loop will only happen once. This code only takes place
143 * on a new max, so it is far from a fast path.
145 while (i < stack_trace_max.nr_entries) {
148 stack_trace_index[x] = this_size;
151 for (; p < top && i < stack_trace_max.nr_entries; p++) {
152 if (stack_dump_trace[i] == ULONG_MAX)
155 * The READ_ONCE_NOCHECK is used to let KASAN know that
156 * this is not a stack-out-of-bounds error.
158 if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
159 stack_dump_trace[x] = stack_dump_trace[i++];
160 this_size = stack_trace_index[x++] =
161 (top - p) * sizeof(unsigned long);
163 /* Start the search from here */
166 * We do not want to show the overhead
167 * of the stack tracer stack in the
168 * max stack. If we haven't figured
169 * out what that is, then figure it out
172 if (unlikely(!tracer_frame)) {
173 tracer_frame = (p - stack) *
174 sizeof(unsigned long);
175 stack_trace_max_size -= tracer_frame;
184 stack_trace_max.nr_entries = x;
186 stack_dump_trace[x] = ULONG_MAX;
188 if (task_stack_end_corrupted(current)) {
194 arch_spin_unlock(&stack_trace_max_lock);
195 local_irq_restore(flags);
199 stack_trace_call(unsigned long ip, unsigned long parent_ip,
200 struct ftrace_ops *op, struct pt_regs *pt_regs)
204 preempt_disable_notrace();
206 /* no atomic needed, we only modify this variable by this cpu */
207 __this_cpu_inc(disable_stack_tracer);
208 if (__this_cpu_read(disable_stack_tracer) != 1)
211 ip += MCOUNT_INSN_SIZE;
213 check_stack(ip, &stack);
216 __this_cpu_dec(disable_stack_tracer);
217 /* prevent recursion in schedule */
218 preempt_enable_notrace();
221 static struct ftrace_ops trace_ops __read_mostly =
223 .func = stack_trace_call,
224 .flags = FTRACE_OPS_FL_RECURSION_SAFE,
228 stack_max_size_read(struct file *filp, char __user *ubuf,
229 size_t count, loff_t *ppos)
231 unsigned long *ptr = filp->private_data;
235 r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
238 return simple_read_from_buffer(ubuf, count, ppos, buf, r);
242 stack_max_size_write(struct file *filp, const char __user *ubuf,
243 size_t count, loff_t *ppos)
245 long *ptr = filp->private_data;
246 unsigned long val, flags;
249 ret = kstrtoul_from_user(ubuf, count, 10, &val);
253 local_irq_save(flags);
256 * In case we trace inside arch_spin_lock() or after (NMI),
257 * we will cause circular lock, so we also need to increase
258 * the percpu disable_stack_tracer here.
260 __this_cpu_inc(disable_stack_tracer);
262 arch_spin_lock(&stack_trace_max_lock);
264 arch_spin_unlock(&stack_trace_max_lock);
266 __this_cpu_dec(disable_stack_tracer);
267 local_irq_restore(flags);
272 static const struct file_operations stack_max_size_fops = {
273 .open = tracing_open_generic,
274 .read = stack_max_size_read,
275 .write = stack_max_size_write,
276 .llseek = default_llseek,
280 __next(struct seq_file *m, loff_t *pos)
284 if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
287 m->private = (void *)n;
292 t_next(struct seq_file *m, void *v, loff_t *pos)
295 return __next(m, pos);
298 static void *t_start(struct seq_file *m, loff_t *pos)
302 __this_cpu_inc(disable_stack_tracer);
304 arch_spin_lock(&stack_trace_max_lock);
307 return SEQ_START_TOKEN;
309 return __next(m, pos);
312 static void t_stop(struct seq_file *m, void *p)
314 arch_spin_unlock(&stack_trace_max_lock);
316 __this_cpu_dec(disable_stack_tracer);
321 static void trace_lookup_stack(struct seq_file *m, long i)
323 unsigned long addr = stack_dump_trace[i];
325 seq_printf(m, "%pS\n", (void *)addr);
328 static void print_disabled(struct seq_file *m)
331 "# Stack tracer disabled\n"
333 "# To enable the stack tracer, either add 'stacktrace' to the\n"
334 "# kernel command line\n"
335 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
339 static int t_show(struct seq_file *m, void *v)
344 if (v == SEQ_START_TOKEN) {
345 seq_printf(m, " Depth Size Location"
347 " ----- ---- --------\n",
348 stack_trace_max.nr_entries);
350 if (!stack_tracer_enabled && !stack_trace_max_size)
358 if (i >= stack_trace_max.nr_entries ||
359 stack_dump_trace[i] == ULONG_MAX)
362 if (i+1 == stack_trace_max.nr_entries ||
363 stack_dump_trace[i+1] == ULONG_MAX)
364 size = stack_trace_index[i];
366 size = stack_trace_index[i] - stack_trace_index[i+1];
368 seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
370 trace_lookup_stack(m, i);
375 static const struct seq_operations stack_trace_seq_ops = {
382 static int stack_trace_open(struct inode *inode, struct file *file)
384 return seq_open(file, &stack_trace_seq_ops);
387 static const struct file_operations stack_trace_fops = {
388 .open = stack_trace_open,
391 .release = seq_release,
394 #ifdef CONFIG_DYNAMIC_FTRACE
397 stack_trace_filter_open(struct inode *inode, struct file *file)
399 struct ftrace_ops *ops = inode->i_private;
401 return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
405 static const struct file_operations stack_trace_filter_fops = {
406 .open = stack_trace_filter_open,
408 .write = ftrace_filter_write,
409 .llseek = tracing_lseek,
410 .release = ftrace_regex_release,
413 #endif /* CONFIG_DYNAMIC_FTRACE */
416 stack_trace_sysctl(struct ctl_table *table, int write,
417 void __user *buffer, size_t *lenp,
422 mutex_lock(&stack_sysctl_mutex);
424 ret = proc_dointvec(table, write, buffer, lenp, ppos);
427 (last_stack_tracer_enabled == !!stack_tracer_enabled))
430 last_stack_tracer_enabled = !!stack_tracer_enabled;
432 if (stack_tracer_enabled)
433 register_ftrace_function(&trace_ops);
435 unregister_ftrace_function(&trace_ops);
438 mutex_unlock(&stack_sysctl_mutex);
442 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
444 static __init int enable_stacktrace(char *str)
446 if (strncmp(str, "_filter=", 8) == 0)
447 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
449 stack_tracer_enabled = 1;
450 last_stack_tracer_enabled = 1;
453 __setup("stacktrace", enable_stacktrace);
455 static __init int stack_trace_init(void)
457 struct dentry *d_tracer;
459 d_tracer = tracing_init_dentry();
460 if (IS_ERR(d_tracer))
463 trace_create_file("stack_max_size", 0644, d_tracer,
464 &stack_trace_max_size, &stack_max_size_fops);
466 trace_create_file("stack_trace", 0444, d_tracer,
467 NULL, &stack_trace_fops);
469 #ifdef CONFIG_DYNAMIC_FTRACE
470 trace_create_file("stack_trace_filter", 0444, d_tracer,
471 &trace_ops, &stack_trace_filter_fops);
474 if (stack_trace_filter_buf[0])
475 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
477 if (stack_tracer_enabled)
478 register_ftrace_function(&trace_ops);
483 device_initcall(stack_trace_init);