xref: /openbmc/linux/kernel/trace/trace_stack.c (revision 8ee90c5c)
1 /*
2  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
3  *
4  */
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>
15 
16 #include <asm/setup.h>
17 
18 #include "trace.h"
19 
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];
23 
24 /*
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.
28  */
29 struct stack_trace stack_trace_max = {
30 	.max_entries		= STACK_TRACE_ENTRIES - 1,
31 	.entries		= &stack_dump_trace[0],
32 };
33 
34 unsigned long stack_trace_max_size;
35 arch_spinlock_t stack_trace_max_lock =
36 	(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
37 
38 DEFINE_PER_CPU(int, disable_stack_tracer);
39 static DEFINE_MUTEX(stack_sysctl_mutex);
40 
41 int stack_tracer_enabled;
42 static int last_stack_tracer_enabled;
43 
44 void stack_trace_print(void)
45 {
46 	long i;
47 	int size;
48 
49 	pr_emerg("        Depth    Size   Location    (%d entries)\n"
50 			   "        -----    ----   --------\n",
51 			   stack_trace_max.nr_entries);
52 
53 	for (i = 0; i < stack_trace_max.nr_entries; i++) {
54 		if (stack_dump_trace[i] == ULONG_MAX)
55 			break;
56 		if (i+1 == stack_trace_max.nr_entries ||
57 				stack_dump_trace[i+1] == ULONG_MAX)
58 			size = stack_trace_index[i];
59 		else
60 			size = stack_trace_index[i] - stack_trace_index[i+1];
61 
62 		pr_emerg("%3ld) %8d   %5d   %pS\n", i, stack_trace_index[i],
63 				size, (void *)stack_dump_trace[i]);
64 	}
65 }
66 
67 /*
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.
71  *     stack_trace_index[]
72  *     stack_trace_max
73  *     stack_trace_max_size
74  */
75 void __weak
76 check_stack(unsigned long ip, unsigned long *stack)
77 {
78 	unsigned long this_size, flags; unsigned long *p, *top, *start;
79 	static int tracer_frame;
80 	int frame_size = ACCESS_ONCE(tracer_frame);
81 	int i, x;
82 
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;
87 
88 	if (this_size <= stack_trace_max_size)
89 		return;
90 
91 	/* we do not handle interrupt stacks yet */
92 	if (!object_is_on_stack(stack))
93 		return;
94 
95 	/* Can't do this from NMI context (can cause deadlocks) */
96 	if (in_nmi())
97 		return;
98 
99 	local_irq_save(flags);
100 	arch_spin_lock(&stack_trace_max_lock);
101 
102 	/* In case another CPU set the tracer_frame on us */
103 	if (unlikely(!frame_size))
104 		this_size -= tracer_frame;
105 
106 	/* a race could have already updated it */
107 	if (this_size <= stack_trace_max_size)
108 		goto out;
109 
110 	stack_trace_max_size = this_size;
111 
112 	stack_trace_max.nr_entries = 0;
113 	stack_trace_max.skip = 3;
114 
115 	save_stack_trace(&stack_trace_max);
116 
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)
120 			break;
121 	}
122 
123 	/*
124 	 * Some archs may not have the passed in ip in the dump.
125 	 * If that happens, we need to show everything.
126 	 */
127 	if (i == stack_trace_max.nr_entries)
128 		i = 0;
129 
130 	/*
131 	 * Now find where in the stack these are.
132 	 */
133 	x = 0;
134 	start = stack;
135 	top = (unsigned long *)
136 		(((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
137 
138 	/*
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.
144 	 */
145 	while (i < stack_trace_max.nr_entries) {
146 		int found = 0;
147 
148 		stack_trace_index[x] = this_size;
149 		p = start;
150 
151 		for (; p < top && i < stack_trace_max.nr_entries; p++) {
152 			if (stack_dump_trace[i] == ULONG_MAX)
153 				break;
154 			/*
155 			 * The READ_ONCE_NOCHECK is used to let KASAN know that
156 			 * this is not a stack-out-of-bounds error.
157 			 */
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);
162 				found = 1;
163 				/* Start the search from here */
164 				start = p + 1;
165 				/*
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
170 				 * now.
171 				 */
172 				if (unlikely(!tracer_frame)) {
173 					tracer_frame = (p - stack) *
174 						sizeof(unsigned long);
175 					stack_trace_max_size -= tracer_frame;
176 				}
177 			}
178 		}
179 
180 		if (!found)
181 			i++;
182 	}
183 
184 	stack_trace_max.nr_entries = x;
185 	for (; x < i; x++)
186 		stack_dump_trace[x] = ULONG_MAX;
187 
188 	if (task_stack_end_corrupted(current)) {
189 		stack_trace_print();
190 		BUG();
191 	}
192 
193  out:
194 	arch_spin_unlock(&stack_trace_max_lock);
195 	local_irq_restore(flags);
196 }
197 
198 static void
199 stack_trace_call(unsigned long ip, unsigned long parent_ip,
200 		 struct ftrace_ops *op, struct pt_regs *pt_regs)
201 {
202 	unsigned long stack;
203 
204 	preempt_disable_notrace();
205 
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)
209 		goto out;
210 
211 	ip += MCOUNT_INSN_SIZE;
212 
213 	check_stack(ip, &stack);
214 
215  out:
216 	__this_cpu_dec(disable_stack_tracer);
217 	/* prevent recursion in schedule */
218 	preempt_enable_notrace();
219 }
220 
221 static struct ftrace_ops trace_ops __read_mostly =
222 {
223 	.func = stack_trace_call,
224 	.flags = FTRACE_OPS_FL_RECURSION_SAFE,
225 };
226 
227 static ssize_t
228 stack_max_size_read(struct file *filp, char __user *ubuf,
229 		    size_t count, loff_t *ppos)
230 {
231 	unsigned long *ptr = filp->private_data;
232 	char buf[64];
233 	int r;
234 
235 	r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
236 	if (r > sizeof(buf))
237 		r = sizeof(buf);
238 	return simple_read_from_buffer(ubuf, count, ppos, buf, r);
239 }
240 
241 static ssize_t
242 stack_max_size_write(struct file *filp, const char __user *ubuf,
243 		     size_t count, loff_t *ppos)
244 {
245 	long *ptr = filp->private_data;
246 	unsigned long val, flags;
247 	int ret;
248 
249 	ret = kstrtoul_from_user(ubuf, count, 10, &val);
250 	if (ret)
251 		return ret;
252 
253 	local_irq_save(flags);
254 
255 	/*
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.
259 	 */
260 	__this_cpu_inc(disable_stack_tracer);
261 
262 	arch_spin_lock(&stack_trace_max_lock);
263 	*ptr = val;
264 	arch_spin_unlock(&stack_trace_max_lock);
265 
266 	__this_cpu_dec(disable_stack_tracer);
267 	local_irq_restore(flags);
268 
269 	return count;
270 }
271 
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,
277 };
278 
279 static void *
280 __next(struct seq_file *m, loff_t *pos)
281 {
282 	long n = *pos - 1;
283 
284 	if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
285 		return NULL;
286 
287 	m->private = (void *)n;
288 	return &m->private;
289 }
290 
291 static void *
292 t_next(struct seq_file *m, void *v, loff_t *pos)
293 {
294 	(*pos)++;
295 	return __next(m, pos);
296 }
297 
298 static void *t_start(struct seq_file *m, loff_t *pos)
299 {
300 	local_irq_disable();
301 
302 	__this_cpu_inc(disable_stack_tracer);
303 
304 	arch_spin_lock(&stack_trace_max_lock);
305 
306 	if (*pos == 0)
307 		return SEQ_START_TOKEN;
308 
309 	return __next(m, pos);
310 }
311 
312 static void t_stop(struct seq_file *m, void *p)
313 {
314 	arch_spin_unlock(&stack_trace_max_lock);
315 
316 	__this_cpu_dec(disable_stack_tracer);
317 
318 	local_irq_enable();
319 }
320 
321 static void trace_lookup_stack(struct seq_file *m, long i)
322 {
323 	unsigned long addr = stack_dump_trace[i];
324 
325 	seq_printf(m, "%pS\n", (void *)addr);
326 }
327 
328 static void print_disabled(struct seq_file *m)
329 {
330 	seq_puts(m, "#\n"
331 		 "#  Stack tracer disabled\n"
332 		 "#\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"
336 		 "#\n");
337 }
338 
339 static int t_show(struct seq_file *m, void *v)
340 {
341 	long i;
342 	int size;
343 
344 	if (v == SEQ_START_TOKEN) {
345 		seq_printf(m, "        Depth    Size   Location"
346 			   "    (%d entries)\n"
347 			   "        -----    ----   --------\n",
348 			   stack_trace_max.nr_entries);
349 
350 		if (!stack_tracer_enabled && !stack_trace_max_size)
351 			print_disabled(m);
352 
353 		return 0;
354 	}
355 
356 	i = *(long *)v;
357 
358 	if (i >= stack_trace_max.nr_entries ||
359 	    stack_dump_trace[i] == ULONG_MAX)
360 		return 0;
361 
362 	if (i+1 == stack_trace_max.nr_entries ||
363 	    stack_dump_trace[i+1] == ULONG_MAX)
364 		size = stack_trace_index[i];
365 	else
366 		size = stack_trace_index[i] - stack_trace_index[i+1];
367 
368 	seq_printf(m, "%3ld) %8d   %5d   ", i, stack_trace_index[i], size);
369 
370 	trace_lookup_stack(m, i);
371 
372 	return 0;
373 }
374 
375 static const struct seq_operations stack_trace_seq_ops = {
376 	.start		= t_start,
377 	.next		= t_next,
378 	.stop		= t_stop,
379 	.show		= t_show,
380 };
381 
382 static int stack_trace_open(struct inode *inode, struct file *file)
383 {
384 	return seq_open(file, &stack_trace_seq_ops);
385 }
386 
387 static const struct file_operations stack_trace_fops = {
388 	.open		= stack_trace_open,
389 	.read		= seq_read,
390 	.llseek		= seq_lseek,
391 	.release	= seq_release,
392 };
393 
394 #ifdef CONFIG_DYNAMIC_FTRACE
395 
396 static int
397 stack_trace_filter_open(struct inode *inode, struct file *file)
398 {
399 	struct ftrace_ops *ops = inode->i_private;
400 
401 	return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
402 				 inode, file);
403 }
404 
405 static const struct file_operations stack_trace_filter_fops = {
406 	.open = stack_trace_filter_open,
407 	.read = seq_read,
408 	.write = ftrace_filter_write,
409 	.llseek = tracing_lseek,
410 	.release = ftrace_regex_release,
411 };
412 
413 #endif /* CONFIG_DYNAMIC_FTRACE */
414 
415 int
416 stack_trace_sysctl(struct ctl_table *table, int write,
417 		   void __user *buffer, size_t *lenp,
418 		   loff_t *ppos)
419 {
420 	int ret;
421 
422 	mutex_lock(&stack_sysctl_mutex);
423 
424 	ret = proc_dointvec(table, write, buffer, lenp, ppos);
425 
426 	if (ret || !write ||
427 	    (last_stack_tracer_enabled == !!stack_tracer_enabled))
428 		goto out;
429 
430 	last_stack_tracer_enabled = !!stack_tracer_enabled;
431 
432 	if (stack_tracer_enabled)
433 		register_ftrace_function(&trace_ops);
434 	else
435 		unregister_ftrace_function(&trace_ops);
436 
437  out:
438 	mutex_unlock(&stack_sysctl_mutex);
439 	return ret;
440 }
441 
442 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
443 
444 static __init int enable_stacktrace(char *str)
445 {
446 	if (strncmp(str, "_filter=", 8) == 0)
447 		strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
448 
449 	stack_tracer_enabled = 1;
450 	last_stack_tracer_enabled = 1;
451 	return 1;
452 }
453 __setup("stacktrace", enable_stacktrace);
454 
455 static __init int stack_trace_init(void)
456 {
457 	struct dentry *d_tracer;
458 
459 	d_tracer = tracing_init_dentry();
460 	if (IS_ERR(d_tracer))
461 		return 0;
462 
463 	trace_create_file("stack_max_size", 0644, d_tracer,
464 			&stack_trace_max_size, &stack_max_size_fops);
465 
466 	trace_create_file("stack_trace", 0444, d_tracer,
467 			NULL, &stack_trace_fops);
468 
469 #ifdef CONFIG_DYNAMIC_FTRACE
470 	trace_create_file("stack_trace_filter", 0444, d_tracer,
471 			  &trace_ops, &stack_trace_filter_fops);
472 #endif
473 
474 	if (stack_trace_filter_buf[0])
475 		ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
476 
477 	if (stack_tracer_enabled)
478 		register_ftrace_function(&trace_ops);
479 
480 	return 0;
481 }
482 
483 device_initcall(stack_trace_init);
484