1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/stacktrace.c
4 *
5 * Stack trace management functions
6 *
7 *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8 */
9#include <linux/sched/task_stack.h>
10#include <linux/sched/debug.h>
11#include <linux/sched.h>
12#include <linux/kernel.h>
13#include <linux/export.h>
14#include <linux/kallsyms.h>
15#include <linux/stacktrace.h>
16#include <linux/interrupt.h>
17
18/**
19 * stack_trace_print - Print the entries in the stack trace
20 * @entries:	Pointer to storage array
21 * @nr_entries:	Number of entries in the storage array
22 * @spaces:	Number of leading spaces to print
23 */
24void stack_trace_print(const unsigned long *entries, unsigned int nr_entries,
25		       int spaces)
26{
27	unsigned int i;
28
29	if (WARN_ON(!entries))
30		return;
31
32	for (i = 0; i < nr_entries; i++)
33		printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
34}
35EXPORT_SYMBOL_GPL(stack_trace_print);
36
37/**
38 * stack_trace_snprint - Print the entries in the stack trace into a buffer
39 * @buf:	Pointer to the print buffer
40 * @size:	Size of the print buffer
41 * @entries:	Pointer to storage array
42 * @nr_entries:	Number of entries in the storage array
43 * @spaces:	Number of leading spaces to print
44 *
45 * Return: Number of bytes printed.
46 */
47int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
48			unsigned int nr_entries, int spaces)
49{
50	unsigned int generated, i, total = 0;
51
52	if (WARN_ON(!entries))
53		return 0;
54
55	for (i = 0; i < nr_entries && size; i++) {
56		generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
57				     (void *)entries[i]);
58
59		total += generated;
60		if (generated >= size) {
61			buf += size;
62			size = 0;
63		} else {
64			buf += generated;
65			size -= generated;
66		}
67	}
68
69	return total;
70}
71EXPORT_SYMBOL_GPL(stack_trace_snprint);
72
73#ifdef CONFIG_ARCH_STACKWALK
74
75struct stacktrace_cookie {
76	unsigned long	*store;
77	unsigned int	size;
78	unsigned int	skip;
79	unsigned int	len;
80};
81
82static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
83{
84	struct stacktrace_cookie *c = cookie;
85
86	if (c->len >= c->size)
87		return false;
88
89	if (c->skip > 0) {
90		c->skip--;
91		return true;
92	}
93	c->store[c->len++] = addr;
94	return c->len < c->size;
95}
96
97static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
98{
99	if (in_sched_functions(addr))
100		return true;
101	return stack_trace_consume_entry(cookie, addr);
102}
103
104/**
105 * stack_trace_save - Save a stack trace into a storage array
106 * @store:	Pointer to storage array
107 * @size:	Size of the storage array
108 * @skipnr:	Number of entries to skip at the start of the stack trace
109 *
110 * Return: Number of trace entries stored.
111 */
112unsigned int stack_trace_save(unsigned long *store, unsigned int size,
113			      unsigned int skipnr)
114{
115	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
116	struct stacktrace_cookie c = {
117		.store	= store,
118		.size	= size,
119		.skip	= skipnr + 1,
120	};
121
122	arch_stack_walk(consume_entry, &c, current, NULL);
123	return c.len;
124}
125EXPORT_SYMBOL_GPL(stack_trace_save);
126
127/**
128 * stack_trace_save_tsk - Save a task stack trace into a storage array
129 * @tsk:	The task to examine
130 * @store:	Pointer to storage array
131 * @size:	Size of the storage array
132 * @skipnr:	Number of entries to skip at the start of the stack trace
133 *
134 * Return: Number of trace entries stored.
135 */
136unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
137				  unsigned int size, unsigned int skipnr)
138{
139	stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
140	struct stacktrace_cookie c = {
141		.store	= store,
142		.size	= size,
143		/* skip this function if they are tracing us */
144		.skip	= skipnr + (current == tsk),
145	};
146
147	if (!try_get_task_stack(tsk))
148		return 0;
149
150	arch_stack_walk(consume_entry, &c, tsk, NULL);
151	put_task_stack(tsk);
152	return c.len;
153}
154EXPORT_SYMBOL_GPL(stack_trace_save_tsk);
155
156/**
157 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
158 * @regs:	Pointer to pt_regs to examine
159 * @store:	Pointer to storage array
160 * @size:	Size of the storage array
161 * @skipnr:	Number of entries to skip at the start of the stack trace
162 *
163 * Return: Number of trace entries stored.
164 */
165unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
166				   unsigned int size, unsigned int skipnr)
167{
168	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
169	struct stacktrace_cookie c = {
170		.store	= store,
171		.size	= size,
172		.skip	= skipnr,
173	};
174
175	arch_stack_walk(consume_entry, &c, current, regs);
176	return c.len;
177}
178
179#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
180/**
181 * stack_trace_save_tsk_reliable - Save task stack with verification
182 * @tsk:	Pointer to the task to examine
183 * @store:	Pointer to storage array
184 * @size:	Size of the storage array
185 *
186 * Return:	An error if it detects any unreliable features of the
187 *		stack. Otherwise it guarantees that the stack trace is
188 *		reliable and returns the number of entries stored.
189 *
190 * If the task is not 'current', the caller *must* ensure the task is inactive.
191 */
192int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
193				  unsigned int size)
194{
195	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
196	struct stacktrace_cookie c = {
197		.store	= store,
198		.size	= size,
199	};
200	int ret;
201
202	/*
203	 * If the task doesn't have a stack (e.g., a zombie), the stack is
204	 * "reliably" empty.
205	 */
206	if (!try_get_task_stack(tsk))
207		return 0;
208
209	ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
210	put_task_stack(tsk);
211	return ret ? ret : c.len;
212}
213#endif
214
215#ifdef CONFIG_USER_STACKTRACE_SUPPORT
216/**
217 * stack_trace_save_user - Save a user space stack trace into a storage array
218 * @store:	Pointer to storage array
219 * @size:	Size of the storage array
220 *
221 * Return: Number of trace entries stored.
222 */
223unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
224{
225	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
226	struct stacktrace_cookie c = {
227		.store	= store,
228		.size	= size,
229	};
230
231	/* Trace user stack if not a kernel thread */
232	if (current->flags & PF_KTHREAD)
233		return 0;
234
235	arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
236
237	return c.len;
238}
239#endif
240
241#else /* CONFIG_ARCH_STACKWALK */
242
243/*
244 * Architectures that do not implement save_stack_trace_*()
245 * get these weak aliases and once-per-bootup warnings
246 * (whenever this facility is utilized - for example by procfs):
247 */
248__weak void
249save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
250{
251	WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
252}
253
254__weak void
255save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
256{
257	WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
258}
259
260/**
261 * stack_trace_save - Save a stack trace into a storage array
262 * @store:	Pointer to storage array
263 * @size:	Size of the storage array
264 * @skipnr:	Number of entries to skip at the start of the stack trace
265 *
266 * Return: Number of trace entries stored
267 */
268unsigned int stack_trace_save(unsigned long *store, unsigned int size,
269			      unsigned int skipnr)
270{
271	struct stack_trace trace = {
272		.entries	= store,
273		.max_entries	= size,
274		.skip		= skipnr + 1,
275	};
276
277	save_stack_trace(&trace);
278	return trace.nr_entries;
279}
280EXPORT_SYMBOL_GPL(stack_trace_save);
281
282/**
283 * stack_trace_save_tsk - Save a task stack trace into a storage array
284 * @task:	The task to examine
285 * @store:	Pointer to storage array
286 * @size:	Size of the storage array
287 * @skipnr:	Number of entries to skip at the start of the stack trace
288 *
289 * Return: Number of trace entries stored
290 */
291unsigned int stack_trace_save_tsk(struct task_struct *task,
292				  unsigned long *store, unsigned int size,
293				  unsigned int skipnr)
294{
295	struct stack_trace trace = {
296		.entries	= store,
297		.max_entries	= size,
298		/* skip this function if they are tracing us */
299		.skip	= skipnr + (current == task),
300	};
301
302	save_stack_trace_tsk(task, &trace);
303	return trace.nr_entries;
304}
305EXPORT_SYMBOL_GPL(stack_trace_save_tsk);
306
307/**
308 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
309 * @regs:	Pointer to pt_regs to examine
310 * @store:	Pointer to storage array
311 * @size:	Size of the storage array
312 * @skipnr:	Number of entries to skip at the start of the stack trace
313 *
314 * Return: Number of trace entries stored
315 */
316unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
317				   unsigned int size, unsigned int skipnr)
318{
319	struct stack_trace trace = {
320		.entries	= store,
321		.max_entries	= size,
322		.skip		= skipnr,
323	};
324
325	save_stack_trace_regs(regs, &trace);
326	return trace.nr_entries;
327}
328
329#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
330/**
331 * stack_trace_save_tsk_reliable - Save task stack with verification
332 * @tsk:	Pointer to the task to examine
333 * @store:	Pointer to storage array
334 * @size:	Size of the storage array
335 *
336 * Return:	An error if it detects any unreliable features of the
337 *		stack. Otherwise it guarantees that the stack trace is
338 *		reliable and returns the number of entries stored.
339 *
340 * If the task is not 'current', the caller *must* ensure the task is inactive.
341 */
342int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
343				  unsigned int size)
344{
345	struct stack_trace trace = {
346		.entries	= store,
347		.max_entries	= size,
348	};
349	int ret = save_stack_trace_tsk_reliable(tsk, &trace);
350
351	return ret ? ret : trace.nr_entries;
352}
353#endif
354
355#ifdef CONFIG_USER_STACKTRACE_SUPPORT
356/**
357 * stack_trace_save_user - Save a user space stack trace into a storage array
358 * @store:	Pointer to storage array
359 * @size:	Size of the storage array
360 *
361 * Return: Number of trace entries stored
362 */
363unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
364{
365	struct stack_trace trace = {
366		.entries	= store,
367		.max_entries	= size,
368	};
369
370	save_stack_trace_user(&trace);
371	return trace.nr_entries;
372}
373#endif /* CONFIG_USER_STACKTRACE_SUPPORT */
374
375#endif /* !CONFIG_ARCH_STACKWALK */
376
377static inline bool in_irqentry_text(unsigned long ptr)
378{
379	return (ptr >= (unsigned long)&__irqentry_text_start &&
380		ptr < (unsigned long)&__irqentry_text_end) ||
381		(ptr >= (unsigned long)&__softirqentry_text_start &&
382		 ptr < (unsigned long)&__softirqentry_text_end);
383}
384
385/**
386 * filter_irq_stacks - Find first IRQ stack entry in trace
387 * @entries:	Pointer to stack trace array
388 * @nr_entries:	Number of entries in the storage array
389 *
390 * Return: Number of trace entries until IRQ stack starts.
391 */
392unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries)
393{
394	unsigned int i;
395
396	for (i = 0; i < nr_entries; i++) {
397		if (in_irqentry_text(entries[i])) {
398			/* Include the irqentry function into the stack. */
399			return i + 1;
400		}
401	}
402	return nr_entries;
403}
404EXPORT_SYMBOL_GPL(filter_irq_stacks);
405