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  */
stack_trace_print(const unsigned long * entries,unsigned int nr_entries,int spaces)24 void 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 }
35 EXPORT_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  */
stack_trace_snprint(char * buf,size_t size,const unsigned long * entries,unsigned int nr_entries,int spaces)47 int 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 }
71 EXPORT_SYMBOL_GPL(stack_trace_snprint);
72 
73 #ifdef CONFIG_ARCH_STACKWALK
74 
75 struct stacktrace_cookie {
76 	unsigned long	*store;
77 	unsigned int	size;
78 	unsigned int	skip;
79 	unsigned int	len;
80 };
81 
stack_trace_consume_entry(void * cookie,unsigned long addr)82 static 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 
stack_trace_consume_entry_nosched(void * cookie,unsigned long addr)97 static 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  */
stack_trace_save(unsigned long * store,unsigned int size,unsigned int skipnr)112 unsigned 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 }
125 EXPORT_SYMBOL_GPL(stack_trace_save);
126 
127 /**
128  * stack_trace_save_tsk - Save a task stack trace into a storage array
129  * @task:	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  */
stack_trace_save_tsk(struct task_struct * tsk,unsigned long * store,unsigned int size,unsigned int skipnr)136 unsigned 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 }
154 
155 /**
156  * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
157  * @regs:	Pointer to pt_regs to examine
158  * @store:	Pointer to storage array
159  * @size:	Size of the storage array
160  * @skipnr:	Number of entries to skip at the start of the stack trace
161  *
162  * Return: Number of trace entries stored.
163  */
stack_trace_save_regs(struct pt_regs * regs,unsigned long * store,unsigned int size,unsigned int skipnr)164 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
165 				   unsigned int size, unsigned int skipnr)
166 {
167 	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
168 	struct stacktrace_cookie c = {
169 		.store	= store,
170 		.size	= size,
171 		.skip	= skipnr,
172 	};
173 
174 	arch_stack_walk(consume_entry, &c, current, regs);
175 	return c.len;
176 }
177 
178 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
179 /**
180  * stack_trace_save_tsk_reliable - Save task stack with verification
181  * @tsk:	Pointer to the task to examine
182  * @store:	Pointer to storage array
183  * @size:	Size of the storage array
184  *
185  * Return:	An error if it detects any unreliable features of the
186  *		stack. Otherwise it guarantees that the stack trace is
187  *		reliable and returns the number of entries stored.
188  *
189  * If the task is not 'current', the caller *must* ensure the task is inactive.
190  */
stack_trace_save_tsk_reliable(struct task_struct * tsk,unsigned long * store,unsigned int size)191 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
192 				  unsigned int size)
193 {
194 	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
195 	struct stacktrace_cookie c = {
196 		.store	= store,
197 		.size	= size,
198 	};
199 	int ret;
200 
201 	/*
202 	 * If the task doesn't have a stack (e.g., a zombie), the stack is
203 	 * "reliably" empty.
204 	 */
205 	if (!try_get_task_stack(tsk))
206 		return 0;
207 
208 	ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
209 	put_task_stack(tsk);
210 	return ret ? ret : c.len;
211 }
212 #endif
213 
214 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
215 /**
216  * stack_trace_save_user - Save a user space stack trace into a storage array
217  * @store:	Pointer to storage array
218  * @size:	Size of the storage array
219  *
220  * Return: Number of trace entries stored.
221  */
stack_trace_save_user(unsigned long * store,unsigned int size)222 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
223 {
224 	stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
225 	struct stacktrace_cookie c = {
226 		.store	= store,
227 		.size	= size,
228 	};
229 
230 	/* Trace user stack if not a kernel thread */
231 	if (current->flags & PF_KTHREAD)
232 		return 0;
233 
234 	arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
235 
236 	return c.len;
237 }
238 #endif
239 
240 #else /* CONFIG_ARCH_STACKWALK */
241 
242 /*
243  * Architectures that do not implement save_stack_trace_*()
244  * get these weak aliases and once-per-bootup warnings
245  * (whenever this facility is utilized - for example by procfs):
246  */
247 __weak void
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)248 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
249 {
250 	WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
251 }
252 
253 __weak void
save_stack_trace_regs(struct pt_regs * regs,struct stack_trace * trace)254 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
255 {
256 	WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
257 }
258 
259 /**
260  * stack_trace_save - Save a stack trace into a storage array
261  * @store:	Pointer to storage array
262  * @size:	Size of the storage array
263  * @skipnr:	Number of entries to skip at the start of the stack trace
264  *
265  * Return: Number of trace entries stored
266  */
stack_trace_save(unsigned long * store,unsigned int size,unsigned int skipnr)267 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
268 			      unsigned int skipnr)
269 {
270 	struct stack_trace trace = {
271 		.entries	= store,
272 		.max_entries	= size,
273 		.skip		= skipnr + 1,
274 	};
275 
276 	save_stack_trace(&trace);
277 	return trace.nr_entries;
278 }
279 EXPORT_SYMBOL_GPL(stack_trace_save);
280 
281 /**
282  * stack_trace_save_tsk - Save a task stack trace into a storage array
283  * @task:	The task to examine
284  * @store:	Pointer to storage array
285  * @size:	Size of the storage array
286  * @skipnr:	Number of entries to skip at the start of the stack trace
287  *
288  * Return: Number of trace entries stored
289  */
stack_trace_save_tsk(struct task_struct * task,unsigned long * store,unsigned int size,unsigned int skipnr)290 unsigned int stack_trace_save_tsk(struct task_struct *task,
291 				  unsigned long *store, unsigned int size,
292 				  unsigned int skipnr)
293 {
294 	struct stack_trace trace = {
295 		.entries	= store,
296 		.max_entries	= size,
297 		/* skip this function if they are tracing us */
298 		.skip	= skipnr + (current == task),
299 	};
300 
301 	save_stack_trace_tsk(task, &trace);
302 	return trace.nr_entries;
303 }
304 
305 /**
306  * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
307  * @regs:	Pointer to pt_regs to examine
308  * @store:	Pointer to storage array
309  * @size:	Size of the storage array
310  * @skipnr:	Number of entries to skip at the start of the stack trace
311  *
312  * Return: Number of trace entries stored
313  */
stack_trace_save_regs(struct pt_regs * regs,unsigned long * store,unsigned int size,unsigned int skipnr)314 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
315 				   unsigned int size, unsigned int skipnr)
316 {
317 	struct stack_trace trace = {
318 		.entries	= store,
319 		.max_entries	= size,
320 		.skip		= skipnr,
321 	};
322 
323 	save_stack_trace_regs(regs, &trace);
324 	return trace.nr_entries;
325 }
326 
327 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
328 /**
329  * stack_trace_save_tsk_reliable - Save task stack with verification
330  * @tsk:	Pointer to the task to examine
331  * @store:	Pointer to storage array
332  * @size:	Size of the storage array
333  *
334  * Return:	An error if it detects any unreliable features of the
335  *		stack. Otherwise it guarantees that the stack trace is
336  *		reliable and returns the number of entries stored.
337  *
338  * If the task is not 'current', the caller *must* ensure the task is inactive.
339  */
stack_trace_save_tsk_reliable(struct task_struct * tsk,unsigned long * store,unsigned int size)340 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
341 				  unsigned int size)
342 {
343 	struct stack_trace trace = {
344 		.entries	= store,
345 		.max_entries	= size,
346 	};
347 	int ret = save_stack_trace_tsk_reliable(tsk, &trace);
348 
349 	return ret ? ret : trace.nr_entries;
350 }
351 #endif
352 
353 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
354 /**
355  * stack_trace_save_user - Save a user space stack trace into a storage array
356  * @store:	Pointer to storage array
357  * @size:	Size of the storage array
358  *
359  * Return: Number of trace entries stored
360  */
stack_trace_save_user(unsigned long * store,unsigned int size)361 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
362 {
363 	struct stack_trace trace = {
364 		.entries	= store,
365 		.max_entries	= size,
366 	};
367 
368 	save_stack_trace_user(&trace);
369 	return trace.nr_entries;
370 }
371 #endif /* CONFIG_USER_STACKTRACE_SUPPORT */
372 
373 #endif /* !CONFIG_ARCH_STACKWALK */
374 
in_irqentry_text(unsigned long ptr)375 static inline bool in_irqentry_text(unsigned long ptr)
376 {
377 	return (ptr >= (unsigned long)&__irqentry_text_start &&
378 		ptr < (unsigned long)&__irqentry_text_end) ||
379 		(ptr >= (unsigned long)&__softirqentry_text_start &&
380 		 ptr < (unsigned long)&__softirqentry_text_end);
381 }
382 
383 /**
384  * filter_irq_stacks - Find first IRQ stack entry in trace
385  * @entries:	Pointer to stack trace array
386  * @nr_entries:	Number of entries in the storage array
387  *
388  * Return: Number of trace entries until IRQ stack starts.
389  */
filter_irq_stacks(unsigned long * entries,unsigned int nr_entries)390 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries)
391 {
392 	unsigned int i;
393 
394 	for (i = 0; i < nr_entries; i++) {
395 		if (in_irqentry_text(entries[i])) {
396 			/* Include the irqentry function into the stack. */
397 			return i + 1;
398 		}
399 	}
400 	return nr_entries;
401 }
402 EXPORT_SYMBOL_GPL(filter_irq_stacks);
403