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
17 /**
18 * stack_trace_print - Print the entries in the stack trace
19 * @entries: Pointer to storage array
20 * @nr_entries: Number of entries in the storage array
21 * @spaces: Number of leading spaces to print
22 */
stack_trace_print(const unsigned long * entries,unsigned int nr_entries,int spaces)23 void stack_trace_print(const unsigned long *entries, unsigned int nr_entries,
24 int spaces)
25 {
26 unsigned int i;
27
28 if (WARN_ON(!entries))
29 return;
30
31 for (i = 0; i < nr_entries; i++)
32 printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
33 }
34 EXPORT_SYMBOL_GPL(stack_trace_print);
35
36 /**
37 * stack_trace_snprint - Print the entries in the stack trace into a buffer
38 * @buf: Pointer to the print buffer
39 * @size: Size of the print buffer
40 * @entries: Pointer to storage array
41 * @nr_entries: Number of entries in the storage array
42 * @spaces: Number of leading spaces to print
43 *
44 * Return: Number of bytes printed.
45 */
stack_trace_snprint(char * buf,size_t size,const unsigned long * entries,unsigned int nr_entries,int spaces)46 int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
47 unsigned int nr_entries, int spaces)
48 {
49 unsigned int generated, i, total = 0;
50
51 if (WARN_ON(!entries))
52 return 0;
53
54 for (i = 0; i < nr_entries && size; i++) {
55 generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
56 (void *)entries[i]);
57
58 total += generated;
59 if (generated >= size) {
60 buf += size;
61 size = 0;
62 } else {
63 buf += generated;
64 size -= generated;
65 }
66 }
67
68 return total;
69 }
70 EXPORT_SYMBOL_GPL(stack_trace_snprint);
71
72 #ifdef CONFIG_ARCH_STACKWALK
73
74 struct stacktrace_cookie {
75 unsigned long *store;
76 unsigned int size;
77 unsigned int skip;
78 unsigned int len;
79 };
80
stack_trace_consume_entry(void * cookie,unsigned long addr)81 static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
82 {
83 struct stacktrace_cookie *c = cookie;
84
85 if (c->len >= c->size)
86 return false;
87
88 if (c->skip > 0) {
89 c->skip--;
90 return true;
91 }
92 c->store[c->len++] = addr;
93 return c->len < c->size;
94 }
95
stack_trace_consume_entry_nosched(void * cookie,unsigned long addr)96 static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
97 {
98 if (in_sched_functions(addr))
99 return true;
100 return stack_trace_consume_entry(cookie, addr);
101 }
102
103 /**
104 * stack_trace_save - Save a stack trace into a storage array
105 * @store: Pointer to storage array
106 * @size: Size of the storage array
107 * @skipnr: Number of entries to skip at the start of the stack trace
108 *
109 * Return: Number of trace entries stored.
110 */
stack_trace_save(unsigned long * store,unsigned int size,unsigned int skipnr)111 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
112 unsigned int skipnr)
113 {
114 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
115 struct stacktrace_cookie c = {
116 .store = store,
117 .size = size,
118 .skip = skipnr + 1,
119 };
120
121 arch_stack_walk(consume_entry, &c, current, NULL);
122 return c.len;
123 }
124 EXPORT_SYMBOL_GPL(stack_trace_save);
125
126 /**
127 * stack_trace_save_tsk - Save a task stack trace into a storage array
128 * @task: The task to examine
129 * @store: Pointer to storage array
130 * @size: Size of the storage array
131 * @skipnr: Number of entries to skip at the start of the stack trace
132 *
133 * Return: Number of trace entries stored.
134 */
stack_trace_save_tsk(struct task_struct * tsk,unsigned long * store,unsigned int size,unsigned int skipnr)135 unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
136 unsigned int size, unsigned int skipnr)
137 {
138 stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
139 struct stacktrace_cookie c = {
140 .store = store,
141 .size = size,
142 /* skip this function if they are tracing us */
143 .skip = skipnr + (current == tsk),
144 };
145
146 if (!try_get_task_stack(tsk))
147 return 0;
148
149 arch_stack_walk(consume_entry, &c, tsk, NULL);
150 put_task_stack(tsk);
151 return c.len;
152 }
153
154 /**
155 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
156 * @regs: Pointer to pt_regs to examine
157 * @store: Pointer to storage array
158 * @size: Size of the storage array
159 * @skipnr: Number of entries to skip at the start of the stack trace
160 *
161 * Return: Number of trace entries stored.
162 */
stack_trace_save_regs(struct pt_regs * regs,unsigned long * store,unsigned int size,unsigned int skipnr)163 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
164 unsigned int size, unsigned int skipnr)
165 {
166 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
167 struct stacktrace_cookie c = {
168 .store = store,
169 .size = size,
170 .skip = skipnr,
171 };
172
173 arch_stack_walk(consume_entry, &c, current, regs);
174 return c.len;
175 }
176
177 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
178 /**
179 * stack_trace_save_tsk_reliable - Save task stack with verification
180 * @tsk: Pointer to the task to examine
181 * @store: Pointer to storage array
182 * @size: Size of the storage array
183 *
184 * Return: An error if it detects any unreliable features of the
185 * stack. Otherwise it guarantees that the stack trace is
186 * reliable and returns the number of entries stored.
187 *
188 * If the task is not 'current', the caller *must* ensure the task is inactive.
189 */
stack_trace_save_tsk_reliable(struct task_struct * tsk,unsigned long * store,unsigned int size)190 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
191 unsigned int size)
192 {
193 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
194 struct stacktrace_cookie c = {
195 .store = store,
196 .size = size,
197 };
198 int ret;
199
200 /*
201 * If the task doesn't have a stack (e.g., a zombie), the stack is
202 * "reliably" empty.
203 */
204 if (!try_get_task_stack(tsk))
205 return 0;
206
207 ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
208 put_task_stack(tsk);
209 return ret ? ret : c.len;
210 }
211 #endif
212
213 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
214 /**
215 * stack_trace_save_user - Save a user space stack trace into a storage array
216 * @store: Pointer to storage array
217 * @size: Size of the storage array
218 *
219 * Return: Number of trace entries stored.
220 */
stack_trace_save_user(unsigned long * store,unsigned int size)221 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
222 {
223 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
224 struct stacktrace_cookie c = {
225 .store = store,
226 .size = size,
227 };
228 mm_segment_t fs;
229
230 /* Trace user stack if not a kernel thread */
231 if (current->flags & PF_KTHREAD)
232 return 0;
233
234 fs = force_uaccess_begin();
235 arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
236 force_uaccess_end(fs);
237
238 return c.len;
239 }
240 #endif
241
242 #else /* CONFIG_ARCH_STACKWALK */
243
244 /*
245 * Architectures that do not implement save_stack_trace_*()
246 * get these weak aliases and once-per-bootup warnings
247 * (whenever this facility is utilized - for example by procfs):
248 */
249 __weak void
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)250 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
251 {
252 WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
253 }
254
255 __weak void
save_stack_trace_regs(struct pt_regs * regs,struct stack_trace * trace)256 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
257 {
258 WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
259 }
260
261 /**
262 * stack_trace_save - Save a stack trace into a storage array
263 * @store: Pointer to storage array
264 * @size: Size of the storage array
265 * @skipnr: Number of entries to skip at the start of the stack trace
266 *
267 * Return: Number of trace entries stored
268 */
stack_trace_save(unsigned long * store,unsigned int size,unsigned int skipnr)269 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
270 unsigned int skipnr)
271 {
272 struct stack_trace trace = {
273 .entries = store,
274 .max_entries = size,
275 .skip = skipnr + 1,
276 };
277
278 save_stack_trace(&trace);
279 return trace.nr_entries;
280 }
281 EXPORT_SYMBOL_GPL(stack_trace_save);
282
283 /**
284 * stack_trace_save_tsk - Save a task stack trace into a storage array
285 * @task: The task to examine
286 * @store: Pointer to storage array
287 * @size: Size of the storage array
288 * @skipnr: Number of entries to skip at the start of the stack trace
289 *
290 * Return: Number of trace entries stored
291 */
stack_trace_save_tsk(struct task_struct * task,unsigned long * store,unsigned int size,unsigned int skipnr)292 unsigned int stack_trace_save_tsk(struct task_struct *task,
293 unsigned long *store, unsigned int size,
294 unsigned int skipnr)
295 {
296 struct stack_trace trace = {
297 .entries = store,
298 .max_entries = size,
299 /* skip this function if they are tracing us */
300 .skip = skipnr + (current == task),
301 };
302
303 save_stack_trace_tsk(task, &trace);
304 return trace.nr_entries;
305 }
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 */
stack_trace_save_regs(struct pt_regs * regs,unsigned long * store,unsigned int size,unsigned int skipnr)316 unsigned 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 */
stack_trace_save_tsk_reliable(struct task_struct * tsk,unsigned long * store,unsigned int size)342 int 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 */
stack_trace_save_user(unsigned long * store,unsigned int size)363 unsigned 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
