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 */ 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 */ 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 81 static bool stack_trace_consume_entry(void *cookie, unsigned long addr, 82 bool reliable) 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 97 static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr, 98 bool reliable) 99 { 100 if (in_sched_functions(addr)) 101 return true; 102 return stack_trace_consume_entry(cookie, addr, reliable); 103 } 104 105 /** 106 * stack_trace_save - Save a stack trace into a storage array 107 * @store: Pointer to storage array 108 * @size: Size of the storage array 109 * @skipnr: Number of entries to skip at the start of the stack trace 110 * 111 * Return: Number of trace entries stored. 112 */ 113 unsigned int stack_trace_save(unsigned long *store, unsigned int size, 114 unsigned int skipnr) 115 { 116 stack_trace_consume_fn consume_entry = stack_trace_consume_entry; 117 struct stacktrace_cookie c = { 118 .store = store, 119 .size = size, 120 .skip = skipnr + 1, 121 }; 122 123 arch_stack_walk(consume_entry, &c, current, NULL); 124 return c.len; 125 } 126 EXPORT_SYMBOL_GPL(stack_trace_save); 127 128 /** 129 * stack_trace_save_tsk - Save a task stack trace into a storage array 130 * @task: The task to examine 131 * @store: Pointer to storage array 132 * @size: Size of the storage array 133 * @skipnr: Number of entries to skip at the start of the stack trace 134 * 135 * Return: Number of trace entries stored. 136 */ 137 unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store, 138 unsigned int size, unsigned int skipnr) 139 { 140 stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched; 141 struct stacktrace_cookie c = { 142 .store = store, 143 .size = size, 144 .skip = skipnr + 1, 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 */ 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 */ 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 */ 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 mm_segment_t fs; 230 231 /* Trace user stack if not a kernel thread */ 232 if (current->flags & PF_KTHREAD) 233 return 0; 234 235 fs = get_fs(); 236 set_fs(USER_DS); 237 arch_stack_walk_user(consume_entry, &c, task_pt_regs(current)); 238 set_fs(fs); 239 240 return c.len; 241 } 242 #endif 243 244 #else /* CONFIG_ARCH_STACKWALK */ 245 246 /* 247 * Architectures that do not implement save_stack_trace_*() 248 * get these weak aliases and once-per-bootup warnings 249 * (whenever this facility is utilized - for example by procfs): 250 */ 251 __weak void 252 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 253 { 254 WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n"); 255 } 256 257 __weak void 258 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 259 { 260 WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n"); 261 } 262 263 /** 264 * stack_trace_save - Save a stack trace into a storage array 265 * @store: Pointer to storage array 266 * @size: Size of the storage array 267 * @skipnr: Number of entries to skip at the start of the stack trace 268 * 269 * Return: Number of trace entries stored 270 */ 271 unsigned int stack_trace_save(unsigned long *store, unsigned int size, 272 unsigned int skipnr) 273 { 274 struct stack_trace trace = { 275 .entries = store, 276 .max_entries = size, 277 .skip = skipnr + 1, 278 }; 279 280 save_stack_trace(&trace); 281 return trace.nr_entries; 282 } 283 EXPORT_SYMBOL_GPL(stack_trace_save); 284 285 /** 286 * stack_trace_save_tsk - Save a task stack trace into a storage array 287 * @task: The task to examine 288 * @store: Pointer to storage array 289 * @size: Size of the storage array 290 * @skipnr: Number of entries to skip at the start of the stack trace 291 * 292 * Return: Number of trace entries stored 293 */ 294 unsigned int stack_trace_save_tsk(struct task_struct *task, 295 unsigned long *store, unsigned int size, 296 unsigned int skipnr) 297 { 298 struct stack_trace trace = { 299 .entries = store, 300 .max_entries = size, 301 .skip = skipnr + 1, 302 }; 303 304 save_stack_trace_tsk(task, &trace); 305 return trace.nr_entries; 306 } 307 308 /** 309 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array 310 * @regs: Pointer to pt_regs to examine 311 * @store: Pointer to storage array 312 * @size: Size of the storage array 313 * @skipnr: Number of entries to skip at the start of the stack trace 314 * 315 * Return: Number of trace entries stored 316 */ 317 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store, 318 unsigned int size, unsigned int skipnr) 319 { 320 struct stack_trace trace = { 321 .entries = store, 322 .max_entries = size, 323 .skip = skipnr, 324 }; 325 326 save_stack_trace_regs(regs, &trace); 327 return trace.nr_entries; 328 } 329 330 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE 331 /** 332 * stack_trace_save_tsk_reliable - Save task stack with verification 333 * @tsk: Pointer to the task to examine 334 * @store: Pointer to storage array 335 * @size: Size of the storage array 336 * 337 * Return: An error if it detects any unreliable features of the 338 * stack. Otherwise it guarantees that the stack trace is 339 * reliable and returns the number of entries stored. 340 * 341 * If the task is not 'current', the caller *must* ensure the task is inactive. 342 */ 343 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store, 344 unsigned int size) 345 { 346 struct stack_trace trace = { 347 .entries = store, 348 .max_entries = size, 349 }; 350 int ret = save_stack_trace_tsk_reliable(tsk, &trace); 351 352 return ret ? ret : trace.nr_entries; 353 } 354 #endif 355 356 #ifdef CONFIG_USER_STACKTRACE_SUPPORT 357 /** 358 * stack_trace_save_user - Save a user space stack trace into a storage array 359 * @store: Pointer to storage array 360 * @size: Size of the storage array 361 * 362 * Return: Number of trace entries stored 363 */ 364 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size) 365 { 366 struct stack_trace trace = { 367 .entries = store, 368 .max_entries = size, 369 }; 370 371 save_stack_trace_user(&trace); 372 return trace.nr_entries; 373 } 374 #endif /* CONFIG_USER_STACKTRACE_SUPPORT */ 375 376 #endif /* !CONFIG_ARCH_STACKWALK */ 377