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 */ 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 */ 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 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 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 */ 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 */ 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 */ 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 = force_uaccess_begin(); 236 arch_stack_walk_user(consume_entry, &c, task_pt_regs(current)); 237 force_uaccess_end(fs); 238 239 return c.len; 240 } 241 #endif 242 243 #else /* CONFIG_ARCH_STACKWALK */ 244 245 /* 246 * Architectures that do not implement save_stack_trace_*() 247 * get these weak aliases and once-per-bootup warnings 248 * (whenever this facility is utilized - for example by procfs): 249 */ 250 __weak void 251 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 252 { 253 WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n"); 254 } 255 256 __weak void 257 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 258 { 259 WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n"); 260 } 261 262 /** 263 * stack_trace_save - Save a stack trace into a storage array 264 * @store: Pointer to storage array 265 * @size: Size of the storage array 266 * @skipnr: Number of entries to skip at the start of the stack trace 267 * 268 * Return: Number of trace entries stored 269 */ 270 unsigned int stack_trace_save(unsigned long *store, unsigned int size, 271 unsigned int skipnr) 272 { 273 struct stack_trace trace = { 274 .entries = store, 275 .max_entries = size, 276 .skip = skipnr + 1, 277 }; 278 279 save_stack_trace(&trace); 280 return trace.nr_entries; 281 } 282 EXPORT_SYMBOL_GPL(stack_trace_save); 283 284 /** 285 * stack_trace_save_tsk - Save a task stack trace into a storage array 286 * @task: The task to examine 287 * @store: Pointer to storage array 288 * @size: Size of the storage array 289 * @skipnr: Number of entries to skip at the start of the stack trace 290 * 291 * Return: Number of trace entries stored 292 */ 293 unsigned int stack_trace_save_tsk(struct task_struct *task, 294 unsigned long *store, unsigned int size, 295 unsigned int skipnr) 296 { 297 struct stack_trace trace = { 298 .entries = store, 299 .max_entries = size, 300 /* skip this function if they are tracing us */ 301 .skip = skipnr + (current == task), 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 */ 377 378 static inline bool in_irqentry_text(unsigned long ptr) 379 { 380 return (ptr >= (unsigned long)&__irqentry_text_start && 381 ptr < (unsigned long)&__irqentry_text_end) || 382 (ptr >= (unsigned long)&__softirqentry_text_start && 383 ptr < (unsigned long)&__softirqentry_text_end); 384 } 385 386 /** 387 * filter_irq_stacks - Find first IRQ stack entry in trace 388 * @entries: Pointer to stack trace array 389 * @nr_entries: Number of entries in the storage array 390 * 391 * Return: Number of trace entries until IRQ stack starts. 392 */ 393 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries) 394 { 395 unsigned int i; 396 397 for (i = 0; i < nr_entries; i++) { 398 if (in_irqentry_text(entries[i])) { 399 /* Include the irqentry function into the stack. */ 400 return i + 1; 401 } 402 } 403 return nr_entries; 404 } 405 EXPORT_SYMBOL_GPL(filter_irq_stacks); 406