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 this function if they are tracing us */ 145 .skip = skipnr + (current == tsk), 146 }; 147 148 if (!try_get_task_stack(tsk)) 149 return 0; 150 151 arch_stack_walk(consume_entry, &c, tsk, NULL); 152 put_task_stack(tsk); 153 return c.len; 154 } 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 */ 165 unsigned 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 */ 192 int 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 */ 223 unsigned 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 mm_segment_t fs; 231 232 /* Trace user stack if not a kernel thread */ 233 if (current->flags & PF_KTHREAD) 234 return 0; 235 236 fs = force_uaccess_begin(); 237 arch_stack_walk_user(consume_entry, &c, task_pt_regs(current)); 238 force_uaccess_end(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 this function if they are tracing us */ 302 .skip = skipnr + (current == task), 303 }; 304 305 save_stack_trace_tsk(task, &trace); 306 return trace.nr_entries; 307 } 308 309 /** 310 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array 311 * @regs: Pointer to pt_regs to examine 312 * @store: Pointer to storage array 313 * @size: Size of the storage array 314 * @skipnr: Number of entries to skip at the start of the stack trace 315 * 316 * Return: Number of trace entries stored 317 */ 318 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store, 319 unsigned int size, unsigned int skipnr) 320 { 321 struct stack_trace trace = { 322 .entries = store, 323 .max_entries = size, 324 .skip = skipnr, 325 }; 326 327 save_stack_trace_regs(regs, &trace); 328 return trace.nr_entries; 329 } 330 331 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE 332 /** 333 * stack_trace_save_tsk_reliable - Save task stack with verification 334 * @tsk: Pointer to the task to examine 335 * @store: Pointer to storage array 336 * @size: Size of the storage array 337 * 338 * Return: An error if it detects any unreliable features of the 339 * stack. Otherwise it guarantees that the stack trace is 340 * reliable and returns the number of entries stored. 341 * 342 * If the task is not 'current', the caller *must* ensure the task is inactive. 343 */ 344 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store, 345 unsigned int size) 346 { 347 struct stack_trace trace = { 348 .entries = store, 349 .max_entries = size, 350 }; 351 int ret = save_stack_trace_tsk_reliable(tsk, &trace); 352 353 return ret ? ret : trace.nr_entries; 354 } 355 #endif 356 357 #ifdef CONFIG_USER_STACKTRACE_SUPPORT 358 /** 359 * stack_trace_save_user - Save a user space stack trace into a storage array 360 * @store: Pointer to storage array 361 * @size: Size of the storage array 362 * 363 * Return: Number of trace entries stored 364 */ 365 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size) 366 { 367 struct stack_trace trace = { 368 .entries = store, 369 .max_entries = size, 370 }; 371 372 save_stack_trace_user(&trace); 373 return trace.nr_entries; 374 } 375 #endif /* CONFIG_USER_STACKTRACE_SUPPORT */ 376 377 #endif /* !CONFIG_ARCH_STACKWALK */ 378