kernel/stacktrace.c

   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  * @tsk:        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 EXPORT_SYMBOL_GPL(stack_trace_save_tsk);
 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
 231         /* Trace user stack if not a kernel thread */
 232         if (current->flags & PF_KTHREAD)
 233                 return 0;
 234
 235         arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
 236
 237         return c.len;
 238 }
 239 #endif
 240
 241 #else /* CONFIG_ARCH_STACKWALK */
 242
 243 /*
 244  * Architectures that do not implement save_stack_trace_*()
 245  * get these weak aliases and once-per-bootup warnings
 246  * (whenever this facility is utilized - for example by procfs):
 247  */
 248 __weak void
 249 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 250 {
 251         WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
 252 }
 253
 254 __weak void
 255 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 256 {
 257         WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
 258 }
 259
 260 /**
 261  * stack_trace_save - Save a stack trace into a storage array
 262  * @store:      Pointer to storage array
 263  * @size:       Size of the storage array
 264  * @skipnr:     Number of entries to skip at the start of the stack trace
 265  *
 266  * Return: Number of trace entries stored
 267  */
 268 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
 269                               unsigned int skipnr)
 270 {
 271         struct stack_trace trace = {
 272                 .entries        = store,
 273                 .max_entries    = size,
 274                 .skip           = skipnr + 1,
 275         };
 276
 277         save_stack_trace(&trace);
 278         return trace.nr_entries;
 279 }
 280 EXPORT_SYMBOL_GPL(stack_trace_save);
 281
 282 /**
 283  * stack_trace_save_tsk - Save a task stack trace into a storage array
 284  * @task:       The task to examine
 285  * @store:      Pointer to storage array
 286  * @size:       Size of the storage array
 287  * @skipnr:     Number of entries to skip at the start of the stack trace
 288  *
 289  * Return: Number of trace entries stored
 290  */
 291 unsigned int stack_trace_save_tsk(struct task_struct *task,
 292                                   unsigned long *store, unsigned int size,
 293                                   unsigned int skipnr)
 294 {
 295         struct stack_trace trace = {
 296                 .entries        = store,
 297                 .max_entries    = size,
 298                 /* skip this function if they are tracing us */
 299                 .skip   = skipnr + (current == task),
 300         };
 301
 302         save_stack_trace_tsk(task, &trace);
 303         return trace.nr_entries;
 304 }
 305 EXPORT_SYMBOL_GPL(stack_trace_save_tsk);
 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  */
 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  */
 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  */
 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
 377 static inline bool in_irqentry_text(unsigned long ptr)
 378 {
 379         return (ptr >= (unsigned long)&__irqentry_text_start &&
 380                 ptr < (unsigned long)&__irqentry_text_end) ||
 381                 (ptr >= (unsigned long)&__softirqentry_text_start &&
 382                  ptr < (unsigned long)&__softirqentry_text_end);
 383 }
 384
 385 /**
 386  * filter_irq_stacks - Find first IRQ stack entry in trace
 387  * @entries:    Pointer to stack trace array
 388  * @nr_entries: Number of entries in the storage array
 389  *
 390  * Return: Number of trace entries until IRQ stack starts.
 391  */
 392 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries)
 393 {
 394         unsigned int i;
 395
 396         for (i = 0; i < nr_entries; i++) {
 397                 if (in_irqentry_text(entries[i])) {
 398                         /* Include the irqentry function into the stack. */
 399                         return i + 1;
 400                 }
 401         }
 402         return nr_entries;
 403 }
 404 EXPORT_SYMBOL_GPL(filter_irq_stacks);