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  * @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);