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
  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 = get_fs();
 237         set_fs(USER_DS);
 238         arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
 239         set_fs(fs);
 240
 241         return c.len;
 242 }
 243 #endif
 244
 245 #else /* CONFIG_ARCH_STACKWALK */
 246
 247 /*
 248  * Architectures that do not implement save_stack_trace_*()
 249  * get these weak aliases and once-per-bootup warnings
 250  * (whenever this facility is utilized - for example by procfs):
 251  */
 252 __weak void
 253 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 254 {
 255         WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
 256 }
 257
 258 __weak void
 259 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 260 {
 261         WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
 262 }
 263
 264 /**
 265  * stack_trace_save - Save a stack trace into a storage array
 266  * @store:      Pointer to storage array
 267  * @size:       Size of the storage array
 268  * @skipnr:     Number of entries to skip at the start of the stack trace
 269  *
 270  * Return: Number of trace entries stored
 271  */
 272 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
 273                               unsigned int skipnr)
 274 {
 275         struct stack_trace trace = {
 276                 .entries        = store,
 277                 .max_entries    = size,
 278                 .skip           = skipnr + 1,
 279         };
 280
 281         save_stack_trace(&trace);
 282         return trace.nr_entries;
 283 }
 284 EXPORT_SYMBOL_GPL(stack_trace_save);
 285
 286 /**
 287  * stack_trace_save_tsk - Save a task stack trace into a storage array
 288  * @task:       The task to examine
 289  * @store:      Pointer to storage array
 290  * @size:       Size of the storage array
 291  * @skipnr:     Number of entries to skip at the start of the stack trace
 292  *
 293  * Return: Number of trace entries stored
 294  */
 295 unsigned int stack_trace_save_tsk(struct task_struct *task,
 296                                   unsigned long *store, unsigned int size,
 297                                   unsigned int skipnr)
 298 {
 299         struct stack_trace trace = {
 300                 .entries        = store,
 301                 .max_entries    = size,
 302                 /* skip this function if they are tracing us */
 303                 .skip   = skipnr + (current == task),
 304         };
 305
 306         save_stack_trace_tsk(task, &trace);
 307         return trace.nr_entries;
 308 }
 309
 310 /**
 311  * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
 312  * @regs:       Pointer to pt_regs to examine
 313  * @store:      Pointer to storage array
 314  * @size:       Size of the storage array
 315  * @skipnr:     Number of entries to skip at the start of the stack trace
 316  *
 317  * Return: Number of trace entries stored
 318  */
 319 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
 320                                    unsigned int size, unsigned int skipnr)
 321 {
 322         struct stack_trace trace = {
 323                 .entries        = store,
 324                 .max_entries    = size,
 325                 .skip           = skipnr,
 326         };
 327
 328         save_stack_trace_regs(regs, &trace);
 329         return trace.nr_entries;
 330 }
 331
 332 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
 333 /**
 334  * stack_trace_save_tsk_reliable - Save task stack with verification
 335  * @tsk:        Pointer to the task to examine
 336  * @store:      Pointer to storage array
 337  * @size:       Size of the storage array
 338  *
 339  * Return:      An error if it detects any unreliable features of the
 340  *              stack. Otherwise it guarantees that the stack trace is
 341  *              reliable and returns the number of entries stored.
 342  *
 343  * If the task is not 'current', the caller *must* ensure the task is inactive.
 344  */
 345 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
 346                                   unsigned int size)
 347 {
 348         struct stack_trace trace = {
 349                 .entries        = store,
 350                 .max_entries    = size,
 351         };
 352         int ret = save_stack_trace_tsk_reliable(tsk, &trace);
 353
 354         return ret ? ret : trace.nr_entries;
 355 }
 356 #endif
 357
 358 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
 359 /**
 360  * stack_trace_save_user - Save a user space stack trace into a storage array
 361  * @store:      Pointer to storage array
 362  * @size:       Size of the storage array
 363  *
 364  * Return: Number of trace entries stored
 365  */
 366 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
 367 {
 368         struct stack_trace trace = {
 369                 .entries        = store,
 370                 .max_entries    = size,
 371         };
 372
 373         save_stack_trace_user(&trace);
 374         return trace.nr_entries;
 375 }
 376 #endif /* CONFIG_USER_STACKTRACE_SUPPORT */
 377
 378 #endif /* !CONFIG_ARCH_STACKWALK */