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   = skipnr + 1,
 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 = get_fs();
 236         set_fs(USER_DS);
 237         arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
 238         set_fs(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           = skipnr + 1,
 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 */