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 {
  83         struct stacktrace_cookie *c = cookie;
  84
  85         if (c->len >= c->size)
  86                 return false;
  87
  88         if (c->skip > 0) {
  89                 c->skip--;
  90                 return true;
  91         }
  92         c->store[c->len++] = addr;
  93         return c->len < c->size;
  94 }
  95
  96 static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
  97 {
  98         if (in_sched_functions(addr))
  99                 return true;
 100         return stack_trace_consume_entry(cookie, addr);
 101 }
 102
 103 /**
 104  * stack_trace_save - Save a stack trace into a storage array
 105  * @store:      Pointer to storage array
 106  * @size:       Size of the storage array
 107  * @skipnr:     Number of entries to skip at the start of the stack trace
 108  *
 109  * Return: Number of trace entries stored.
 110  */
 111 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
 112                               unsigned int skipnr)
 113 {
 114         stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
 115         struct stacktrace_cookie c = {
 116                 .store  = store,
 117                 .size   = size,
 118                 .skip   = skipnr + 1,
 119         };
 120
 121         arch_stack_walk(consume_entry, &c, current, NULL);
 122         return c.len;
 123 }
 124 EXPORT_SYMBOL_GPL(stack_trace_save);
 125
 126 /**
 127  * stack_trace_save_tsk - Save a task stack trace into a storage array
 128  * @task:       The task to examine
 129  * @store:      Pointer to storage array
 130  * @size:       Size of the storage array
 131  * @skipnr:     Number of entries to skip at the start of the stack trace
 132  *
 133  * Return: Number of trace entries stored.
 134  */
 135 unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
 136                                   unsigned int size, unsigned int skipnr)
 137 {
 138         stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
 139         struct stacktrace_cookie c = {
 140                 .store  = store,
 141                 .size   = size,
 142                 /* skip this function if they are tracing us */
 143                 .skip   = skipnr + (current == tsk),
 144         };
 145
 146         if (!try_get_task_stack(tsk))
 147                 return 0;
 148
 149         arch_stack_walk(consume_entry, &c, tsk, NULL);
 150         put_task_stack(tsk);
 151         return c.len;
 152 }
 153
 154 /**
 155  * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
 156  * @regs:       Pointer to pt_regs to examine
 157  * @store:      Pointer to storage array
 158  * @size:       Size of the storage array
 159  * @skipnr:     Number of entries to skip at the start of the stack trace
 160  *
 161  * Return: Number of trace entries stored.
 162  */
 163 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
 164                                    unsigned int size, unsigned int skipnr)
 165 {
 166         stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
 167         struct stacktrace_cookie c = {
 168                 .store  = store,
 169                 .size   = size,
 170                 .skip   = skipnr,
 171         };
 172
 173         arch_stack_walk(consume_entry, &c, current, regs);
 174         return c.len;
 175 }
 176
 177 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
 178 /**
 179  * stack_trace_save_tsk_reliable - Save task stack with verification
 180  * @tsk:        Pointer to the task to examine
 181  * @store:      Pointer to storage array
 182  * @size:       Size of the storage array
 183  *
 184  * Return:      An error if it detects any unreliable features of the
 185  *              stack. Otherwise it guarantees that the stack trace is
 186  *              reliable and returns the number of entries stored.
 187  *
 188  * If the task is not 'current', the caller *must* ensure the task is inactive.
 189  */
 190 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
 191                                   unsigned int size)
 192 {
 193         stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
 194         struct stacktrace_cookie c = {
 195                 .store  = store,
 196                 .size   = size,
 197         };
 198         int ret;
 199
 200         /*
 201          * If the task doesn't have a stack (e.g., a zombie), the stack is
 202          * "reliably" empty.
 203          */
 204         if (!try_get_task_stack(tsk))
 205                 return 0;
 206
 207         ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
 208         put_task_stack(tsk);
 209         return ret ? ret : c.len;
 210 }
 211 #endif
 212
 213 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
 214 /**
 215  * stack_trace_save_user - Save a user space stack trace into a storage array
 216  * @store:      Pointer to storage array
 217  * @size:       Size of the storage array
 218  *
 219  * Return: Number of trace entries stored.
 220  */
 221 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
 222 {
 223         stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
 224         struct stacktrace_cookie c = {
 225                 .store  = store,
 226                 .size   = size,
 227         };
 228         mm_segment_t fs;
 229
 230         /* Trace user stack if not a kernel thread */
 231         if (current->flags & PF_KTHREAD)
 232                 return 0;
 233
 234         fs = force_uaccess_begin();
 235         arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
 236         force_uaccess_end(fs);
 237
 238         return c.len;
 239 }
 240 #endif
 241
 242 #else /* CONFIG_ARCH_STACKWALK */
 243
 244 /*
 245  * Architectures that do not implement save_stack_trace_*()
 246  * get these weak aliases and once-per-bootup warnings
 247  * (whenever this facility is utilized - for example by procfs):
 248  */
 249 __weak void
 250 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 251 {
 252         WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
 253 }
 254
 255 __weak void
 256 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 257 {
 258         WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
 259 }
 260
 261 /**
 262  * stack_trace_save - Save a stack trace into a storage array
 263  * @store:      Pointer to storage array
 264  * @size:       Size of the storage array
 265  * @skipnr:     Number of entries to skip at the start of the stack trace
 266  *
 267  * Return: Number of trace entries stored
 268  */
 269 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
 270                               unsigned int skipnr)
 271 {
 272         struct stack_trace trace = {
 273                 .entries        = store,
 274                 .max_entries    = size,
 275                 .skip           = skipnr + 1,
 276         };
 277
 278         save_stack_trace(&trace);
 279         return trace.nr_entries;
 280 }
 281 EXPORT_SYMBOL_GPL(stack_trace_save);
 282
 283 /**
 284  * stack_trace_save_tsk - Save a task stack trace into a storage array
 285  * @task:       The task to examine
 286  * @store:      Pointer to storage array
 287  * @size:       Size of the storage array
 288  * @skipnr:     Number of entries to skip at the start of the stack trace
 289  *
 290  * Return: Number of trace entries stored
 291  */
 292 unsigned int stack_trace_save_tsk(struct task_struct *task,
 293                                   unsigned long *store, unsigned int size,
 294                                   unsigned int skipnr)
 295 {
 296         struct stack_trace trace = {
 297                 .entries        = store,
 298                 .max_entries    = size,
 299                 /* skip this function if they are tracing us */
 300                 .skip   = skipnr + (current == task),
 301         };
 302
 303         save_stack_trace_tsk(task, &trace);
 304         return trace.nr_entries;
 305 }
 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 */