kernel/trace/trace_stack.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   4  *
   5  */
   6 #include <linux/sched/task_stack.h>
   7 #include <linux/stacktrace.h>
   8 #include <linux/kallsyms.h>
   9 #include <linux/seq_file.h>
  10 #include <linux/spinlock.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/module.h>
  14 #include <linux/sysctl.h>
  15 #include <linux/init.h>
  16
  17 #include <asm/setup.h>
  18
  19 #include "trace.h"
  20
  21 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
  22          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
  23 unsigned stack_trace_index[STACK_TRACE_ENTRIES];
  24
  25 /*
  26  * Reserve one entry for the passed in ip. This will allow
  27  * us to remove most or all of the stack size overhead
  28  * added by the stack tracer itself.
  29  */
  30 struct stack_trace stack_trace_max = {
  31         .max_entries            = STACK_TRACE_ENTRIES - 1,
  32         .entries                = &stack_dump_trace[0],
  33 };
  34
  35 unsigned long stack_trace_max_size;
  36 arch_spinlock_t stack_trace_max_lock =
  37         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
  38
  39 DEFINE_PER_CPU(int, disable_stack_tracer);
  40 static DEFINE_MUTEX(stack_sysctl_mutex);
  41
  42 int stack_tracer_enabled;
  43 static int last_stack_tracer_enabled;
  44
  45 void stack_trace_print(void)
  46 {
  47         long i;
  48         int size;
  49
  50         pr_emerg("        Depth    Size   Location    (%d entries)\n"
  51                            "        -----    ----   --------\n",
  52                            stack_trace_max.nr_entries);
  53
  54         for (i = 0; i < stack_trace_max.nr_entries; i++) {
  55                 if (stack_dump_trace[i] == ULONG_MAX)
  56                         break;
  57                 if (i+1 == stack_trace_max.nr_entries ||
  58                                 stack_dump_trace[i+1] == ULONG_MAX)
  59                         size = stack_trace_index[i];
  60                 else
  61                         size = stack_trace_index[i] - stack_trace_index[i+1];
  62
  63                 pr_emerg("%3ld) %8d   %5d   %pS\n", i, stack_trace_index[i],
  64                                 size, (void *)stack_dump_trace[i]);
  65         }
  66 }
  67
  68 /*
  69  * When arch-specific code overrides this function, the following
  70  * data should be filled up, assuming stack_trace_max_lock is held to
  71  * prevent concurrent updates.
  72  *     stack_trace_index[]
  73  *     stack_trace_max
  74  *     stack_trace_max_size
  75  */
  76 void __weak
  77 check_stack(unsigned long ip, unsigned long *stack)
  78 {
  79         unsigned long this_size, flags; unsigned long *p, *top, *start;
  80         static int tracer_frame;
  81         int frame_size = READ_ONCE(tracer_frame);
  82         int i, x;
  83
  84         this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
  85         this_size = THREAD_SIZE - this_size;
  86         /* Remove the frame of the tracer */
  87         this_size -= frame_size;
  88
  89         if (this_size <= stack_trace_max_size)
  90                 return;
  91
  92         /* we do not handle interrupt stacks yet */
  93         if (!object_is_on_stack(stack))
  94                 return;
  95
  96         /* Can't do this from NMI context (can cause deadlocks) */
  97         if (in_nmi())
  98                 return;
  99
 100         local_irq_save(flags);
 101         arch_spin_lock(&stack_trace_max_lock);
 102
 103         /* In case another CPU set the tracer_frame on us */
 104         if (unlikely(!frame_size))
 105                 this_size -= tracer_frame;
 106
 107         /* a race could have already updated it */
 108         if (this_size <= stack_trace_max_size)
 109                 goto out;
 110
 111         stack_trace_max_size = this_size;
 112
 113         stack_trace_max.nr_entries = 0;
 114         stack_trace_max.skip = 0;
 115
 116         save_stack_trace(&stack_trace_max);
 117
 118         /* Skip over the overhead of the stack tracer itself */
 119         for (i = 0; i < stack_trace_max.nr_entries; i++) {
 120                 if (stack_dump_trace[i] == ip)
 121                         break;
 122         }
 123
 124         /*
 125          * Some archs may not have the passed in ip in the dump.
 126          * If that happens, we need to show everything.
 127          */
 128         if (i == stack_trace_max.nr_entries)
 129                 i = 0;
 130
 131         /*
 132          * Now find where in the stack these are.
 133          */
 134         x = 0;
 135         start = stack;
 136         top = (unsigned long *)
 137                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
 138
 139         /*
 140          * Loop through all the entries. One of the entries may
 141          * for some reason be missed on the stack, so we may
 142          * have to account for them. If they are all there, this
 143          * loop will only happen once. This code only takes place
 144          * on a new max, so it is far from a fast path.
 145          */
 146         while (i < stack_trace_max.nr_entries) {
 147                 int found = 0;
 148
 149                 stack_trace_index[x] = this_size;
 150                 p = start;
 151
 152                 for (; p < top && i < stack_trace_max.nr_entries; p++) {
 153                         if (stack_dump_trace[i] == ULONG_MAX)
 154                                 break;
 155                         /*
 156                          * The READ_ONCE_NOCHECK is used to let KASAN know that
 157                          * this is not a stack-out-of-bounds error.
 158                          */
 159                         if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
 160                                 stack_dump_trace[x] = stack_dump_trace[i++];
 161                                 this_size = stack_trace_index[x++] =
 162                                         (top - p) * sizeof(unsigned long);
 163                                 found = 1;
 164                                 /* Start the search from here */
 165                                 start = p + 1;
 166                                 /*
 167                                  * We do not want to show the overhead
 168                                  * of the stack tracer stack in the
 169                                  * max stack. If we haven't figured
 170                                  * out what that is, then figure it out
 171                                  * now.
 172                                  */
 173                                 if (unlikely(!tracer_frame)) {
 174                                         tracer_frame = (p - stack) *
 175                                                 sizeof(unsigned long);
 176                                         stack_trace_max_size -= tracer_frame;
 177                                 }
 178                         }
 179                 }
 180
 181                 if (!found)
 182                         i++;
 183         }
 184
 185         stack_trace_max.nr_entries = x;
 186         for (; x < i; x++)
 187                 stack_dump_trace[x] = ULONG_MAX;
 188
 189         if (task_stack_end_corrupted(current)) {
 190                 stack_trace_print();
 191                 BUG();
 192         }
 193
 194  out:
 195         arch_spin_unlock(&stack_trace_max_lock);
 196         local_irq_restore(flags);
 197 }
 198
 199 static void
 200 stack_trace_call(unsigned long ip, unsigned long parent_ip,
 201                  struct ftrace_ops *op, struct pt_regs *pt_regs)
 202 {
 203         unsigned long stack;
 204
 205         preempt_disable_notrace();
 206
 207         /* no atomic needed, we only modify this variable by this cpu */
 208         __this_cpu_inc(disable_stack_tracer);
 209         if (__this_cpu_read(disable_stack_tracer) != 1)
 210                 goto out;
 211
 212         /* If rcu is not watching, then save stack trace can fail */
 213         if (!rcu_is_watching())
 214                 goto out;
 215
 216         ip += MCOUNT_INSN_SIZE;
 217
 218         check_stack(ip, &stack);
 219
 220  out:
 221         __this_cpu_dec(disable_stack_tracer);
 222         /* prevent recursion in schedule */
 223         preempt_enable_notrace();
 224 }
 225
 226 static struct ftrace_ops trace_ops __read_mostly =
 227 {
 228         .func = stack_trace_call,
 229         .flags = FTRACE_OPS_FL_RECURSION_SAFE,
 230 };
 231
 232 static ssize_t
 233 stack_max_size_read(struct file *filp, char __user *ubuf,
 234                     size_t count, loff_t *ppos)
 235 {
 236         unsigned long *ptr = filp->private_data;
 237         char buf[64];
 238         int r;
 239
 240         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 241         if (r > sizeof(buf))
 242                 r = sizeof(buf);
 243         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 244 }
 245
 246 static ssize_t
 247 stack_max_size_write(struct file *filp, const char __user *ubuf,
 248                      size_t count, loff_t *ppos)
 249 {
 250         long *ptr = filp->private_data;
 251         unsigned long val, flags;
 252         int ret;
 253
 254         ret = kstrtoul_from_user(ubuf, count, 10, &val);
 255         if (ret)
 256                 return ret;
 257
 258         local_irq_save(flags);
 259
 260         /*
 261          * In case we trace inside arch_spin_lock() or after (NMI),
 262          * we will cause circular lock, so we also need to increase
 263          * the percpu disable_stack_tracer here.
 264          */
 265         __this_cpu_inc(disable_stack_tracer);
 266
 267         arch_spin_lock(&stack_trace_max_lock);
 268         *ptr = val;
 269         arch_spin_unlock(&stack_trace_max_lock);
 270
 271         __this_cpu_dec(disable_stack_tracer);
 272         local_irq_restore(flags);
 273
 274         return count;
 275 }
 276
 277 static const struct file_operations stack_max_size_fops = {
 278         .open           = tracing_open_generic,
 279         .read           = stack_max_size_read,
 280         .write          = stack_max_size_write,
 281         .llseek         = default_llseek,
 282 };
 283
 284 static void *
 285 __next(struct seq_file *m, loff_t *pos)
 286 {
 287         long n = *pos - 1;
 288
 289         if (n >= stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
 290                 return NULL;
 291
 292         m->private = (void *)n;
 293         return &m->private;
 294 }
 295
 296 static void *
 297 t_next(struct seq_file *m, void *v, loff_t *pos)
 298 {
 299         (*pos)++;
 300         return __next(m, pos);
 301 }
 302
 303 static void *t_start(struct seq_file *m, loff_t *pos)
 304 {
 305         local_irq_disable();
 306
 307         __this_cpu_inc(disable_stack_tracer);
 308
 309         arch_spin_lock(&stack_trace_max_lock);
 310
 311         if (*pos == 0)
 312                 return SEQ_START_TOKEN;
 313
 314         return __next(m, pos);
 315 }
 316
 317 static void t_stop(struct seq_file *m, void *p)
 318 {
 319         arch_spin_unlock(&stack_trace_max_lock);
 320
 321         __this_cpu_dec(disable_stack_tracer);
 322
 323         local_irq_enable();
 324 }
 325
 326 static void trace_lookup_stack(struct seq_file *m, long i)
 327 {
 328         unsigned long addr = stack_dump_trace[i];
 329
 330         seq_printf(m, "%pS\n", (void *)addr);
 331 }
 332
 333 static void print_disabled(struct seq_file *m)
 334 {
 335         seq_puts(m, "#\n"
 336                  "#  Stack tracer disabled\n"
 337                  "#\n"
 338                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
 339                  "# kernel command line\n"
 340                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
 341                  "#\n");
 342 }
 343
 344 static int t_show(struct seq_file *m, void *v)
 345 {
 346         long i;
 347         int size;
 348
 349         if (v == SEQ_START_TOKEN) {
 350                 seq_printf(m, "        Depth    Size   Location"
 351                            "    (%d entries)\n"
 352                            "        -----    ----   --------\n",
 353                            stack_trace_max.nr_entries);
 354
 355                 if (!stack_tracer_enabled && !stack_trace_max_size)
 356                         print_disabled(m);
 357
 358                 return 0;
 359         }
 360
 361         i = *(long *)v;
 362
 363         if (i >= stack_trace_max.nr_entries ||
 364             stack_dump_trace[i] == ULONG_MAX)
 365                 return 0;
 366
 367         if (i+1 == stack_trace_max.nr_entries ||
 368             stack_dump_trace[i+1] == ULONG_MAX)
 369                 size = stack_trace_index[i];
 370         else
 371                 size = stack_trace_index[i] - stack_trace_index[i+1];
 372
 373         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_trace_index[i], size);
 374
 375         trace_lookup_stack(m, i);
 376
 377         return 0;
 378 }
 379
 380 static const struct seq_operations stack_trace_seq_ops = {
 381         .start          = t_start,
 382         .next           = t_next,
 383         .stop           = t_stop,
 384         .show           = t_show,
 385 };
 386
 387 static int stack_trace_open(struct inode *inode, struct file *file)
 388 {
 389         return seq_open(file, &stack_trace_seq_ops);
 390 }
 391
 392 static const struct file_operations stack_trace_fops = {
 393         .open           = stack_trace_open,
 394         .read           = seq_read,
 395         .llseek         = seq_lseek,
 396         .release        = seq_release,
 397 };
 398
 399 #ifdef CONFIG_DYNAMIC_FTRACE
 400
 401 static int
 402 stack_trace_filter_open(struct inode *inode, struct file *file)
 403 {
 404         struct ftrace_ops *ops = inode->i_private;
 405
 406         return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
 407                                  inode, file);
 408 }
 409
 410 static const struct file_operations stack_trace_filter_fops = {
 411         .open = stack_trace_filter_open,
 412         .read = seq_read,
 413         .write = ftrace_filter_write,
 414         .llseek = tracing_lseek,
 415         .release = ftrace_regex_release,
 416 };
 417
 418 #endif /* CONFIG_DYNAMIC_FTRACE */
 419
 420 int
 421 stack_trace_sysctl(struct ctl_table *table, int write,
 422                    void __user *buffer, size_t *lenp,
 423                    loff_t *ppos)
 424 {
 425         int ret;
 426
 427         mutex_lock(&stack_sysctl_mutex);
 428
 429         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 430
 431         if (ret || !write ||
 432             (last_stack_tracer_enabled == !!stack_tracer_enabled))
 433                 goto out;
 434
 435         last_stack_tracer_enabled = !!stack_tracer_enabled;
 436
 437         if (stack_tracer_enabled)
 438                 register_ftrace_function(&trace_ops);
 439         else
 440                 unregister_ftrace_function(&trace_ops);
 441
 442  out:
 443         mutex_unlock(&stack_sysctl_mutex);
 444         return ret;
 445 }
 446
 447 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
 448
 449 static __init int enable_stacktrace(char *str)
 450 {
 451         int len;
 452
 453         if ((len = str_has_prefix(str, "_filter=")))
 454                 strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
 455
 456         stack_tracer_enabled = 1;
 457         last_stack_tracer_enabled = 1;
 458         return 1;
 459 }
 460 __setup("stacktrace", enable_stacktrace);
 461
 462 static __init int stack_trace_init(void)
 463 {
 464         struct dentry *d_tracer;
 465
 466         d_tracer = tracing_init_dentry();
 467         if (IS_ERR(d_tracer))
 468                 return 0;
 469
 470         trace_create_file("stack_max_size", 0644, d_tracer,
 471                         &stack_trace_max_size, &stack_max_size_fops);
 472
 473         trace_create_file("stack_trace", 0444, d_tracer,
 474                         NULL, &stack_trace_fops);
 475
 476 #ifdef CONFIG_DYNAMIC_FTRACE
 477         trace_create_file("stack_trace_filter", 0644, d_tracer,
 478                           &trace_ops, &stack_trace_filter_fops);
 479 #endif
 480
 481         if (stack_trace_filter_buf[0])
 482                 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
 483
 484         if (stack_tracer_enabled)
 485                 register_ftrace_function(&trace_ops);
 486
 487         return 0;
 488 }
 489
 490 device_initcall(stack_trace_init);