kernel/trace/trace_stack.c

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