kernel/trace/trace_stack.c

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