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 #define STACK_TRACE_ENTRIES 500
  20
  21 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
  22          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
  23 static unsigned stack_dump_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 static struct stack_trace max_stack_trace = {
  31         .max_entries            = STACK_TRACE_ENTRIES - 1,
  32         .entries                = &stack_dump_trace[0],
  33 };
  34
  35 static unsigned long max_stack_size;
  36 static arch_spinlock_t max_stack_lock =
  37         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
  38
  39 static DEFINE_PER_CPU(int, trace_active);
  40 static DEFINE_MUTEX(stack_sysctl_mutex);
  41
  42 int stack_tracer_enabled;
  43 static int last_stack_tracer_enabled;
  44
  45 static inline void print_max_stack(void)
  46 {
  47         long i;
  48         int size;
  49
  50         pr_emerg("        Depth    Size   Location    (%d entries)\n"
  51                            "        -----    ----   --------\n",
  52                            max_stack_trace.nr_entries);
  53
  54         for (i = 0; i < max_stack_trace.nr_entries; i++) {
  55                 if (stack_dump_trace[i] == ULONG_MAX)
  56                         break;
  57                 if (i+1 == max_stack_trace.nr_entries ||
  58                                 stack_dump_trace[i+1] == ULONG_MAX)
  59                         size = stack_dump_index[i];
  60                 else
  61                         size = stack_dump_index[i] - stack_dump_index[i+1];
  62
  63                 pr_emerg("%3ld) %8d   %5d   %pS\n", i, stack_dump_index[i],
  64                                 size, (void *)stack_dump_trace[i]);
  65         }
  66 }
  67
  68 static inline void
  69 check_stack(unsigned long ip, unsigned long *stack)
  70 {
  71         unsigned long this_size, flags; unsigned long *p, *top, *start;
  72         static int tracer_frame;
  73         int frame_size = ACCESS_ONCE(tracer_frame);
  74         int i, x;
  75
  76         this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
  77         this_size = THREAD_SIZE - this_size;
  78         /* Remove the frame of the tracer */
  79         this_size -= frame_size;
  80
  81         if (this_size <= max_stack_size)
  82                 return;
  83
  84         /* we do not handle interrupt stacks yet */
  85         if (!object_is_on_stack(stack))
  86                 return;
  87
  88         /* Can't do this from NMI context (can cause deadlocks) */
  89         if (in_nmi())
  90                 return;
  91
  92         local_irq_save(flags);
  93         arch_spin_lock(&max_stack_lock);
  94
  95         /*
  96          * RCU may not be watching, make it see us.
  97          * The stack trace code uses rcu_sched.
  98          */
  99         rcu_irq_enter();
 100
 101         /* In case another CPU set the tracer_frame on us */
 102         if (unlikely(!frame_size))
 103                 this_size -= tracer_frame;
 104
 105         /* a race could have already updated it */
 106         if (this_size <= max_stack_size)
 107                 goto out;
 108
 109         max_stack_size = this_size;
 110
 111         max_stack_trace.nr_entries = 0;
 112         max_stack_trace.skip = 3;
 113
 114         save_stack_trace(&max_stack_trace);
 115
 116         /* Skip over the overhead of the stack tracer itself */
 117         for (i = 0; i < max_stack_trace.nr_entries; i++) {
 118                 if (stack_dump_trace[i] == ip)
 119                         break;
 120         }
 121
 122         /*
 123          * Now find where in the stack these are.
 124          */
 125         x = 0;
 126         start = stack;
 127         top = (unsigned long *)
 128                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
 129
 130         /*
 131          * Loop through all the entries. One of the entries may
 132          * for some reason be missed on the stack, so we may
 133          * have to account for them. If they are all there, this
 134          * loop will only happen once. This code only takes place
 135          * on a new max, so it is far from a fast path.
 136          */
 137         while (i < max_stack_trace.nr_entries) {
 138                 int found = 0;
 139
 140                 stack_dump_index[x] = this_size;
 141                 p = start;
 142
 143                 for (; p < top && i < max_stack_trace.nr_entries; p++) {
 144                         if (stack_dump_trace[i] == ULONG_MAX)
 145                                 break;
 146                         if (*p == stack_dump_trace[i]) {
 147                                 stack_dump_trace[x] = stack_dump_trace[i++];
 148                                 this_size = stack_dump_index[x++] =
 149                                         (top - p) * sizeof(unsigned long);
 150                                 found = 1;
 151                                 /* Start the search from here */
 152                                 start = p + 1;
 153                                 /*
 154                                  * We do not want to show the overhead
 155                                  * of the stack tracer stack in the
 156                                  * max stack. If we haven't figured
 157                                  * out what that is, then figure it out
 158                                  * now.
 159                                  */
 160                                 if (unlikely(!tracer_frame)) {
 161                                         tracer_frame = (p - stack) *
 162                                                 sizeof(unsigned long);
 163                                         max_stack_size -= tracer_frame;
 164                                 }
 165                         }
 166                 }
 167
 168                 if (!found)
 169                         i++;
 170         }
 171
 172         max_stack_trace.nr_entries = x;
 173         for (; x < i; x++)
 174                 stack_dump_trace[x] = ULONG_MAX;
 175
 176         if (task_stack_end_corrupted(current)) {
 177                 print_max_stack();
 178                 BUG();
 179         }
 180
 181  out:
 182         rcu_irq_exit();
 183         arch_spin_unlock(&max_stack_lock);
 184         local_irq_restore(flags);
 185 }
 186
 187 static void
 188 stack_trace_call(unsigned long ip, unsigned long parent_ip,
 189                  struct ftrace_ops *op, struct pt_regs *pt_regs)
 190 {
 191         unsigned long stack;
 192         int cpu;
 193
 194         preempt_disable_notrace();
 195
 196         cpu = raw_smp_processor_id();
 197         /* no atomic needed, we only modify this variable by this cpu */
 198         if (per_cpu(trace_active, cpu)++ != 0)
 199                 goto out;
 200
 201         ip += MCOUNT_INSN_SIZE;
 202
 203         check_stack(ip, &stack);
 204
 205  out:
 206         per_cpu(trace_active, cpu)--;
 207         /* prevent recursion in schedule */
 208         preempt_enable_notrace();
 209 }
 210
 211 static struct ftrace_ops trace_ops __read_mostly =
 212 {
 213         .func = stack_trace_call,
 214         .flags = FTRACE_OPS_FL_RECURSION_SAFE,
 215 };
 216
 217 static ssize_t
 218 stack_max_size_read(struct file *filp, char __user *ubuf,
 219                     size_t count, loff_t *ppos)
 220 {
 221         unsigned long *ptr = filp->private_data;
 222         char buf[64];
 223         int r;
 224
 225         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 226         if (r > sizeof(buf))
 227                 r = sizeof(buf);
 228         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 229 }
 230
 231 static ssize_t
 232 stack_max_size_write(struct file *filp, const char __user *ubuf,
 233                      size_t count, loff_t *ppos)
 234 {
 235         long *ptr = filp->private_data;
 236         unsigned long val, flags;
 237         int ret;
 238         int cpu;
 239
 240         ret = kstrtoul_from_user(ubuf, count, 10, &val);
 241         if (ret)
 242                 return ret;
 243
 244         local_irq_save(flags);
 245
 246         /*
 247          * In case we trace inside arch_spin_lock() or after (NMI),
 248          * we will cause circular lock, so we also need to increase
 249          * the percpu trace_active here.
 250          */
 251         cpu = smp_processor_id();
 252         per_cpu(trace_active, cpu)++;
 253
 254         arch_spin_lock(&max_stack_lock);
 255         *ptr = val;
 256         arch_spin_unlock(&max_stack_lock);
 257
 258         per_cpu(trace_active, cpu)--;
 259         local_irq_restore(flags);
 260
 261         return count;
 262 }
 263
 264 static const struct file_operations stack_max_size_fops = {
 265         .open           = tracing_open_generic,
 266         .read           = stack_max_size_read,
 267         .write          = stack_max_size_write,
 268         .llseek         = default_llseek,
 269 };
 270
 271 static void *
 272 __next(struct seq_file *m, loff_t *pos)
 273 {
 274         long n = *pos - 1;
 275
 276         if (n > max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
 277                 return NULL;
 278
 279         m->private = (void *)n;
 280         return &m->private;
 281 }
 282
 283 static void *
 284 t_next(struct seq_file *m, void *v, loff_t *pos)
 285 {
 286         (*pos)++;
 287         return __next(m, pos);
 288 }
 289
 290 static void *t_start(struct seq_file *m, loff_t *pos)
 291 {
 292         int cpu;
 293
 294         local_irq_disable();
 295
 296         cpu = smp_processor_id();
 297         per_cpu(trace_active, cpu)++;
 298
 299         arch_spin_lock(&max_stack_lock);
 300
 301         if (*pos == 0)
 302                 return SEQ_START_TOKEN;
 303
 304         return __next(m, pos);
 305 }
 306
 307 static void t_stop(struct seq_file *m, void *p)
 308 {
 309         int cpu;
 310
 311         arch_spin_unlock(&max_stack_lock);
 312
 313         cpu = smp_processor_id();
 314         per_cpu(trace_active, cpu)--;
 315
 316         local_irq_enable();
 317 }
 318
 319 static void trace_lookup_stack(struct seq_file *m, long i)
 320 {
 321         unsigned long addr = stack_dump_trace[i];
 322
 323         seq_printf(m, "%pS\n", (void *)addr);
 324 }
 325
 326 static void print_disabled(struct seq_file *m)
 327 {
 328         seq_puts(m, "#\n"
 329                  "#  Stack tracer disabled\n"
 330                  "#\n"
 331                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
 332                  "# kernel command line\n"
 333                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
 334                  "#\n");
 335 }
 336
 337 static int t_show(struct seq_file *m, void *v)
 338 {
 339         long i;
 340         int size;
 341
 342         if (v == SEQ_START_TOKEN) {
 343                 seq_printf(m, "        Depth    Size   Location"
 344                            "    (%d entries)\n"
 345                            "        -----    ----   --------\n",
 346                            max_stack_trace.nr_entries);
 347
 348                 if (!stack_tracer_enabled && !max_stack_size)
 349                         print_disabled(m);
 350
 351                 return 0;
 352         }
 353
 354         i = *(long *)v;
 355
 356         if (i >= max_stack_trace.nr_entries ||
 357             stack_dump_trace[i] == ULONG_MAX)
 358                 return 0;
 359
 360         if (i+1 == max_stack_trace.nr_entries ||
 361             stack_dump_trace[i+1] == ULONG_MAX)
 362                 size = stack_dump_index[i];
 363         else
 364                 size = stack_dump_index[i] - stack_dump_index[i+1];
 365
 366         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 367
 368         trace_lookup_stack(m, i);
 369
 370         return 0;
 371 }
 372
 373 static const struct seq_operations stack_trace_seq_ops = {
 374         .start          = t_start,
 375         .next           = t_next,
 376         .stop           = t_stop,
 377         .show           = t_show,
 378 };
 379
 380 static int stack_trace_open(struct inode *inode, struct file *file)
 381 {
 382         return seq_open(file, &stack_trace_seq_ops);
 383 }
 384
 385 static const struct file_operations stack_trace_fops = {
 386         .open           = stack_trace_open,
 387         .read           = seq_read,
 388         .llseek         = seq_lseek,
 389         .release        = seq_release,
 390 };
 391
 392 static int
 393 stack_trace_filter_open(struct inode *inode, struct file *file)
 394 {
 395         return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
 396                                  inode, file);
 397 }
 398
 399 static const struct file_operations stack_trace_filter_fops = {
 400         .open = stack_trace_filter_open,
 401         .read = seq_read,
 402         .write = ftrace_filter_write,
 403         .llseek = tracing_lseek,
 404         .release = ftrace_regex_release,
 405 };
 406
 407 int
 408 stack_trace_sysctl(struct ctl_table *table, int write,
 409                    void __user *buffer, size_t *lenp,
 410                    loff_t *ppos)
 411 {
 412         int ret;
 413
 414         mutex_lock(&stack_sysctl_mutex);
 415
 416         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 417
 418         if (ret || !write ||
 419             (last_stack_tracer_enabled == !!stack_tracer_enabled))
 420                 goto out;
 421
 422         last_stack_tracer_enabled = !!stack_tracer_enabled;
 423
 424         if (stack_tracer_enabled)
 425                 register_ftrace_function(&trace_ops);
 426         else
 427                 unregister_ftrace_function(&trace_ops);
 428
 429  out:
 430         mutex_unlock(&stack_sysctl_mutex);
 431         return ret;
 432 }
 433
 434 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
 435
 436 static __init int enable_stacktrace(char *str)
 437 {
 438         if (strncmp(str, "_filter=", 8) == 0)
 439                 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
 440
 441         stack_tracer_enabled = 1;
 442         last_stack_tracer_enabled = 1;
 443         return 1;
 444 }
 445 __setup("stacktrace", enable_stacktrace);
 446
 447 static __init int stack_trace_init(void)
 448 {
 449         struct dentry *d_tracer;
 450
 451         d_tracer = tracing_init_dentry();
 452         if (IS_ERR(d_tracer))
 453                 return 0;
 454
 455         trace_create_file("stack_max_size", 0644, d_tracer,
 456                         &max_stack_size, &stack_max_size_fops);
 457
 458         trace_create_file("stack_trace", 0444, d_tracer,
 459                         NULL, &stack_trace_fops);
 460
 461         trace_create_file("stack_trace_filter", 0444, d_tracer,
 462                         NULL, &stack_trace_filter_fops);
 463
 464         if (stack_trace_filter_buf[0])
 465                 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
 466
 467         if (stack_tracer_enabled)
 468                 register_ftrace_function(&trace_ops);
 469
 470         return 0;
 471 }
 472
 473 device_initcall(stack_trace_init);