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/debugfs.h>
  11 #include <linux/ftrace.h>
  12 #include <linux/module.h>
  13 #include <linux/sysctl.h>
  14 #include <linux/init.h>
  15 #include <linux/fs.h>
  16
  17 #include <asm/setup.h>
  18
  19 #include "trace.h"
  20
  21 #define STACK_TRACE_ENTRIES 500
  22
  23 #ifdef CC_USING_FENTRY
  24 # define fentry         1
  25 #else
  26 # define fentry         0
  27 #endif
  28
  29 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
  30          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
  31 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
  32
  33 /*
  34  * Reserve one entry for the passed in ip. This will allow
  35  * us to remove most or all of the stack size overhead
  36  * added by the stack tracer itself.
  37  */
  38 static struct stack_trace max_stack_trace = {
  39         .max_entries            = STACK_TRACE_ENTRIES - 1,
  40         .entries                = &stack_dump_trace[1],
  41 };
  42
  43 static unsigned long max_stack_size;
  44 static arch_spinlock_t max_stack_lock =
  45         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
  46
  47 static DEFINE_PER_CPU(int, trace_active);
  48 static DEFINE_MUTEX(stack_sysctl_mutex);
  49
  50 int stack_tracer_enabled;
  51 static int last_stack_tracer_enabled;
  52
  53 static inline void print_max_stack(void)
  54 {
  55         long i;
  56         int size;
  57
  58         pr_emerg("        Depth    Size   Location    (%d entries)\n"
  59                            "        -----    ----   --------\n",
  60                            max_stack_trace.nr_entries - 1);
  61
  62         for (i = 0; i < max_stack_trace.nr_entries; i++) {
  63                 if (stack_dump_trace[i] == ULONG_MAX)
  64                         break;
  65                 if (i+1 == max_stack_trace.nr_entries ||
  66                                 stack_dump_trace[i+1] == ULONG_MAX)
  67                         size = stack_dump_index[i];
  68                 else
  69                         size = stack_dump_index[i] - stack_dump_index[i+1];
  70
  71                 pr_emerg("%3ld) %8d   %5d   %pS\n", i, stack_dump_index[i],
  72                                 size, (void *)stack_dump_trace[i]);
  73         }
  74 }
  75
  76 static inline void
  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 = ACCESS_ONCE(tracer_frame);
  82         int i;
  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 <= max_stack_size)
  90                 return;
  91
  92         /* we do not handle interrupt stacks yet */
  93         if (!object_is_on_stack(stack))
  94                 return;
  95
  96         local_irq_save(flags);
  97         arch_spin_lock(&max_stack_lock);
  98
  99         /* In case another CPU set the tracer_frame on us */
 100         if (unlikely(!frame_size))
 101                 this_size -= tracer_frame;
 102
 103         /* a race could have already updated it */
 104         if (this_size <= max_stack_size)
 105                 goto out;
 106
 107         max_stack_size = this_size;
 108
 109         max_stack_trace.nr_entries = 0;
 110
 111         if (using_ftrace_ops_list_func())
 112                 max_stack_trace.skip = 4;
 113         else
 114                 max_stack_trace.skip = 3;
 115
 116         save_stack_trace(&max_stack_trace);
 117
 118         /*
 119          * Add the passed in ip from the function tracer.
 120          * Searching for this on the stack will skip over
 121          * most of the overhead from the stack tracer itself.
 122          */
 123         stack_dump_trace[0] = ip;
 124         max_stack_trace.nr_entries++;
 125
 126         /*
 127          * Now find where in the stack these are.
 128          */
 129         i = 0;
 130         start = stack;
 131         top = (unsigned long *)
 132                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
 133
 134         /*
 135          * Loop through all the entries. One of the entries may
 136          * for some reason be missed on the stack, so we may
 137          * have to account for them. If they are all there, this
 138          * loop will only happen once. This code only takes place
 139          * on a new max, so it is far from a fast path.
 140          */
 141         while (i < max_stack_trace.nr_entries) {
 142                 int found = 0;
 143
 144                 stack_dump_index[i] = this_size;
 145                 p = start;
 146
 147                 for (; p < top && i < max_stack_trace.nr_entries; p++) {
 148                         if (*p == stack_dump_trace[i]) {
 149                                 this_size = stack_dump_index[i++] =
 150                                         (top - p) * sizeof(unsigned long);
 151                                 found = 1;
 152                                 /* Start the search from here */
 153                                 start = p + 1;
 154                                 /*
 155                                  * We do not want to show the overhead
 156                                  * of the stack tracer stack in the
 157                                  * max stack. If we haven't figured
 158                                  * out what that is, then figure it out
 159                                  * now.
 160                                  */
 161                                 if (unlikely(!tracer_frame) && i == 1) {
 162                                         tracer_frame = (p - stack) *
 163                                                 sizeof(unsigned long);
 164                                         max_stack_size -= tracer_frame;
 165                                 }
 166                         }
 167                 }
 168
 169                 if (!found)
 170                         i++;
 171         }
 172
 173         if (task_stack_end_corrupted(current)) {
 174                 print_max_stack();
 175                 BUG();
 176         }
 177
 178  out:
 179         arch_spin_unlock(&max_stack_lock);
 180         local_irq_restore(flags);
 181 }
 182
 183 static void
 184 stack_trace_call(unsigned long ip, unsigned long parent_ip,
 185                  struct ftrace_ops *op, struct pt_regs *pt_regs)
 186 {
 187         unsigned long stack;
 188         int cpu;
 189
 190         preempt_disable_notrace();
 191
 192         cpu = raw_smp_processor_id();
 193         /* no atomic needed, we only modify this variable by this cpu */
 194         if (per_cpu(trace_active, cpu)++ != 0)
 195                 goto out;
 196
 197         /*
 198          * When fentry is used, the traced function does not get
 199          * its stack frame set up, and we lose the parent.
 200          * The ip is pretty useless because the function tracer
 201          * was called before that function set up its stack frame.
 202          * In this case, we use the parent ip.
 203          *
 204          * By adding the return address of either the parent ip
 205          * or the current ip we can disregard most of the stack usage
 206          * caused by the stack tracer itself.
 207          *
 208          * The function tracer always reports the address of where the
 209          * mcount call was, but the stack will hold the return address.
 210          */
 211         if (fentry)
 212                 ip = parent_ip;
 213         else
 214                 ip += MCOUNT_INSN_SIZE;
 215
 216         check_stack(ip, &stack);
 217
 218  out:
 219         per_cpu(trace_active, cpu)--;
 220         /* prevent recursion in schedule */
 221         preempt_enable_notrace();
 222 }
 223
 224 static struct ftrace_ops trace_ops __read_mostly =
 225 {
 226         .func = stack_trace_call,
 227         .flags = FTRACE_OPS_FL_RECURSION_SAFE,
 228 };
 229
 230 static ssize_t
 231 stack_max_size_read(struct file *filp, char __user *ubuf,
 232                     size_t count, loff_t *ppos)
 233 {
 234         unsigned long *ptr = filp->private_data;
 235         char buf[64];
 236         int r;
 237
 238         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 239         if (r > sizeof(buf))
 240                 r = sizeof(buf);
 241         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 242 }
 243
 244 static ssize_t
 245 stack_max_size_write(struct file *filp, const char __user *ubuf,
 246                      size_t count, loff_t *ppos)
 247 {
 248         long *ptr = filp->private_data;
 249         unsigned long val, flags;
 250         int ret;
 251         int cpu;
 252
 253         ret = kstrtoul_from_user(ubuf, count, 10, &val);
 254         if (ret)
 255                 return ret;
 256
 257         local_irq_save(flags);
 258
 259         /*
 260          * In case we trace inside arch_spin_lock() or after (NMI),
 261          * we will cause circular lock, so we also need to increase
 262          * the percpu trace_active here.
 263          */
 264         cpu = smp_processor_id();
 265         per_cpu(trace_active, cpu)++;
 266
 267         arch_spin_lock(&max_stack_lock);
 268         *ptr = val;
 269         arch_spin_unlock(&max_stack_lock);
 270
 271         per_cpu(trace_active, cpu)--;
 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 >= max_stack_trace.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         int cpu;
 306
 307         local_irq_disable();
 308
 309         cpu = smp_processor_id();
 310         per_cpu(trace_active, cpu)++;
 311
 312         arch_spin_lock(&max_stack_lock);
 313
 314         if (*pos == 0)
 315                 return SEQ_START_TOKEN;
 316
 317         return __next(m, pos);
 318 }
 319
 320 static void t_stop(struct seq_file *m, void *p)
 321 {
 322         int cpu;
 323
 324         arch_spin_unlock(&max_stack_lock);
 325
 326         cpu = smp_processor_id();
 327         per_cpu(trace_active, cpu)--;
 328
 329         local_irq_enable();
 330 }
 331
 332 static int trace_lookup_stack(struct seq_file *m, long i)
 333 {
 334         unsigned long addr = stack_dump_trace[i];
 335
 336         return seq_printf(m, "%pS\n", (void *)addr);
 337 }
 338
 339 static void print_disabled(struct seq_file *m)
 340 {
 341         seq_puts(m, "#\n"
 342                  "#  Stack tracer disabled\n"
 343                  "#\n"
 344                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
 345                  "# kernel command line\n"
 346                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
 347                  "#\n");
 348 }
 349
 350 static int t_show(struct seq_file *m, void *v)
 351 {
 352         long i;
 353         int size;
 354
 355         if (v == SEQ_START_TOKEN) {
 356                 seq_printf(m, "        Depth    Size   Location"
 357                            "    (%d entries)\n"
 358                            "        -----    ----   --------\n",
 359                            max_stack_trace.nr_entries - 1);
 360
 361                 if (!stack_tracer_enabled && !max_stack_size)
 362                         print_disabled(m);
 363
 364                 return 0;
 365         }
 366
 367         i = *(long *)v;
 368
 369         if (i >= max_stack_trace.nr_entries ||
 370             stack_dump_trace[i] == ULONG_MAX)
 371                 return 0;
 372
 373         if (i+1 == max_stack_trace.nr_entries ||
 374             stack_dump_trace[i+1] == ULONG_MAX)
 375                 size = stack_dump_index[i];
 376         else
 377                 size = stack_dump_index[i] - stack_dump_index[i+1];
 378
 379         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 380
 381         trace_lookup_stack(m, i);
 382
 383         return 0;
 384 }
 385
 386 static const struct seq_operations stack_trace_seq_ops = {
 387         .start          = t_start,
 388         .next           = t_next,
 389         .stop           = t_stop,
 390         .show           = t_show,
 391 };
 392
 393 static int stack_trace_open(struct inode *inode, struct file *file)
 394 {
 395         return seq_open(file, &stack_trace_seq_ops);
 396 }
 397
 398 static const struct file_operations stack_trace_fops = {
 399         .open           = stack_trace_open,
 400         .read           = seq_read,
 401         .llseek         = seq_lseek,
 402         .release        = seq_release,
 403 };
 404
 405 static int
 406 stack_trace_filter_open(struct inode *inode, struct file *file)
 407 {
 408         return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
 409                                  inode, file);
 410 }
 411
 412 static const struct file_operations stack_trace_filter_fops = {
 413         .open = stack_trace_filter_open,
 414         .read = seq_read,
 415         .write = ftrace_filter_write,
 416         .llseek = tracing_lseek,
 417         .release = ftrace_regex_release,
 418 };
 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         if (strncmp(str, "_filter=", 8) == 0)
 452                 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
 453
 454         stack_tracer_enabled = 1;
 455         last_stack_tracer_enabled = 1;
 456         return 1;
 457 }
 458 __setup("stacktrace", enable_stacktrace);
 459
 460 static __init int stack_trace_init(void)
 461 {
 462         struct dentry *d_tracer;
 463
 464         d_tracer = tracing_init_dentry();
 465         if (!d_tracer)
 466                 return 0;
 467
 468         trace_create_file("stack_max_size", 0644, d_tracer,
 469                         &max_stack_size, &stack_max_size_fops);
 470
 471         trace_create_file("stack_trace", 0444, d_tracer,
 472                         NULL, &stack_trace_fops);
 473
 474         trace_create_file("stack_trace_filter", 0444, d_tracer,
 475                         NULL, &stack_trace_filter_fops);
 476
 477         if (stack_trace_filter_buf[0])
 478                 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
 479
 480         if (stack_tracer_enabled)
 481                 register_ftrace_function(&trace_ops);
 482
 483         return 0;
 484 }
 485
 486 device_initcall(stack_trace_init);