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