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 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
  24          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
  25 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
  26
  27 static struct stack_trace max_stack_trace = {
  28         .max_entries            = STACK_TRACE_ENTRIES,
  29         .entries                = stack_dump_trace,
  30 };
  31
  32 static unsigned long max_stack_size;
  33 static arch_spinlock_t max_stack_lock =
  34         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
  35
  36 static int stack_trace_disabled __read_mostly;
  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 static inline void check_stack(void)
  44 {
  45         unsigned long this_size, flags;
  46         unsigned long *p, *top, *start;
  47         int i;
  48
  49         this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
  50         this_size = THREAD_SIZE - this_size;
  51
  52         if (this_size <= max_stack_size)
  53                 return;
  54
  55         /* we do not handle interrupt stacks yet */
  56         if (!object_is_on_stack(&this_size))
  57                 return;
  58
  59         local_irq_save(flags);
  60         arch_spin_lock(&max_stack_lock);
  61
  62         /* a race could have already updated it */
  63         if (this_size <= max_stack_size)
  64                 goto out;
  65
  66         max_stack_size = this_size;
  67
  68         max_stack_trace.nr_entries      = 0;
  69         max_stack_trace.skip            = 3;
  70
  71         save_stack_trace(&max_stack_trace);
  72
  73         /*
  74          * Now find where in the stack these are.
  75          */
  76         i = 0;
  77         start = &this_size;
  78         top = (unsigned long *)
  79                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
  80
  81         /*
  82          * Loop through all the entries. One of the entries may
  83          * for some reason be missed on the stack, so we may
  84          * have to account for them. If they are all there, this
  85          * loop will only happen once. This code only takes place
  86          * on a new max, so it is far from a fast path.
  87          */
  88         while (i < max_stack_trace.nr_entries) {
  89                 int found = 0;
  90
  91                 stack_dump_index[i] = this_size;
  92                 p = start;
  93
  94                 for (; p < top && i < max_stack_trace.nr_entries; p++) {
  95                         if (*p == stack_dump_trace[i]) {
  96                                 this_size = stack_dump_index[i++] =
  97                                         (top - p) * sizeof(unsigned long);
  98                                 found = 1;
  99                                 /* Start the search from here */
 100                                 start = p + 1;
 101                         }
 102                 }
 103
 104                 if (!found)
 105                         i++;
 106         }
 107
 108  out:
 109         arch_spin_unlock(&max_stack_lock);
 110         local_irq_restore(flags);
 111 }
 112
 113 static void
 114 stack_trace_call(unsigned long ip, unsigned long parent_ip)
 115 {
 116         int cpu;
 117
 118         if (unlikely(!ftrace_enabled || stack_trace_disabled))
 119                 return;
 120
 121         preempt_disable_notrace();
 122
 123         cpu = raw_smp_processor_id();
 124         /* no atomic needed, we only modify this variable by this cpu */
 125         if (per_cpu(trace_active, cpu)++ != 0)
 126                 goto out;
 127
 128         check_stack();
 129
 130  out:
 131         per_cpu(trace_active, cpu)--;
 132         /* prevent recursion in schedule */
 133         preempt_enable_notrace();
 134 }
 135
 136 static struct ftrace_ops trace_ops __read_mostly =
 137 {
 138         .func = stack_trace_call,
 139 };
 140
 141 static ssize_t
 142 stack_max_size_read(struct file *filp, char __user *ubuf,
 143                     size_t count, loff_t *ppos)
 144 {
 145         unsigned long *ptr = filp->private_data;
 146         char buf[64];
 147         int r;
 148
 149         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 150         if (r > sizeof(buf))
 151                 r = sizeof(buf);
 152         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 153 }
 154
 155 static ssize_t
 156 stack_max_size_write(struct file *filp, const char __user *ubuf,
 157                      size_t count, loff_t *ppos)
 158 {
 159         long *ptr = filp->private_data;
 160         unsigned long val, flags;
 161         int ret;
 162         int cpu;
 163
 164         ret = kstrtoul_from_user(ubuf, count, 10, &val);
 165         if (ret)
 166                 return ret;
 167
 168         local_irq_save(flags);
 169
 170         /*
 171          * In case we trace inside arch_spin_lock() or after (NMI),
 172          * we will cause circular lock, so we also need to increase
 173          * the percpu trace_active here.
 174          */
 175         cpu = smp_processor_id();
 176         per_cpu(trace_active, cpu)++;
 177
 178         arch_spin_lock(&max_stack_lock);
 179         *ptr = val;
 180         arch_spin_unlock(&max_stack_lock);
 181
 182         per_cpu(trace_active, cpu)--;
 183         local_irq_restore(flags);
 184
 185         return count;
 186 }
 187
 188 static const struct file_operations stack_max_size_fops = {
 189         .open           = tracing_open_generic,
 190         .read           = stack_max_size_read,
 191         .write          = stack_max_size_write,
 192         .llseek         = default_llseek,
 193 };
 194
 195 static void *
 196 __next(struct seq_file *m, loff_t *pos)
 197 {
 198         long n = *pos - 1;
 199
 200         if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
 201                 return NULL;
 202
 203         m->private = (void *)n;
 204         return &m->private;
 205 }
 206
 207 static void *
 208 t_next(struct seq_file *m, void *v, loff_t *pos)
 209 {
 210         (*pos)++;
 211         return __next(m, pos);
 212 }
 213
 214 static void *t_start(struct seq_file *m, loff_t *pos)
 215 {
 216         int cpu;
 217
 218         local_irq_disable();
 219
 220         cpu = smp_processor_id();
 221         per_cpu(trace_active, cpu)++;
 222
 223         arch_spin_lock(&max_stack_lock);
 224
 225         if (*pos == 0)
 226                 return SEQ_START_TOKEN;
 227
 228         return __next(m, pos);
 229 }
 230
 231 static void t_stop(struct seq_file *m, void *p)
 232 {
 233         int cpu;
 234
 235         arch_spin_unlock(&max_stack_lock);
 236
 237         cpu = smp_processor_id();
 238         per_cpu(trace_active, cpu)--;
 239
 240         local_irq_enable();
 241 }
 242
 243 static int trace_lookup_stack(struct seq_file *m, long i)
 244 {
 245         unsigned long addr = stack_dump_trace[i];
 246
 247         return seq_printf(m, "%pS\n", (void *)addr);
 248 }
 249
 250 static void print_disabled(struct seq_file *m)
 251 {
 252         seq_puts(m, "#\n"
 253                  "#  Stack tracer disabled\n"
 254                  "#\n"
 255                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
 256                  "# kernel command line\n"
 257                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
 258                  "#\n");
 259 }
 260
 261 static int t_show(struct seq_file *m, void *v)
 262 {
 263         long i;
 264         int size;
 265
 266         if (v == SEQ_START_TOKEN) {
 267                 seq_printf(m, "        Depth    Size   Location"
 268                            "    (%d entries)\n"
 269                            "        -----    ----   --------\n",
 270                            max_stack_trace.nr_entries - 1);
 271
 272                 if (!stack_tracer_enabled && !max_stack_size)
 273                         print_disabled(m);
 274
 275                 return 0;
 276         }
 277
 278         i = *(long *)v;
 279
 280         if (i >= max_stack_trace.nr_entries ||
 281             stack_dump_trace[i] == ULONG_MAX)
 282                 return 0;
 283
 284         if (i+1 == max_stack_trace.nr_entries ||
 285             stack_dump_trace[i+1] == ULONG_MAX)
 286                 size = stack_dump_index[i];
 287         else
 288                 size = stack_dump_index[i] - stack_dump_index[i+1];
 289
 290         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 291
 292         trace_lookup_stack(m, i);
 293
 294         return 0;
 295 }
 296
 297 static const struct seq_operations stack_trace_seq_ops = {
 298         .start          = t_start,
 299         .next           = t_next,
 300         .stop           = t_stop,
 301         .show           = t_show,
 302 };
 303
 304 static int stack_trace_open(struct inode *inode, struct file *file)
 305 {
 306         return seq_open(file, &stack_trace_seq_ops);
 307 }
 308
 309 static const struct file_operations stack_trace_fops = {
 310         .open           = stack_trace_open,
 311         .read           = seq_read,
 312         .llseek         = seq_lseek,
 313         .release        = seq_release,
 314 };
 315
 316 static int
 317 stack_trace_filter_open(struct inode *inode, struct file *file)
 318 {
 319         return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
 320                                  inode, file);
 321 }
 322
 323 static const struct file_operations stack_trace_filter_fops = {
 324         .open = stack_trace_filter_open,
 325         .read = seq_read,
 326         .write = ftrace_filter_write,
 327         .llseek = ftrace_regex_lseek,
 328         .release = ftrace_regex_release,
 329 };
 330
 331 int
 332 stack_trace_sysctl(struct ctl_table *table, int write,
 333                    void __user *buffer, size_t *lenp,
 334                    loff_t *ppos)
 335 {
 336         int ret;
 337
 338         mutex_lock(&stack_sysctl_mutex);
 339
 340         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 341
 342         if (ret || !write ||
 343             (last_stack_tracer_enabled == !!stack_tracer_enabled))
 344                 goto out;
 345
 346         last_stack_tracer_enabled = !!stack_tracer_enabled;
 347
 348         if (stack_tracer_enabled)
 349                 register_ftrace_function(&trace_ops);
 350         else
 351                 unregister_ftrace_function(&trace_ops);
 352
 353  out:
 354         mutex_unlock(&stack_sysctl_mutex);
 355         return ret;
 356 }
 357
 358 static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
 359
 360 static __init int enable_stacktrace(char *str)
 361 {
 362         if (strncmp(str, "_filter=", 8) == 0)
 363                 strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
 364
 365         stack_tracer_enabled = 1;
 366         last_stack_tracer_enabled = 1;
 367         return 1;
 368 }
 369 __setup("stacktrace", enable_stacktrace);
 370
 371 static __init int stack_trace_init(void)
 372 {
 373         struct dentry *d_tracer;
 374
 375         d_tracer = tracing_init_dentry();
 376
 377         trace_create_file("stack_max_size", 0644, d_tracer,
 378                         &max_stack_size, &stack_max_size_fops);
 379
 380         trace_create_file("stack_trace", 0444, d_tracer,
 381                         NULL, &stack_trace_fops);
 382
 383         trace_create_file("stack_trace_filter", 0444, d_tracer,
 384                         NULL, &stack_trace_filter_fops);
 385
 386         if (stack_trace_filter_buf[0])
 387                 ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
 388
 389         if (stack_tracer_enabled)
 390                 register_ftrace_function(&trace_ops);
 391
 392         return 0;
 393 }
 394
 395 device_initcall(stack_trace_init);