kernel/2.6.29.6-aldebaran-rt/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 #include "trace.h"
  17
  18 #define STACK_TRACE_ENTRIES 500
  19
  20 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
  21          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
  22 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
  23
  24 static struct stack_trace max_stack_trace = {
  25         .max_entries            = STACK_TRACE_ENTRIES,
  26         .entries                = stack_dump_trace,
  27 };
  28
  29 static unsigned long max_stack_size;
  30 static __raw_spinlock_t max_stack_lock = __RAW_SPIN_LOCK_UNLOCKED;
  31
  32 static int stack_trace_disabled __read_mostly;
  33 static DEFINE_PER_CPU(int, trace_active);
  34 static DEFINE_MUTEX(stack_sysctl_mutex);
  35
  36 int stack_tracer_enabled;
  37 static int last_stack_tracer_enabled;
  38
  39 static inline void check_stack(void)
  40 {
  41         unsigned long this_size, flags;
  42         unsigned long *p, *top, *start;
  43         int i;
  44
  45         this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
  46         this_size = THREAD_SIZE - this_size;
  47
  48         if (this_size <= max_stack_size)
  49                 return;
  50
  51         /* we do not handle interrupt stacks yet */
  52         if (!object_is_on_stack(&this_size))
  53                 return;
  54
  55         local_irq_save(flags);
  56         __raw_spin_lock(&max_stack_lock);
  57
  58         /* a race could have already updated it */
  59         if (this_size <= max_stack_size)
  60                 goto out;
  61
  62         max_stack_size = this_size;
  63
  64         max_stack_trace.nr_entries      = 0;
  65         max_stack_trace.skip            = 3;
  66
  67         save_stack_trace(&max_stack_trace);
  68
  69         /*
  70          * Now find where in the stack these are.
  71          */
  72         i = 0;
  73         start = &this_size;
  74         top = (unsigned long *)
  75                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
  76
  77         /*
  78          * Loop through all the entries. One of the entries may
  79          * for some reason be missed on the stack, so we may
  80          * have to account for them. If they are all there, this
  81          * loop will only happen once. This code only takes place
  82          * on a new max, so it is far from a fast path.
  83          */
  84         while (i < max_stack_trace.nr_entries) {
  85                 int found = 0;
  86
  87                 stack_dump_index[i] = this_size;
  88                 p = start;
  89
  90                 for (; p < top && i < max_stack_trace.nr_entries; p++) {
  91                         if (*p == stack_dump_trace[i]) {
  92                                 this_size = stack_dump_index[i++] =
  93                                         (top - p) * sizeof(unsigned long);
  94                                 found = 1;
  95                                 /* Start the search from here */
  96                                 start = p + 1;
  97                         }
  98                 }
  99
 100                 if (!found)
 101                         i++;
 102         }
 103
 104  out:
 105         __raw_spin_unlock(&max_stack_lock);
 106         local_irq_restore(flags);
 107 }
 108
 109 static void
 110 stack_trace_call(unsigned long ip, unsigned long parent_ip)
 111 {
 112         int cpu, resched;
 113
 114         if (unlikely(!ftrace_enabled || stack_trace_disabled))
 115                 return;
 116
 117         resched = ftrace_preempt_disable();
 118
 119         cpu = raw_smp_processor_id();
 120         /* no atomic needed, we only modify this variable by this cpu */
 121         if (per_cpu(trace_active, cpu)++ != 0)
 122                 goto out;
 123
 124         check_stack();
 125
 126  out:
 127         per_cpu(trace_active, cpu)--;
 128         /* prevent recursion in schedule */
 129         ftrace_preempt_enable(resched);
 130 }
 131
 132 static struct ftrace_ops trace_ops __read_mostly =
 133 {
 134         .func = stack_trace_call,
 135 };
 136
 137 static ssize_t
 138 stack_max_size_read(struct file *filp, char __user *ubuf,
 139                     size_t count, loff_t *ppos)
 140 {
 141         unsigned long *ptr = filp->private_data;
 142         char buf[64];
 143         int r;
 144
 145         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 146         if (r > sizeof(buf))
 147                 r = sizeof(buf);
 148         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 149 }
 150
 151 static ssize_t
 152 stack_max_size_write(struct file *filp, const char __user *ubuf,
 153                      size_t count, loff_t *ppos)
 154 {
 155         long *ptr = filp->private_data;
 156         unsigned long val, flags;
 157         char buf[64];
 158         int ret;
 159
 160         if (count >= sizeof(buf))
 161                 return -EINVAL;
 162
 163         if (copy_from_user(&buf, ubuf, count))
 164                 return -EFAULT;
 165
 166         buf[count] = 0;
 167
 168         ret = strict_strtoul(buf, 10, &val);
 169         if (ret < 0)
 170                 return ret;
 171
 172         local_irq_save(flags);
 173         __raw_spin_lock(&max_stack_lock);
 174         *ptr = val;
 175         __raw_spin_unlock(&max_stack_lock);
 176         local_irq_restore(flags);
 177
 178         return count;
 179 }
 180
 181 static const struct file_operations stack_max_size_fops = {
 182         .open           = tracing_open_generic,
 183         .read           = stack_max_size_read,
 184         .write          = stack_max_size_write,
 185 };
 186
 187 static void *
 188 t_next(struct seq_file *m, void *v, loff_t *pos)
 189 {
 190         long i;
 191
 192         (*pos)++;
 193
 194         if (v == SEQ_START_TOKEN)
 195                 i = 0;
 196         else {
 197                 i = *(long *)v;
 198                 i++;
 199         }
 200
 201         if (i >= max_stack_trace.nr_entries ||
 202             stack_dump_trace[i] == ULONG_MAX)
 203                 return NULL;
 204
 205         m->private = (void *)i;
 206
 207         return &m->private;
 208 }
 209
 210 static void *t_start(struct seq_file *m, loff_t *pos)
 211 {
 212         void *t = SEQ_START_TOKEN;
 213         loff_t l = 0;
 214
 215         local_irq_disable();
 216         __raw_spin_lock(&max_stack_lock);
 217
 218         if (*pos == 0)
 219                 return SEQ_START_TOKEN;
 220
 221         for (; t && l < *pos; t = t_next(m, t, &l))
 222                 ;
 223
 224         return t;
 225 }
 226
 227 static void t_stop(struct seq_file *m, void *p)
 228 {
 229         __raw_spin_unlock(&max_stack_lock);
 230         local_irq_enable();
 231 }
 232
 233 static int trace_lookup_stack(struct seq_file *m, long i)
 234 {
 235         unsigned long addr = stack_dump_trace[i];
 236 #ifdef CONFIG_KALLSYMS
 237         char str[KSYM_SYMBOL_LEN];
 238
 239         sprint_symbol(str, addr);
 240
 241         return seq_printf(m, "%s\n", str);
 242 #else
 243         return seq_printf(m, "%p\n", (void*)addr);
 244 #endif
 245 }
 246
 247 static void print_disabled(struct seq_file *m)
 248 {
 249         seq_puts(m, "#\n"
 250                  "#  Stack tracer disabled\n"
 251                  "#\n"
 252                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
 253                  "# kernel command line\n"
 254                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
 255                  "#\n");
 256 }
 257
 258 static int t_show(struct seq_file *m, void *v)
 259 {
 260         long i;
 261         int size;
 262
 263         if (v == SEQ_START_TOKEN) {
 264                 seq_printf(m, "        Depth    Size   Location"
 265                            "    (%d entries)\n"
 266                            "        -----    ----   --------\n",
 267                            max_stack_trace.nr_entries);
 268
 269                 if (!stack_tracer_enabled && !max_stack_size)
 270                         print_disabled(m);
 271
 272                 return 0;
 273         }
 274
 275         i = *(long *)v;
 276
 277         if (i >= max_stack_trace.nr_entries ||
 278             stack_dump_trace[i] == ULONG_MAX)
 279                 return 0;
 280
 281         if (i+1 == max_stack_trace.nr_entries ||
 282             stack_dump_trace[i+1] == ULONG_MAX)
 283                 size = stack_dump_index[i];
 284         else
 285                 size = stack_dump_index[i] - stack_dump_index[i+1];
 286
 287         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 288
 289         trace_lookup_stack(m, i);
 290
 291         return 0;
 292 }
 293
 294 static const struct seq_operations stack_trace_seq_ops = {
 295         .start          = t_start,
 296         .next           = t_next,
 297         .stop           = t_stop,
 298         .show           = t_show,
 299 };
 300
 301 static int stack_trace_open(struct inode *inode, struct file *file)
 302 {
 303         int ret;
 304
 305         ret = seq_open(file, &stack_trace_seq_ops);
 306
 307         return ret;
 308 }
 309
 310 static const struct file_operations stack_trace_fops = {
 311         .open           = stack_trace_open,
 312         .read           = seq_read,
 313         .llseek         = seq_lseek,
 314 };
 315
 316 int
 317 stack_trace_sysctl(struct ctl_table *table, int write,
 318                    struct file *file, void __user *buffer, size_t *lenp,
 319                    loff_t *ppos)
 320 {
 321         int ret;
 322
 323         mutex_lock(&stack_sysctl_mutex);
 324
 325         ret = proc_dointvec(table, write, file, buffer, lenp, ppos);
 326
 327         if (ret || !write ||
 328             (last_stack_tracer_enabled == stack_tracer_enabled))
 329                 goto out;
 330
 331         last_stack_tracer_enabled = stack_tracer_enabled;
 332
 333         if (stack_tracer_enabled)
 334                 register_ftrace_function(&trace_ops);
 335         else
 336                 unregister_ftrace_function(&trace_ops);
 337
 338  out:
 339         mutex_unlock(&stack_sysctl_mutex);
 340         return ret;
 341 }
 342
 343 static __init int enable_stacktrace(char *str)
 344 {
 345         stack_tracer_enabled = 1;
 346         last_stack_tracer_enabled = 1;
 347         return 1;
 348 }
 349 __setup("stacktrace", enable_stacktrace);
 350
 351 static __init int stack_trace_init(void)
 352 {
 353         struct dentry *d_tracer;
 354         struct dentry *entry;
 355
 356         d_tracer = tracing_init_dentry();
 357
 358         entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
 359                                     &max_stack_size, &stack_max_size_fops);
 360         if (!entry)
 361                 pr_warning("Could not create debugfs 'stack_max_size' entry\n");
 362
 363         entry = debugfs_create_file("stack_trace", 0444, d_tracer,
 364                                     NULL, &stack_trace_fops);
 365         if (!entry)
 366                 pr_warning("Could not create debugfs 'stack_trace' entry\n");
 367
 368         if (stack_tracer_enabled)
 369                 register_ftrace_function(&trace_ops);
 370
 371         return 0;
 372 }
 373
 374 device_initcall(stack_trace_init);