SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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/init.h>
  14 #include <linux/fs.h>
  15 #include "trace.h"
  16
  17 #define STACK_TRACE_ENTRIES 500
  18
  19 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
  20          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
  21 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
  22
  23 static struct stack_trace max_stack_trace = {
  24         .max_entries            = STACK_TRACE_ENTRIES,
  25         .entries                = stack_dump_trace,
  26 };
  27
  28 static unsigned long max_stack_size;
  29 static raw_spinlock_t max_stack_lock =
  30         (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
  31
  32 static int stack_trace_disabled __read_mostly;
  33 static DEFINE_PER_CPU(int, trace_active);
  34
  35 static inline void check_stack(void)
  36 {
  37         unsigned long this_size, flags;
  38         unsigned long *p, *top, *start;
  39         int i;
  40
  41         this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
  42         this_size = THREAD_SIZE - this_size;
  43
  44         if (this_size <= max_stack_size)
  45                 return;
  46
  47         /* we do not handle interrupt stacks yet */
  48         if (!object_is_on_stack(&this_size))
  49                 return;
  50
  51         local_irq_save(flags);
  52         __raw_spin_lock(&max_stack_lock);
  53
  54         /* a race could have already updated it */
  55         if (this_size <= max_stack_size)
  56                 goto out;
  57
  58         max_stack_size = this_size;
  59
  60         max_stack_trace.nr_entries      = 0;
  61         max_stack_trace.skip            = 3;
  62
  63         save_stack_trace(&max_stack_trace);
  64
  65         /*
  66          * Now find where in the stack these are.
  67          */
  68         i = 0;
  69         start = &this_size;
  70         top = (unsigned long *)
  71                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
  72
  73         /*
  74          * Loop through all the entries. One of the entries may
  75          * for some reason be missed on the stack, so we may
  76          * have to account for them. If they are all there, this
  77          * loop will only happen once. This code only takes place
  78          * on a new max, so it is far from a fast path.
  79          */
  80         while (i < max_stack_trace.nr_entries) {
  81                 int found = 0;
  82
  83                 stack_dump_index[i] = this_size;
  84                 p = start;
  85
  86                 for (; p < top && i < max_stack_trace.nr_entries; p++) {
  87                         if (*p == stack_dump_trace[i]) {
  88                                 this_size = stack_dump_index[i++] =
  89                                         (top - p) * sizeof(unsigned long);
  90                                 found = 1;
  91                                 /* Start the search from here */
  92                                 start = p + 1;
  93                         }
  94                 }
  95
  96                 if (!found)
  97                         i++;
  98         }
  99
 100  out:
 101         __raw_spin_unlock(&max_stack_lock);
 102         local_irq_restore(flags);
 103 }
 104
 105 static void
 106 stack_trace_call(unsigned long ip, unsigned long parent_ip)
 107 {
 108         int cpu, resched;
 109
 110         if (unlikely(!ftrace_enabled || stack_trace_disabled))
 111                 return;
 112
 113         resched = ftrace_preempt_disable();
 114
 115         cpu = raw_smp_processor_id();
 116         /* no atomic needed, we only modify this variable by this cpu */
 117         if (per_cpu(trace_active, cpu)++ != 0)
 118                 goto out;
 119
 120         check_stack();
 121
 122  out:
 123         per_cpu(trace_active, cpu)--;
 124         /* prevent recursion in schedule */
 125         ftrace_preempt_enable(resched);
 126 }
 127
 128 static struct ftrace_ops trace_ops __read_mostly =
 129 {
 130         .func = stack_trace_call,
 131 };
 132
 133 static ssize_t
 134 stack_max_size_read(struct file *filp, char __user *ubuf,
 135                     size_t count, loff_t *ppos)
 136 {
 137         unsigned long *ptr = filp->private_data;
 138         char buf[64];
 139         int r;
 140
 141         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 142         if (r > sizeof(buf))
 143                 r = sizeof(buf);
 144         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 145 }
 146
 147 static ssize_t
 148 stack_max_size_write(struct file *filp, const char __user *ubuf,
 149                      size_t count, loff_t *ppos)
 150 {
 151         long *ptr = filp->private_data;
 152         unsigned long val, flags;
 153         char buf[64];
 154         int ret;
 155
 156         if (count >= sizeof(buf))
 157                 return -EINVAL;
 158
 159         if (copy_from_user(&buf, ubuf, count))
 160                 return -EFAULT;
 161
 162         buf[count] = 0;
 163
 164         ret = strict_strtoul(buf, 10, &val);
 165         if (ret < 0)
 166                 return ret;
 167
 168         local_irq_save(flags);
 169         __raw_spin_lock(&max_stack_lock);
 170         *ptr = val;
 171         __raw_spin_unlock(&max_stack_lock);
 172         local_irq_restore(flags);
 173
 174         return count;
 175 }
 176
 177 static struct file_operations stack_max_size_fops = {
 178         .open           = tracing_open_generic,
 179         .read           = stack_max_size_read,
 180         .write          = stack_max_size_write,
 181 };
 182
 183 static void *
 184 t_next(struct seq_file *m, void *v, loff_t *pos)
 185 {
 186         long i;
 187
 188         (*pos)++;
 189
 190         if (v == SEQ_START_TOKEN)
 191                 i = 0;
 192         else {
 193                 i = *(long *)v;
 194                 i++;
 195         }
 196
 197         if (i >= max_stack_trace.nr_entries ||
 198             stack_dump_trace[i] == ULONG_MAX)
 199                 return NULL;
 200
 201         m->private = (void *)i;
 202
 203         return &m->private;
 204 }
 205
 206 static void *t_start(struct seq_file *m, loff_t *pos)
 207 {
 208         void *t = SEQ_START_TOKEN;
 209         loff_t l = 0;
 210
 211         local_irq_disable();
 212         __raw_spin_lock(&max_stack_lock);
 213
 214         if (*pos == 0)
 215                 return SEQ_START_TOKEN;
 216
 217         for (; t && l < *pos; t = t_next(m, t, &l))
 218                 ;
 219
 220         return t;
 221 }
 222
 223 static void t_stop(struct seq_file *m, void *p)
 224 {
 225         __raw_spin_unlock(&max_stack_lock);
 226         local_irq_enable();
 227 }
 228
 229 static int trace_lookup_stack(struct seq_file *m, long i)
 230 {
 231         unsigned long addr = stack_dump_trace[i];
 232 #ifdef CONFIG_KALLSYMS
 233         char str[KSYM_SYMBOL_LEN];
 234
 235         sprint_symbol(str, addr);
 236
 237         return seq_printf(m, "%s\n", str);
 238 #else
 239         return seq_printf(m, "%p\n", (void*)addr);
 240 #endif
 241 }
 242
 243 static int t_show(struct seq_file *m, void *v)
 244 {
 245         long i;
 246         int size;
 247
 248         if (v == SEQ_START_TOKEN) {
 249                 seq_printf(m, "        Depth   Size      Location"
 250                            "    (%d entries)\n"
 251                            "        -----   ----      --------\n",
 252                            max_stack_trace.nr_entries);
 253                 return 0;
 254         }
 255
 256         i = *(long *)v;
 257
 258         if (i >= max_stack_trace.nr_entries ||
 259             stack_dump_trace[i] == ULONG_MAX)
 260                 return 0;
 261
 262         if (i+1 == max_stack_trace.nr_entries ||
 263             stack_dump_trace[i+1] == ULONG_MAX)
 264                 size = stack_dump_index[i];
 265         else
 266                 size = stack_dump_index[i] - stack_dump_index[i+1];
 267
 268         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 269
 270         trace_lookup_stack(m, i);
 271
 272         return 0;
 273 }
 274
 275 static struct seq_operations stack_trace_seq_ops = {
 276         .start          = t_start,
 277         .next           = t_next,
 278         .stop           = t_stop,
 279         .show           = t_show,
 280 };
 281
 282 static int stack_trace_open(struct inode *inode, struct file *file)
 283 {
 284         int ret;
 285
 286         ret = seq_open(file, &stack_trace_seq_ops);
 287
 288         return ret;
 289 }
 290
 291 static struct file_operations stack_trace_fops = {
 292         .open           = stack_trace_open,
 293         .read           = seq_read,
 294         .llseek         = seq_lseek,
 295 };
 296
 297 static __init int stack_trace_init(void)
 298 {
 299         struct dentry *d_tracer;
 300         struct dentry *entry;
 301
 302         d_tracer = tracing_init_dentry();
 303
 304         entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
 305                                     &max_stack_size, &stack_max_size_fops);
 306         if (!entry)
 307                 pr_warning("Could not create debugfs 'stack_max_size' entry\n");
 308
 309         entry = debugfs_create_file("stack_trace", 0444, d_tracer,
 310                                     NULL, &stack_trace_fops);
 311         if (!entry)
 312                 pr_warning("Could not create debugfs 'stack_trace' entry\n");
 313
 314         register_ftrace_function(&trace_ops);
 315
 316         return 0;
 317 }
 318
 319 device_initcall(stack_trace_init);