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         raw_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
  82                 stack_dump_index[i] = this_size;
  83                 p = start;
  84
  85                 for (; p < top && i < max_stack_trace.nr_entries; p++) {
  86                         if (*p == stack_dump_trace[i]) {
  87                                 this_size = stack_dump_index[i++] =
  88                                         (top - p) * sizeof(unsigned long);
  89                                 /* Start the search from here */
  90                                 start = p + 1;
  91                         }
  92                 }
  93
  94                 i++;
  95         }
  96
  97  out:
  98         __raw_spin_unlock(&max_stack_lock);
  99         raw_local_irq_restore(flags);
 100 }
 101
 102 static void
 103 stack_trace_call(unsigned long ip, unsigned long parent_ip)
 104 {
 105         int cpu, resched;
 106
 107         if (unlikely(!ftrace_enabled || stack_trace_disabled))
 108                 return;
 109
 110         resched = need_resched();
 111         preempt_disable_notrace();
 112
 113         cpu = raw_smp_processor_id();
 114         /* no atomic needed, we only modify this variable by this cpu */
 115         if (per_cpu(trace_active, cpu)++ != 0)
 116                 goto out;
 117
 118         check_stack();
 119
 120  out:
 121         per_cpu(trace_active, cpu)--;
 122         /* prevent recursion in schedule */
 123         if (resched)
 124                 preempt_enable_no_resched_notrace();
 125         else
 126                 preempt_enable_notrace();
 127 }
 128
 129 static struct ftrace_ops trace_ops __read_mostly =
 130 {
 131         .func = stack_trace_call,
 132 };
 133
 134 static ssize_t
 135 stack_max_size_read(struct file *filp, char __user *ubuf,
 136                     size_t count, loff_t *ppos)
 137 {
 138         unsigned long *ptr = filp->private_data;
 139         char buf[64];
 140         int r;
 141
 142         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 143         if (r > sizeof(buf))
 144                 r = sizeof(buf);
 145         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 146 }
 147
 148 static ssize_t
 149 stack_max_size_write(struct file *filp, const char __user *ubuf,
 150                      size_t count, loff_t *ppos)
 151 {
 152         long *ptr = filp->private_data;
 153         unsigned long val, flags;
 154         char buf[64];
 155         int ret;
 156
 157         if (count >= sizeof(buf))
 158                 return -EINVAL;
 159
 160         if (copy_from_user(&buf, ubuf, count))
 161                 return -EFAULT;
 162
 163         buf[count] = 0;
 164
 165         ret = strict_strtoul(buf, 10, &val);
 166         if (ret < 0)
 167                 return ret;
 168
 169         raw_local_irq_save(flags);
 170         __raw_spin_lock(&max_stack_lock);
 171         *ptr = val;
 172         __raw_spin_unlock(&max_stack_lock);
 173         raw_local_irq_restore(flags);
 174
 175         return count;
 176 }
 177
 178 static struct file_operations stack_max_size_fops = {
 179         .open           = tracing_open_generic,
 180         .read           = stack_max_size_read,
 181         .write          = stack_max_size_write,
 182 };
 183
 184 static void *
 185 t_next(struct seq_file *m, void *v, loff_t *pos)
 186 {
 187         long i = (long)m->private;
 188
 189         (*pos)++;
 190
 191         i++;
 192
 193         if (i >= max_stack_trace.nr_entries ||
 194             stack_dump_trace[i] == ULONG_MAX)
 195                 return NULL;
 196
 197         m->private = (void *)i;
 198
 199         return &m->private;
 200 }
 201
 202 static void *t_start(struct seq_file *m, loff_t *pos)
 203 {
 204         void *t = &m->private;
 205         loff_t l = 0;
 206
 207         local_irq_disable();
 208         __raw_spin_lock(&max_stack_lock);
 209
 210         for (; t && l < *pos; t = t_next(m, t, &l))
 211                 ;
 212
 213         return t;
 214 }
 215
 216 static void t_stop(struct seq_file *m, void *p)
 217 {
 218         __raw_spin_unlock(&max_stack_lock);
 219         local_irq_enable();
 220 }
 221
 222 static int trace_lookup_stack(struct seq_file *m, long i)
 223 {
 224         unsigned long addr = stack_dump_trace[i];
 225 #ifdef CONFIG_KALLSYMS
 226         char str[KSYM_SYMBOL_LEN];
 227
 228         sprint_symbol(str, addr);
 229
 230         return seq_printf(m, "%s\n", str);
 231 #else
 232         return seq_printf(m, "%p\n", (void*)addr);
 233 #endif
 234 }
 235
 236 static int t_show(struct seq_file *m, void *v)
 237 {
 238         long i = *(long *)v;
 239         int size;
 240
 241         if (i < 0) {
 242                 seq_printf(m, "        Depth   Size      Location"
 243                            "    (%d entries)\n"
 244                            "        -----   ----      --------\n",
 245                            max_stack_trace.nr_entries);
 246                 return 0;
 247         }
 248
 249         if (i >= max_stack_trace.nr_entries ||
 250             stack_dump_trace[i] == ULONG_MAX)
 251                 return 0;
 252
 253         if (i+1 == max_stack_trace.nr_entries ||
 254             stack_dump_trace[i+1] == ULONG_MAX)
 255                 size = stack_dump_index[i];
 256         else
 257                 size = stack_dump_index[i] - stack_dump_index[i+1];
 258
 259         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 260
 261         trace_lookup_stack(m, i);
 262
 263         return 0;
 264 }
 265
 266 static struct seq_operations stack_trace_seq_ops = {
 267         .start          = t_start,
 268         .next           = t_next,
 269         .stop           = t_stop,
 270         .show           = t_show,
 271 };
 272
 273 static int stack_trace_open(struct inode *inode, struct file *file)
 274 {
 275         int ret;
 276
 277         ret = seq_open(file, &stack_trace_seq_ops);
 278         if (!ret) {
 279                 struct seq_file *m = file->private_data;
 280                 m->private = (void *)-1;
 281         }
 282
 283         return ret;
 284 }
 285
 286 static struct file_operations stack_trace_fops = {
 287         .open           = stack_trace_open,
 288         .read           = seq_read,
 289         .llseek         = seq_lseek,
 290 };
 291
 292 static __init int stack_trace_init(void)
 293 {
 294         struct dentry *d_tracer;
 295         struct dentry *entry;
 296
 297         d_tracer = tracing_init_dentry();
 298
 299         entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
 300                                     &max_stack_size, &stack_max_size_fops);
 301         if (!entry)
 302                 pr_warning("Could not create debugfs 'stack_max_size' entry\n");
 303
 304         entry = debugfs_create_file("stack_trace", 0444, d_tracer,
 305                                     NULL, &stack_trace_fops);
 306         if (!entry)
 307                 pr_warning("Could not create debugfs 'stack_trace' entry\n");
 308
 309         register_ftrace_function(&trace_ops);
 310
 311         return 0;
 312 }
 313
 314 device_initcall(stack_trace_init);