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