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
  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         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 = ftrace_preempt_disable();
 111
 112         cpu = raw_smp_processor_id();
 113         /* no atomic needed, we only modify this variable by this cpu */
 114         if (per_cpu(trace_active, cpu)++ != 0)
 115                 goto out;
 116
 117         check_stack();
 118
 119  out:
 120         per_cpu(trace_active, cpu)--;
 121         /* prevent recursion in schedule */
 122         ftrace_preempt_enable(resched);
 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         local_irq_save(flags);
 166         __raw_spin_lock(&max_stack_lock);
 167         *ptr = val;
 168         __raw_spin_unlock(&max_stack_lock);
 169         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;
 184
 185         (*pos)++;
 186
 187         if (v == SEQ_START_TOKEN)
 188                 i = 0;
 189         else {
 190                 i = *(long *)v;
 191                 i++;
 192         }
 193
 194         if (i >= max_stack_trace.nr_entries ||
 195             stack_dump_trace[i] == ULONG_MAX)
 196                 return NULL;
 197
 198         m->private = (void *)i;
 199
 200         return &m->private;
 201 }
 202
 203 static void *t_start(struct seq_file *m, loff_t *pos)
 204 {
 205         void *t = SEQ_START_TOKEN;
 206         loff_t l = 0;
 207
 208         local_irq_disable();
 209         __raw_spin_lock(&max_stack_lock);
 210
 211         if (*pos == 0)
 212                 return SEQ_START_TOKEN;
 213
 214         for (; t && l < *pos; t = t_next(m, t, &l))
 215                 ;
 216
 217         return t;
 218 }
 219
 220 static void t_stop(struct seq_file *m, void *p)
 221 {
 222         __raw_spin_unlock(&max_stack_lock);
 223         local_irq_enable();
 224 }
 225
 226 static int trace_lookup_stack(struct seq_file *m, long i)
 227 {
 228         unsigned long addr = stack_dump_trace[i];
 229 #ifdef CONFIG_KALLSYMS
 230         char str[KSYM_SYMBOL_LEN];
 231
 232         sprint_symbol(str, addr);
 233
 234         return seq_printf(m, "%s\n", str);
 235 #else
 236         return seq_printf(m, "%p\n", (void*)addr);
 237 #endif
 238 }
 239
 240 static int t_show(struct seq_file *m, void *v)
 241 {
 242         long i;
 243         int size;
 244
 245         if (v == SEQ_START_TOKEN) {
 246                 seq_printf(m, "        Depth   Size      Location"
 247                            "    (%d entries)\n"
 248                            "        -----   ----      --------\n",
 249                            max_stack_trace.nr_entries);
 250                 return 0;
 251         }
 252
 253         i = *(long *)v;
 254
 255         if (i >= max_stack_trace.nr_entries ||
 256             stack_dump_trace[i] == ULONG_MAX)
 257                 return 0;
 258
 259         if (i+1 == max_stack_trace.nr_entries ||
 260             stack_dump_trace[i+1] == ULONG_MAX)
 261                 size = stack_dump_index[i];
 262         else
 263                 size = stack_dump_index[i] - stack_dump_index[i+1];
 264
 265         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 266
 267         trace_lookup_stack(m, i);
 268
 269         return 0;
 270 }
 271
 272 static struct seq_operations stack_trace_seq_ops = {
 273         .start          = t_start,
 274         .next           = t_next,
 275         .stop           = t_stop,
 276         .show           = t_show,
 277 };
 278
 279 static int stack_trace_open(struct inode *inode, struct file *file)
 280 {
 281         int ret;
 282
 283         ret = seq_open(file, &stack_trace_seq_ops);
 284
 285         return ret;
 286 }
 287
 288 static struct file_operations stack_trace_fops = {
 289         .open           = stack_trace_open,
 290         .read           = seq_read,
 291         .llseek         = seq_lseek,
 292 };
 293
 294 static __init int stack_trace_init(void)
 295 {
 296         struct dentry *d_tracer;
 297         struct dentry *entry;
 298
 299         d_tracer = tracing_init_dentry();
 300
 301         entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
 302                                     &max_stack_size, &stack_max_size_fops);
 303         if (!entry)
 304                 pr_warning("Could not create debugfs 'stack_max_size' entry\n");
 305
 306         entry = debugfs_create_file("stack_trace", 0444, d_tracer,
 307                                     NULL, &stack_trace_fops);
 308         if (!entry)
 309                 pr_warning("Could not create debugfs 'stack_trace' entry\n");
 310
 311         register_ftrace_function(&trace_ops);
 312
 313         return 0;
 314 }
 315
 316 device_initcall(stack_trace_init);