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