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 arch_spinlock_t max_stack_lock =
  31         (arch_spinlock_t)__ARCH_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         arch_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         arch_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;
 114
 115         if (unlikely(!ftrace_enabled || stack_trace_disabled))
 116                 return;
 117
 118         preempt_disable_notrace();
 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         preempt_enable_notrace();
 131 }
 132
 133 static struct ftrace_ops trace_ops __read_mostly =
 134 {
 135         .func = stack_trace_call,
 136         .flags = FTRACE_OPS_FL_GLOBAL,
 137 };
 138
 139 static ssize_t
 140 stack_max_size_read(struct file *filp, char __user *ubuf,
 141                     size_t count, loff_t *ppos)
 142 {
 143         unsigned long *ptr = filp->private_data;
 144         char buf[64];
 145         int r;
 146
 147         r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
 148         if (r > sizeof(buf))
 149                 r = sizeof(buf);
 150         return simple_read_from_buffer(ubuf, count, ppos, buf, r);
 151 }
 152
 153 static ssize_t
 154 stack_max_size_write(struct file *filp, const char __user *ubuf,
 155                      size_t count, loff_t *ppos)
 156 {
 157         long *ptr = filp->private_data;
 158         unsigned long val, flags;
 159         char buf[64];
 160         int ret;
 161         int cpu;
 162
 163         if (count >= sizeof(buf))
 164                 return -EINVAL;
 165
 166         if (copy_from_user(&buf, ubuf, count))
 167                 return -EFAULT;
 168
 169         buf[count] = 0;
 170
 171         ret = strict_strtoul(buf, 10, &val);
 172         if (ret < 0)
 173                 return ret;
 174
 175         local_irq_save(flags);
 176
 177         /*
 178          * In case we trace inside arch_spin_lock() or after (NMI),
 179          * we will cause circular lock, so we also need to increase
 180          * the percpu trace_active here.
 181          */
 182         cpu = smp_processor_id();
 183         per_cpu(trace_active, cpu)++;
 184
 185         arch_spin_lock(&max_stack_lock);
 186         *ptr = val;
 187         arch_spin_unlock(&max_stack_lock);
 188
 189         per_cpu(trace_active, cpu)--;
 190         local_irq_restore(flags);
 191
 192         return count;
 193 }
 194
 195 static const struct file_operations stack_max_size_fops = {
 196         .open           = tracing_open_generic,
 197         .read           = stack_max_size_read,
 198         .write          = stack_max_size_write,
 199         .llseek         = default_llseek,
 200 };
 201
 202 static void *
 203 __next(struct seq_file *m, loff_t *pos)
 204 {
 205         long n = *pos - 1;
 206
 207         if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)
 208                 return NULL;
 209
 210         m->private = (void *)n;
 211         return &m->private;
 212 }
 213
 214 static void *
 215 t_next(struct seq_file *m, void *v, loff_t *pos)
 216 {
 217         (*pos)++;
 218         return __next(m, pos);
 219 }
 220
 221 static void *t_start(struct seq_file *m, loff_t *pos)
 222 {
 223         int cpu;
 224
 225         local_irq_disable();
 226
 227         cpu = smp_processor_id();
 228         per_cpu(trace_active, cpu)++;
 229
 230         arch_spin_lock(&max_stack_lock);
 231
 232         if (*pos == 0)
 233                 return SEQ_START_TOKEN;
 234
 235         return __next(m, pos);
 236 }
 237
 238 static void t_stop(struct seq_file *m, void *p)
 239 {
 240         int cpu;
 241
 242         arch_spin_unlock(&max_stack_lock);
 243
 244         cpu = smp_processor_id();
 245         per_cpu(trace_active, cpu)--;
 246
 247         local_irq_enable();
 248 }
 249
 250 static int trace_lookup_stack(struct seq_file *m, long i)
 251 {
 252         unsigned long addr = stack_dump_trace[i];
 253
 254         return seq_printf(m, "%pS\n", (void *)addr);
 255 }
 256
 257 static void print_disabled(struct seq_file *m)
 258 {
 259         seq_puts(m, "#\n"
 260                  "#  Stack tracer disabled\n"
 261                  "#\n"
 262                  "# To enable the stack tracer, either add 'stacktrace' to the\n"
 263                  "# kernel command line\n"
 264                  "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
 265                  "#\n");
 266 }
 267
 268 static int t_show(struct seq_file *m, void *v)
 269 {
 270         long i;
 271         int size;
 272
 273         if (v == SEQ_START_TOKEN) {
 274                 seq_printf(m, "        Depth    Size   Location"
 275                            "    (%d entries)\n"
 276                            "        -----    ----   --------\n",
 277                            max_stack_trace.nr_entries - 1);
 278
 279                 if (!stack_tracer_enabled && !max_stack_size)
 280                         print_disabled(m);
 281
 282                 return 0;
 283         }
 284
 285         i = *(long *)v;
 286
 287         if (i >= max_stack_trace.nr_entries ||
 288             stack_dump_trace[i] == ULONG_MAX)
 289                 return 0;
 290
 291         if (i+1 == max_stack_trace.nr_entries ||
 292             stack_dump_trace[i+1] == ULONG_MAX)
 293                 size = stack_dump_index[i];
 294         else
 295                 size = stack_dump_index[i] - stack_dump_index[i+1];
 296
 297         seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size);
 298
 299         trace_lookup_stack(m, i);
 300
 301         return 0;
 302 }
 303
 304 static const struct seq_operations stack_trace_seq_ops = {
 305         .start          = t_start,
 306         .next           = t_next,
 307         .stop           = t_stop,
 308         .show           = t_show,
 309 };
 310
 311 static int stack_trace_open(struct inode *inode, struct file *file)
 312 {
 313         return seq_open(file, &stack_trace_seq_ops);
 314 }
 315
 316 static const struct file_operations stack_trace_fops = {
 317         .open           = stack_trace_open,
 318         .read           = seq_read,
 319         .llseek         = seq_lseek,
 320         .release        = seq_release,
 321 };
 322
 323 int
 324 stack_trace_sysctl(struct ctl_table *table, int write,
 325                    void __user *buffer, size_t *lenp,
 326                    loff_t *ppos)
 327 {
 328         int ret;
 329
 330         mutex_lock(&stack_sysctl_mutex);
 331
 332         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 333
 334         if (ret || !write ||
 335             (last_stack_tracer_enabled == !!stack_tracer_enabled))
 336                 goto out;
 337
 338         last_stack_tracer_enabled = !!stack_tracer_enabled;
 339
 340         if (stack_tracer_enabled)
 341                 register_ftrace_function(&trace_ops);
 342         else
 343                 unregister_ftrace_function(&trace_ops);
 344
 345  out:
 346         mutex_unlock(&stack_sysctl_mutex);
 347         return ret;
 348 }
 349
 350 static __init int enable_stacktrace(char *str)
 351 {
 352         stack_tracer_enabled = 1;
 353         last_stack_tracer_enabled = 1;
 354         return 1;
 355 }
 356 __setup("stacktrace", enable_stacktrace);
 357
 358 static __init int stack_trace_init(void)
 359 {
 360         struct dentry *d_tracer;
 361
 362         d_tracer = tracing_init_dentry();
 363
 364         trace_create_file("stack_max_size", 0644, d_tracer,
 365                         &max_stack_size, &stack_max_size_fops);
 366
 367         trace_create_file("stack_trace", 0444, d_tracer,
 368                         NULL, &stack_trace_fops);
 369
 370         if (stack_tracer_enabled)
 371                 register_ftrace_function(&trace_ops);
 372
 373         return 0;
 374 }
 375
 376 device_initcall(stack_trace_init);