kernel/trace/trace_sysprof.c

   1 /*
   2  * trace stack traces
   3  *
   4  * Copyright (C) 2004-2008, Soeren Sandmann
   5  * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
   6  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   7  */
   8 #include <linux/kallsyms.h>
   9 #include <linux/debugfs.h>
  10 #include <linux/hrtimer.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/module.h>
  14 #include <linux/irq.h>
  15 #include <linux/fs.h>
  16
  17 #include <asm/stacktrace.h>
  18
  19 #include "trace.h"
  20
  21 static struct trace_array       *sysprof_trace;
  22 static int __read_mostly        tracer_enabled;
  23
  24 /*
  25  * 1 msec sample interval by default:
  26  */
  27 static unsigned long sample_period = 1000000;
  28 static const unsigned int sample_max_depth = 512;
  29
  30 static DEFINE_MUTEX(sample_timer_lock);
  31 /*
  32  * Per CPU hrtimers that do the profiling:
  33  */
  34 static DEFINE_PER_CPU(struct hrtimer, stack_trace_hrtimer);
  35
  36 struct stack_frame {
  37         const void __user       *next_fp;
  38         unsigned long           return_address;
  39 };
  40
  41 static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
  42 {
  43         int ret;
  44
  45         if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
  46                 return 0;
  47
  48         ret = 1;
  49         pagefault_disable();
  50         if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
  51                 ret = 0;
  52         pagefault_enable();
  53
  54         return ret;
  55 }
  56
  57 struct backtrace_info {
  58         struct trace_array_cpu  *data;
  59         struct trace_array      *tr;
  60         int                     pos;
  61 };
  62
  63 static void
  64 backtrace_warning_symbol(void *data, char *msg, unsigned long symbol)
  65 {
  66         /* Ignore warnings */
  67 }
  68
  69 static void backtrace_warning(void *data, char *msg)
  70 {
  71         /* Ignore warnings */
  72 }
  73
  74 static int backtrace_stack(void *data, char *name)
  75 {
  76         /* Don't bother with IRQ stacks for now */
  77         return -1;
  78 }
  79
  80 static void backtrace_address(void *data, unsigned long addr, int reliable)
  81 {
  82         struct backtrace_info *info = data;
  83
  84         if (info->pos < sample_max_depth && reliable) {
  85                 __trace_special(info->tr, info->data, 1, addr, 0);
  86
  87                 info->pos++;
  88         }
  89 }
  90
  91 static const struct stacktrace_ops backtrace_ops = {
  92         .warning                = backtrace_warning,
  93         .warning_symbol         = backtrace_warning_symbol,
  94         .stack                  = backtrace_stack,
  95         .address                = backtrace_address,
  96         .walk_stack             = print_context_stack,
  97 };
  98
  99 static int
 100 trace_kernel(struct pt_regs *regs, struct trace_array *tr,
 101              struct trace_array_cpu *data)
 102 {
 103         struct backtrace_info info;
 104         unsigned long bp;
 105         char *stack;
 106
 107         info.tr = tr;
 108         info.data = data;
 109         info.pos = 1;
 110
 111         __trace_special(info.tr, info.data, 1, regs->ip, 0);
 112
 113         stack = ((char *)regs + sizeof(struct pt_regs));
 114 #ifdef CONFIG_FRAME_POINTER
 115         bp = regs->bp;
 116 #else
 117         bp = 0;
 118 #endif
 119
 120         dump_trace(NULL, regs, (void *)stack, bp, &backtrace_ops, &info);
 121
 122         return info.pos;
 123 }
 124
 125 static void timer_notify(struct pt_regs *regs, int cpu)
 126 {
 127         struct trace_array_cpu *data;
 128         struct stack_frame frame;
 129         struct trace_array *tr;
 130         const void __user *fp;
 131         int is_user;
 132         int i;
 133
 134         if (!regs)
 135                 return;
 136
 137         tr = sysprof_trace;
 138         data = tr->data[cpu];
 139         is_user = user_mode(regs);
 140
 141         if (!current || current->pid == 0)
 142                 return;
 143
 144         if (is_user && current->state != TASK_RUNNING)
 145                 return;
 146
 147         __trace_special(tr, data, 0, 0, current->pid);
 148
 149         if (!is_user)
 150                 i = trace_kernel(regs, tr, data);
 151         else
 152                 i = 0;
 153
 154         /*
 155          * Trace user stack if we are not a kernel thread
 156          */
 157         if (current->mm && i < sample_max_depth) {
 158                 regs = (struct pt_regs *)current->thread.sp0 - 1;
 159
 160                 fp = (void __user *)regs->bp;
 161
 162                 __trace_special(tr, data, 2, regs->ip, 0);
 163
 164                 while (i < sample_max_depth) {
 165                         frame.next_fp = NULL;
 166                         frame.return_address = 0;
 167                         if (!copy_stack_frame(fp, &frame))
 168                                 break;
 169                         if ((unsigned long)fp < regs->sp)
 170                                 break;
 171
 172                         __trace_special(tr, data, 2, frame.return_address,
 173                                         (unsigned long)fp);
 174                         fp = frame.next_fp;
 175
 176                         i++;
 177                 }
 178
 179         }
 180
 181         /*
 182          * Special trace entry if we overflow the max depth:
 183          */
 184         if (i == sample_max_depth)
 185                 __trace_special(tr, data, -1, -1, -1);
 186
 187         __trace_special(tr, data, 3, current->pid, i);
 188 }
 189
 190 static enum hrtimer_restart stack_trace_timer_fn(struct hrtimer *hrtimer)
 191 {
 192         /* trace here */
 193         timer_notify(get_irq_regs(), smp_processor_id());
 194
 195         hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 196
 197         return HRTIMER_RESTART;
 198 }
 199
 200 static void start_stack_timer(void *unused)
 201 {
 202         struct hrtimer *hrtimer = &__get_cpu_var(stack_trace_hrtimer);
 203
 204         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 205         hrtimer->function = stack_trace_timer_fn;
 206
 207         hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 208                       HRTIMER_MODE_REL_PINNED);
 209 }
 210
 211 static void start_stack_timers(void)
 212 {
 213         on_each_cpu(start_stack_timer, NULL, 1);
 214 }
 215
 216 static void stop_stack_timer(int cpu)
 217 {
 218         struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);
 219
 220         hrtimer_cancel(hrtimer);
 221 }
 222
 223 static void stop_stack_timers(void)
 224 {
 225         int cpu;
 226
 227         for_each_online_cpu(cpu)
 228                 stop_stack_timer(cpu);
 229 }
 230
 231 static void stop_stack_trace(struct trace_array *tr)
 232 {
 233         mutex_lock(&sample_timer_lock);
 234         stop_stack_timers();
 235         tracer_enabled = 0;
 236         mutex_unlock(&sample_timer_lock);
 237 }
 238
 239 static int stack_trace_init(struct trace_array *tr)
 240 {
 241         sysprof_trace = tr;
 242
 243         tracing_start_cmdline_record();
 244
 245         mutex_lock(&sample_timer_lock);
 246         start_stack_timers();
 247         tracer_enabled = 1;
 248         mutex_unlock(&sample_timer_lock);
 249         return 0;
 250 }
 251
 252 static void stack_trace_reset(struct trace_array *tr)
 253 {
 254         tracing_stop_cmdline_record();
 255         stop_stack_trace(tr);
 256 }
 257
 258 static struct tracer stack_trace __read_mostly =
 259 {
 260         .name           = "sysprof",
 261         .init           = stack_trace_init,
 262         .reset          = stack_trace_reset,
 263 #ifdef CONFIG_FTRACE_SELFTEST
 264         .selftest    = trace_selftest_startup_sysprof,
 265 #endif
 266 };
 267
 268 __init static int init_stack_trace(void)
 269 {
 270         return register_tracer(&stack_trace);
 271 }
 272 device_initcall(init_stack_trace);
 273
 274 #define MAX_LONG_DIGITS 22
 275
 276 static ssize_t
 277 sysprof_sample_read(struct file *filp, char __user *ubuf,
 278                     size_t cnt, loff_t *ppos)
 279 {
 280         char buf[MAX_LONG_DIGITS];
 281         int r;
 282
 283         r = sprintf(buf, "%ld\n", nsecs_to_usecs(sample_period));
 284
 285         return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 286 }
 287
 288 static ssize_t
 289 sysprof_sample_write(struct file *filp, const char __user *ubuf,
 290                      size_t cnt, loff_t *ppos)
 291 {
 292         char buf[MAX_LONG_DIGITS];
 293         unsigned long val;
 294
 295         if (cnt > MAX_LONG_DIGITS-1)
 296                 cnt = MAX_LONG_DIGITS-1;
 297
 298         if (copy_from_user(&buf, ubuf, cnt))
 299                 return -EFAULT;
 300
 301         buf[cnt] = 0;
 302
 303         val = simple_strtoul(buf, NULL, 10);
 304         /*
 305          * Enforce a minimum sample period of 100 usecs:
 306          */
 307         if (val < 100)
 308                 val = 100;
 309
 310         mutex_lock(&sample_timer_lock);
 311         stop_stack_timers();
 312         sample_period = val * 1000;
 313         start_stack_timers();
 314         mutex_unlock(&sample_timer_lock);
 315
 316         return cnt;
 317 }
 318
 319 static const struct file_operations sysprof_sample_fops = {
 320         .read           = sysprof_sample_read,
 321         .write          = sysprof_sample_write,
 322 };
 323
 324 void init_tracer_sysprof_debugfs(struct dentry *d_tracer)
 325 {
 326
 327         trace_create_file("sysprof_sample_period", 0644,
 328                         d_tracer, NULL, &sysprof_sample_fops);
 329 }