kernel/trace/trace_functions.c

   1 /*
   2  * ring buffer based function tracer
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * Based on code from the latency_tracer, that is:
   8  *
   9  *  Copyright (C) 2004-2006 Ingo Molnar
  10  *  Copyright (C) 2004 Nadia Yvette Chambers
  11  */
  12 #include <linux/ring_buffer.h>
  13 #include <linux/debugfs.h>
  14 #include <linux/uaccess.h>
  15 #include <linux/ftrace.h>
  16 #include <linux/fs.h>
  17
  18 #include "trace.h"
  19
  20 /* function tracing enabled */
  21 static int                      ftrace_function_enabled;
  22
  23 static struct trace_array       *func_trace;
  24
  25 static void tracing_start_function_trace(void);
  26 static void tracing_stop_function_trace(void);
  27
  28 static int function_trace_init(struct trace_array *tr)
  29 {
  30         func_trace = tr;
  31         tr->cpu = get_cpu();
  32         put_cpu();
  33
  34         tracing_start_cmdline_record();
  35         tracing_start_function_trace();
  36         return 0;
  37 }
  38
  39 static void function_trace_reset(struct trace_array *tr)
  40 {
  41         tracing_stop_function_trace();
  42         tracing_stop_cmdline_record();
  43 }
  44
  45 static void function_trace_start(struct trace_array *tr)
  46 {
  47         tracing_reset_online_cpus(tr);
  48 }
  49
  50 /* Our option */
  51 enum {
  52         TRACE_FUNC_OPT_STACK    = 0x1,
  53 };
  54
  55 static struct tracer_flags func_flags;
  56
  57 static void
  58 function_trace_call(unsigned long ip, unsigned long parent_ip,
  59                     struct ftrace_ops *op, struct pt_regs *pt_regs)
  60 {
  61         struct trace_array *tr = func_trace;
  62         struct trace_array_cpu *data;
  63         unsigned long flags;
  64         int bit;
  65         int cpu;
  66         int pc;
  67
  68         if (unlikely(!ftrace_function_enabled))
  69                 return;
  70
  71         pc = preempt_count();
  72         preempt_disable_notrace();
  73
  74         bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);
  75         if (bit < 0)
  76                 goto out;
  77
  78         cpu = smp_processor_id();
  79         data = tr->data[cpu];
  80         if (!atomic_read(&data->disabled)) {
  81                 local_save_flags(flags);
  82                 trace_function(tr, ip, parent_ip, flags, pc);
  83         }
  84         trace_clear_recursion(bit);
  85
  86  out:
  87         preempt_enable_notrace();
  88 }
  89
  90 static void
  91 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
  92                           struct ftrace_ops *op, struct pt_regs *pt_regs)
  93 {
  94         struct trace_array *tr = func_trace;
  95         struct trace_array_cpu *data;
  96         unsigned long flags;
  97         long disabled;
  98         int cpu;
  99         int pc;
 100
 101         if (unlikely(!ftrace_function_enabled))
 102                 return;
 103
 104         /*
 105          * Need to use raw, since this must be called before the
 106          * recursive protection is performed.
 107          */
 108         local_irq_save(flags);
 109         cpu = raw_smp_processor_id();
 110         data = tr->data[cpu];
 111         disabled = atomic_inc_return(&data->disabled);
 112
 113         if (likely(disabled == 1)) {
 114                 pc = preempt_count();
 115                 trace_function(tr, ip, parent_ip, flags, pc);
 116                 /*
 117                  * skip over 5 funcs:
 118                  *    __ftrace_trace_stack,
 119                  *    __trace_stack,
 120                  *    function_stack_trace_call
 121                  *    ftrace_list_func
 122                  *    ftrace_call
 123                  */
 124                 __trace_stack(tr, flags, 5, pc);
 125         }
 126
 127         atomic_dec(&data->disabled);
 128         local_irq_restore(flags);
 129 }
 130
 131
 132 static struct ftrace_ops trace_ops __read_mostly =
 133 {
 134         .func = function_trace_call,
 135         .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
 136 };
 137
 138 static struct ftrace_ops trace_stack_ops __read_mostly =
 139 {
 140         .func = function_stack_trace_call,
 141         .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
 142 };
 143
 144 static struct tracer_opt func_opts[] = {
 145 #ifdef CONFIG_STACKTRACE
 146         { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 147 #endif
 148         { } /* Always set a last empty entry */
 149 };
 150
 151 static struct tracer_flags func_flags = {
 152         .val = 0, /* By default: all flags disabled */
 153         .opts = func_opts
 154 };
 155
 156 static void tracing_start_function_trace(void)
 157 {
 158         ftrace_function_enabled = 0;
 159
 160         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 161                 register_ftrace_function(&trace_stack_ops);
 162         else
 163                 register_ftrace_function(&trace_ops);
 164
 165         ftrace_function_enabled = 1;
 166 }
 167
 168 static void tracing_stop_function_trace(void)
 169 {
 170         ftrace_function_enabled = 0;
 171
 172         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 173                 unregister_ftrace_function(&trace_stack_ops);
 174         else
 175                 unregister_ftrace_function(&trace_ops);
 176 }
 177
 178 static int func_set_flag(u32 old_flags, u32 bit, int set)
 179 {
 180         switch (bit) {
 181         case TRACE_FUNC_OPT_STACK:
 182                 /* do nothing if already set */
 183                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 184                         break;
 185
 186                 if (set) {
 187                         unregister_ftrace_function(&trace_ops);
 188                         register_ftrace_function(&trace_stack_ops);
 189                 } else {
 190                         unregister_ftrace_function(&trace_stack_ops);
 191                         register_ftrace_function(&trace_ops);
 192                 }
 193
 194                 break;
 195         default:
 196                 return -EINVAL;
 197         }
 198
 199         return 0;
 200 }
 201
 202 static struct tracer function_trace __read_mostly =
 203 {
 204         .name           = "function",
 205         .init           = function_trace_init,
 206         .reset          = function_trace_reset,
 207         .start          = function_trace_start,
 208         .wait_pipe      = poll_wait_pipe,
 209         .flags          = &func_flags,
 210         .set_flag       = func_set_flag,
 211 #ifdef CONFIG_FTRACE_SELFTEST
 212         .selftest       = trace_selftest_startup_function,
 213 #endif
 214 };
 215
 216 #ifdef CONFIG_DYNAMIC_FTRACE
 217 static void
 218 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 219 {
 220         long *count = (long *)data;
 221
 222         if (tracing_is_on())
 223                 return;
 224
 225         if (!*count)
 226                 return;
 227
 228         if (*count != -1)
 229                 (*count)--;
 230
 231         tracing_on();
 232 }
 233
 234 static void
 235 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 236 {
 237         long *count = (long *)data;
 238
 239         if (!tracing_is_on())
 240                 return;
 241
 242         if (!*count)
 243                 return;
 244
 245         if (*count != -1)
 246                 (*count)--;
 247
 248         tracing_off();
 249 }
 250
 251 static int
 252 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 253                          struct ftrace_probe_ops *ops, void *data);
 254
 255 static struct ftrace_probe_ops traceon_probe_ops = {
 256         .func                   = ftrace_traceon,
 257         .print                  = ftrace_trace_onoff_print,
 258 };
 259
 260 static struct ftrace_probe_ops traceoff_probe_ops = {
 261         .func                   = ftrace_traceoff,
 262         .print                  = ftrace_trace_onoff_print,
 263 };
 264
 265 static int
 266 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 267                          struct ftrace_probe_ops *ops, void *data)
 268 {
 269         long count = (long)data;
 270
 271         seq_printf(m, "%ps:", (void *)ip);
 272
 273         if (ops == &traceon_probe_ops)
 274                 seq_printf(m, "traceon");
 275         else
 276                 seq_printf(m, "traceoff");
 277
 278         if (count == -1)
 279                 seq_printf(m, ":unlimited\n");
 280         else
 281                 seq_printf(m, ":count=%ld\n", count);
 282
 283         return 0;
 284 }
 285
 286 static int
 287 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
 288 {
 289         struct ftrace_probe_ops *ops;
 290
 291         /* we register both traceon and traceoff to this callback */
 292         if (strcmp(cmd, "traceon") == 0)
 293                 ops = &traceon_probe_ops;
 294         else
 295                 ops = &traceoff_probe_ops;
 296
 297         unregister_ftrace_function_probe_func(glob, ops);
 298
 299         return 0;
 300 }
 301
 302 static int
 303 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
 304                             char *glob, char *cmd, char *param, int enable)
 305 {
 306         struct ftrace_probe_ops *ops;
 307         void *count = (void *)-1;
 308         char *number;
 309         int ret;
 310
 311         /* hash funcs only work with set_ftrace_filter */
 312         if (!enable)
 313                 return -EINVAL;
 314
 315         if (glob[0] == '!')
 316                 return ftrace_trace_onoff_unreg(glob+1, cmd, param);
 317
 318         /* we register both traceon and traceoff to this callback */
 319         if (strcmp(cmd, "traceon") == 0)
 320                 ops = &traceon_probe_ops;
 321         else
 322                 ops = &traceoff_probe_ops;
 323
 324         if (!param)
 325                 goto out_reg;
 326
 327         number = strsep(&param, ":");
 328
 329         if (!strlen(number))
 330                 goto out_reg;
 331
 332         /*
 333          * We use the callback data field (which is a pointer)
 334          * as our counter.
 335          */
 336         ret = kstrtoul(number, 0, (unsigned long *)&count);
 337         if (ret)
 338                 return ret;
 339
 340  out_reg:
 341         ret = register_ftrace_function_probe(glob, ops, count);
 342
 343         return ret < 0 ? ret : 0;
 344 }
 345
 346 static struct ftrace_func_command ftrace_traceon_cmd = {
 347         .name                   = "traceon",
 348         .func                   = ftrace_trace_onoff_callback,
 349 };
 350
 351 static struct ftrace_func_command ftrace_traceoff_cmd = {
 352         .name                   = "traceoff",
 353         .func                   = ftrace_trace_onoff_callback,
 354 };
 355
 356 static int __init init_func_cmd_traceon(void)
 357 {
 358         int ret;
 359
 360         ret = register_ftrace_command(&ftrace_traceoff_cmd);
 361         if (ret)
 362                 return ret;
 363
 364         ret = register_ftrace_command(&ftrace_traceon_cmd);
 365         if (ret)
 366                 unregister_ftrace_command(&ftrace_traceoff_cmd);
 367         return ret;
 368 }
 369 #else
 370 static inline int init_func_cmd_traceon(void)
 371 {
 372         return 0;
 373 }
 374 #endif /* CONFIG_DYNAMIC_FTRACE */
 375
 376 static __init int init_function_trace(void)
 377 {
 378         init_func_cmd_traceon();
 379         return register_tracer(&function_trace);
 380 }
 381 core_initcall(init_function_trace);