linux/kernel/trace/trace_functions.c
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   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 William Lee Irwin III
  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/pstore.h>
  17#include <linux/fs.h>
  18
  19#include "trace.h"
  20
  21/* function tracing enabled */
  22static int                      ftrace_function_enabled;
  23
  24static struct trace_array       *func_trace;
  25
  26static void tracing_start_function_trace(void);
  27static void tracing_stop_function_trace(void);
  28
  29static int function_trace_init(struct trace_array *tr)
  30{
  31        func_trace = tr;
  32        tr->cpu = get_cpu();
  33        put_cpu();
  34
  35        tracing_start_cmdline_record();
  36        tracing_start_function_trace();
  37        return 0;
  38}
  39
  40static void function_trace_reset(struct trace_array *tr)
  41{
  42        tracing_stop_function_trace();
  43        tracing_stop_cmdline_record();
  44}
  45
  46static void function_trace_start(struct trace_array *tr)
  47{
  48        tracing_reset_online_cpus(tr);
  49}
  50
  51static void
  52function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
  53{
  54        struct trace_array *tr = func_trace;
  55        struct trace_array_cpu *data;
  56        unsigned long flags;
  57        long disabled;
  58        int cpu;
  59        int pc;
  60
  61        if (unlikely(!ftrace_function_enabled))
  62                return;
  63
  64        pc = preempt_count();
  65        preempt_disable_notrace();
  66        local_save_flags(flags);
  67        cpu = raw_smp_processor_id();
  68        data = tr->data[cpu];
  69        disabled = atomic_inc_return(&data->disabled);
  70
  71        if (likely(disabled == 1))
  72                trace_function(tr, ip, parent_ip, flags, pc);
  73
  74        atomic_dec(&data->disabled);
  75        preempt_enable_notrace();
  76}
  77
  78/* Our two options */
  79enum {
  80        TRACE_FUNC_OPT_STACK    = 0x1,
  81        TRACE_FUNC_OPT_PSTORE   = 0x2,
  82};
  83
  84static struct tracer_flags func_flags;
  85
  86static void
  87function_trace_call(unsigned long ip, unsigned long parent_ip)
  88{
  89        struct trace_array *tr = func_trace;
  90        struct trace_array_cpu *data;
  91        unsigned long flags;
  92        long disabled;
  93        int cpu;
  94        int pc;
  95
  96        if (unlikely(!ftrace_function_enabled))
  97                return;
  98
  99        /*
 100         * Need to use raw, since this must be called before the
 101         * recursive protection is performed.
 102         */
 103        local_irq_save(flags);
 104        cpu = raw_smp_processor_id();
 105        data = tr->data[cpu];
 106        disabled = atomic_inc_return(&data->disabled);
 107
 108        if (likely(disabled == 1)) {
 109                /*
 110                 * So far tracing doesn't support multiple buffers, so
 111                 * we make an explicit call for now.
 112                 */
 113                if (unlikely(func_flags.val & TRACE_FUNC_OPT_PSTORE))
 114                        pstore_ftrace_call(ip, parent_ip);
 115                pc = preempt_count();
 116                trace_function(tr, ip, parent_ip, flags, pc);
 117        }
 118
 119        atomic_dec(&data->disabled);
 120        local_irq_restore(flags);
 121}
 122
 123static void
 124function_stack_trace_call(unsigned long ip, unsigned long parent_ip)
 125{
 126        struct trace_array *tr = func_trace;
 127        struct trace_array_cpu *data;
 128        unsigned long flags;
 129        long disabled;
 130        int cpu;
 131        int pc;
 132
 133        if (unlikely(!ftrace_function_enabled))
 134                return;
 135
 136        /*
 137         * Need to use raw, since this must be called before the
 138         * recursive protection is performed.
 139         */
 140        local_irq_save(flags);
 141        cpu = raw_smp_processor_id();
 142        data = tr->data[cpu];
 143        disabled = atomic_inc_return(&data->disabled);
 144
 145        if (likely(disabled == 1)) {
 146                pc = preempt_count();
 147                trace_function(tr, ip, parent_ip, flags, pc);
 148                /*
 149                 * skip over 5 funcs:
 150                 *    __ftrace_trace_stack,
 151                 *    __trace_stack,
 152                 *    function_stack_trace_call
 153                 *    ftrace_list_func
 154                 *    ftrace_call
 155                 */
 156                __trace_stack(tr, flags, 5, pc);
 157        }
 158
 159        atomic_dec(&data->disabled);
 160        local_irq_restore(flags);
 161}
 162
 163
 164static struct ftrace_ops trace_ops __read_mostly =
 165{
 166        .func = function_trace_call,
 167        .flags = FTRACE_OPS_FL_GLOBAL,
 168};
 169
 170static struct ftrace_ops trace_stack_ops __read_mostly =
 171{
 172        .func = function_stack_trace_call,
 173        .flags = FTRACE_OPS_FL_GLOBAL,
 174};
 175
 176static struct tracer_opt func_opts[] = {
 177#ifdef CONFIG_STACKTRACE
 178        { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 179#endif
 180#ifdef CONFIG_PSTORE_FTRACE
 181        { TRACER_OPT(func_pstore, TRACE_FUNC_OPT_PSTORE) },
 182#endif
 183        { } /* Always set a last empty entry */
 184};
 185
 186static struct tracer_flags func_flags = {
 187        .val = 0, /* By default: all flags disabled */
 188        .opts = func_opts
 189};
 190
 191static void tracing_start_function_trace(void)
 192{
 193        ftrace_function_enabled = 0;
 194
 195        if (trace_flags & TRACE_ITER_PREEMPTONLY)
 196                trace_ops.func = function_trace_call_preempt_only;
 197        else
 198                trace_ops.func = function_trace_call;
 199
 200        if (func_flags.val & TRACE_FUNC_OPT_STACK)
 201                register_ftrace_function(&trace_stack_ops);
 202        else
 203                register_ftrace_function(&trace_ops);
 204
 205        ftrace_function_enabled = 1;
 206}
 207
 208static void tracing_stop_function_trace(void)
 209{
 210        ftrace_function_enabled = 0;
 211
 212        if (func_flags.val & TRACE_FUNC_OPT_STACK)
 213                unregister_ftrace_function(&trace_stack_ops);
 214        else
 215                unregister_ftrace_function(&trace_ops);
 216}
 217
 218static int func_set_flag(u32 old_flags, u32 bit, int set)
 219{
 220        switch (bit) {
 221        case TRACE_FUNC_OPT_STACK:
 222                /* do nothing if already set */
 223                if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 224                        break;
 225
 226                if (set) {
 227                        unregister_ftrace_function(&trace_ops);
 228                        register_ftrace_function(&trace_stack_ops);
 229                } else {
 230                        unregister_ftrace_function(&trace_stack_ops);
 231                        register_ftrace_function(&trace_ops);
 232                }
 233
 234                break;
 235        case TRACE_FUNC_OPT_PSTORE:
 236                break;
 237        default:
 238                return -EINVAL;
 239        }
 240
 241        return 0;
 242}
 243
 244static struct tracer function_trace __read_mostly =
 245{
 246        .name           = "function",
 247        .init           = function_trace_init,
 248        .reset          = function_trace_reset,
 249        .start          = function_trace_start,
 250        .wait_pipe      = poll_wait_pipe,
 251        .flags          = &func_flags,
 252        .set_flag       = func_set_flag,
 253#ifdef CONFIG_FTRACE_SELFTEST
 254        .selftest       = trace_selftest_startup_function,
 255#endif
 256};
 257
 258#ifdef CONFIG_DYNAMIC_FTRACE
 259static void
 260ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
 261{
 262        long *count = (long *)data;
 263
 264        if (tracing_is_on())
 265                return;
 266
 267        if (!*count)
 268                return;
 269
 270        if (*count != -1)
 271                (*count)--;
 272
 273        tracing_on();
 274}
 275
 276static void
 277ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
 278{
 279        long *count = (long *)data;
 280
 281        if (!tracing_is_on())
 282                return;
 283
 284        if (!*count)
 285                return;
 286
 287        if (*count != -1)
 288                (*count)--;
 289
 290        tracing_off();
 291}
 292
 293static int
 294ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 295                         struct ftrace_probe_ops *ops, void *data);
 296
 297static struct ftrace_probe_ops traceon_probe_ops = {
 298        .func                   = ftrace_traceon,
 299        .print                  = ftrace_trace_onoff_print,
 300};
 301
 302static struct ftrace_probe_ops traceoff_probe_ops = {
 303        .func                   = ftrace_traceoff,
 304        .print                  = ftrace_trace_onoff_print,
 305};
 306
 307static int
 308ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 309                         struct ftrace_probe_ops *ops, void *data)
 310{
 311        long count = (long)data;
 312
 313        seq_printf(m, "%ps:", (void *)ip);
 314
 315        if (ops == &traceon_probe_ops)
 316                seq_printf(m, "traceon");
 317        else
 318                seq_printf(m, "traceoff");
 319
 320        if (count == -1)
 321                seq_printf(m, ":unlimited\n");
 322        else
 323                seq_printf(m, ":count=%ld\n", count);
 324
 325        return 0;
 326}
 327
 328static int
 329ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
 330{
 331        struct ftrace_probe_ops *ops;
 332
 333        /* we register both traceon and traceoff to this callback */
 334        if (strcmp(cmd, "traceon") == 0)
 335                ops = &traceon_probe_ops;
 336        else
 337                ops = &traceoff_probe_ops;
 338
 339        unregister_ftrace_function_probe_func(glob, ops);
 340
 341        return 0;
 342}
 343
 344static int
 345ftrace_trace_onoff_callback(struct ftrace_hash *hash,
 346                            char *glob, char *cmd, char *param, int enable)
 347{
 348        struct ftrace_probe_ops *ops;
 349        void *count = (void *)-1;
 350        char *number;
 351        int ret;
 352
 353        /* hash funcs only work with set_ftrace_filter */
 354        if (!enable)
 355                return -EINVAL;
 356
 357        if (glob[0] == '!')
 358                return ftrace_trace_onoff_unreg(glob+1, cmd, param);
 359
 360        /* we register both traceon and traceoff to this callback */
 361        if (strcmp(cmd, "traceon") == 0)
 362                ops = &traceon_probe_ops;
 363        else
 364                ops = &traceoff_probe_ops;
 365
 366        if (!param)
 367                goto out_reg;
 368
 369        number = strsep(&param, ":");
 370
 371        if (!strlen(number))
 372                goto out_reg;
 373
 374        /*
 375         * We use the callback data field (which is a pointer)
 376         * as our counter.
 377         */
 378        ret = strict_strtoul(number, 0, (unsigned long *)&count);
 379        if (ret)
 380                return ret;
 381
 382 out_reg:
 383        ret = register_ftrace_function_probe(glob, ops, count);
 384
 385        return ret < 0 ? ret : 0;
 386}
 387
 388static struct ftrace_func_command ftrace_traceon_cmd = {
 389        .name                   = "traceon",
 390        .func                   = ftrace_trace_onoff_callback,
 391};
 392
 393static struct ftrace_func_command ftrace_traceoff_cmd = {
 394        .name                   = "traceoff",
 395        .func                   = ftrace_trace_onoff_callback,
 396};
 397
 398static int __init init_func_cmd_traceon(void)
 399{
 400        int ret;
 401
 402        ret = register_ftrace_command(&ftrace_traceoff_cmd);
 403        if (ret)
 404                return ret;
 405
 406        ret = register_ftrace_command(&ftrace_traceon_cmd);
 407        if (ret)
 408                unregister_ftrace_command(&ftrace_traceoff_cmd);
 409        return ret;
 410}
 411#else
 412static inline int init_func_cmd_traceon(void)
 413{
 414        return 0;
 415}
 416#endif /* CONFIG_DYNAMIC_FTRACE */
 417
 418static __init int init_function_trace(void)
 419{
 420        init_func_cmd_traceon();
 421        return register_tracer(&function_trace);
 422}
 423device_initcall(init_function_trace);
 424
 425
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