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