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 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 */
  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
  50/* Our option */
  51enum {
  52        TRACE_FUNC_OPT_STACK    = 0x1,
  53};
  54
  55static struct tracer_flags func_flags;
  56
  57static void
  58function_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
  90static void
  91function_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
 132static 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
 138static 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
 144static 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
 151static struct tracer_flags func_flags = {
 152        .val = 0, /* By default: all flags disabled */
 153        .opts = func_opts
 154};
 155
 156static 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
 168static 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
 178static 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
 202static 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
 217static void
 218ftrace_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
 234static void
 235ftrace_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
 251static int
 252ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
 253                         struct ftrace_probe_ops *ops, void *data);
 254
 255static struct ftrace_probe_ops traceon_probe_ops = {
 256        .func                   = ftrace_traceon,
 257        .print                  = ftrace_trace_onoff_print,
 258};
 259
 260static struct ftrace_probe_ops traceoff_probe_ops = {
 261        .func                   = ftrace_traceoff,
 262        .print                  = ftrace_trace_onoff_print,
 263};
 264
 265static int
 266ftrace_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
 286static int
 287ftrace_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
 302static int
 303ftrace_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
 346static struct ftrace_func_command ftrace_traceon_cmd = {
 347        .name                   = "traceon",
 348        .func                   = ftrace_trace_onoff_callback,
 349};
 350
 351static struct ftrace_func_command ftrace_traceoff_cmd = {
 352        .name                   = "traceoff",
 353        .func                   = ftrace_trace_onoff_callback,
 354};
 355
 356static 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
 370static inline int init_func_cmd_traceon(void)
 371{
 372        return 0;
 373}
 374#endif /* CONFIG_DYNAMIC_FTRACE */
 375
 376static __init int init_function_trace(void)
 377{
 378        init_func_cmd_traceon();
 379        return register_tracer(&function_trace);
 380}
 381core_initcall(init_function_trace);
 382
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