trace_functions.c

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/*
 * ring buffer based function tracer
 *
 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
 * Copyright (C) 2008 Ingo Molnar <[email protected]>
 *
 * Based on code from the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */
#include <linux/ring_buffer.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/fs.h>

#include "trace.h"

/* function tracing enabled */
static int          ftrace_function_enabled;

static struct trace_array   *func_trace;

static void tracing_start_function_trace(void);
static void tracing_stop_function_trace(void);

static int function_trace_init(struct trace_array *tr)
{
    func_trace = tr;
    tr->cpu = get_cpu();
    put_cpu();

    tracing_start_cmdline_record();
    tracing_start_function_trace();
    return 0;
}

static void function_trace_reset(struct trace_array *tr)
{
    tracing_stop_function_trace();
    tracing_stop_cmdline_record();
}

static void function_trace_start(struct trace_array *tr)
{
    tracing_reset_online_cpus(tr);
}

static void
function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip,
                 struct ftrace_ops *op, struct pt_regs *pt_regs)
{
    struct trace_array *tr = func_trace;
    struct trace_array_cpu *data;
    unsigned long flags;
    long disabled;
    int cpu;
    int pc;

    if (unlikely(!ftrace_function_enabled))
        return;

    pc = preempt_count();
    preempt_disable_notrace();
    local_save_flags(flags);
    cpu = raw_smp_processor_id();
    data = tr->data[cpu];
    disabled = atomic_inc_return(&data->disabled);

    if (likely(disabled == 1))
        trace_function(tr, ip, parent_ip, flags, pc);

    atomic_dec(&data->disabled);
    preempt_enable_notrace();
}

/* Our option */
enum {
    TRACE_FUNC_OPT_STACK    = 0x1,
};

static struct tracer_flags func_flags;

static void
function_trace_call(unsigned long ip, unsigned long parent_ip,
            struct ftrace_ops *op, struct pt_regs *pt_regs)

{
    struct trace_array *tr = func_trace;
    struct trace_array_cpu *data;
    unsigned long flags;
    long disabled;
    int cpu;
    int pc;

    if (unlikely(!ftrace_function_enabled))
        return;

    /*
     * Need to use raw, since this must be called before the
     * recursive protection is performed.
     */
    local_irq_save(flags);
    cpu = raw_smp_processor_id();
    data = tr->data[cpu];
    disabled = atomic_inc_return(&data->disabled);

    if (likely(disabled == 1)) {
        pc = preempt_count();
        trace_function(tr, ip, parent_ip, flags, pc);
    }

    atomic_dec(&data->disabled);
    local_irq_restore(flags);
}

static void
function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
              struct ftrace_ops *op, struct pt_regs *pt_regs)
{
    struct trace_array *tr = func_trace;
    struct trace_array_cpu *data;
    unsigned long flags;
    long disabled;
    int cpu;
    int pc;

    if (unlikely(!ftrace_function_enabled))
        return;

    /*
     * Need to use raw, since this must be called before the
     * recursive protection is performed.
     */
    local_irq_save(flags);
    cpu = raw_smp_processor_id();
    data = tr->data[cpu];
    disabled = atomic_inc_return(&data->disabled);

    if (likely(disabled == 1)) {
        pc = preempt_count();
        trace_function(tr, ip, parent_ip, flags, pc);
        /*
         * skip over 5 funcs:
         *    __ftrace_trace_stack,
         *    __trace_stack,
         *    function_stack_trace_call
         *    ftrace_list_func
         *    ftrace_call
         */
        __trace_stack(tr, flags, 5, pc);
    }

    atomic_dec(&data->disabled);
    local_irq_restore(flags);
}


static struct ftrace_ops trace_ops __read_mostly =
{
    .func = function_trace_call,
    .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
};

static struct ftrace_ops trace_stack_ops __read_mostly =
{
    .func = function_stack_trace_call,
    .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
};

static struct tracer_opt func_opts[] = {
#ifdef CONFIG_STACKTRACE
    { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
#endif
    { } /* Always set a last empty entry */
};

static struct tracer_flags func_flags = {
    .val = 0, /* By default: all flags disabled */
    .opts = func_opts
};

static void tracing_start_function_trace(void)
{
    ftrace_function_enabled = 0;

    if (trace_flags & TRACE_ITER_PREEMPTONLY)
        trace_ops.func = function_trace_call_preempt_only;
    else
        trace_ops.func = function_trace_call;

    if (func_flags.val & TRACE_FUNC_OPT_STACK)
        register_ftrace_function(&trace_stack_ops);
    else
        register_ftrace_function(&trace_ops);

    ftrace_function_enabled = 1;
}

static void tracing_stop_function_trace(void)
{
    ftrace_function_enabled = 0;

    if (func_flags.val & TRACE_FUNC_OPT_STACK)
        unregister_ftrace_function(&trace_stack_ops);
    else
        unregister_ftrace_function(&trace_ops);
}

static int func_set_flag(u32 old_flags, u32 bit, int set)
{
    switch (bit) {
    case TRACE_FUNC_OPT_STACK:
        /* do nothing if already set */
        if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
            break;

        if (set) {
            unregister_ftrace_function(&trace_ops);
            register_ftrace_function(&trace_stack_ops);
        } else {
            unregister_ftrace_function(&trace_stack_ops);
            register_ftrace_function(&trace_ops);
        }

        break;
    default:
        return -EINVAL;
    }

    return 0;
}

static struct tracer function_trace __read_mostly =
{
    .name       = "function",
    .init       = function_trace_init,
    .reset      = function_trace_reset,
    .start      = function_trace_start,
    .wait_pipe  = poll_wait_pipe,
    .flags      = &func_flags,
    .set_flag   = func_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
    .selftest   = trace_selftest_startup_function,
#endif
};

#ifdef CONFIG_DYNAMIC_FTRACE
static void
ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
{
    long *count = (long *)data;

    if (tracing_is_on())
        return;

    if (!*count)
        return;

    if (*count != -1)
        (*count)--;

    tracing_on();
}

static void
ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
{
    long *count = (long *)data;

    if (!tracing_is_on())
        return;

    if (!*count)
        return;

    if (*count != -1)
        (*count)--;

    tracing_off();
}

static int
ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
             struct ftrace_probe_ops *ops, void *data);

static struct ftrace_probe_ops traceon_probe_ops = {
    .func           = ftrace_traceon,
    .print          = ftrace_trace_onoff_print,
};

static struct ftrace_probe_ops traceoff_probe_ops = {
    .func           = ftrace_traceoff,
    .print          = ftrace_trace_onoff_print,
};

static int
ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
             struct ftrace_probe_ops *ops, void *data)
{
    long count = (long)data;

    seq_printf(m, "%ps:", (void *)ip);

    if (ops == &traceon_probe_ops)
        seq_printf(m, "traceon");
    else
        seq_printf(m, "traceoff");

    if (count == -1)
        seq_printf(m, ":unlimited\n");
    else
        seq_printf(m, ":count=%ld\n", count);

    return 0;
}

static int
ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
{
    struct ftrace_probe_ops *ops;

    /* we register both traceon and traceoff to this callback */
    if (strcmp(cmd, "traceon") == 0)
        ops = &traceon_probe_ops;
    else
        ops = &traceoff_probe_ops;

    unregister_ftrace_function_probe_func(glob, ops);

    return 0;
}

static int
ftrace_trace_onoff_callback(struct ftrace_hash *hash,
                char *glob, char *cmd, char *param, int enable)
{
    struct ftrace_probe_ops *ops;
    void *count = (void *)-1;
    char *number;
    int ret;

    /* hash funcs only work with set_ftrace_filter */
    if (!enable)
        return -EINVAL;

    if (glob[0] == '!')
        return ftrace_trace_onoff_unreg(glob+1, cmd, param);

    /* we register both traceon and traceoff to this callback */
    if (strcmp(cmd, "traceon") == 0)
        ops = &traceon_probe_ops;
    else
        ops = &traceoff_probe_ops;

    if (!param)
        goto out_reg;

    number = strsep(&param, ":");

    if (!strlen(number))
        goto out_reg;

    /*
     * We use the callback data field (which is a pointer)
     * as our counter.
     */
    ret = strict_strtoul(number, 0, (unsigned long *)&count);
    if (ret)
        return ret;

 out_reg:
    ret = register_ftrace_function_probe(glob, ops, count);

    return ret < 0 ? ret : 0;
}

static struct ftrace_func_command ftrace_traceon_cmd = {
    .name           = "traceon",
    .func           = ftrace_trace_onoff_callback,
};

static struct ftrace_func_command ftrace_traceoff_cmd = {
    .name           = "traceoff",
    .func           = ftrace_trace_onoff_callback,
};

static int __init init_func_cmd_traceon(void)
{
    int ret;

    ret = register_ftrace_command(&ftrace_traceoff_cmd);
    if (ret)
        return ret;

    ret = register_ftrace_command(&ftrace_traceon_cmd);
    if (ret)
        unregister_ftrace_command(&ftrace_traceoff_cmd);
    return ret;
}
#else
static inline int init_func_cmd_traceon(void)
{
    return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */

static __init int init_function_trace(void)
{
    init_func_cmd_traceon();
    return register_tracer(&function_trace);
}
device_initcall(init_function_trace);