/*
 * ring buffer based function tracer
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * Based on code from the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 Nadia Yvette Chambers
 */
#include <linux/ring_buffer.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/slab.h>
#include <linux/fs.h>

#include "trace.h"

static void tracing_start_function_trace(struct trace_array *tr);
static void tracing_stop_function_trace(struct trace_array *tr);
static void
function_trace_call(unsigned long ip, unsigned long parent_ip,
                    struct ftrace_ops *op, struct pt_regs *pt_regs);
static void
function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
                          struct ftrace_ops *op, struct pt_regs *pt_regs);
static struct tracer_flags func_flags;

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

static int allocate_ftrace_ops(struct trace_array *tr)
{
        struct ftrace_ops *ops;

        ops = kzalloc(sizeof(*ops), GFP_KERNEL);
        if (!ops)
                return -ENOMEM;

        /* Currently only the non stack verision is supported */
        ops->func = function_trace_call;
        ops->flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_PID;

        tr->ops = ops;
        ops->private = tr;
        return 0;
}


int ftrace_create_function_files(struct trace_array *tr,
                                 struct dentry *parent)
{
        int ret;

        /*
         * The top level array uses the "global_ops", and the files are
         * created on boot up.
         */
        if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
                return 0;

        ret = allocate_ftrace_ops(tr);
        if (ret)
                return ret;

        ftrace_create_filter_files(tr->ops, parent);

        return 0;
}

void ftrace_destroy_function_files(struct trace_array *tr)
{
        ftrace_destroy_filter_files(tr->ops);
        kfree(tr->ops);
        tr->ops = NULL;
}

static int function_trace_init(struct trace_array *tr)
{
        ftrace_func_t func;

        /*
         * Instance trace_arrays get their ops allocated
         * at instance creation. Unless it failed
         * the allocation.
         */
        if (!tr->ops)
                return -ENOMEM;

        /* Currently only the global instance can do stack tracing */
        if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
            func_flags.val & TRACE_FUNC_OPT_STACK)
                func = function_stack_trace_call;
        else
                func = function_trace_call;

        ftrace_init_array_ops(tr, func);

        tr->trace_buffer.cpu = get_cpu();
        put_cpu();

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

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

static void function_trace_start(struct trace_array *tr)
{
        tracing_reset_online_cpus(&tr->trace_buffer);
}

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 = op->private;
        struct trace_array_cpu *data;
        unsigned long flags;
        int bit;
        int cpu;
        int pc;

        if (unlikely(!tr->function_enabled))
                return;

        pc = preempt_count();
        preempt_disable_notrace();

        bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);
        if (bit < 0)
                goto out;

        cpu = smp_processor_id();
        data = per_cpu_ptr(tr->trace_buffer.data, cpu);
        if (!atomic_read(&data->disabled)) {
                local_save_flags(flags);
                trace_function(tr, ip, parent_ip, flags, pc);
        }
        trace_clear_recursion(bit);

 out:
        preempt_enable_notrace();
}

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 = op->private;
        struct trace_array_cpu *data;
        unsigned long flags;
        long disabled;
        int cpu;
        int pc;

        if (unlikely(!tr->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 = per_cpu_ptr(tr->trace_buffer.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 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(struct trace_array *tr)
{
        tr->function_enabled = 0;
        register_ftrace_function(tr->ops);
        tr->function_enabled = 1;
}

static void tracing_stop_function_trace(struct trace_array *tr)
{
        tr->function_enabled = 0;
        unregister_ftrace_function(tr->ops);
}

static struct tracer function_trace;

static int
func_set_flag(struct trace_array *tr, 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;

                /* We can change this flag when not running. */
                if (tr->current_trace != &function_trace)
                        break;

                unregister_ftrace_function(tr->ops);

                if (set) {
                        tr->ops->func = function_stack_trace_call;
                        register_ftrace_function(tr->ops);
                } else {
                        tr->ops->func = function_trace_call;
                        register_ftrace_function(tr->ops);
                }

                break;
        default:
                return -EINVAL;
        }

        return 0;
}

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

#ifdef CONFIG_DYNAMIC_FTRACE
static void update_traceon_count(void **data, bool on)
{
        long *count = (long *)data;
        long old_count = *count;

        /*
         * Tracing gets disabled (or enabled) once per count.
         * This function can be called at the same time on multiple CPUs.
         * It is fine if both disable (or enable) tracing, as disabling
         * (or enabling) the second time doesn't do anything as the
         * state of the tracer is already disabled (or enabled).
         * What needs to be synchronized in this case is that the count
         * only gets decremented once, even if the tracer is disabled
         * (or enabled) twice, as the second one is really a nop.
         *
         * The memory barriers guarantee that we only decrement the
         * counter once. First the count is read to a local variable
         * and a read barrier is used to make sure that it is loaded
         * before checking if the tracer is in the state we want.
         * If the tracer is not in the state we want, then the count
         * is guaranteed to be the old count.
         *
         * Next the tracer is set to the state we want (disabled or enabled)
         * then a write memory barrier is used to make sure that
         * the new state is visible before changing the counter by
         * one minus the old counter. This guarantees that another CPU
         * executing this code will see the new state before seeing
         * the new counter value, and would not do anything if the new
         * counter is seen.
         *
         * Note, there is no synchronization between this and a user
         * setting the tracing_on file. But we currently don't care
         * about that.
         */
        if (!old_count)
                return;

        /* Make sure we see count before checking tracing state */
        smp_rmb();

        if (on == !!tracing_is_on())
                return;

        if (on)
                tracing_on();
        else
                tracing_off();

        /* unlimited? */
        if (old_count == -1)
                return;

        /* Make sure tracing state is visible before updating count */
        smp_wmb();

        *count = old_count - 1;
}

static void
ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data)
{
        update_traceon_count(data, 1);
}

static void
ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data)
{
        update_traceon_count(data, 0);
}

static void
ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
{
        if (tracing_is_on())
                return;

        tracing_on();
}

static void
ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
{
        if (!tracing_is_on())
                return;

        tracing_off();
}

/*
 * Skip 4:
 *   ftrace_stacktrace()
 *   function_trace_probe_call()
 *   ftrace_ops_list_func()
 *   ftrace_call()
 */
#define STACK_SKIP 4

static void
ftrace_stacktrace(unsigned long ip, unsigned long parent_ip, void **data)
{
        trace_dump_stack(STACK_SKIP);
}

static void
ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
{
        long *count = (long *)data;
        long old_count;
        long new_count;

        /*
         * Stack traces should only execute the number of times the
         * user specified in the counter.
         */
        do {

                if (!tracing_is_on())
                        return;

                old_count = *count;

                if (!old_count)
                        return;

                /* unlimited? */
                if (old_count == -1) {
                        trace_dump_stack(STACK_SKIP);
                        return;
                }

                new_count = old_count - 1;
                new_count = cmpxchg(count, old_count, new_count);
                if (new_count == old_count)
                        trace_dump_stack(STACK_SKIP);

        } while (new_count != old_count);
}

static int update_count(void **data)
{
        unsigned long *count = (long *)data;

        if (!*count)
                return 0;

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

        return 1;
}

static void
ftrace_dump_probe(unsigned long ip, unsigned long parent_ip, void **data)
{
        if (update_count(data))
                ftrace_dump(DUMP_ALL);
}

/* Only dump the current CPU buffer. */
static void
ftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip, void **data)
{
        if (update_count(data))
                ftrace_dump(DUMP_ORIG);
}

static int
ftrace_probe_print(const char *name, struct seq_file *m,
                   unsigned long ip, void *data)
{
        long count = (long)data;

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

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

        return 0;
}

static int
ftrace_traceon_print(struct seq_file *m, unsigned long ip,
                         struct ftrace_probe_ops *ops, void *data)
{
        return ftrace_probe_print("traceon", m, ip, data);
}

static int
ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
                         struct ftrace_probe_ops *ops, void *data)
{
        return ftrace_probe_print("traceoff", m, ip, data);
}

static int
ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
                        struct ftrace_probe_ops *ops, void *data)
{
        return ftrace_probe_print("stacktrace", m, ip, data);
}

static int
ftrace_dump_print(struct seq_file *m, unsigned long ip,
                        struct ftrace_probe_ops *ops, void *data)
{
        return ftrace_probe_print("dump", m, ip, data);
}

static int
ftrace_cpudump_print(struct seq_file *m, unsigned long ip,
                        struct ftrace_probe_ops *ops, void *data)
{
        return ftrace_probe_print("cpudump", m, ip, data);
}

static struct ftrace_probe_ops traceon_count_probe_ops = {
        .func                   = ftrace_traceon_count,
        .print                  = ftrace_traceon_print,
};

static struct ftrace_probe_ops traceoff_count_probe_ops = {
        .func                   = ftrace_traceoff_count,
        .print                  = ftrace_traceoff_print,
};

static struct ftrace_probe_ops stacktrace_count_probe_ops = {
        .func                   = ftrace_stacktrace_count,
        .print                  = ftrace_stacktrace_print,
};

static struct ftrace_probe_ops dump_probe_ops = {
        .func                   = ftrace_dump_probe,
        .print                  = ftrace_dump_print,
};

static struct ftrace_probe_ops cpudump_probe_ops = {
        .func                   = ftrace_cpudump_probe,
        .print                  = ftrace_cpudump_print,
};

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

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

static struct ftrace_probe_ops stacktrace_probe_ops = {
        .func                   = ftrace_stacktrace,
        .print                  = ftrace_stacktrace_print,
};

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

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

        if (glob[0] == '!') {
                unregister_ftrace_function_probe_func(glob+1, ops);
                return 0;
        }

        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 = kstrtoul(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 int
ftrace_trace_onoff_callback(struct ftrace_hash *hash,
                            char *glob, char *cmd, char *param, int enable)
{
        struct ftrace_probe_ops *ops;

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

        return ftrace_trace_probe_callback(ops, hash, glob, cmd,
                                           param, enable);
}

static int
ftrace_stacktrace_callback(struct ftrace_hash *hash,
                           char *glob, char *cmd, char *param, int enable)
{
        struct ftrace_probe_ops *ops;

        ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;

        return ftrace_trace_probe_callback(ops, hash, glob, cmd,
                                           param, enable);
}

static int
ftrace_dump_callback(struct ftrace_hash *hash,
                           char *glob, char *cmd, char *param, int enable)
{
        struct ftrace_probe_ops *ops;

        ops = &dump_probe_ops;

        /* Only dump once. */
        return ftrace_trace_probe_callback(ops, hash, glob, cmd,
                                           "1", enable);
}

static int
ftrace_cpudump_callback(struct ftrace_hash *hash,
                           char *glob, char *cmd, char *param, int enable)
{
        struct ftrace_probe_ops *ops;

        ops = &cpudump_probe_ops;

        /* Only dump once. */
        return ftrace_trace_probe_callback(ops, hash, glob, cmd,
                                           "1", enable);
}

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 struct ftrace_func_command ftrace_stacktrace_cmd = {
        .name                   = "stacktrace",
        .func                   = ftrace_stacktrace_callback,
};

static struct ftrace_func_command ftrace_dump_cmd = {
        .name                   = "dump",
        .func                   = ftrace_dump_callback,
};

static struct ftrace_func_command ftrace_cpudump_cmd = {
        .name                   = "cpudump",
        .func                   = ftrace_cpudump_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)
                goto out_free_traceoff;

        ret = register_ftrace_command(&ftrace_stacktrace_cmd);
        if (ret)
                goto out_free_traceon;

        ret = register_ftrace_command(&ftrace_dump_cmd);
        if (ret)
                goto out_free_stacktrace;

        ret = register_ftrace_command(&ftrace_cpudump_cmd);
        if (ret)
                goto out_free_dump;

        return 0;

 out_free_dump:
        unregister_ftrace_command(&ftrace_dump_cmd);
 out_free_stacktrace:
        unregister_ftrace_command(&ftrace_stacktrace_cmd);
 out_free_traceon:
        unregister_ftrace_command(&ftrace_traceon_cmd);
 out_free_traceoff:
        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);
}
core_initcall(init_function_trace);