/*
 * trace stack traces
 *
 * Copyright (C) 2004-2008, Soeren Sandmann
 * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 */
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/hrtimer.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/irq.h>
#include <linux/fs.h>

#include <asm/stacktrace.h>

#include "trace.h"

static struct trace_array       *sysprof_trace;
static int __read_mostly        tracer_enabled;

/*
 * 1 msec sample interval by default:
 */
static unsigned long sample_period = 1000000;
static const unsigned int sample_max_depth = 512;

static DEFINE_MUTEX(sample_timer_lock);
/*
 * Per CPU hrtimers that do the profiling:
 */
static DEFINE_PER_CPU(struct hrtimer, stack_trace_hrtimer);

struct stack_frame {
        const void __user       *next_fp;
        unsigned long           return_address;
};

static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
{
        int ret;

        if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
                return 0;

        ret = 1;
        pagefault_disable();
        if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
                ret = 0;
        pagefault_enable();

        return ret;
}

struct backtrace_info {
        struct trace_array_cpu  *data;
        struct trace_array      *tr;
        int                     pos;
};

static void
backtrace_warning_symbol(void *data, char *msg, unsigned long symbol)
{
        /* Ignore warnings */
}

static void backtrace_warning(void *data, char *msg)
{
        /* Ignore warnings */
}

static int backtrace_stack(void *data, char *name)
{
        /* Don't bother with IRQ stacks for now */
        return -1;
}

static void backtrace_address(void *data, unsigned long addr, int reliable)
{
        struct backtrace_info *info = data;

        if (info->pos < sample_max_depth && reliable) {
                __trace_special(info->tr, info->data, 1, addr, 0);

                info->pos++;
        }
}

static const struct stacktrace_ops backtrace_ops = {
        .warning                = backtrace_warning,
        .warning_symbol         = backtrace_warning_symbol,
        .stack                  = backtrace_stack,
        .address                = backtrace_address,
        .walk_stack             = print_context_stack,
};

static int
trace_kernel(struct pt_regs *regs, struct trace_array *tr,
             struct trace_array_cpu *data)
{
        struct backtrace_info info;
        unsigned long bp;
        char *stack;

        info.tr = tr;
        info.data = data;
        info.pos = 1;

        __trace_special(info.tr, info.data, 1, regs->ip, 0);

        stack = ((char *)regs + sizeof(struct pt_regs));
#ifdef CONFIG_FRAME_POINTER
        bp = regs->bp;
#else
        bp = 0;
#endif

        dump_trace(NULL, regs, (void *)stack, bp, &backtrace_ops, &info);

        return info.pos;
}

static void timer_notify(struct pt_regs *regs, int cpu)
{
        struct trace_array_cpu *data;
        struct stack_frame frame;
        struct trace_array *tr;
        const void __user *fp;
        int is_user;
        int i;

        if (!regs)
                return;

        tr = sysprof_trace;
        data = tr->data[cpu];
        is_user = user_mode(regs);

        if (!current || current->pid == 0)
                return;

        if (is_user && current->state != TASK_RUNNING)
                return;

        __trace_special(tr, data, 0, 0, current->pid);

        if (!is_user)
                i = trace_kernel(regs, tr, data);
        else
                i = 0;

        /*
         * Trace user stack if we are not a kernel thread
         */
        if (current->mm && i < sample_max_depth) {
                regs = (struct pt_regs *)current->thread.sp0 - 1;

                fp = (void __user *)regs->bp;

                __trace_special(tr, data, 2, regs->ip, 0);

                while (i < sample_max_depth) {
                        frame.next_fp = NULL;
                        frame.return_address = 0;
                        if (!copy_stack_frame(fp, &frame))
                                break;
                        if ((unsigned long)fp < regs->sp)
                                break;

                        __trace_special(tr, data, 2, frame.return_address,
                                        (unsigned long)fp);
                        fp = frame.next_fp;

                        i++;
                }

        }

        /*
         * Special trace entry if we overflow the max depth:
         */
        if (i == sample_max_depth)
                __trace_special(tr, data, -1, -1, -1);

        __trace_special(tr, data, 3, current->pid, i);
}

static enum hrtimer_restart stack_trace_timer_fn(struct hrtimer *hrtimer)
{
        /* trace here */
        timer_notify(get_irq_regs(), smp_processor_id());

        hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));

        return HRTIMER_RESTART;
}

static void start_stack_timer(void *unused)
{
        struct hrtimer *hrtimer = &__get_cpu_var(stack_trace_hrtimer);

        hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        hrtimer->function = stack_trace_timer_fn;

        hrtimer_start(hrtimer, ns_to_ktime(sample_period),
                      HRTIMER_MODE_REL_PINNED);
}

static void start_stack_timers(void)
{
        on_each_cpu(start_stack_timer, NULL, 1);
}

static void stop_stack_timer(int cpu)
{
        struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);

        hrtimer_cancel(hrtimer);
}

static void stop_stack_timers(void)
{
        int cpu;

        for_each_online_cpu(cpu)
                stop_stack_timer(cpu);
}

static void stop_stack_trace(struct trace_array *tr)
{
        mutex_lock(&sample_timer_lock);
        stop_stack_timers();
        tracer_enabled = 0;
        mutex_unlock(&sample_timer_lock);
}

static int stack_trace_init(struct trace_array *tr)
{
        sysprof_trace = tr;

        tracing_start_cmdline_record();

        mutex_lock(&sample_timer_lock);
        start_stack_timers();
        tracer_enabled = 1;
        mutex_unlock(&sample_timer_lock);
        return 0;
}

static void stack_trace_reset(struct trace_array *tr)
{
        tracing_stop_cmdline_record();
        stop_stack_trace(tr);
}

static struct tracer stack_trace __read_mostly =
{
        .name           = "sysprof",
        .init           = stack_trace_init,
        .reset          = stack_trace_reset,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_sysprof,
#endif
};

__init static int init_stack_trace(void)
{
        return register_tracer(&stack_trace);
}
device_initcall(init_stack_trace);

#define MAX_LONG_DIGITS 22

static ssize_t
sysprof_sample_read(struct file *filp, char __user *ubuf,
                    size_t cnt, loff_t *ppos)
{
        char buf[MAX_LONG_DIGITS];
        int r;

        r = sprintf(buf, "%ld\n", nsecs_to_usecs(sample_period));

        return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

static ssize_t
sysprof_sample_write(struct file *filp, const char __user *ubuf,
                     size_t cnt, loff_t *ppos)
{
        char buf[MAX_LONG_DIGITS];
        unsigned long val;

        if (cnt > MAX_LONG_DIGITS-1)
                cnt = MAX_LONG_DIGITS-1;

        if (copy_from_user(&buf, ubuf, cnt))
                return -EFAULT;

        buf[cnt] = 0;

        val = simple_strtoul(buf, NULL, 10);
        /*
         * Enforce a minimum sample period of 100 usecs:
         */
        if (val < 100)
                val = 100;

        mutex_lock(&sample_timer_lock);
        stop_stack_timers();
        sample_period = val * 1000;
        start_stack_timers();
        mutex_unlock(&sample_timer_lock);

        return cnt;
}

static const struct file_operations sysprof_sample_fops = {
        .read           = sysprof_sample_read,
        .write          = sysprof_sample_write,
};

void init_tracer_sysprof_debugfs(struct dentry *d_tracer)
{

        trace_create_file("sysprof_sample_period", 0644,
                        d_tracer, NULL, &sysprof_sample_fops);
}