/*
 * kvm trace
 *
 * It is designed to allow debugging traces of kvm to be generated
 * on UP / SMP machines.  Each trace entry can be timestamped so that
 * it's possible to reconstruct a chronological record of trace events.
 * The implementation refers to blktrace kernel support.
 *
 * Copyright (c) 2008 Intel Corporation
 * Copyright (C) 2006 Jens Axboe <axboe@kernel.dk>
 *
 * Authors: Feng(Eric) Liu, eric.e.liu@intel.com
 *
 * Date:    Feb 2008
 */

#include <linux/module.h>
#include <linux/relay.h>
#include <linux/debugfs.h>
#include <linux/ktime.h>

#include <linux/kvm_host.h>

#define KVM_TRACE_STATE_RUNNING         (1 << 0)
#define KVM_TRACE_STATE_PAUSE           (1 << 1)
#define KVM_TRACE_STATE_CLEARUP         (1 << 2)

struct kvm_trace {
        int trace_state;
        struct rchan *rchan;
        struct dentry *lost_file;
        atomic_t lost_records;
};
static struct kvm_trace *kvm_trace;

struct kvm_trace_probe {
        const char *name;
        const char *format;
        u32 timestamp_in;
        marker_probe_func *probe_func;
};

static inline int calc_rec_size(int timestamp, int extra)
{
        int rec_size = KVM_TRC_HEAD_SIZE;

        rec_size += extra;
        return timestamp ? rec_size += KVM_TRC_CYCLE_SIZE : rec_size;
}

static void kvm_add_trace(void *probe_private, void *call_data,
                          const char *format, va_list *args)
{
        struct kvm_trace_probe *p = probe_private;
        struct kvm_trace *kt = kvm_trace;
        struct kvm_trace_rec rec;
        struct kvm_vcpu *vcpu;
        int    i, size;
        u32    extra;

        if (unlikely(kt->trace_state != KVM_TRACE_STATE_RUNNING))
                return;

        rec.rec_val     = TRACE_REC_EVENT_ID(va_arg(*args, u32));
        vcpu            = va_arg(*args, struct kvm_vcpu *);
        rec.pid         = current->tgid;
        rec.vcpu_id     = vcpu->vcpu_id;

        extra           = va_arg(*args, u32);
        WARN_ON(!(extra <= KVM_TRC_EXTRA_MAX));
        extra           = min_t(u32, extra, KVM_TRC_EXTRA_MAX);

        rec.rec_val |= TRACE_REC_TCS(p->timestamp_in)
                        | TRACE_REC_NUM_DATA_ARGS(extra);

        if (p->timestamp_in) {
                rec.u.timestamp.timestamp = ktime_to_ns(ktime_get());

                for (i = 0; i < extra; i++)
                        rec.u.timestamp.extra_u32[i] = va_arg(*args, u32);
        } else {
                for (i = 0; i < extra; i++)
                        rec.u.notimestamp.extra_u32[i] = va_arg(*args, u32);
        }

        size = calc_rec_size(p->timestamp_in, extra * sizeof(u32));
        relay_write(kt->rchan, &rec, size);
}

static struct kvm_trace_probe kvm_trace_probes[] = {
        { "kvm_trace_entryexit", "%u %p %u %u %u %u %u %u", 1, kvm_add_trace },
        { "kvm_trace_handler", "%u %p %u %u %u %u %u %u", 0, kvm_add_trace },
};

static int lost_records_get(void *data, u64 *val)
{
        struct kvm_trace *kt = data;

        *val = atomic_read(&kt->lost_records);
        return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(kvm_trace_lost_ops, lost_records_get, NULL, "%llu\n");

/*
 *  The relay channel is used in "no-overwrite" mode, it keeps trace of how
 *  many times we encountered a full subbuffer, to tell user space app the
 *  lost records there were.
 */
static int kvm_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
                                     void *prev_subbuf, size_t prev_padding)
{
        struct kvm_trace *kt;

        if (!relay_buf_full(buf)) {
                if (!prev_subbuf) {
                        /*
                         * executed only once when the channel is opened
                         * save metadata as first record
                         */
                        subbuf_start_reserve(buf, sizeof(u32));
                        *(u32 *)subbuf = 0x12345678;
                }

                return 1;
        }

        kt = buf->chan->private_data;
        atomic_inc(&kt->lost_records);

        return 0;
}

static struct dentry *kvm_create_buf_file_callack(const char *filename,
                                                 struct dentry *parent,
                                                 int mode,
                                                 struct rchan_buf *buf,
                                                 int *is_global)
{
        return debugfs_create_file(filename, mode, parent, buf,
                                   &relay_file_operations);
}

static int kvm_remove_buf_file_callback(struct dentry *dentry)
{
        debugfs_remove(dentry);
        return 0;
}

static struct rchan_callbacks kvm_relay_callbacks = {
        .subbuf_start           = kvm_subbuf_start_callback,
        .create_buf_file        = kvm_create_buf_file_callack,
        .remove_buf_file        = kvm_remove_buf_file_callback,
};

static int do_kvm_trace_enable(struct kvm_user_trace_setup *kuts)
{
        struct kvm_trace *kt;
        int i, r = -ENOMEM;

        if (!kuts->buf_size || !kuts->buf_nr)
                return -EINVAL;

        kt = kzalloc(sizeof(*kt), GFP_KERNEL);
        if (!kt)
                goto err;

        r = -EIO;
        atomic_set(&kt->lost_records, 0);
        kt->lost_file = debugfs_create_file("lost_records", 0444, kvm_debugfs_dir,
                                            kt, &kvm_trace_lost_ops);
        if (!kt->lost_file)
                goto err;

        kt->rchan = relay_open("trace", kvm_debugfs_dir, kuts->buf_size,
                                kuts->buf_nr, &kvm_relay_callbacks, kt);
        if (!kt->rchan)
                goto err;

        kvm_trace = kt;

        for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
                struct kvm_trace_probe *p = &kvm_trace_probes[i];

                r = marker_probe_register(p->name, p->format, p->probe_func, p);
                if (r)
                        printk(KERN_INFO "Unable to register probe %s\n",
                               p->name);
        }

        kvm_trace->trace_state = KVM_TRACE_STATE_RUNNING;

        return 0;
err:
        if (kt) {
                if (kt->lost_file)
                        debugfs_remove(kt->lost_file);
                if (kt->rchan)
                        relay_close(kt->rchan);
                kfree(kt);
        }
        return r;
}

static int kvm_trace_enable(char __user *arg)
{
        struct kvm_user_trace_setup kuts;
        int ret;

        ret = copy_from_user(&kuts, arg, sizeof(kuts));
        if (ret)
                return -EFAULT;

        ret = do_kvm_trace_enable(&kuts);
        if (ret)
                return ret;

        return 0;
}

static int kvm_trace_pause(void)
{
        struct kvm_trace *kt = kvm_trace;
        int r = -EINVAL;

        if (kt == NULL)
                return r;

        if (kt->trace_state == KVM_TRACE_STATE_RUNNING) {
                kt->trace_state = KVM_TRACE_STATE_PAUSE;
                relay_flush(kt->rchan);
                r = 0;
        }

        return r;
}

void kvm_trace_cleanup(void)
{
        struct kvm_trace *kt = kvm_trace;
        int i;

        if (kt == NULL)
                return;

        if (kt->trace_state == KVM_TRACE_STATE_RUNNING ||
            kt->trace_state == KVM_TRACE_STATE_PAUSE) {

                kt->trace_state = KVM_TRACE_STATE_CLEARUP;

                for (i = 0; i < ARRAY_SIZE(kvm_trace_probes); i++) {
                        struct kvm_trace_probe *p = &kvm_trace_probes[i];
                        marker_probe_unregister(p->name, p->probe_func, p);
                }
                marker_synchronize_unregister();

                relay_close(kt->rchan);
                debugfs_remove(kt->lost_file);
                kfree(kt);
        }
}

int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        long r = -EINVAL;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        switch (ioctl) {
        case KVM_TRACE_ENABLE:
                r = kvm_trace_enable(argp);
                break;
        case KVM_TRACE_PAUSE:
                r = kvm_trace_pause();
                break;
        case KVM_TRACE_DISABLE:
                r = 0;
                kvm_trace_cleanup();
                break;
        }

        return r;
}