// Copyright © 2022 Intel Corporation

//

// SPDX-License-Identifier: Apache-2.0

#![no_main]

use std::fs::File;

use std::io::Write;

use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};

use std::sync::Arc;

use libfuzzer_sys::{fuzz_target, Corpus};

use seccompiler::SeccompAction;

use virtio_devices::{VirtioDevice, VirtioInterrupt, VirtioInterruptType};

use virtio_queue::{Queue, QueueT};

use vm_memory::bitmap::AtomicBitmap;

use vm_memory::{Bytes, GuestAddress, GuestMemoryAtomic};

use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK};

type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;

macro_rules! align {

    ($n:expr, $align:expr) => {{

        $n.div_ceil($align) * $align

    }};

}

const CONSOLE_INPUT_SIZE: usize = 128;

const QUEUE_DATA_SIZE: usize = 4;

const MEM_SIZE: usize = 32 * 1024 * 1024;

// Guest memory gap

const GUEST_MEM_GAP: u64 = 1 * 1024 * 1024;

// Guest physical address for the first virt queue

const BASE_VIRT_QUEUE_ADDR: u64 = MEM_SIZE as u64 + GUEST_MEM_GAP;

// Number of queues

const QUEUE_NUM: usize = 2;

// Max entries in the queue.

const QUEUE_SIZE: u16 = 256;

// Descriptor table alignment

const DESC_TABLE_ALIGN_SIZE: u64 = 16;

// Used ring alignment

const USED_RING_ALIGN_SIZE: u64 = 4;

// Descriptor table size

const DESC_TABLE_SIZE: u64 = 16_u64 * QUEUE_SIZE as u64;

// Available ring size

const AVAIL_RING_SIZE: u64 = 6_u64 + 2 * QUEUE_SIZE as u64;

// Padding size before used ring

const PADDING_SIZE: u64 = align!(AVAIL_RING_SIZE, USED_RING_ALIGN_SIZE) - AVAIL_RING_SIZE;

// Used ring size

const USED_RING_SIZE: u64 = 6_u64 + 8 * QUEUE_SIZE as u64;

// Virtio-queue size in bytes

const QUEUE_BYTES_SIZE: usize = align!(

    DESC_TABLE_SIZE + AVAIL_RING_SIZE + PADDING_SIZE + USED_RING_SIZE,

    DESC_TABLE_ALIGN_SIZE

) as usize;

fuzz_target!(|bytes: &[u8]| -> Corpus {

    if bytes.len() < (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM + CONSOLE_INPUT_SIZE

        || bytes.len()

            > (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM + CONSOLE_INPUT_SIZE + MEM_SIZE

    {

        return Corpus::Reject;

    }

    let (pipe_rx, mut pipe_tx) = create_pipe().unwrap();

    let output = unsafe {

        File::from_raw_fd(

            memfd_create(&std::ffi::CString::new("fuzz_console_output").unwrap()).unwrap(),

        )

    };

    let endpoint = virtio_devices::Endpoint::FilePair(Arc::new(output), Arc::new(pipe_rx));

    let (mut console, _) = virtio_devices::Console::new(

        "fuzzer_console".to_owned(),

        endpoint,

        None,  // resize_pipe

        false, // iommu

        SeccompAction::Allow,

        EventFd::new(EFD_NONBLOCK).unwrap(),

        None,

    )

    .unwrap();

    let console_input_bytes = &bytes[..CONSOLE_INPUT_SIZE];

    let queue_data = &bytes[CONSOLE_INPUT_SIZE..CONSOLE_INPUT_SIZE + QUEUE_DATA_SIZE * QUEUE_NUM];

    let queue_bytes = &bytes[CONSOLE_INPUT_SIZE + QUEUE_DATA_SIZE * QUEUE_NUM

        ..CONSOLE_INPUT_SIZE + (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM];

    let mem_bytes = &bytes[CONSOLE_INPUT_SIZE + (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM..];

    // Setup the virt queues with the input bytes

    let mut queues = setup_virt_queues(

        &[

            &queue_data[..QUEUE_DATA_SIZE].try_into().unwrap(),

            &queue_data[QUEUE_DATA_SIZE..QUEUE_DATA_SIZE * 2]

                .try_into()

                .unwrap(),

        ],

        BASE_VIRT_QUEUE_ADDR,

    );

    // Setup the guest memory with the input bytes

    let mem = GuestMemoryMmap::from_ranges(&[

        (GuestAddress(0), MEM_SIZE),

        (GuestAddress(BASE_VIRT_QUEUE_ADDR), queue_bytes.len()),

    ])

    .unwrap();

    if mem

        .write_slice(queue_bytes, GuestAddress(BASE_VIRT_QUEUE_ADDR))

        .is_err()

    {

        return Corpus::Reject;

    }

    if mem.write_slice(mem_bytes, GuestAddress(0 as u64)).is_err() {

        return Corpus::Reject;

    }

    let guest_memory = GuestMemoryAtomic::new(mem);

    let input_queue = queues.remove(0);

    let input_evt = EventFd::new(0).unwrap();

    let input_queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(input_evt.as_raw_fd())) };

    let output_queue = queues.remove(0);

    let output_evt = EventFd::new(0).unwrap();

    let output_queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(output_evt.as_raw_fd())) };

    // Kick the 'queue' events and endpoint event before activate the console device

    input_queue_evt.write(1).unwrap();

    output_queue_evt.write(1).unwrap();

    pipe_tx.write_all(console_input_bytes).unwrap(); // To use fuzzed data;

    console

        .activate(

            guest_memory,

            Arc::new(NoopVirtioInterrupt {}),

            vec![(0, input_queue, input_evt), (1, output_queue, output_evt)],

        )

        .unwrap();

    // Wait for the events to finish and console device worker thread to return

    console.wait_for_epoll_threads();

    Corpus::Keep

});

pub struct NoopVirtioInterrupt {}

impl VirtioInterrupt for NoopVirtioInterrupt {

    fn trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error> {

        Ok(())

    }

}

fn setup_virt_queues(bytes: &[&[u8; QUEUE_DATA_SIZE]], base_addr: u64) -> Vec<Queue> {

    let mut queues = Vec::new();

    for (i, b) in bytes.iter().enumerate() {

        let mut q = Queue::new(QUEUE_SIZE).unwrap();

        let desc_table_addr = base_addr + (QUEUE_BYTES_SIZE * i) as u64;

        let avail_ring_addr = desc_table_addr + DESC_TABLE_SIZE;

        let used_ring_addr = avail_ring_addr + PADDING_SIZE + AVAIL_RING_SIZE;

        q.try_set_desc_table_address(GuestAddress(desc_table_addr))

            .unwrap();

        q.try_set_avail_ring_address(GuestAddress(avail_ring_addr))

            .unwrap();

        q.try_set_used_ring_address(GuestAddress(used_ring_addr))

            .unwrap();

        q.set_next_avail(b[0] as u16); // 'u8' is enough given the 'QUEUE_SIZE' is small

        q.set_next_used(b[1] as u16);

        q.set_event_idx(b[2] % 2 != 0);

        q.set_size(b[3] as u16 % QUEUE_SIZE);

        q.set_ready(true);

        queues.push(q);

    }

    queues

}

fn memfd_create(name: &std::ffi::CStr) -> Result<RawFd, std::io::Error> {

    let res = unsafe { libc::syscall(libc::SYS_memfd_create, name.as_ptr(), 0) };

    if res < 0 {

        Err(std::io::Error::last_os_error())

    } else {

        Ok(res as RawFd)

    }

}

fn create_pipe() -> Result<(File, File), std::io::Error> {

    let mut pipe = [-1; 2];

    if unsafe { libc::pipe2(pipe.as_mut_ptr(), libc::O_CLOEXEC) } == -1 {

        return Err(std::io::Error::last_os_error());

    }

    let rx = unsafe { File::from_raw_fd(pipe[0]) };

    let tx = unsafe { File::from_raw_fd(pipe[1]) };

    Ok((rx, tx))

}