// Copyright © 2025 Microsoft

//

// SPDX-License-Identifier: Apache-2.0

#![no_main]

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

use std::sync::Arc;

use libfuzzer_sys::{fuzz_target, Corpus};

use seccompiler::SeccompAction;

use virtio_devices::vsock::unit_tests::TestBackend;

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};

use vmm_sys_util::tempdir::TempDir;

type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;

macro_rules! align {

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

        $n.div_ceil($align) * $align

    }};

}

const QUEUE_DATA_SIZE: usize = 4;

const MEM_SIZE: usize = 1 * 1024 * 1024;

// Max entries in the queue.

const QUEUE_SIZE: u16 = 256;

// Descriptor table alignment

const DESC_TABLE_ALIGN_SIZE: u64 = 16;

// Available ring alignment

const AVAIL_RING_ALIGN_SIZE: u64 = 2;

// 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;

// Used ring size

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

// Guest memory gap

const GUEST_MEM_GAP: u64 = 1 * 1024 * 1024;

// Guest physical address for descriptor table.

const DESC_TABLE_ADDR: u64 = align!(MEM_SIZE as u64 + GUEST_MEM_GAP, DESC_TABLE_ALIGN_SIZE);

// Guest physical address for available ring

const AVAIL_RING_ADDR: u64 = align!(DESC_TABLE_ADDR + DESC_TABLE_SIZE, AVAIL_RING_ALIGN_SIZE);

// Guest physical address for used ring

const USED_RING_ADDR: u64 = align!(AVAIL_RING_ADDR + AVAIL_RING_SIZE, USED_RING_ALIGN_SIZE);

// Virtio-queue size in bytes

const QUEUE_BYTES_SIZE: usize = (USED_RING_ADDR + USED_RING_SIZE - DESC_TABLE_ADDR) as usize;

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

    if bytes.len() < (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE)

        || bytes.len() > (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE + MEM_SIZE)

    {

        return Corpus::Reject;

    }

    let queue_data = &bytes[..QUEUE_DATA_SIZE];

    let queue_bytes = &bytes[QUEUE_DATA_SIZE..QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE];

    let mem_bytes = &bytes[QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE..];

    let q = setup_virt_queue(queue_data.try_into().unwrap());

    let tmp_dir = TempDir::new_with_prefix("/tmp/fuzz_virtio_vsock").unwrap();

    let vsock_path = tmp_dir.as_path().join("vsock.sock");

    let backend = TestBackend::new();

    // Setup the guest memory with the input bytes

    let mem = GuestMemoryMmap::from_ranges(&[

        (GuestAddress(0), MEM_SIZE),

        (GuestAddress(DESC_TABLE_ADDR), QUEUE_BYTES_SIZE),

    ])

    .unwrap();

    if mem

        .write_slice(queue_bytes, GuestAddress(DESC_TABLE_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 evt = EventFd::new(0).unwrap();

    let queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(evt.as_raw_fd())) };

    // Kick the 'queue' event before activate the rng device

    queue_evt.write(1).unwrap();

    let mut vsock = virtio_devices::Vsock::new(

        "fuzzer_vsock".to_owned(),

        0,

        vsock_path,

        backend,

        false,

        SeccompAction::Allow,

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

        None,

    )

    .unwrap();

    vsock

        .activate(

            guest_memory,

            Arc::new(NoopVirtioInterrupt {}),

            vec![(0, q, evt)],

        )

        .ok();

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

    vsock.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_queue(bytes: &[u8; QUEUE_DATA_SIZE]) -> Queue {

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

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

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

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

    q.set_size(bytes[3] as u16 % QUEUE_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_ready(true);

    q

}