// Copyright © 2022 Intel Corporation

//

// SPDX-License-Identifier: Apache-2.0

#![no_main]

use std::fs::File;

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

use std::sync::Arc;

use std::{ffi, io};

use libc::{MAP_NORESERVE, MAP_PRIVATE, PROT_READ, PROT_WRITE};

use libfuzzer_sys::{fuzz_target, Corpus};

use seccompiler::SeccompAction;

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

use virtio_queue::{Queue, QueueT};

use vm_device::UserspaceMapping;

use vm_memory::bitmap::AtomicBitmap;

use vm_memory::guest_memory::FileOffset;

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

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

type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;

const QUEUE_DATA_SIZE: usize = 4;

const MEM_SIZE: usize = 256 * 1024 * 1024;

const PMEM_FILE_SIZE: usize = 128 * 1024 * 1024;

// Max entries in the queue.

const QUEUE_SIZE: u16 = 256;

// Guest physical address for descriptor table.

const DESC_TABLE_ADDR: u64 = 0;

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

// Guest physical address for available ring

const AVAIL_RING_ADDR: u64 = DESC_TABLE_ADDR + DESC_TABLE_SIZE;

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

// Guest physical address for used ring (requires to 4-bytes aligned)

const USED_RING_ADDR: u64 = (AVAIL_RING_ADDR + AVAIL_RING_SIZE + 3) & !3_u64;

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

    if bytes.len() < QUEUE_DATA_SIZE || bytes.len() > (QUEUE_DATA_SIZE + MEM_SIZE) {

        return Corpus::Reject;

    }

    let mut pmem = create_dummy_pmem();

    let queue_data = &bytes[..QUEUE_DATA_SIZE];

    let mem_bytes = &bytes[QUEUE_DATA_SIZE..];

    // Setup the virt queue with the input bytes

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

    // Setup the guest memory with the input bytes

    let mem = GuestMemoryMmap::from_ranges(&[(GuestAddress(0), MEM_SIZE)]).unwrap();

    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 pmem device

    queue_evt.write(1).unwrap();

    pmem.activate(

        guest_memory,

        Arc::new(NoopVirtioInterrupt {}),

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

    )

    .ok();

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

    pmem.wait_for_epoll_threads();

    Corpus::Keep

});

fn memfd_create_with_size(name: &ffi::CStr, flags: u32, size: usize) -> Result<RawFd, io::Error> {

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

    if fd < 0 {

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

    }

    let res = unsafe { libc::syscall(libc::SYS_ftruncate, fd, size) };

    if res < 0 {

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

    }

    Ok(fd as RawFd)

}

pub struct NoopVirtioInterrupt {}

impl VirtioInterrupt for NoopVirtioInterrupt {

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

        Ok(())

    }

}

// Create a dummy virtio-pmem device for fuzzing purpose only

fn create_dummy_pmem() -> Pmem {

    let shm =

        memfd_create_with_size(&ffi::CString::new("fuzz").unwrap(), 0, PMEM_FILE_SIZE).unwrap();

    let file: File = unsafe { File::from_raw_fd(shm) };

    // The fuzzer is focusing on the virtio-pmem code that processes guest inputs (e.g. virt queues),

    // so dummy mappings (both mmap and user mapping) does the job and is faster (using smaller amount of memory).

    let dummy_mapping_size = 1;

    let cloned_file = file.try_clone().unwrap();

    let dummy_mmap_region = MmapRegion::build(

        Some(FileOffset::new(cloned_file, 0)),

        dummy_mapping_size,

        PROT_READ | PROT_WRITE,

        MAP_NORESERVE | MAP_PRIVATE,

    )

    .unwrap();

    let guest_addr = GuestAddress(0);

    let dummy_user_mapping = UserspaceMapping {

        mem_slot: 0,

        addr: guest_addr,

        mapping: Arc::new(dummy_mmap_region),

        mergeable: false,

    };

    Pmem::new(

        "tmp".to_owned(),

        file,

        guest_addr,

        dummy_user_mapping,

        false,

        SeccompAction::Allow,

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

        None,

    )

    .unwrap()

}

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

}