// Copyright 2020 Arm Limited (or its affiliates). All rights reserved.
// Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//
// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the THIRD-PARTY file.

use libc::{c_char, c_int, c_void};
use std::collections::HashMap;
use std::ffi::{CStr, CString, NulError};
use std::fmt::Debug;
use std::ptr::null;
use std::{io, result};

use super::super::DeviceType;
use super::super::InitramfsConfig;
use super::get_fdt_addr;
use super::gic::GICDevice;
use super::layout::{
    FDT_MAX_SIZE, MEM_32BIT_DEVICES_SIZE, MEM_32BIT_DEVICES_START, PCI_MMCONFIG_SIZE,
    PCI_MMCONFIG_START,
};
use crate::aarch64::fdt::Error::CstringFDTTransform;
use vm_memory::{Address, Bytes, GuestAddress, GuestMemory, GuestMemoryError, GuestMemoryMmap};

// This is a value for uniquely identifying the FDT node declaring the interrupt controller.
const GIC_PHANDLE: u32 = 1;
// This is a value for uniquely identifying the FDT node declaring the MSI controller.
const MSI_PHANDLE: u32 = 2;
// This is a value for uniquely identifying the FDT node containing the clock definition.
const CLOCK_PHANDLE: u32 = 3;
// This is a value for uniquely identifying the FDT node containing the gpio controller.
const GPIO_PHANDLE: u32 = 4;

// Read the documentation specified when appending the root node to the FDT.
const ADDRESS_CELLS: u32 = 0x2;
const SIZE_CELLS: u32 = 0x2;

// As per kvm tool and
// https://www.kernel.org/doc/Documentation/devicetree/bindings/interrupt-controller/arm%2Cgic.txt
// Look for "The 1st cell..."
const GIC_FDT_IRQ_TYPE_SPI: u32 = 0;
const GIC_FDT_IRQ_TYPE_PPI: u32 = 1;

// From https://elixir.bootlin.com/linux/v4.9.62/source/include/dt-bindings/interrupt-controller/irq.h#L17
const IRQ_TYPE_EDGE_RISING: u32 = 1;
const IRQ_TYPE_LEVEL_HI: u32 = 4;

// Keys and Buttons
// System Power Down
const KEY_POWER: u32 = 116;

// This links to libfdt which handles the creation of the binary blob
// flattened device tree (fdt) that is passed to the kernel and indicates
// the hardware configuration of the machine.
#[link(name = "fdt")]
extern "C" {
    fn fdt_create(buf: *mut c_void, bufsize: c_int) -> c_int;
    fn fdt_finish_reservemap(fdt: *mut c_void) -> c_int;
    fn fdt_begin_node(fdt: *mut c_void, name: *const c_char) -> c_int;
    fn fdt_property(fdt: *mut c_void, name: *const c_char, val: *const c_void, len: c_int)
        -> c_int;
    fn fdt_end_node(fdt: *mut c_void) -> c_int;
    fn fdt_open_into(fdt: *const c_void, buf: *mut c_void, bufsize: c_int) -> c_int;
    fn fdt_finish(fdt: *const c_void) -> c_int;
    fn fdt_pack(fdt: *mut c_void) -> c_int;
}

/// Trait for devices to be added to the Flattened Device Tree.
pub trait DeviceInfoForFDT {
    /// Returns the address where this device will be loaded.
    fn addr(&self) -> u64;
    /// Returns the associated interrupt for this device.
    fn irq(&self) -> u32;
    /// Returns the amount of memory that needs to be reserved for this device.
    fn length(&self) -> u64;
}

/// Errors thrown while configuring the Flattened Device Tree for aarch64.
#[derive(Debug)]
pub enum Error {
    /// Failed to append node to the FDT.
    AppendFDTNode(io::Error),
    /// Failed to append a property to the FDT.
    AppendFDTProperty(io::Error),
    /// Syscall for creating FDT failed.
    CreateFDT(io::Error),
    /// Failed to obtain a C style string.
    CstringFDTTransform(NulError),
    /// Failure in calling syscall for terminating this FDT.
    FinishFDTReserveMap(io::Error),
    /// Failure in writing FDT in memory.
    WriteFDTToMemory(GuestMemoryError),
}
type Result<T> = result::Result<T, Error>;

/// Creates the flattened device tree for this aarch64 VM.
pub fn create_fdt<T: DeviceInfoForFDT + Clone + Debug, S: ::std::hash::BuildHasher>(
    guest_mem: &GuestMemoryMmap,
    cmdline: &CStr,
    vcpu_mpidr: Vec<u64>,
    device_info: &HashMap<(DeviceType, String), T, S>,
    gic_device: &dyn GICDevice,
    initrd: &Option<InitramfsConfig>,
    pci_space_address: &(u64, u64),
) -> Result<Vec<u8>> {
    // Allocate stuff necessary for the holding the blob.
    let mut fdt = vec![0; FDT_MAX_SIZE];

    allocate_fdt(&mut fdt)?;

    // For an explanation why these nodes were introduced in the blob take a look at
    // https://github.com/torvalds/linux/blob/master/Documentation/devicetree/booting-without-of.txt#L845
    // Look for "Required nodes and properties".

    // Header or the root node as per above mentioned documentation.
    append_begin_node(&mut fdt, "")?;
    append_property_string(&mut fdt, "compatible", "linux,dummy-virt")?;
    // For info on #address-cells and size-cells read "Note about cells and address representation"
    // from the above mentioned txt file.
    append_property_u32(&mut fdt, "#address-cells", ADDRESS_CELLS)?;
    append_property_u32(&mut fdt, "#size-cells", SIZE_CELLS)?;
    // This is not mandatory but we use it to point the root node to the node
    // containing description of the interrupt controller for this VM.
    append_property_u32(&mut fdt, "interrupt-parent", GIC_PHANDLE)?;
    create_cpu_nodes(&mut fdt, &vcpu_mpidr)?;
    create_memory_node(&mut fdt, guest_mem)?;
    create_chosen_node(&mut fdt, cmdline, initrd)?;
    create_gic_node(&mut fdt, gic_device)?;
    create_timer_node(&mut fdt)?;
    create_clock_node(&mut fdt)?;
    create_psci_node(&mut fdt)?;
    create_devices_node(&mut fdt, device_info)?;
    create_pci_nodes(&mut fdt, pci_space_address.0, pci_space_address.1)?;

    // End Header node.
    append_end_node(&mut fdt)?;

    // Allocate another buffer so we can format and then write fdt to guest.
    let mut fdt_final = vec![0; FDT_MAX_SIZE];
    finish_fdt(&mut fdt, &mut fdt_final)?;

    // Write FDT to memory.
    let fdt_address = GuestAddress(get_fdt_addr(&guest_mem));
    guest_mem
        .write_slice(fdt_final.as_slice(), fdt_address)
        .map_err(Error::WriteFDTToMemory)?;
    Ok(fdt_final)
}

// Following are auxiliary functions for allocating and finishing the FDT.
fn allocate_fdt(fdt: &mut Vec<u8>) -> Result<()> {
    // Safe since we allocated this array with FDT_MAX_SIZE.
    let mut fdt_ret = unsafe { fdt_create(fdt.as_mut_ptr() as *mut c_void, FDT_MAX_SIZE as c_int) };

    if fdt_ret != 0 {
        return Err(Error::CreateFDT(io::Error::last_os_error()));
    }

    // The flattened device trees created with fdt_create() contains a list of
    // reserved memory areas. We need to call `fdt_finish_reservemap` so as to make sure that there is a
    // terminator in the reservemap list and whatever happened to be at the
    // start of the FDT data section would end up being interpreted as
    // reservemap entries.
    // Safe since we previously allocated this array.
    fdt_ret = unsafe { fdt_finish_reservemap(fdt.as_mut_ptr() as *mut c_void) };
    if fdt_ret != 0 {
        return Err(Error::FinishFDTReserveMap(io::Error::last_os_error()));
    }
    Ok(())
}

fn finish_fdt(from_fdt: &mut Vec<u8>, to_fdt: &mut Vec<u8>) -> Result<()> {
    // Safe since we allocated `fdt_final` and previously passed in its size.
    let mut fdt_ret = unsafe { fdt_finish(from_fdt.as_mut_ptr() as *mut c_void) };
    if fdt_ret != 0 {
        return Err(Error::FinishFDTReserveMap(io::Error::last_os_error()));
    }

    // Safe because we allocated both arrays with the correct size.
    fdt_ret = unsafe {
        fdt_open_into(
            from_fdt.as_mut_ptr() as *mut c_void,
            to_fdt.as_mut_ptr() as *mut c_void,
            FDT_MAX_SIZE as i32,
        )
    };
    if fdt_ret != 0 {
        return Err(Error::FinishFDTReserveMap(io::Error::last_os_error()));
    }

    // Safe since we allocated `to_fdt`.
    fdt_ret = unsafe { fdt_pack(to_fdt.as_mut_ptr() as *mut c_void) };
    if fdt_ret != 0 {
        return Err(Error::FinishFDTReserveMap(io::Error::last_os_error()));
    }
    Ok(())
}

// Following are auxiliary functions for appending nodes to FDT.
fn append_begin_node(fdt: &mut Vec<u8>, name: &str) -> Result<()> {
    let cstr_name = CString::new(name).map_err(CstringFDTTransform)?;

    // Safe because we allocated fdt and converted name to a CString
    let fdt_ret = unsafe { fdt_begin_node(fdt.as_mut_ptr() as *mut c_void, cstr_name.as_ptr()) };
    if fdt_ret != 0 {
        return Err(Error::AppendFDTNode(io::Error::last_os_error()));
    }
    Ok(())
}

fn append_end_node(fdt: &mut Vec<u8>) -> Result<()> {
    // Safe because we allocated fdt.
    let fdt_ret = unsafe { fdt_end_node(fdt.as_mut_ptr() as *mut c_void) };
    if fdt_ret != 0 {
        return Err(Error::AppendFDTNode(io::Error::last_os_error()));
    }
    Ok(())
}

// Following are auxiliary functions for appending property nodes to the nodes of the FDT.
fn append_property_u32(fdt: &mut Vec<u8>, name: &str, val: u32) -> Result<()> {
    append_property(fdt, name, &to_be32(val))
}

fn append_property_u64(fdt: &mut Vec<u8>, name: &str, val: u64) -> Result<()> {
    append_property(fdt, name, &to_be64(val))
}

fn append_property_string(fdt: &mut Vec<u8>, name: &str, value: &str) -> Result<()> {
    let cstr_value = CString::new(value).map_err(CstringFDTTransform)?;
    append_property_cstring(fdt, name, &cstr_value)
}

fn append_property_cstring(fdt: &mut Vec<u8>, name: &str, cstr_value: &CStr) -> Result<()> {
    let value_bytes = cstr_value.to_bytes_with_nul();
    let cstr_name = CString::new(name).map_err(CstringFDTTransform)?;
    // Safe because we allocated fdt, converted name and value to CStrings
    let fdt_ret = unsafe {
        fdt_property(
            fdt.as_mut_ptr() as *mut c_void,
            cstr_name.as_ptr(),
            value_bytes.as_ptr() as *mut c_void,
            value_bytes.len() as i32,
        )
    };
    if fdt_ret != 0 {
        return Err(Error::AppendFDTProperty(io::Error::last_os_error()));
    }
    Ok(())
}

fn append_property_null(fdt: &mut Vec<u8>, name: &str) -> Result<()> {
    let cstr_name = CString::new(name).map_err(CstringFDTTransform)?;

    // Safe because we allocated fdt, converted name to a CString
    let fdt_ret = unsafe {
        fdt_property(
            fdt.as_mut_ptr() as *mut c_void,
            cstr_name.as_ptr(),
            null(),
            0,
        )
    };
    if fdt_ret != 0 {
        return Err(Error::AppendFDTProperty(io::Error::last_os_error()));
    }
    Ok(())
}

fn append_property(fdt: &mut Vec<u8>, name: &str, val: &[u8]) -> Result<()> {
    let cstr_name = CString::new(name).map_err(CstringFDTTransform)?;
    let val_ptr = val.as_ptr() as *const c_void;

    // Safe because we allocated fdt and converted name to a CString
    let fdt_ret = unsafe {
        fdt_property(
            fdt.as_mut_ptr() as *mut c_void,
            cstr_name.as_ptr(),
            val_ptr,
            val.len() as i32,
        )
    };
    if fdt_ret != 0 {
        return Err(Error::AppendFDTProperty(io::Error::last_os_error()));
    }
    Ok(())
}

// Auxiliary functions for writing u32/u64 numbers in big endian order.
fn to_be32(input: u32) -> [u8; 4] {
    u32::to_be_bytes(input)
}

fn to_be64(input: u64) -> [u8; 8] {
    u64::to_be_bytes(input)
}

// Helper functions for generating a properly formatted byte vector using 32-bit/64-bit cells.
fn generate_prop32(cells: &[u32]) -> Vec<u8> {
    let mut ret: Vec<u8> = Vec::new();
    for &e in cells {
        ret.extend(to_be32(e).iter());
    }
    ret
}

fn generate_prop64(cells: &[u64]) -> Vec<u8> {
    let mut ret: Vec<u8> = Vec::new();
    for &e in cells {
        ret.extend(to_be64(e).iter());
    }
    ret
}

// Following are the auxiliary function for creating the different nodes that we append to our FDT.
fn create_cpu_nodes(fdt: &mut Vec<u8>, vcpu_mpidr: &[u64]) -> Result<()> {
    // See https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/arm/cpus.yaml.
    append_begin_node(fdt, "cpus")?;
    // As per documentation, on ARM v8 64-bit systems value should be set to 2.
    append_property_u32(fdt, "#address-cells", 0x02)?;
    append_property_u32(fdt, "#size-cells", 0x0)?;
    let num_cpus = vcpu_mpidr.len();

    for (cpu_index, mpidr) in vcpu_mpidr.iter().enumerate().take(num_cpus) {
        let cpu_name = format!("cpu@{:x}", cpu_index);
        append_begin_node(fdt, &cpu_name)?;
        append_property_string(fdt, "device_type", "cpu")?;
        append_property_string(fdt, "compatible", "arm,arm-v8")?;
        if num_cpus > 1 {
            // This is required on armv8 64-bit. See aforementioned documentation.
            append_property_string(fdt, "enable-method", "psci")?;
        }
        // Set the field to first 24 bits of the MPIDR - Multiprocessor Affinity Register.
        // See http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0488c/BABHBJCI.html.
        append_property_u64(fdt, "reg", mpidr & 0x7FFFFF)?;
        append_end_node(fdt)?;
    }
    append_end_node(fdt)?;
    Ok(())
}

fn create_memory_node(fdt: &mut Vec<u8>, guest_mem: &GuestMemoryMmap) -> Result<()> {
    let mem_size = guest_mem.last_addr().raw_value() - super::layout::RAM_64BIT_START + 1;
    // See https://github.com/torvalds/linux/blob/master/Documentation/devicetree/booting-without-of.txt#L960
    // for an explanation of this.
    let mem_reg_prop = generate_prop64(&[super::layout::RAM_64BIT_START as u64, mem_size as u64]);

    append_begin_node(fdt, "memory")?;
    append_property_string(fdt, "device_type", "memory")?;
    append_property(fdt, "reg", &mem_reg_prop)?;
    append_end_node(fdt)?;
    Ok(())
}

fn create_chosen_node(
    fdt: &mut Vec<u8>,
    cmdline: &CStr,
    initrd: &Option<InitramfsConfig>,
) -> Result<()> {
    append_begin_node(fdt, "chosen")?;
    append_property_cstring(fdt, "bootargs", cmdline)?;

    if let Some(initrd_config) = initrd {
        append_property_u64(
            fdt,
            "linux,initrd-start",
            initrd_config.address.raw_value() as u64,
        )?;
        append_property_u64(
            fdt,
            "linux,initrd-end",
            initrd_config.address.raw_value() + initrd_config.size as u64,
        )?;
    }

    append_end_node(fdt)?;

    Ok(())
}

fn create_gic_node(fdt: &mut Vec<u8>, gic_device: &dyn GICDevice) -> Result<()> {
    let gic_reg_prop = generate_prop64(gic_device.device_properties());

    append_begin_node(fdt, "intc")?;
    append_property_string(fdt, "compatible", gic_device.fdt_compatibility())?;
    append_property_null(fdt, "interrupt-controller")?;
    // "interrupt-cells" field specifies the number of cells needed to encode an
    // interrupt source. The type shall be a <u32> and the value shall be 3 if no PPI affinity description
    // is required.
    append_property_u32(fdt, "#interrupt-cells", 3)?;
    append_property(fdt, "reg", &gic_reg_prop)?;
    append_property_u32(fdt, "phandle", GIC_PHANDLE)?;
    append_property_u32(fdt, "#address-cells", 2)?;
    append_property_u32(fdt, "#size-cells", 2)?;
    append_property_null(fdt, "ranges")?;
    let gic_intr = [
        GIC_FDT_IRQ_TYPE_PPI,
        gic_device.fdt_maint_irq(),
        IRQ_TYPE_LEVEL_HI,
    ];
    let gic_intr_prop = generate_prop32(&gic_intr);

    append_property(fdt, "interrupts", &gic_intr_prop)?;

    if gic_device.msi_compatible() {
        append_begin_node(fdt, "msic")?;
        append_property_string(fdt, "compatible", gic_device.msi_compatibility())?;
        append_property_null(fdt, "msi-controller")?;
        append_property_u32(fdt, "phandle", MSI_PHANDLE)?;
        let msi_reg_prop = generate_prop64(gic_device.msi_properties());
        append_property(fdt, "reg", &msi_reg_prop)?;
        append_end_node(fdt)?;
    }

    append_end_node(fdt)?;

    Ok(())
}

fn create_clock_node(fdt: &mut Vec<u8>) -> Result<()> {
    // The Advanced Peripheral Bus (APB) is part of the Advanced Microcontroller Bus Architecture
    // (AMBA) protocol family. It defines a low-cost interface that is optimized for minimal power
    // consumption and reduced interface complexity.
    // PCLK is the clock source and this node defines exactly the clock for the APB.
    append_begin_node(fdt, "apb-pclk")?;
    append_property_string(fdt, "compatible", "fixed-clock")?;
    append_property_u32(fdt, "#clock-cells", 0x0)?;
    append_property_u32(fdt, "clock-frequency", 24000000)?;
    append_property_string(fdt, "clock-output-names", "clk24mhz")?;
    append_property_u32(fdt, "phandle", CLOCK_PHANDLE)?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_timer_node(fdt: &mut Vec<u8>) -> Result<()> {
    // See
    // https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/interrupt-controller/arch_timer.txt
    // These are fixed interrupt numbers for the timer device.
    let irqs = [13, 14, 11, 10];
    let compatible = "arm,armv8-timer";

    let mut timer_reg_cells: Vec<u32> = Vec::new();
    for &irq in irqs.iter() {
        timer_reg_cells.push(GIC_FDT_IRQ_TYPE_PPI);
        timer_reg_cells.push(irq);
        timer_reg_cells.push(IRQ_TYPE_LEVEL_HI);
    }
    let timer_reg_prop = generate_prop32(timer_reg_cells.as_slice());

    append_begin_node(fdt, "timer")?;
    append_property_string(fdt, "compatible", compatible)?;
    append_property_null(fdt, "always-on")?;
    append_property(fdt, "interrupts", &timer_reg_prop)?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_psci_node(fdt: &mut Vec<u8>) -> Result<()> {
    let compatible = "arm,psci-0.2";
    append_begin_node(fdt, "psci")?;
    append_property_string(fdt, "compatible", compatible)?;
    // Two methods available: hvc and smc.
    // As per documentation, PSCI calls between a guest and hypervisor may use the HVC conduit instead of SMC.
    // So, since we are using kvm, we need to use hvc.
    append_property_string(fdt, "method", "hvc")?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_virtio_node<T: DeviceInfoForFDT + Clone + Debug>(
    fdt: &mut Vec<u8>,
    dev_info: &T,
) -> Result<()> {
    let device_reg_prop = generate_prop64(&[dev_info.addr(), dev_info.length()]);
    let irq = generate_prop32(&[GIC_FDT_IRQ_TYPE_SPI, dev_info.irq(), IRQ_TYPE_EDGE_RISING]);

    append_begin_node(fdt, &format!("virtio_mmio@{:x}", dev_info.addr()))?;
    append_property_string(fdt, "compatible", "virtio,mmio")?;
    append_property(fdt, "reg", &device_reg_prop)?;
    append_property(fdt, "interrupts", &irq)?;
    append_property_u32(fdt, "interrupt-parent", GIC_PHANDLE)?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_serial_node<T: DeviceInfoForFDT + Clone + Debug>(
    fdt: &mut Vec<u8>,
    dev_info: &T,
) -> Result<()> {
    let compatible = b"arm,pl011\0arm,primecell\0";
    let serial_reg_prop = generate_prop64(&[dev_info.addr(), dev_info.length()]);
    let irq = generate_prop32(&[GIC_FDT_IRQ_TYPE_SPI, dev_info.irq(), IRQ_TYPE_EDGE_RISING]);

    append_begin_node(fdt, &format!("pl011@{:x}", dev_info.addr()))?;
    append_property(fdt, "compatible", compatible)?;
    append_property(fdt, "reg", &serial_reg_prop)?;
    append_property_u32(fdt, "clocks", CLOCK_PHANDLE)?;
    append_property_string(fdt, "clock-names", "apb_pclk")?;
    append_property(fdt, "interrupts", &irq)?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_rtc_node<T: DeviceInfoForFDT + Clone + Debug>(
    fdt: &mut Vec<u8>,
    dev_info: &T,
) -> Result<()> {
    let compatible = b"arm,pl031\0arm,primecell\0";
    let rtc_reg_prop = generate_prop64(&[dev_info.addr(), dev_info.length()]);
    let irq = generate_prop32(&[GIC_FDT_IRQ_TYPE_SPI, dev_info.irq(), IRQ_TYPE_LEVEL_HI]);
    append_begin_node(fdt, &format!("rtc@{:x}", dev_info.addr()))?;
    append_property(fdt, "compatible", compatible)?;
    append_property(fdt, "reg", &rtc_reg_prop)?;
    append_property(fdt, "interrupts", &irq)?;
    append_property_u32(fdt, "clocks", CLOCK_PHANDLE)?;
    append_property_string(fdt, "clock-names", "apb_pclk")?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_gpio_node<T: DeviceInfoForFDT + Clone + Debug>(
    fdt: &mut Vec<u8>,
    dev_info: &T,
) -> Result<()> {
    // PL061 GPIO controller node
    let compatible = b"arm,pl061\0arm,primecell\0";
    let gpio_reg_prop = generate_prop64(&[dev_info.addr(), dev_info.length()]);
    let irq = generate_prop32(&[GIC_FDT_IRQ_TYPE_SPI, dev_info.irq(), IRQ_TYPE_EDGE_RISING]);
    append_begin_node(fdt, &format!("pl061@{:x}", dev_info.addr()))?;
    append_property(fdt, "compatible", compatible)?;
    append_property(fdt, "reg", &gpio_reg_prop)?;
    append_property(fdt, "interrupts", &irq)?;
    append_property_null(fdt, "gpio-controller")?;
    append_property_u32(fdt, "#gpio-cells", 2)?;
    append_property_u32(fdt, "clocks", CLOCK_PHANDLE)?;
    append_property_string(fdt, "clock-names", "apb_pclk")?;
    append_property_u32(fdt, "phandle", GPIO_PHANDLE)?;
    append_end_node(fdt)?;

    // gpio-keys node
    append_begin_node(fdt, "/gpio-keys")?;
    append_property_string(fdt, "compatible", "gpio-keys")?;
    append_property_u32(fdt, "#size-cells", 0)?;
    append_property_u32(fdt, "#address-cells", 1)?;
    append_begin_node(fdt, "/gpio-keys/poweroff")?;
    append_property_string(fdt, "label", "GPIO Key Poweroff")?;
    append_property_u32(fdt, "linux,code", KEY_POWER)?;
    let gpios = generate_prop32(&[GPIO_PHANDLE, 3, 0]);
    append_property(fdt, "gpios", &gpios)?;
    append_end_node(fdt)?;
    append_end_node(fdt)?;

    Ok(())
}

fn create_devices_node<T: DeviceInfoForFDT + Clone + Debug, S: ::std::hash::BuildHasher>(
    fdt: &mut Vec<u8>,
    dev_info: &HashMap<(DeviceType, String), T, S>,
) -> Result<()> {
    // Create one temp Vec to store all virtio devices
    let mut ordered_virtio_device: Vec<&T> = Vec::new();

    for ((device_type, _device_id), info) in dev_info {
        match device_type {
            DeviceType::GPIO => create_gpio_node(fdt, info)?,
            DeviceType::RTC => create_rtc_node(fdt, info)?,
            DeviceType::Serial => create_serial_node(fdt, info)?,
            DeviceType::Virtio(_) => {
                ordered_virtio_device.push(info);
            }
        }
    }

    // Sort out virtio devices by address from low to high and insert them into fdt table.
    ordered_virtio_device.sort_by_key(|&a| a.addr());
    // Current address allocation strategy in cloud-hypervisor is: the first created device
    // will be allocated to higher address. Here we reverse the vector to make sure that
    // the older created device will appear in front of the newer created device in FDT.
    ordered_virtio_device.reverse();
    for ordered_device_info in ordered_virtio_device.drain(..) {
        create_virtio_node(fdt, ordered_device_info)?;
    }

    Ok(())
}

fn create_pci_nodes(fdt: &mut Vec<u8>, pci_device_base: u64, pci_device_size: u64) -> Result<()> {
    // Add node for PCIe controller.
    // See Documentation/devicetree/bindings/pci/host-generic-pci.txt in the kernel
    // and https://elinux.org/Device_Tree_Usage.
    let ranges = generate_prop32(&[
        // mmio addresses
        0x2000000,                                // (ss = 10: 32-bit memory space)
        (MEM_32BIT_DEVICES_START.0 >> 32) as u32, // PCI address
        MEM_32BIT_DEVICES_START.0 as u32,
        (MEM_32BIT_DEVICES_START.0 >> 32) as u32, // CPU address
        MEM_32BIT_DEVICES_START.0 as u32,
        (MEM_32BIT_DEVICES_SIZE >> 32) as u32, // size
        MEM_32BIT_DEVICES_SIZE as u32,
        // device addresses
        0x3000000,                      // (ss = 11: 64-bit memory space)
        (pci_device_base >> 32) as u32, // PCI address
        pci_device_base as u32,
        (pci_device_base >> 32) as u32, // CPU address
        pci_device_base as u32,
        (pci_device_size >> 32) as u32, // size
        pci_device_size as u32,
    ]);
    let bus_range = generate_prop32(&[0, 0]); // Only bus 0
    let reg = generate_prop64(&[PCI_MMCONFIG_START.0, PCI_MMCONFIG_SIZE]);

    append_begin_node(fdt, "pci")?;
    append_property_string(fdt, "compatible", "pci-host-ecam-generic")?;
    append_property_string(fdt, "device_type", "pci")?;
    append_property(fdt, "ranges", &ranges)?;
    append_property(fdt, "bus-range", &bus_range)?;
    append_property_u32(fdt, "#address-cells", 3)?;
    append_property_u32(fdt, "#size-cells", 2)?;
    append_property(fdt, "reg", &reg)?;
    append_property_u32(fdt, "#interrupt-cells", 1)?;
    append_property_null(fdt, "interrupt-map")?;
    append_property_null(fdt, "interrupt-map-mask")?;
    append_property_null(fdt, "dma-coherent")?;
    append_property_u32(fdt, "msi-parent", MSI_PHANDLE)?;
    append_end_node(fdt)?;

    Ok(())
}