write bootparams in memory for Linux & PVH protos

This commit introduces a new configurator module that takes
boot parameters created in the VMM (boot_params / start_info
+ e820 map) and writes them into guest memory. The module is
meant to be extended in order to include *building* the boot
parameters as well.

Fixes #15

Signed-off-by: Alexandra Iordache <aghecen@amazon.com>

src/configurator/aarch64/mod.rs

@@ -0,0 +1,29 @@
+// Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+
+//! Traits and structs for configuring and loading boot parameters on `aarch64`.
+
+#![cfg(target_arch = "aarch64")]
+
+use std::error::Error as StdError;
+use std::fmt;
+
+/// Placeholder error type.
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    /// Placeholder error value.
+    Placeholder,
+}
+
+impl StdError for Error {
+    fn description(&self) -> &str {
+        unimplemented!()
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, _f: &mut fmt::Formatter) -> fmt::Result {
+        unimplemented!()
+    }
+}

src/configurator/mod.rs

@@ -0,0 +1,116 @@
+// Copyright © 2020, Oracle and/or its affiliates.
+//
+// Copyright (c) 2019 Intel Corporation. All rights reserved.
+// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// 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 LICENSE-BSD-3-Clause file.
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+
+//! Traits and structs for configuring and loading boot parameters.
+//! - [BootConfigurator](trait.BootConfigurator.html): configure boot parameters.
+//! - [LinuxBootConfigurator](linux/struct.LinuxBootConfigurator.html): Linux boot protocol
+//!   parameters configurator.
+//! - [PvhBootConfigurator](pvh/struct.PvhBootConfigurator.html): PVH boot protocol parameters
+//!   configurator.
+
+use vm_memory::{ByteValued, GuestAddress, GuestMemory};
+
+use std::error::Error as StdError;
+use std::fmt;
+
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+mod x86_64;
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+pub use x86_64::*;
+
+#[cfg(target_arch = "aarch64")]
+mod aarch64;
+#[cfg(target_arch = "aarch64")]
+pub use aarch64::Error as ArmError;
+
+/// Errors specific to boot protocol configuration.
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    /// Errors specific to the Linux boot protocol configuration.
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+    Linux(linux::Error),
+    /// Errors specific to the PVH boot protocol configuration.
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+    Pvh(pvh::Error),
+    /// Errors specific to device tree boot configuration.
+    #[cfg(target_arch = "aarch64")]
+    Arm(ArmError),
+}
+
+impl StdError for Error {
+    fn description(&self) -> &str {
+        use Error::*;
+        match self {
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+            Linux(ref e) => e.description(),
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+            Pvh(ref e) => e.description(),
+            #[cfg(target_arch = "aarch64")]
+            Arm(ref e) => e.description(),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Boot Configurator Error: {}",
+            StdError::description(self)
+        )
+    }
+}
+
+/// A specialized `Result` type for the boot configurator.
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Trait that defines interfaces for building (TBD) and configuring boot parameters.
+///
+/// Currently, this trait exposes a single function which writes user-provided boot parameters into
+/// guest memory at the user-specified addresses. It's meant to be called after the kernel is
+/// loaded and after the boot parameters are built externally (in the VMM).
+///
+/// This trait will be extended with additional functionality to build boot parameters.
+pub trait BootConfigurator {
+    /// Writes the boot parameters (configured elsewhere) into guest memory.
+    ///
+    /// The arguments are split into `header` and `sections` to accommodate different boot
+    /// protocols like Linux boot and PVH. In Linux boot, the e820 map could be considered as
+    /// `sections`, but it's already encapsulated in the `boot_params` and thus all the boot
+    /// parameters are passed through a single struct. In PVH, the memory map table is separated
+    /// from the `hvm_start_info` struct, therefore it's passed separately.
+    ///
+    /// # Arguments
+    ///
+    /// * `header` - header section of the boot parameters and address where to write it in guest
+    ///              memory. The first element must be a POD struct that implements [`ByteValued`].
+    ///              For the Linux protocol it's the [`boot_params`] struct, and for PVH the
+    ///             [`hvm_start_info`] struct.
+    /// * `sections` - vector of sections that compose the boot parameters and address where to
+    ///                write them in guest memory. Unused for the Linux protocol. For PVH, it's the
+    ///                memory map table represented as a vector of [`hvm_memmap_table_entry`]. Must
+    ///                be a `Vec` of POD data structs that implement [`ByteValued`].
+    /// * `guest_memory` - guest's physical memory.
+    ///
+    /// [`boot_params`]: ../loader/bootparam/struct.boot_e820_entry.html
+    /// [`hvm_memmap_table_entry`]: ../loader/elf/start_info/struct.hvm_memmap_table_entry.html
+    /// [`hvm_start_info`]: ../loader/elf/start_info/struct.hvm_start_info.html
+    /// [`ByteValued`]: https://docs.rs/vm-memory/latest/vm_memory/bytes/trait.ByteValued.html
+    fn write_bootparams<T, S, M>(
+        header: (T, GuestAddress),
+        sections: Option<(Vec<S>, GuestAddress)>,
+        guest_memory: &M,
+    ) -> Result<()>
+    where
+        T: ByteValued,
+        S: ByteValued,
+        M: GuestMemory;
+}

src/configurator/x86_64/linux.rs

@@ -0,0 +1,153 @@
+// Copyright © 2020, Oracle and/or its affiliates.
+//
+// Copyright (c) 2019 Intel Corporation. All rights reserved.
+// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// 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 LICENSE-BSD-3-Clause file.
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+
+//! Traits and structs for configuring and loading boot parameters on `x86_64` using the Linux
+//! boot protocol.
+
+use vm_memory::{ByteValued, Bytes, GuestAddress, GuestMemory};
+
+use super::super::{BootConfigurator, Error as BootConfiguratorError, Result};
+use crate::loader::bootparam::boot_params;
+
+use std::error::Error as StdError;
+use std::fmt;
+use std::mem;
+
+/// Boot configurator for the Linux boot protocol.
+pub struct LinuxBootConfigurator {}
+
+/// Errors specific to the Linux boot protocol configuration.
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    /// The zero page extends past the end of guest memory.
+    ZeroPagePastRamEnd,
+    /// Error writing to the zero page of guest memory.
+    ZeroPageSetup,
+}
+
+impl StdError for Error {
+    fn description(&self) -> &str {
+        use Error::*;
+        match self {
+            ZeroPagePastRamEnd => "The zero page extends past the end of guest memory.",
+            ZeroPageSetup => "Error writing to the zero page of guest memory.",
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Linux Boot Configurator Error: {}",
+            StdError::description(self)
+        )
+    }
+}
+
+impl From<Error> for BootConfiguratorError {
+    fn from(err: Error) -> Self {
+        BootConfiguratorError::Linux(err)
+    }
+}
+
+impl BootConfigurator for LinuxBootConfigurator {
+    /// Writes the boot parameters (configured elsewhere) into guest memory.
+    ///
+    /// # Arguments
+    ///
+    /// * `header` - boot parameters encapsulated in a [`boot_params`] struct.
+    /// * `sections` - unused.
+    /// * `guest_memory` - guest's physical memory.
+    ///
+    /// [`boot_params`]: ../loader/bootparam/struct.boot_e820_entry.html
+    fn write_bootparams<T, S, M>(
+        header: (T, GuestAddress),
+        _sections: Option<(Vec<S>, GuestAddress)>,
+        guest_memory: &M,
+    ) -> Result<()>
+    where
+        T: ByteValued,
+        S: ByteValued,
+        M: GuestMemory,
+    {
+        // The VMM has filled a `boot_params` struct and its e820 map.
+        // This will be written in guest memory at the zero page.
+        guest_memory
+            .checked_offset(header.1, mem::size_of::<boot_params>())
+            .ok_or(Error::ZeroPagePastRamEnd)?;
+        guest_memory
+            .write_obj(header.0, header.1)
+            .map_err(|_| Error::ZeroPageSetup)?;
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::mem;
+    use vm_memory::{Address, GuestAddress, GuestMemoryMmap};
+
+    const KERNEL_BOOT_FLAG_MAGIC: u16 = 0xaa55;
+    const KERNEL_HDR_MAGIC: u32 = 0x53726448;
+    const KERNEL_LOADER_OTHER: u8 = 0xff;
+    const KERNEL_MIN_ALIGNMENT_BYTES: u32 = 0x1000000;
+    const MEM_SIZE: u64 = 0x1000000;
+
+    fn create_guest_mem() -> GuestMemoryMmap {
+        GuestMemoryMmap::from_ranges(&[(GuestAddress(0x0), (MEM_SIZE as usize))]).unwrap()
+    }
+
+    fn build_bootparams_common() -> boot_params {
+        let mut params = boot_params::default();
+        params.hdr.boot_flag = KERNEL_BOOT_FLAG_MAGIC;
+        params.hdr.header = KERNEL_HDR_MAGIC;
+        params.hdr.kernel_alignment = KERNEL_MIN_ALIGNMENT_BYTES;
+        params.hdr.type_of_loader = KERNEL_LOADER_OTHER;
+        params
+    }
+
+    #[test]
+    fn test_configure_linux_boot() {
+        let zero_page_addr = GuestAddress(0x30000);
+
+        let params = build_bootparams_common();
+        // This is where we'd append e820 entries, cmdline, PCI, ACPI etc.
+
+        let guest_memory = create_guest_mem();
+
+        // Error case: boot params don't fit in guest memory (zero page address too close to end).
+        let bad_zeropg_addr = GuestAddress(
+            guest_memory.last_addr().raw_value() - mem::size_of::<boot_params>() as u64 + 1,
+        );
+        assert_eq!(
+            LinuxBootConfigurator::write_bootparams::<boot_params, boot_params, GuestMemoryMmap>(
+                (params, bad_zeropg_addr),
+                None,
+                &guest_memory,
+            )
+            .err(),
+            Some(Error::ZeroPagePastRamEnd.into()),
+        );
+
+        // Success case.
+        assert!(
+            LinuxBootConfigurator::write_bootparams::<boot_params, boot_params, GuestMemoryMmap>(
+                (params, zero_page_addr),
+                None,
+                &guest_memory
+            )
+            .is_ok()
+        );
+    }
+}

src/configurator/x86_64/mod.rs

@@ -0,0 +1,17 @@
+// Copyright © 2020, Oracle and/or its affiliates.
+//
+// Copyright (c) 2019 Intel Corporation. All rights reserved.
+// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// 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 LICENSE-BSD-3-Clause file.
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+
+//! Traits and structs for configuring and loading boot parameters on `x86_64`.
+
+#![cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+
+pub mod linux;
+pub mod pvh;