tdx: Add support for parsing TDVF metadata

Add support extracting the sections out for a TDVF file which can be
then used to load the TDVF and TD HOB data into their appropriate
locations.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

arch/src/x86_64/tdx/mod.rs

@@ -1,4 +1,127 @@
 // Copyright © 2021 Intel Corporation
 //
 // SPDX-License-Identifier: Apache-2.0
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom};
+use thiserror::Error;
 
+#[derive(Error, Debug)]
+pub enum TdvfError {
+    #[error("Failed read TDVF descriptor: {0}")]
+    ReadDescriptor(#[source] std::io::Error),
+    #[error("Failed read TDVF descriptor offset: {0}")]
+    ReadDescriptorOffset(#[source] std::io::Error),
+    #[error("Invalid descriptor signature")]
+    InvalidDescriptorSignature,
+    #[error("Invalid descriptor size")]
+    InvalidDescriptorSize,
+    #[error("Invalid descriptor version")]
+    InvalidDescriptorVersion,
+}
+
+// TDVF_DESCRIPTOR
+#[repr(packed)]
+pub struct TdvfDescriptor {
+    signature: [u8; 4],
+    length: u32,
+    version: u32,
+    num_sections: u32, // NumberOfSectionEntry
+}
+
+// TDVF_SECTION
+#[repr(packed)]
+#[derive(Clone, Copy, Default, Debug)]
+pub struct TdvfSection {
+    pub data_offset: u32,
+    pub data_size: u32, // RawDataSize
+    pub address: u64,   // MemoryAddress
+    pub size: u64,      // MemoryDataSize
+    pub r#type: TdvfSectionType,
+    pub attributes: u32,
+}
+
+#[repr(u32)]
+#[derive(Clone, Copy, Debug)]
+pub enum TdvfSectionType {
+    Bfv,
+    Cfv,
+    TdHob,
+    TempMem,
+    Reserved = 0xffffffff,
+}
+
+impl Default for TdvfSectionType {
+    fn default() -> Self {
+        TdvfSectionType::Reserved
+    }
+}
+
+pub fn parse_tdvf_sections(file: &mut File) -> Result<Vec<TdvfSection>, TdvfError> {
+    // The 32-bit offset to the TDVF metadata is located 32 bytes from
+    // the end of the file.
+    // See "TDVF Metadata Pointer" in "TDX Virtual Firmware Design Guide
+    file.seek(SeekFrom::End(-0x20))
+        .map_err(TdvfError::ReadDescriptorOffset)?;
+
+    let mut descriptor_offset: [u8; 4] = [0; 4];
+    file.read_exact(&mut descriptor_offset)
+        .map_err(TdvfError::ReadDescriptorOffset)?;
+    let descriptor_offset = u32::from_le_bytes(descriptor_offset) as u64;
+
+    file.seek(SeekFrom::Start(descriptor_offset))
+        .map_err(TdvfError::ReadDescriptor)?;
+
+    let mut descriptor: TdvfDescriptor = unsafe { std::mem::zeroed() };
+    // Safe as we read exactly the size of the descriptor header
+    file.read_exact(unsafe {
+        std::slice::from_raw_parts_mut(
+            &mut descriptor as *mut _ as *mut u8,
+            std::mem::size_of::<TdvfDescriptor>(),
+        )
+    })
+    .map_err(TdvfError::ReadDescriptor)?;
+
+    if &descriptor.signature != b"TDVF" {
+        return Err(TdvfError::InvalidDescriptorSignature);
+    }
+
+    if descriptor.length as usize
+        != std::mem::size_of::<TdvfDescriptor>()
+            + std::mem::size_of::<TdvfSection>() * descriptor.num_sections as usize
+    {
+        return Err(TdvfError::InvalidDescriptorSize);
+    }
+
+    if descriptor.version != 1 {
+        return Err(TdvfError::InvalidDescriptorVersion);
+    }
+
+    let mut sections = Vec::new();
+    sections.resize_with(descriptor.num_sections as usize, TdvfSection::default);
+
+    // Safe as we read exactly the advertised sections
+    file.read_exact(unsafe {
+        std::slice::from_raw_parts_mut(
+            sections.as_mut_ptr() as *mut u8,
+            descriptor.num_sections as usize * std::mem::size_of::<TdvfSection>(),
+        )
+    })
+    .map_err(TdvfError::ReadDescriptor)?;
+
+    Ok(sections)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[ignore]
+    fn test_parse_tdvf_sections() {
+        let mut f = std::fs::File::open("tdvf.fd").unwrap();
+        let sections = parse_tdvf_sections(&mut f).unwrap();
+        for section in sections {
+            eprintln!("{:x?}", section)
+        }
+    }
+}