vmm/
initrd.rs

1// Copyright 2025 Amazon.com, Inc. or its affiliates. All Rights Reserved.
2// SPDX-License-Identifier: Apache-2.0
3
4use std::fs::File;
5use std::os::unix::fs::MetadataExt;
6
7use vm_memory::{GuestAddress, GuestMemory, ReadVolatile, VolatileMemoryError};
8
9use crate::arch::initrd_load_addr;
10use crate::utils::u64_to_usize;
11use crate::vmm_config::boot_source::BootConfig;
12use crate::vstate::memory::GuestMemoryMmap;
13
14/// Errors associated with initrd loading.
15#[derive(Debug, thiserror::Error, displaydoc::Display)]
16pub enum InitrdError {
17    /// Failed to compute the initrd address.
18    Address,
19    /// Cannot load initrd due to an invalid memory configuration.
20    Load,
21    /// Cannot image metadata: {0}
22    Metadata(std::io::Error),
23    /// Cannot copy initrd file fd: {0}
24    CloneFd(std::io::Error),
25    /// Cannot load initrd due to an invalid image: {0}
26    Read(VolatileMemoryError),
27}
28
29/// Type for passing information about the initrd in the guest memory.
30#[derive(Debug)]
31pub struct InitrdConfig {
32    /// Load address of initrd in guest memory
33    pub address: GuestAddress,
34    /// Size of initrd in guest memory
35    pub size: usize,
36}
37
38impl InitrdConfig {
39    /// Load initrd into guest memory based on the boot config.
40    pub fn from_config(
41        boot_cfg: &BootConfig,
42        vm_memory: &GuestMemoryMmap,
43    ) -> Result<Option<Self>, InitrdError> {
44        Ok(match &boot_cfg.initrd_file {
45            Some(f) => {
46                let f = f.try_clone().map_err(InitrdError::CloneFd)?;
47                Some(Self::from_file(vm_memory, f)?)
48            }
49            None => None,
50        })
51    }
52
53    /// Loads the initrd from a file into guest memory.
54    pub fn from_file(vm_memory: &GuestMemoryMmap, mut file: File) -> Result<Self, InitrdError> {
55        let size = file.metadata().map_err(InitrdError::Metadata)?.size();
56        let size = u64_to_usize(size);
57        let Some(address) = initrd_load_addr(vm_memory, size) else {
58            return Err(InitrdError::Address);
59        };
60        let mut slice = vm_memory
61            .get_slice(GuestAddress(address), size)
62            .map_err(|_| InitrdError::Load)?;
63        file.read_exact_volatile(&mut slice)
64            .map_err(InitrdError::Read)?;
65
66        Ok(InitrdConfig {
67            address: GuestAddress(address),
68            size,
69        })
70    }
71}
72
73#[cfg(test)]
74mod tests {
75    use std::io::{Seek, SeekFrom, Write};
76
77    use vmm_sys_util::tempfile::TempFile;
78
79    use super::*;
80    use crate::arch::GUEST_PAGE_SIZE;
81    use crate::test_utils::{single_region_mem, single_region_mem_at};
82
83    fn make_test_bin() -> Vec<u8> {
84        let mut fake_bin = Vec::new();
85        fake_bin.resize(1_000_000, 0xAA);
86        fake_bin
87    }
88
89    #[test]
90    // Test that loading the initrd is successful on different archs.
91    fn test_load_initrd() {
92        let image = make_test_bin();
93
94        let mem_size: usize = image.len() * 2 + GUEST_PAGE_SIZE;
95
96        let tempfile = TempFile::new().unwrap();
97        let mut tempfile = tempfile.into_file();
98        tempfile.write_all(&image).unwrap();
99
100        #[cfg(target_arch = "x86_64")]
101        let gm = single_region_mem(mem_size);
102
103        #[cfg(target_arch = "aarch64")]
104        let gm = single_region_mem(mem_size + crate::arch::aarch64::layout::FDT_MAX_SIZE);
105
106        // Need to reset the cursor to read initrd properly.
107        tempfile.seek(SeekFrom::Start(0)).unwrap();
108        let initrd = InitrdConfig::from_file(&gm, tempfile).unwrap();
109        assert!(gm.address_in_range(initrd.address));
110        assert_eq!(initrd.size, image.len());
111    }
112
113    #[test]
114    fn test_load_initrd_no_memory() {
115        let gm = single_region_mem(79);
116        let image = make_test_bin();
117        let tempfile = TempFile::new().unwrap();
118        let mut tempfile = tempfile.into_file();
119        tempfile.write_all(&image).unwrap();
120
121        // Need to reset the cursor to read initrd properly.
122        tempfile.seek(SeekFrom::Start(0)).unwrap();
123        let res = InitrdConfig::from_file(&gm, tempfile);
124        assert!(matches!(res, Err(InitrdError::Address)), "{:?}", res);
125    }
126
127    #[test]
128    fn test_load_initrd_unaligned() {
129        let image = vec![1, 2, 3, 4];
130        let tempfile = TempFile::new().unwrap();
131        let mut tempfile = tempfile.into_file();
132        tempfile.write_all(&image).unwrap();
133        let gm = single_region_mem_at(GUEST_PAGE_SIZE as u64 + 1, image.len() * 2);
134
135        // Need to reset the cursor to read initrd properly.
136        tempfile.seek(SeekFrom::Start(0)).unwrap();
137        let res = InitrdConfig::from_file(&gm, tempfile);
138        assert!(matches!(res, Err(InitrdError::Address)), "{:?}", res);
139    }
140}
vmm/initrd.rs

vmm/
initrd.rs
