lanzaboote/rust/tool/src/generation.rs

171 lines
5.3 KiB
Rust

use std::fmt;
use std::fs;
use std::os::unix::fs::MetadataExt;
use std::path::{Path, PathBuf};
use anyhow::{anyhow, Context, Result};
use bootspec::generation::Generation as BootspecGeneration;
use bootspec::BootJson;
use bootspec::SpecialisationName;
/// (Possibly) extended Bootspec.
///
/// This struct currently does not have any extensions. We keep it around so that extension becomes
/// easy if/when we have to do it.
#[derive(Debug, Clone)]
pub struct ExtendedBootJson {
pub bootspec: BootJson,
}
/// A system configuration.
///
/// Can be built from a GenerationLink.
///
/// NixOS represents a generation as a symlink to a toplevel derivation. This toplevel derivation
/// contains most of the information necessary to install the generation onto the EFI System
/// Partition. The only information missing is the version number which is encoded in the file name
/// of the generation link.
#[derive(Debug)]
pub struct Generation {
/// Profile symlink index
version: u64,
/// Top-level specialisation name
specialisation_name: Option<SpecialisationName>,
/// Top-level extended boot specification
pub spec: ExtendedBootJson,
}
impl Generation {
pub fn from_link(link: &GenerationLink) -> Result<Self> {
let bootspec_path = link.path.join("boot.json");
let generation: BootspecGeneration = serde_json::from_slice(
&fs::read(bootspec_path).context("Failed to read bootspec file")?,
)
.context("Failed to parse bootspec json")?;
let bootspec: BootJson = generation
.try_into()
.map_err(|err: &'static str| anyhow!(err))?;
Ok(Self {
version: link.version,
specialisation_name: None,
spec: ExtendedBootJson { bootspec },
})
}
pub fn specialise(&self, name: &SpecialisationName, bootspec: &BootJson) -> Result<Self> {
Ok(Self {
version: self.version,
specialisation_name: Some(name.clone()),
spec: ExtendedBootJson {
bootspec: bootspec.clone(),
},
})
}
pub fn is_specialised(&self) -> Option<SpecialisationName> {
self.specialisation_name.clone()
}
/// Describe the generation in a single line.
///
/// Emulates how NixOS's current systemd-boot-builder.py describes generations so that the user
/// interface remains similar.
///
/// This is currently implemented by poking around the filesystem to find the necessary data.
/// Ideally, the needed data should be included in the bootspec.
pub fn describe(&self) -> Result<String> {
let toplevel = &self.spec.bootspec.toplevel.0;
let nixos_version = fs::read_to_string(toplevel.join("nixos-version"))
.unwrap_or_else(|_| String::from("Unknown"));
let kernel_version =
read_kernel_version(toplevel).context("Failed to read kernel version.")?;
let build_time = read_build_time(toplevel).unwrap_or_else(|_| String::from("Unknown"));
Ok(format!(
"Generation {} NixOS {}, Linux Kernel {}, Built on {}",
self.version, nixos_version, kernel_version, build_time
))
}
}
impl fmt::Display for Generation {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}", self.version)
}
}
/// Read the kernel version from the name of a directory inside the toplevel directory.
///
/// The path looks something like this: $toplevel/kernel-modules/lib/modules/6.1.1
fn read_kernel_version(toplevel: &Path) -> Result<String> {
let path = fs::read_dir(toplevel.join("kernel-modules/lib/modules"))?
.into_iter()
.next()
.transpose()?
.map(|x| x.path())
.with_context(|| format!("Failed to read directory {:?}.", toplevel))?;
let file_name = path
.file_name()
.and_then(|x| x.to_str())
.context("Failed to convert path to filename string.")?;
Ok(String::from(file_name))
}
fn read_build_time(path: &Path) -> Result<String> {
let build_time = time::OffsetDateTime::from_unix_timestamp(fs::metadata(path)?.mtime())?
.date()
.to_string();
Ok(build_time)
}
/// A link pointing to a generation.
///
/// Can be built from a symlink in /nix/var/nix/profiles/ alone because the name of the
/// symlink encodes the version number.
#[derive(Debug)]
pub struct GenerationLink {
pub version: u64,
pub path: PathBuf,
}
impl GenerationLink {
pub fn from_path(path: impl AsRef<Path>) -> Result<Self> {
Ok(Self {
version: parse_version(&path).context("Failed to parse version")?,
path: PathBuf::from(path.as_ref()),
})
}
}
/// Parse version number from a path.
///
/// Expects a path in the format of "system-{version}-link".
fn parse_version(path: impl AsRef<Path>) -> Result<u64> {
let generation_version = path
.as_ref()
.file_name()
.and_then(|x| x.to_str())
.and_then(|x| x.split('-').nth(1))
.and_then(|x| x.parse::<u64>().ok())
.with_context(|| format!("Failed to extract version from: {:?}", path.as_ref()))?;
Ok(generation_version)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn parse_version_correctly() {
let path = Path::new("system-2-link");
let parsed_version = parse_version(path).unwrap();
assert_eq!(parsed_version, 2,);
}
}