feat: handle hermit images + config nested in image

Author: fogti

Cargo.lock

@@ -1,4 +1,5 @@
 [workspace]
+members = ["hermit-image-reader", "uhyve-interface"]
 exclude = ["tests/test-kernels", "hermit-rs", "hermit-rs/*", "kernel"]
 
 [package]
@@ -51,6 +52,7 @@ env_logger = "0.11"
 gdbstub = "0.7"
 gdbstub_arch = "0.3"
 hermit-entry = { version = "0.10.5", features = ["loader"] }
+hermit-image-reader = { version = "0.1", path = "hermit-image-reader" }
 libc = "0.2"
 log = "0.4"
 mac_address = "1.1"

Cargo.toml

@@ -0,0 +1,42 @@
+[package]
+name = "hermit-image-reader"
+version = "0.1.0"
+edition = "2024"
+license = "MIT OR Apache-2.0"
+
+[features]
+std = ["compression/std"]
+
+[dependencies]
+
+[dependencies.byte-unit]
+version = "5"
+default-features = false
+features = ["byte", "serde"]
+
+[dependencies.compression]
+version = "0.1"
+default-features = false
+features = ["gzip"]
+
+[dependencies.num-traits]
+version = "0.2"
+default-features = false
+
+[dependencies.serde]
+version = "1"
+default-features = false
+features = ["alloc", "derive"]
+
+[dependencies.toml]
+version = "0.9"
+default-features = false
+features = ["parse", "serde"]
+
+[dependencies.yoke]
+version = "0.8"
+default-features = false
+features = ["derive"]
+
+[dev-dependencies]
+proptest = "1.9.0"

hermit-image-reader/Cargo.toml

@@ -0,0 +1 @@
+../LICENSE-APACHE

hermit-image-reader/LICENSE-APACHE

@@ -0,0 +1 @@
+../LICENSE-MIT

hermit-image-reader/LICENSE-MIT

@@ -0,0 +1,19 @@
+# hermit-image-reader
+
+This Rust crate implements a basic reader for Hermit images.
+Overall, these are just `.tar.gz` (i.e. gzipped tar) files.
+
+For performance reasons, it should be preferred to put the config and kernel
+as the first two entries of the image (tar files don't have any sorting or index,
+except that normally, the latest entry of the file takes precedence).
+If this condition is not adhered to, some hermit / uhyve tools might refuse
+to work with the image, or emit a warning.
+
+They contain at least 2 special entries:
+* The config file (in TOML format), at `hermit_config.toml` in the image root.
+  The expected entries are described in the crate documentation in `hermit_image_reader::config::Config`.
+* A Hermit Kernel ELF file, whose path is specified in the config.
+
+The image itself is mapped (from the Hermit kernel perspective) into a path
+(`mount_point`) specified in the config file.
+

hermit-image-reader/README.md

@@ -0,0 +1,41 @@
+fn main() {
+	for f in std::env::args().skip(1) {
+		println!("# File {}:", f);
+		let data = std::fs::read(f).expect("unable to read image file");
+		let decompressed = hermit_image_reader::decompress_image(&data[..])
+			.expect("unable to decompress image file");
+		for i in hermit_image_reader::ImageParser::new(&decompressed[..]) {
+			let i = i.expect("unable to read image entry");
+			print!("  Entry ");
+			let maybe_name = i.name.try_as_str();
+			if let Some(name) = maybe_name {
+				print!("{:?}", name);
+			} else {
+				print!("{:?}", i.name);
+			}
+			if i.is_exec {
+				print!(" (executable)");
+			}
+			print!(" :: {:?} :: starts with: ", i.value_range);
+			let value_start = &i.value[..core::cmp::min(20, i.value.len())];
+
+			if let Ok(value_start) = str::from_utf8(value_start) {
+				println!("{:?}", value_start);
+			} else {
+				println!("{:?}", value_start);
+			}
+
+			if let Some(name) = maybe_name {
+				if name
+					== hermit_image_reader::StrFilename::One(
+						hermit_image_reader::config::DEFAULT_CONFIG_NAME,
+					) {
+					match hermit_image_reader::config::parse(i.value) {
+						Ok(config) => println!("parsed config ::\n{:#?}\n", config),
+						Err(e) => eprintln!("failed to parse config :: {}", e),
+					}
+				}
+			}
+		}
+	}
+}