feat(scripts): Add get-debian-linux-config

Downloads a linux-image package and extracts the config file from /boot.

Signed-off-by: Loïc Minier <[email protected]>

Author: lool

scripts/get-debian-linux-config.py

@@ -0,0 +1,215 @@
+#!/usr/bin/env python3
+
+import argparse
+import re
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+ARCH = "arm64"
+
+
+def run(cmd, **kwargs):
+    """Run command with verbose logging"""
+    if isinstance(cmd, str):
+        print(f"+ {cmd}", file=sys.stderr)
+    else:
+        print("+", " ".join(cmd), file=sys.stderr)
+    return subprocess.run(cmd, check=True, **kwargs)
+
+
+def ensure_dirs(*paths):
+    for path in paths:
+        Path(path).mkdir(parents=True, exist_ok=True)
+
+
+def write_file(path: Path, content: str):
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(content, encoding="utf-8")
+
+
+def setup_isolated_apt_root(root: Path, sources_content: str, arch: str):
+    etc_apt_sources_list_d = root / "etc" / "apt" / "sources.list.d"
+    var_lib_apt_lists = root / "var" / "lib" / "apt" / "lists"
+
+    ensure_dirs(
+        etc_apt_sources_list_d,
+        var_lib_apt_lists / "partial",
+    )
+
+    write_file(etc_apt_sources_list_d / "sources.sources", sources_content)
+
+
+def apt_env_options(root: Path, arch: str):
+    options = [
+        f"Dir={root}",
+        f"APT::Architecture={arch}",
+        "Acquire::Languages=none",
+        "Debug::NoLocking=false",
+    ]
+    result = []
+    for option in options:
+        result.extend(["-o", option])
+    return result
+
+
+def apt_update(root: Path, arch: str):
+    opts = apt_env_options(root, arch)
+    run(["apt-get", *opts, "update"])
+
+
+def resolve_versioned_kernel_pkg(
+    root: Path, arch: str, package_name: str
+) -> str:
+    opts = apt_env_options(root, arch)
+    res = run(
+        ["apt-cache", *opts, "depends", package_name],
+        capture_output=True,
+        text=True,
+    )
+
+    depends_pattern = re.compile(r"^\s*Depends:\s+(linux-image-\S+)")
+    candidates = [
+        match.group(1)
+        for line in res.stdout.splitlines()
+        if (match := depends_pattern.match(line))
+    ]
+
+    # If no candidates found, assume the provided package is already specific
+    if not candidates:
+        return package_name
+
+    # Prefer non-unsigned packages
+    for pkg in candidates:
+        if "-unsigned-" not in pkg:
+            return pkg
+
+    # Fall back to first candidate if all are unsigned
+    return candidates[0]
+
+
+def apt_download_pkg(
+    root: Path, arch: str, pkg: str, download_dir: Path
+) -> Path:
+    opts = apt_env_options(root, arch)
+    ensure_dirs(download_dir)
+    run(["apt-get", *opts, "download", pkg], cwd=str(download_dir))
+
+    debs = sorted(download_dir.glob(f"{pkg}_*.deb"))
+    if not debs:
+        debs = sorted(download_dir.glob(f"{pkg}*.deb"))
+    if not debs:
+        raise SystemExit(
+            f"Download succeeded but .deb not found for {pkg} in {download_dir}"
+        )
+    return debs[-1]
+
+
+def extract_kernel_config_from_deb(deb_path: Path, output: Path):
+    # List content to find the exact config path using subprocess pipeline
+    with subprocess.Popen(
+        ["dpkg-deb", "--fsys-tarfile", str(deb_path)], stdout=subprocess.PIPE
+    ) as dpkg_proc:
+        tar_result = subprocess.run(
+            ["tar", "-t"],
+            stdin=dpkg_proc.stdout,
+            capture_output=True,
+            text=True,
+            check=True,
+        )
+
+    paths = [line.strip() for line in tar_result.stdout.splitlines()]
+    # Look for './boot/config-*' (tar usually prefixes './')
+    cfg_candidates = [
+        path for path in paths if path.startswith("./boot/config-")
+    ]
+    if not cfg_candidates:
+        raise SystemExit(f"No ./boot/config-* found in {deb_path}")
+    cfg_path = cfg_candidates[0]
+    print(f"# Found config path in deb: {cfg_path}", file=sys.stderr)
+
+    # Stream-extract the config using subprocess pipeline
+    with subprocess.Popen(
+        ["dpkg-deb", "--fsys-tarfile", str(deb_path)], stdout=subprocess.PIPE
+    ) as dpkg_proc:
+        tar_result = subprocess.run(
+            ["tar", "-xO", cfg_path],
+            stdin=dpkg_proc.stdout,
+            capture_output=True,
+            check=True,
+        )
+
+    # Write the extracted config to output file
+    output.write_bytes(tar_result.stdout)
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Download a linux-image package and extract its config"
+    )
+    parser.add_argument(
+        "--sources", required=True, help="path to deb822 style sources file"
+    )
+    parser.add_argument(
+        "--output",
+        default=None,
+        help="output file (default: <resolved-pkg>.config)",
+    )
+    parser.add_argument(
+        "--debug",
+        action="store_true",
+        help="keep working temporary directory",
+    )
+    parser.add_argument(
+        "--package",
+        default=f"linux-image-{ARCH}",
+        help=f"package or metapackage name (default: linux-image-{ARCH})",
+    )
+    args = parser.parse_args()
+
+    sources_path = Path(args.sources)
+    if not sources_path.exists():
+        sys.exit(f"Error: sources file '{args.sources}' not found")
+
+    try:
+        sources_content = sources_path.read_text(encoding="utf-8")
+    except Exception as e:
+        sys.exit(f"Error reading sources file '{args.sources}': {e}")
+
+    top_tmp = tempfile.TemporaryDirectory(
+        prefix="get-debian-linux-config-", delete=not (args.debug)
+    )
+    work_root = Path(top_tmp.name)
+    apt_root = work_root / "aptroot"
+    dl_dir = work_root / "downloads"
+
+    print(
+        f"==> Setting up isolated APT environment in {work_root}...",
+        file=sys.stderr,
+    )
+    setup_isolated_apt_root(apt_root, sources_content, ARCH)
+
+    print("\n==> Updating package lists...", file=sys.stderr)
+    apt_update(apt_root, ARCH)
+
+    print("\n==> Resolving kernel package...", file=sys.stderr)
+    image_pkg = resolve_versioned_kernel_pkg(apt_root, ARCH, args.package)
+    print(f"==> Resolved kernel package: {image_pkg}", file=sys.stderr)
+
+    print(f"\n==> Downloading package: {image_pkg}", file=sys.stderr)
+    deb_path = apt_download_pkg(apt_root, ARCH, image_pkg, dl_dir)
+
+    print(f"\n==> Extracting config from {deb_path.name}", file=sys.stderr)
+    output_path = (
+        Path(args.output)
+        if args.output
+        else Path.cwd() / f"{image_pkg}.config"
+    )
+    extract_kernel_config_from_deb(deb_path, output_path)
+
+    print(f"\nWrote: {output_path}")
+
+
+if __name__ == "__main__":
+    main()