pyrox.dev
1# Create an initramfs containing the closure of the specified
2# file system objects. An initramfs is used during the initial
3# stages of booting a Linux system. It is loaded by the boot loader
4# along with the kernel image. It's supposed to contain everything
5# (such as kernel modules) necessary to allow us to mount the root
6# file system. Once the root file system is mounted, the `real' boot
7# script can be called.
8#
9# An initramfs is a cpio archive, and may be compressed with a number
10# of algorithms.
11let
12 # Some metadata on various compression programs, relevant to naming
13 # the initramfs file and, if applicable, generating a u-boot image
14 # from it.
15 compressors = import ./initrd-compressor-meta.nix;
16 # Get the basename of the actual compression program from the whole
17 # compression command, for the purpose of guessing the u-boot
18 # compression type and filename extension.
19 compressorName = fullCommand: builtins.elemAt (builtins.match "([^ ]*/)?([^ ]+).*" fullCommand) 1;
20in
21{ stdenvNoCC, perl, libarchive, ubootTools, lib, pkgsBuildHost
22# Name of the derivation (not of the resulting file!)
23, name ? "initrd"
24
25# Program used to compress the cpio archive; use "cat" for no compression.
26# This can also be a function which takes a package set and returns the path to the compressor,
27# such as `pkgs: "${pkgs.lzop}/bin/lzop"`.
28, compressor ? "gzip"
29, _compressorFunction ?
30 if lib.isFunction compressor then compressor
31 else if ! builtins.hasContext compressor && builtins.hasAttr compressor compressors then compressors.${compressor}.executable
32 else _: compressor
33, _compressorExecutable ? _compressorFunction pkgsBuildHost
34, _compressorName ? compressorName _compressorExecutable
35, _compressorMeta ? compressors.${_compressorName} or {}
36
37# List of arguments to pass to the compressor program, or null to use its defaults
38, compressorArgs ? null
39, _compressorArgsReal ? if compressorArgs == null then _compressorMeta.defaultArgs or [] else compressorArgs
40
41# Filename extension to use for the compressed initramfs. This is
42# included for clarity, but $out/initrd will always be a symlink to
43# the final image.
44# If this isn't guessed, you may want to complete the metadata above and send a PR :)
45, extension ? _compressorMeta.extension or
46 (throw "Unrecognised compressor ${_compressorName}, please specify filename extension")
47
48# List of { object = path_or_derivation; symlink = "/path"; }
49# The paths are copied into the initramfs in their nix store path
50# form, then linked at the root according to `symlink`.
51, contents
52
53# List of uncompressed cpio files to prepend to the initramfs. This
54# can be used to add files in specified paths without them becoming
55# symlinks to store paths.
56, prepend ? []
57
58# Whether to wrap the initramfs in a u-boot image.
59, makeUInitrd ? stdenvNoCC.hostPlatform.linux-kernel.target == "uImage"
60
61# If generating a u-boot image, the architecture to use. The default
62# guess may not align with u-boot's nomenclature correctly, so it can
63# be overridden.
64# See https://gitlab.denx.de/u-boot/u-boot/-/blob/9bfb567e5f1bfe7de8eb41f8c6d00f49d2b9a426/common/image.c#L81-106 for a list.
65, uInitrdArch ? stdenvNoCC.hostPlatform.linuxArch
66
67# The name of the compression, as recognised by u-boot.
68# See https://gitlab.denx.de/u-boot/u-boot/-/blob/9bfb567e5f1bfe7de8eb41f8c6d00f49d2b9a426/common/image.c#L195-204 for a list.
69# If this isn't guessed, you may want to complete the metadata above and send a PR :)
70, uInitrdCompression ? _compressorMeta.ubootName or
71 (throw "Unrecognised compressor ${_compressorName}, please specify uInitrdCompression")
72}:
73let
74 # !!! Move this into a public lib function, it is probably useful for others
75 toValidStoreName = x: with builtins;
76 lib.concatStringsSep "-" (filter (x: !(isList x)) (split "[^a-zA-Z0-9_=.?-]+" x));
77
78in stdenvNoCC.mkDerivation rec {
79 inherit name makeUInitrd extension uInitrdArch prepend;
80
81 ${if makeUInitrd then "uInitrdCompression" else null} = uInitrdCompression;
82
83 builder = ./make-initrd.sh;
84
85 nativeBuildInputs = [ perl libarchive ]
86 ++ lib.optional makeUInitrd ubootTools;
87
88 compress = "${_compressorExecutable} ${lib.escapeShellArgs _compressorArgsReal}";
89
90 # Pass the function through, for reuse in append-initrd-secrets. The
91 # function is used instead of the string, in order to support
92 # cross-compilation (append-initrd-secrets running on a different
93 # architecture than what the main initramfs is built on).
94 passthru = {
95 compressorExecutableFunction = _compressorFunction;
96 compressorArgs = _compressorArgsReal;
97 };
98
99 # !!! should use XML.
100 objects = map (x: x.object) contents;
101 symlinks = map (x: x.symlink) contents;
102 suffices = map (x: if x ? suffix then x.suffix else "none") contents;
103
104 # For obtaining the closure of `contents'.
105 # Note: we don't use closureInfo yet, as that won't build with nix-1.x.
106 # See #36268.
107 exportReferencesGraph =
108 lib.zipListsWith
109 (x: i: [("closure-${toValidStoreName (baseNameOf x.symlink)}-${toString i}") x.object])
110 contents
111 (lib.range 0 (lib.length contents - 1));
112 pathsFromGraph = ./paths-from-graph.pl;
113}