Skip to content

Commit

Permalink
systemd: rewrite comments
Browse files Browse the repository at this point in the history 
In order to be more readable and fit the the 80-column limit.
  • Loading branch information
@AndersonTorres
AndersonTorres committed Jan 24, 2024
1 parent 1a3a540 commit 92dfeb7
Showing 1 changed file with 61 additions and 44 deletions.
105 changes: 61 additions & 44 deletions pkgs/os-specific/linux/systemd/default.nix
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,16 +68,17 @@
, libpwquality
, qrencode

# the (optional) BPF feature requires bpftool, libbpf, clang and llvm-strip to be available during build time.
# the (optional) BPF feature requires bpftool, libbpf, clang and llvm-strip to
# be available during build time.
# Only libbpf should be a runtime dependency.
# Note: llvmPackages is explicitly taken from buildPackages instead of relying
# on splicing. Splicing will evaluate the adjacent (pkgsHostTarget) llvmPackages
# which is sometimes problematic: llvmPackages.clang looks at targetPackages.stdenv.cc
# which, in the unfortunate case of pkgsCross.ghcjs, `throw`s. If we explicitly
# take buildPackages.llvmPackages, this is no problem because
# `buildPackages.targetPackages.stdenv.cc == stdenv.cc` relative to us. Working
# around this is important, because systemd is in the dependency closure of
# GHC via emscripten and jdk.
# which, in the unfortunate case of pkgsCross.ghcjs, `throw`s. If we
# explicitly take buildPackages.llvmPackages, this is no problem because
# `buildPackages.targetPackages.stdenv.cc == stdenv.cc` relative to
# us. Working around this is important, because systemd is in the dependency
# closure of GHC via emscripten and jdk.
, bpftools
, libbpf

Expand All @@ -93,23 +94,27 @@
&& !stdenv.hostPlatform.isMusl
# "Unknown 64-bit data model"
&& !stdenv.hostPlatform.isRiscV32
, withCompression ? true # adds bzip2, lz4, xz and zstd
# adds bzip2, lz4, xz and zstd
, withCompression ? true
, withCoredump ? true
, withCryptsetup ? true
, withRepart ? true
, withDocumentation ? true
, withEfi ? stdenv.hostPlatform.isEfi
, withFido2 ? true
, withFirstboot ? false # conflicts with the NixOS /etc management
# conflicts with the NixOS /etc management
, withFirstboot ? false
, withHomed ? !stdenv.hostPlatform.isMusl
, withHostnamed ? true
, withHwdb ? true
, withImportd ? !stdenv.hostPlatform.isMusl
, withIptables ? true
, withKmod ? true
, withLibBPF ? lib.versionAtLeast buildPackages.llvmPackages.clang.version "10.0"
&& (stdenv.hostPlatform.isAarch -> lib.versionAtLeast stdenv.hostPlatform.parsed.cpu.version "6") # assumes hard floats
&& !stdenv.hostPlatform.isMips64 # see https://github.com/NixOS/nixpkgs/pull/194149#issuecomment-1266642211
# assumes hard floats
&& (stdenv.hostPlatform.isAarch -> lib.versionAtLeast stdenv.hostPlatform.parsed.cpu.version "6")
# see https://github.com/NixOS/nixpkgs/pull/194149#issuecomment-1266642211
&& !stdenv.hostPlatform.isMips64
# can't find gnu/stubs-32.h
&& (stdenv.hostPlatform.isPower64 -> stdenv.hostPlatform.isBigEndian)
# https://reviews.llvm.org/D43106#1019077
Expand Down Expand Up @@ -139,7 +144,8 @@
, withTimedated ? true
, withTimesyncd ? true
, withTpm2Tss ? true
, withUkify ? false # adds python to closure which is too much by default
# adds python to closure which is too much by default
, withUkify ? false
, withUserDb ? true
, withUtmp ? !stdenv.hostPlatform.isMusl
, withVmspawn ? true
Expand All @@ -148,7 +154,7 @@
# build only libudev and libsystemd
, buildLibsOnly ? false

# name argument
# yes, pname is an argument here
, pname ? "systemd"

, libxslt
Expand All @@ -171,7 +177,8 @@ let
wantGcrypt = withResolved || withImportd;
version = "255.2";

# Bump this variable on every (major) version change. See below (in the meson options list) for why.
# Use the command below to update `releaseTimestamp` on every (major) version
# change. More details in the commentary at mesonFlags.
# command:
# $ curl -s https://api.github.com/repos/systemd/systemd/releases/latest | \
# jq '.created_at|strptime("%Y-%m-%dT%H:%M:%SZ")|mktime'
Expand All @@ -189,11 +196,14 @@ stdenv.mkDerivation (finalAttrs: {
hash = "sha256-8SfJY/pcH4yrDeJi0GfIUpetTbpMwyswvSu+RSfgqfY=";
};

# On major changes, or when otherwise required, you *must* reformat the patches,
# `git am path/to/00*.patch` them into a systemd worktree, rebase to the more recent
# systemd version, and export the patches again via
# `git -c format.signoff=false format-patch v${version} --no-numbered --zero-commit --no-signature`.
# Use `find . -name "*.patch" | sort` to get an up-to-date listing of all patches
# On major changes, or when otherwise required, you *must* :
# 1. reformat the patches,
# 2. `git am path/to/00*.patch` them into a systemd worktree,
# 3. rebase to the more recent systemd version,
# 4. and export the patches again via
# `git -c format.signoff=false format-patch v${version} --no-numbered --zero-commit --no-signature`.
# Use `find . -name "*.patch" | sort` to get an up-to-date listing of all
# patches
patches = [
./0001-Start-device-units-for-uninitialised-encrypted-devic.patch
./0002-Don-t-try-to-unmount-nix-or-nix-store.patch
Expand Down Expand Up @@ -261,8 +271,8 @@ stdenv.mkDerivation (finalAttrs: {
"$out/lib/systemd/boot/efi"
'' + (
let
# The following patches references to dynamic libraries to ensure that
# all the features that are implemented via dlopen(3) are available (or
# The following patches references to dynamic libraries to ensure that all
# the features that are implemented via dlopen(3) are available (or
# explicitly deactivated) by pointing dlopen to the absolute store path
# instead of relying on the linkers runtime lookup code.
#
Expand All @@ -274,11 +284,11 @@ stdenv.mkDerivation (finalAttrs: {
# found` when using e.g. --grep with journalctl. Those errors should
# become less unexpected now.
#
# There are generally two classes of dlopen(3) calls. Those that we want to
# support and those that should be deactivated / unsupported. This change
# enforces that we handle all dlopen calls explicitly. Meaning: There is
# not a single dlopen call in the source code tree that we did not
# explicitly handle.
# There are generally two classes of dlopen(3) calls. Those that we want
# to support and those that should be deactivated / unsupported. This
# change enforces that we handle all dlopen calls explicitly. Meaning:
# There is not a single dlopen call in the source code tree that we did
# not explicitly handle.
#
# In order to do this we introduced a list of attributes that maps from
# shared object name to the package that contains them. The package can be
Expand All @@ -287,7 +297,8 @@ stdenv.mkDerivation (finalAttrs: {
# path location).
#
# To get a list of dynamically loaded libraries issue something like
# `grep -ri '"lib[a-zA-Z0-9-]*\.so[\.0-9a-zA-z]*"'' $src` and update the below list.
# `grep -ri '"lib[a-zA-Z0-9-]*\.so[\.0-9a-zA-z]*"'' $src`
# and update the list below.
dlopenLibs =
let
opt = condition: pkg: if condition then pkg else null;
Expand Down Expand Up @@ -373,7 +384,8 @@ stdenv.mkDerivation (finalAttrs: {
# patch all the dlopen calls to contain absolute paths to the libraries
lib.concatMapStringsSep "\n" patchDlOpen dlopenLibs
)
# finally ensure that there are no left-over dlopen calls (or rather strings pointing to shared libraries) that we didn't handle
# finally ensure that there are no left-over dlopen calls (or rather strings
# pointing to shared libraries) that we didn't handle
+ ''
if grep -qr '"lib[a-zA-Z0-9-]*\.so[\.0-9a-zA-z]*"' src; then
echo "Found unhandled dynamic library calls: "
Expand Down Expand Up @@ -460,12 +472,13 @@ stdenv.mkDerivation (finalAttrs: {
mesonFlags = [
# Options

# We bump this variable on every (major) version change to ensure
# that we have known-good value for a timestamp that is in the (not so distant) past.
# This serves as a lower bound for valid system timestamps during startup. Systemd will
# reset the system timestamp if this date is +- 15 years from the system time.
# We bump this attribute on every (major) version change to ensure that we
# have known-good value for a timestamp that is in the (not so distant)
# past. This serves as a lower bound for valid system timestamps during
# startup. Systemd will reset the system timestamp if this date is +- 15
# years from the system time.
# See the systemd v250 release notes for further details:
# https://github.com/systemd/systemd/blob/60e930fc3e6eb8a36fbc184773119eb8d2f30364/NEWS#L258-L266
# https://github.com/systemd/systemd/blob/60e930fc3e6eb8a36fbc184773119eb8d2f30364/NEWS#L258-L266
(lib.mesonOption "time-epoch" releaseTimestamp)

(lib.mesonOption "version-tag" version)
Expand Down Expand Up @@ -615,8 +628,13 @@ stdenv.mkDerivation (finalAttrs: {
];
preConfigure =
let
# A list of all the runtime binaries that the systemd executables, tests and libraries are referencing in their source code, scripts and unit files.
# As soon as a dependency isn't required anymore we should remove it from the list. The `where` attribute for each of the replacement patterns must be exhaustive. If another (unhandled) case is found in the source code the build fails with an error message.
# A list of all the runtime binaries referenced by the source code (plus
# scripts and unit files) of systemd executables, tests and libraries.
# As soon as a dependency is lo longer required we should remove it from
# the list.
# The `where` attribute for each of the replacement patterns must be
# exhaustive. If another (unhandled) case is found in the source code the
# build fails with an error message.
binaryReplacements = [
{ search = "/usr/bin/getent"; replacement = "${getent}/bin/getent"; where = [ "src/nspawn/nspawn-setuid.c" ]; }

Expand Down Expand Up @@ -777,11 +795,11 @@ stdenv.mkDerivation (finalAttrs: {
mv $out/lib/sysusers.d $out/example
'';

# Avoid *.EFI binary stripping. At least on aarch64-linux strip
# removes too much from PE32+ files:
# Avoid *.EFI binary stripping.
# At least on aarch64-linux strip removes too much from PE32+ files:
# https://github.com/NixOS/nixpkgs/issues/169693
# The hack is to move EFI file out of lib/ before doStrip
# run and return it after doStrip run.
# The hack is to move EFI file out of lib/ before doStrip run and return it
# after doStrip run.
preFixup = lib.optionalString withBootloader ''
mv $out/lib/systemd/boot/efi $out/dont-strip-me
'';
Expand All @@ -806,12 +824,11 @@ stdenv.mkDerivation (finalAttrs: {
(builtins.map (p: p.__spliced.buildHost or p) finalAttrs.nativeBuildInputs);

passthru = {
# The interface version prevents NixOS from switching to an
# incompatible systemd at runtime. (Switching across reboots is
# fine, of course.) It should be increased whenever systemd changes
# in a backwards-incompatible way. If the interface version of two
# systemd builds is the same, then we can switch between them at
# runtime; otherwise we can't and we need to reboot.
# The `interfaceVersion` attribute below points out the incompatibilities
# between systemd versions. When the new systemd build is
# backwards-compatible with the previous one, then they can be switched at
# runtime (the reboot being optional in this case); otherwise, a reboot is
# needed - and therefore `interfaceVersion` should be incremented.
interfaceVersion = 2;

inherit withCryptsetup withHostnamed withImportd withKmod withLocaled withMachined withPortabled withTimedated withUtmp util-linux kmod kbd;
Expand Down

0 comments on commit 92dfeb7

Please sign in to comment.