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liminix/pkgs/preinit/default.nix

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rewrite preinit as very small C program By using the kernel "nolibc" header to avoid requiring a C library, we can bring the initramfs size to around 4k This does involve a tiny bit of inline mips assembly which I'm not sure about. gcc seems unwilling to generate the code to load $gp at function entry of main(), so we do it by hand - but I'd rather find out why gcc doesn't.
2023-04-15 18:35:02 +02:00
{
stdenv
, fetchzip
, gdb
}:
let kernel = fetchzip {
name = "linux";
url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.71.tar.gz";
hash = "sha256-pq6QNa0PJVeheaZkuvAPD0rLuEeKrViKk65dz+y4kqo=";
};
in
stdenv.mkDerivation {
name = "preinit";
src = ./.;
preinit: disable nolibc - it stopped working with 22.11->23.05 - linking statically against musl is about 17k, so this is costing us 11k or so
2023-06-19 00:02:08 +02:00
# NIX_DEBUG=2;
rewrite preinit as very small C program By using the kernel "nolibc" header to avoid requiring a C library, we can bring the initramfs size to around 4k This does involve a tiny bit of inline mips assembly which I'm not sure about. gcc seems unwilling to generate the code to load $gp at function entry of main(), so we do it by hand - but I'd rather find out why gcc doesn't.
2023-04-15 18:35:02 +02:00
hardeningDisable = [ "all" ];
preinit: disable nolibc - it stopped working with 22.11->23.05 - linking statically against musl is about 17k, so this is costing us 11k or so
2023-06-19 00:02:08 +02:00
CFLAGS = "-Os -static -DPREINIT_USE_LIBC -fno-stack-protector -fpic -fPIC -I ./ -I ${kernel}/tools/include/nolibc";
rewrite preinit as very small C program By using the kernel "nolibc" header to avoid requiring a C library, we can bring the initramfs size to around 4k This does involve a tiny bit of inline mips assembly which I'm not sure about. gcc seems unwilling to generate the code to load $gp at function entry of main(), so we do it by hand - but I'd rather find out why gcc doesn't.
2023-04-15 18:35:02 +02:00
postBuild = ''
$STRIP --remove-section=.note --remove-section=.comment preinit
preinit: disable nolibc - it stopped working with 22.11->23.05 - linking statically against musl is about 17k, so this is costing us 11k or so
2023-06-19 00:02:08 +02:00
ls -l preinit
rewrite preinit as very small C program By using the kernel "nolibc" header to avoid requiring a C library, we can bring the initramfs size to around 4k This does involve a tiny bit of inline mips assembly which I'm not sure about. gcc seems unwilling to generate the code to load $gp at function entry of main(), so we do it by hand - but I'd rather find out why gcc doesn't.
2023-04-15 18:35:02 +02:00
'';
makeFlags = ["preinit"];
stripAllList = ["bin"];
installPhase = ''
mkdir -p $out/bin
cp preinit $out/bin
'';
}
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