5dd0c6e3c0
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.
30 lines
682 B
Nix
30 lines
682 B
Nix
{
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stdenv
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, fetchzip
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, gdb
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}:
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let kernel = fetchzip {
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name = "linux";
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url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.71.tar.gz";
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hash = "sha256-pq6QNa0PJVeheaZkuvAPD0rLuEeKrViKk65dz+y4kqo=";
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};
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in
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stdenv.mkDerivation {
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name = "preinit";
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src = ./.;
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# NIX_DEBUG=2;
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hardeningDisable = [ "all" ];
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CFLAGS = "-Os -nostartfiles -nostdlib -fno-stack-protector -fpic -fPIC -I ./ -I ${kernel}/tools/include/nolibc";
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postBuild = ''
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$STRIP --remove-section=.note --remove-section=.comment preinit
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'';
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makeFlags = ["preinit"];
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stripAllList = ["bin"];
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installPhase = ''
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mkdir -p $out/bin
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cp preinit $out/bin
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'';
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}
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