Code change:
Building powerpc kernels (I only tested pkgsCross.powernv, but examination of the kernel source code suggests to me that 32-bit powerpc, and well as big-endian 64-bit will be the same) is broken since This happens because on powerpc, the kernel target we install is vmlinux, rather than any derivative of it like zImage. The kernel build system will strip when creating such a derivative image, but because we install vmlinux directly, we get an unstripped image. This means the kernel contains references to its build directory, which since that PR will be the $dev output. AIUI, 64-bit POWER boots via kexec, and a zImage is a self-extracting kernel ELF image, so hopefully the fix would just be to switch the kernel target for powerpc to zImage, and things will work again, and POWER users will get smaller kernel images as a bonus. I'm not sure about 32-bit PowerPC, but this might be helpful. If we can't use an *Image target for any powerpc targets, there is also a target called that we could fall back to, but let's take the opportunity to evaluate whether anything else is more suitable first, when we're changing this stuff anyway. Apart from powerpc, the only we have that uses vmlinux as its kernel target is a MIPS machine called the Fuloong 2.0. I don't know how it boots.
I'll handle this. I don't have big-endian POWER hardware, but pointed out that qemu can probably boot a BE kernel under emulation at full hardware speeds. So if that works I can take care of the 32-bit POWER (which is mostly BE) too.
For reference, I managed to get a working kernel derivation for Power9 with Just setting building a zImage without fully stripping it afterwards wasn't enough. There still was a reference to in the debug info somewhere.
Yep, very plausible that there are other references as well. We had for x86 and RISC-V, although that specific issue didn't apply to other architectures.
I'll dig into this this evening. thank you for the tip! Also putting this link here so I don't lose it:
Verified (after fixing a bunch of other things) that is affected too. Thanks again for the heads up Working on a fix.
Edit: I meant to post this .
Fixed by

Related discussion:
text: (buildPackages.deterministic-uname.override { inherit modDirVersion; }) ] ++ optional (lib.versionAtLeast version "5.13") zstd; <del> config = let attrName = attr: "CONFIG_" + attr; in { isSet = attr: hasAttr (attrName attr) config; getValue = attr: if config.isSet attr then getAttr (attrName attr) config else null; isYes = attr: (config.getValue attr) == "y"; isNo = attr: (config.getValue attr) == "n"; isModule = attr: (config.getValue attr) == "m"; isEnabled = attr: (config.isModule attr) || (config.isYes attr); isDisabled = attr: (!(config.isSet attr)) || (config.isNo attr); } // config_; isModular = config.isYes "MODULES"; kernelConf = stdenv.hostPlatform.linux-kernel; target = kernelConf.target or "vmlinux"; buildDTBs = kernelConf.DTB or false; </del> <ins> drvAttrs = config_: kernelConf: kernelPatches: configfile: let config = let attrName = attr: "CONFIG_" + attr; in { isSet = attr: hasAttr (attrName attr) config; getValue = attr: if config.isSet attr then getAttr (attrName attr) config else null; isYes = attr: (config.getValue attr) == "y"; isNo = attr: (config.getValue attr) == "n"; isModule = attr: (config.getValue attr) == "m"; isEnabled = attr: (config.isModule attr) || (config.isYes attr); isDisabled = attr: (!(config.isSet attr)) || (config.isNo attr); } // config_; isModular = config.isYes "MODULES"; buildDTBs = kernelConf.DTB or false; in (optionalAttrs isModular { outputs = [ "out" "dev" ]; }) // { passthru = rec { inherit version modDirVersion config kernelPatches configfile moduleBuildDependencies stdenv; inherit isZen isHardened isLibre; isXen = lib.warn "The isXen attribute is deprecated. All Nixpkgs kernels that support it now have Xen enabled." true; baseVersion = lib.head (lib.splitString "-rc" version); kernelOlder = lib.versionOlder baseVersion; kernelAtLeast = lib.versionAtLeast baseVersion; }; inherit src; patches = map (p: p.patch) kernelPatches # Required for deterministic builds along with some postPatch magic. ++ optional (lib.versionOlder version "5.19") ./randstruct-provide-seed.patch ++ optional (lib.versionAtLeast version "5.19") ./randstruct-provide-seed-5.19.patch # Linux 5.12 marked certain PowerPC-only symbols as GPL, which breaks # OpenZFS; this was fixed in Linux 5.19 so we backport the fix # https://github.com/openzfs/zfs/pull/13367 ++ optional (lib.versionAtLeast version "5.12" && lib.versionOlder version "5.19" && stdenv.hostPlatform.isPower) (fetchpatch { url = "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/patch/?id=d9e5c3e9e75162f845880535957b7fd0b4637d23"; hash = "sha256-bBOyJcP6jUvozFJU0SPTOf3cmnTQ6ZZ4PlHjiniHXLU="; }); preUnpack = '' # The same preUnpack is used to build the configfile, # which does not have $dev. if [ -n "$dev" ]; then mkdir -p $dev/lib/modules/${modDirVersion} cd $dev/lib/modules/${modDirVersion} fi ''; postUnpack = '' mv -Tv "$sourceRoot" source 2>/dev/null || : export sourceRoot=$PWD/source ''; postPatch = '' sed -i Makefile -e 's|= depmod|= ${buildPackages.kmod}/bin/depmod|' # fixup for pre-5.4 kernels using the $(cd $foo && /bin/pwd) pattern # FIXME: remove when no longer needed substituteInPlace Makefile tools/scripts/Makefile.include --replace /bin/pwd pwd # Don't include a (random) NT_GNU_BUILD_ID, to make the build more deterministic. # This way kernels can be bit-by-bit reproducible depending on settings # (e.g. MODULE_SIG and SECURITY_LOCKDOWN_LSM need to be disabled). # See also https://kernelnewbies.org/BuildId sed -i Makefile -e 's|--build-id=[^ ]*|--build-id=none|' # Some linux-hardened patches now remove certain files in the scripts directory, so the file may not exist. [[ -f scripts/ld-version.sh ]] && patchShebangs scripts/ld-version.sh # Set randstruct seed to a deterministic but diversified value. Note: # we could have instead patched gen-random-seed.sh to take input from # the buildFlags, but that would require also patching the kernel's # toplevel Makefile to add a variable export. This would be likely to # cause future patch conflicts. for file in scripts/gen-randstruct-seed.sh scripts/gcc-plugins/gen-random-seed.sh; do if [ -f "$file" ]; then substituteInPlace "$file"  --replace NIXOS_RANDSTRUCT_SEED  $(echo ${randstructSeed}${src} ${placeholder "configfile"} | sha256sum | cut -d ' ' -f 1 | tr -d 'n') break fi done patchShebangs scripts # also patch arch-specific install scripts for i in $(find arch -name install.sh); do patchShebangs "$i" done ''; configurePhase = '' runHook preConfigure export buildRoot=$(mktemp -d) echo "manual-config configurePhase buildRoot=$buildRoot pwd=$PWD" if [ -f "$buildRoot/.config" ]; then echo "Could not link $buildRoot/.config : file exists" exit 1 fi ln -sv ${configfile} $buildRoot/.config # reads the existing .config file and prompts the user for options in # the current kernel source that are not found in the file. make $makeFlags "''${makeFlagsArray[@]}" oldconfig runHook postConfigure make $makeFlags "''${makeFlagsArray[@]}" prepare actualModDirVersion="$(cat $buildRoot/include/config/kernel.release)" if [ "$actualModDirVersion" != "${modDirVersion}" ]; then echo "Error: modDirVersion ${modDirVersion} specified in the Nix expression is wrong, it should be: $actualModDirVersion" exit 1 fi buildFlagsArray+=("KBUILD_BUILD_TIMESTAMP=$(date -u -d @$SOURCE_DATE_EPOCH)") cd $buildRoot ''; buildFlags = [ "DTC_FLAGS=-@" "KBUILD_BUILD_VERSION=1-NixOS" # Set by default in the kernel since a73619a845d5, # replicated here to apply to older versions. # Makes __FILE__ relative to the build directory. "KCPPFLAGS=-fmacro-prefix-map=$(sourceRoot)/=" ] ++ extraMakeFlags; installFlags = [ "INSTALL_PATH=$(out)" ] ++ (optional isModular "INSTALL_MOD_PATH=$(out)") ++ optionals buildDTBs ["dtbs_install" "INSTALL_DTBS_PATH=$(out)/dtbs"]; preInstall = let # All we really need to do here is copy the final image and System.map to $out, # and use the kernel's modules_install, firmware_install, dtbs_install, etc. targets # for the rest. Easy, right? # # Unfortunately for us, the obvious way of getting the built image path, # make -s image_name, does not work correctly, because some architectures # (*cough* aarch64 *cough*) change KBUILD_IMAGE on the fly in their install targets, # so we end up attempting to install the thing we didn't actually build. # # Thankfully, there's a way out that doesn't involve just hardcoding everything. # # The kernel has an install target, which runs a pretty simple shell script # (located at scripts/install.sh or arch/$arch/boot/install.sh, depending on # which kernel version you're looking at) that tries to do something sensible. # # (it would be great to hijack this script immediately, as it has all the #   information we need passed to it and we don't need it to try and be smart, #   but unfortunately, the exact location of the scripts differs between kernel #   versions, and they're seemingly not considered to be public API at all) # # One of the ways it tries to discover what "something sensible" actually is # is by delegating to what's supposed to be a user-provided install script # located at ~/bin/installkernel. # # (the other options are: #   - a distribution-specific script at /sbin/installkernel, #        which we can't really create in the sandbox easily #   - an architecture-specific script at arch/$arch/boot/install.sh, #        which attempts to guess _something_ and usually guesses very wrong) # # More specifically, the install script exec's into ~/bin/installkernel, if one # exists, with the following arguments: # # $1: $KERNELRELEASE - full kernel version string # $2: $KBUILD_IMAGE - the final image path # $3: System.map - path to System.map file, seemingly hardcoded everywhere # $4: $INSTALL_PATH - path to the destination directory as specified in installFlags # # $2 is exactly what we want, so hijack the script and use the knowledge given to it # by the makefile overlords for our own nefarious ends. # # Note that the makefiles specifically look in ~/bin/installkernel, and # writeShellScriptBin writes the script to <store path>/bin/installkernel, # so HOME needs to be set to just the store path. # # FIXME: figure out a less roundabout way of doing this. installkernel = buildPackages.writeShellScriptBin "installkernel" '' cp -av $2 $4 cp -av $3 $4 ''; in '' installFlagsArray+=("-j$NIX_BUILD_CORES") export HOME=${installkernel} ''; # Some image types need special install targets (e.g. uImage is installed with make uinstall) installTargets = [ (kernelConf.installTarget or ( /**/ if kernelConf.target == "uImage" then "uinstall" else if kernelConf.target == "zImage" || kernelConf.target == "Image.gz" then "zinstall" else "install")) ]; postInstall = optionalString isModular '' if [ -z "''${dontStrip-}" ]; then installFlagsArray+=("INSTALL_MOD_STRIP=1") fi make modules_install $makeFlags "''${makeFlagsArray[@]}"  $installFlags "''${installFlagsArray[@]}" unlink $out/lib/modules/${modDirVersion}/build unlink $out/lib/modules/${modDirVersion}/source mkdir $dev/lib/modules/${modDirVersion}/build cd $dev/lib/modules/${modDirVersion}/source cp $buildRoot/{.config,Module.symvers} $dev/lib/modules/${modDirVersion}/build make modules_prepare $makeFlags "''${makeFlagsArray[@]}" O=$dev/lib/modules/${modDirVersion}/build # For reproducibility, removes accidental leftovers from a `cc1` call # from a `try-run` call from the Makefile rm -f $dev/lib/modules/${modDirVersion}/build/.[0-9]*.d # Keep some extra files for f in arch/powerpc/lib/crtsavres.o arch/arm64/kernel/ftrace-mod.o  scripts/gdb/linux vmlinux vmlinux-gdb.py do if [ -e "$buildRoot/$f" ]; then mkdir -p "$(dirname "$dev/lib/modules/${modDirVersion}/build/$f")" cp -HR $buildRoot/$f $dev/lib/modules/${modDirVersion}/build/$f fi done ln -s $dev/lib/modules/${modDirVersion}/build/vmlinux $dev # !!! No documentation on how much of the source tree must be kept # If/when kernel builds fail due to missing files, you can add # them here. Note that we may see packages requiring headers # from drivers/ in the future; it adds 50M to keep all of its # headers on 3.10 though. chmod u+w -R .. arch=$(cd $dev/lib/modules/${modDirVersion}/build/arch; ls) # Remove unused arches for d in $(cd arch/; ls); do if [ "$d" = "$arch" ]; then continue; fi if [ "$arch" = arm64 ] && [ "$d" = arm ]; then continue; fi rm -rf arch/$d done # Remove all driver-specific code (50M of which is headers) rm -fR drivers # Keep all headers find .  -type f -name '*.h' -print0 | xargs -0 -r chmod u-w # Keep linker scripts (they are required for out-of-tree modules on aarch64) find .  -type f -name '*.lds' -print0 | xargs -0 -r chmod u-w # Keep root and arch-specific Makefiles chmod u-w Makefile arch/"$arch"/Makefile* # Keep whole scripts dir chmod u-w -R scripts # Delete everything not kept find . -type f -perm -u=w -print0 | xargs -0 -r rm # Delete empty directories find -empty -type d -delete # Remove reference to kmod sed -i Makefile -e 's|= ${buildPackages.kmod}/bin/depmod|= depmod|' ''; preFixup = '' # Don't strip $dev/lib/modules/*/vmlinux stripDebugList="$(cd $dev && echo lib/modules/*/build/*/)" ''; requiredSystemFeatures = [ "big-parallel" ]; meta = { description = "The Linux kernel" + (if kernelPatches == [] then "" else " (with patches: " + lib.concatStringsSep ", " (map (x: x.name) kernelPatches) + ")"); license = lib.licenses.gpl2Only; homepage = "https://www.kernel.org/"; maintainers = lib.teams.linux-kernel.members ++ [ maintainers.thoughtpolice ]; platforms = platforms.linux; timeout = 14400; # 4 hours } // extraMeta; }; </ins> in assert lib.versionOlder version "5.8" -> libelf != null; assert lib.versionAtLeast version "5.8" -> elfutils != null; <del> stdenv.mkDerivation ({ </del> <ins> stdenv.mkDerivation ((drvAttrs config stdenv.hostPlatform.linux-kernel kernelPatches configfile) // { </ins> pname = "linux"; <del> inherit version src; </del> <ins> inherit version; enableParallelBuilding = true; </ins> depsBuildBuild = [ buildPackages.stdenv.cc ]; <del> nativeBuildInputs = [ bc gmp libmpc mpfr nettools openssl perl python3Minimal rsync ubootTools zstd ] ++ optional  (lib.versionOlder version "5.8") libelf ++ optionals (lib.versionAtLeast version "4.16") [ bison flex ] ++ optionals (lib.versionAtLeast version "5.2")  [ cpio pahole zlib ] ++ optional  (lib.versionAtLeast version "5.8")  elfutils; patches = map (p: p.patch) kernelPatches # Required for deterministic builds along with some postPatch magic. ++ optional (lib.versionOlder version "5.19") ./randstruct-provide-seed.patch ++ optional (lib.versionAtLeast version "5.19") ./randstruct-provide-seed-5.19.patch # Linux 5.12 marked certain PowerPC-only symbols as GPL, which breaks # OpenZFS; this was fixed in Linux 5.19 so we backport the fix # https://github.com/openzfs/zfs/pull/13367 ++ optional (lib.versionAtLeast version "5.12" && lib.versionOlder version "5.19" && stdenv.hostPlatform.isPower) (fetchpatch { url = "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/patch/?id=d9e5c3e9e75162f845880535957b7fd0b4637d23"; hash = "sha256-bBOyJcP6jUvozFJU0SPTOf3cmnTQ6ZZ4PlHjiniHXLU="; }); preUnpack = '' # The same preUnpack is used to build the configfile, # which does not have $dev. if [ -n "$dev" ]; then mkdir -p $dev/lib/modules/${modDirVersion} cd $dev/lib/modules/${modDirVersion} fi ''; postUnpack = '' mv -Tv "$sourceRoot" source 2>/dev/null || : export sourceRoot=$PWD/source ''; postPatch = '' sed -i Makefile -e 's|= depmod|= ${buildPackages.kmod}/bin/depmod|' # fixup for pre-4.15 kernels using the $(cd $foo && /bin/pwd) pattern # FIXME: remove when no longer needed substituteInPlace Makefile tools/scripts/Makefile.include --replace /bin/pwd pwd # Don't include a (random) NT_GNU_BUILD_ID, to make the build more deterministic. # This way kernels can be bit-by-bit reproducible depending on settings # (e.g. MODULE_SIG and SECURITY_LOCKDOWN_LSM need to be disabled). # See also https://kernelnewbies.org/BuildId sed -i Makefile -e 's|--build-id=[^ ]*|--build-id=none|' # Some linux-hardened patches now remove certain files in the scripts directory, so the file may not exist. [[ -f scripts/ld-version.sh ]] && patchShebangs scripts/ld-version.sh # Set randstruct seed to a deterministic but diversified value. Note: # we could have instead patched gen-random-seed.sh to take input from # the buildFlags, but that would require also patching the kernel's # toplevel Makefile to add a variable export. This would be likely to # cause future patch conflicts. for file in scripts/gen-randstruct-seed.sh scripts/gcc-plugins/gen-random-seed.sh; do if [ -f "$file" ]; then substituteInPlace "$file"  --replace NIXOS_RANDSTRUCT_SEED  $(echo ${randstructSeed}${src} ${placeholder "configfile"} | sha256sum | cut -d ' ' -f 1 | tr -d 'n') break fi done patchShebangs scripts # also patch arch-specific install scripts for i in $(find arch -name install.sh); do patchShebangs "$i" done ''; configurePhase = '' runHook preConfigure export buildRoot=$TMPDIR/kernel-buildroot mkdir -p $buildRoot echo "manual-config configurePhase buildRoot=$buildRoot pwd=$PWD" if [ -f "$buildRoot/.config" ]; then echo "Could not link $buildRoot/.config : file exists" exit 1 fi ln -sv ${configfile} $buildRoot/.config # reads the existing .config file and prompts the user for options in # the current kernel source that are not found in the file. make $makeFlags "''${makeFlagsArray[@]}" oldconfig runHook postConfigure make $makeFlags "''${makeFlagsArray[@]}" prepare actualModDirVersion="$(cat $buildRoot/include/config/kernel.release)" if [ "$actualModDirVersion" != "${modDirVersion}" ]; then echo "Error: modDirVersion ${modDirVersion} specified in the Nix expression is wrong, it should be: $actualModDirVersion" exit 1 fi buildFlagsArray+=("KBUILD_BUILD_TIMESTAMP=$(date -u -d @$SOURCE_DATE_EPOCH)") cd $buildRoot ''; </del> <ins> nativeBuildInputs = [ perl bc nettools openssl rsync gmp libmpc mpfr zstd python3Minimal ] ++ optional  (stdenv.hostPlatform.linux-kernel.target == "uImage") buildPackages.ubootTools ++ optional  (lib.versionOlder version "5.8") libelf ++ optionals (lib.versionAtLeast version "4.16") [ bison flex ] ++ optionals (lib.versionAtLeast version "5.2")  [ cpio pahole zlib ] ++ optional  (lib.versionAtLeast version "5.8")  elfutils ; </ins> hardeningDisable = [ "bindnow" "format" "fortify" "stackprotector" "pic" "pie" ];