linker problem with Ubuntu 18.04 tool chain: unknown architecture of input file `arch/arm64/boot/vmlinuz.o' is incompatible with aarch64 output

[Lukas Bulwahn]

On Fri, Jan 13, 2023 at 3:30 PM Ard Biesheuvel <ardb at kernel.org> wrote:
>
> On Fri, 13 Jan 2023 at 14:25, Lukas Bulwahn <lukas.bulwahn at gmail.com> wrote:
> >
> > On Fri, Jan 13, 2023 at 12:58 PM Ard Biesheuvel <ardb at kernel.org> wrote:
> > >
> > > On Fri, 13 Jan 2023 at 12:50, Lukas Bulwahn <lukas.bulwahn at gmail.com> wrote:
> > > >
> > > > Dear Ard,
> > > >
> > > > with my Ubuntu 18.04 arm gcc tool chain, I encounter this linker error
> > > > in my allyesconfig build:
> > > >
> > > >  LD      arch/arm64/boot/vmlinuz.efi.elf
> > > > aarch64-linux-gnu-ld: unknown architecture of input file
> > > > `arch/arm64/boot/vmlinuz.o' is incompatible with aarch64 output
> > > > drivers/firmware/efi/libstub/Makefile.zboot:41: recipe for target
> > > > 'arch/arm64/boot/vmlinuz.efi.elf' failed
> > > > make[1]: *** [arch/arm64/boot/vmlinuz.efi.elf] Error 1
> > > > arch/arm64/Makefile:173: recipe for target 'vmlinuz.efi' failed
> > > > make: *** [vmlinuz.efi] Error 2
> > > >
> > > > I bisected it back to happen since commit c37b830fef13 ("arm64: efi:
> > > > enable generic EFI compressed boot"), and it still appears with the
> > > > latest next-20230113 (on linux-next, I have to remove DRM_MSM as it
> > > > currently comes with a build error).
> > > >
> > > > The specific compiler and linker versions on my system are:
> > > >
> > > > $ aarch64-linux-gnu-ld --version
> > > > GNU ld (GNU Binutils for Ubuntu) 2.30
> > > >
> > > > $ aarch64-linux-gnu-gcc --version
> > > > aarch64-linux-gnu-gcc (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0
> > > >
> > > >
> > > > IMHO, I run pretty standard commands:
> > > > make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j 32 mrproper
> > > > make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j 32 allyesconfig
> > > > make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j 32 all
> > > >
> > > > Let me know if you need more information.
> > > >
> > >
> > > Hello Lukas,
> > >
> > > This seems to mean that AArch64 ld.bfd 2.30 is not able to combine
> > > generic ELF objects with AArch64 ELF objects. vmlinuz.o only contains
> > > a compressed blob in an ELF data section, and more modern toolchains
> > > have no issue with this at all.
> > >
> > > Given that building allyesconfig with fairly outdated toolchains is
> > > not something anyone is likely to obsess about, I don't have a strong
> > > preference as to how we work around this, put perhaps the easiest
> > > approach would be for CONFIG_EFI_ZBOOT to depend on !CONFIG_LD_IS_BFD
> > > || CONFIG_LD_VERSION >= 23xxx here? (We'll need to check the exact
> > > version)
> >
> > That sounds reasonable to me.
> >
>
> This is not reproducible with ld.bfd built from the upstream sources
>
> $ ~/build/binutils-build-aarch64/ld/ld-new -v
> GNU ld (GNU Binutils) 2.30
>
> $ ~/build/binutils-build-aarch64/ld/ld-new -EL  -maarch64elf -z
> noexecstack -T /usr/local/google/home/ardb/linux/drivers/firmware/efi/libstub/zboot.lds
> arch/arm64/boot/vmlinuz.o arch/arm64/boot/zboot-header.o
> drivers/firmware/efi/libstub/lib.a -o arch/arm64/boot/vmlinuz.efi.elf
>
> $ file arch/arm64/boot/vmlinuz.efi.elf
> arch/arm64/boot/vmlinuz.efi.elf: ELF 64-bit LSB executable, ARM
> aarch64, version 1 (SYSV), statically linked, with debug_info, not
> stripped
>
> So this could be an issue in Ubuntu's downstream fork, in which case I
> don't think we should do anything about it.

Thanks, I will follow up and check if this is really something
specific in the Ubuntu fork or if it appears only with very selected
binutils versions.

Lukas