Re: [PATCH v2 4/8] KVM: arm64: Generate hyp relocation data

Marc Zyngier
2021-01-30T12:17:41Z

Hi Guenter,

Thanks a lot for the heads up.

On 2021-01-29 21:43, Guenter Roeck wrote:
> Hi,
>
> On Tue, Jan 05, 2021 at 06:05:37PM +0000, David Brazdil wrote:
>> Add a post-processing step to compilation of KVM nVHE hyp code which
>> calls a custom host tool (gen-hyprel) on the partially linked object
>> file (hyp sections' names prefixed).
>>
>> The tool lists all R_AARCH64_ABS64 data relocations targeting hyp
>> sections and generates an assembly file that will form a new section
>> .hyp.reloc in the kernel binary. The new section contains an array of
>> 32-bit offsets to the positions targeted by these relocations.
>>
>> Since these addresses of those positions will not be determined until
>> linking of `vmlinux`, each 32-bit entry carries a R_AARCH64_PREL32
>> relocation with addend <section_base_sym> + <r_offset>. The linker of
>> `vmlinux` will therefore fill the slot accordingly.
>>
>> This relocation data will be used at runtime to convert the kernel VAs
>> at those positions to hyp VAs.
>>
>> Signed-off-by: David Brazdil <dbrazdil@google.com>
>
> This patch results in the following error for me.
>
> error: arch/arm64/kvm/hyp/nvhe/kvm_nvhe.tmp.o: assertion
> elf.ehdr->e_ident[5] == 1 failed (lhs=2, rhs=1, line=250)
>
> The problem is seen when trying to build aarch64 images in big endian
> mode.

Ah, big-endian. of course, the ELF header is in native endianness,
and the sanity checks explode (still much better than generating crap).

I'll have a look shortly. It shouldn't too hard to fix, just a
bit invasive...

Thanks again,

M.
--
Jazz is not dead. It just smells funny...