[PATCH] arm64: vmlinux.lds: make __rela_offset and __dynsym_offset ABSOLUTE

Ard Biesheuvel
2016-07-29T09:30:34Z

On 29 July 2016 at 11:06, Will Deacon <will.deacon@arm.com> wrote:
> Hi Ard,
>
> On Thu, Jul 28, 2016 at 04:15:14PM +0200, Ard Biesheuvel wrote:
>> Due to the untyped KIMAGE_VADDR constant, the linker may not notice
>> that the __rela_offset and __dynsym_offset expressions are absolute
>> values (i.e., are not subject to relocation). This does not matter for
>> KASLR, but it does confuse kallsyms in relative mode, since it uses
>> the lowest non-absolute symbol address as the anchor point, and expects
>> all other symbol addresses to be within 4 GB of it.
>>
>> Fix this by qualifying these expressions as ABSOLUTE() explicitly.
>>
>> Fixes: 0cd3defe0af4 ("arm64: kernel: perform relocation processing from ID map")
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>> arch/arm64/kernel/vmlinux.lds.S | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
>> index 89d6e177ecbd..d49492179967 100644
>> --- a/arch/arm64/kernel/vmlinux.lds.S
>> +++ b/arch/arm64/kernel/vmlinux.lds.S
>> @@ -184,9 +184,9 @@ SECTIONS
>> *(.hash)
>> }
>>
>> - __rela_offset = ADDR(.rela) - KIMAGE_VADDR;
>> + __rela_offset = ABSOLUTE(ADDR(.rela) - KIMAGE_VADDR);
>> __rela_size = SIZEOF(.rela);
>> - __dynsym_offset = ADDR(.dynsym) - KIMAGE_VADDR;
>> + __dynsym_offset = ABSOLUTE(ADDR(.dynsym) - KIMAGE_VADDR);
>
> You removed the __dynsym_offset entry entirely in "arm64: relocatable:
> suppress R_AARCH64_ABS64 relocations in vmlinux", so I'll drop this part
> of the patch and assume you'll do a separate backport for stable. Ok?
>

If you are ok with fixing up patches manually while applying, could we
just reorder them instead?