Re: [PATCH v26 26/30] ELF: Introduce arch_setup_elf_property()

Yu, Yu-cheng
2021-05-19T22:15:03Z

On 5/19/2021 11:10 AM, Borislav Petkov wrote:
> On Tue, Apr 27, 2021 at 01:43:11PM -0700, Yu-cheng Yu wrote:
>> @@ -1951,6 +1951,8 @@ config X86_SHADOW_STACK
>> depends on AS_WRUSS
>> depends on ARCH_HAS_SHADOW_STACK
>> select ARCH_USES_HIGH_VMA_FLAGS
>> + select ARCH_USE_GNU_PROPERTY
>> + select ARCH_BINFMT_ELF_STATE
> ^^^^^^^^
>
> What's that for? Isn't ARCH_USE_GNU_PROPERTY enough?
>

ARCH_USE_GNU_PROPERTY is for defining parsing functions, e.g.
arch_parse_elf_property(),
arch_setup_property().

ARCH_BINFMT_ELF_STATE is for defining "struct arch_elf_state".

However, those parsing functions take (struct arch_elf_state *) as an
input. It probably makes sense to have ARCH_USE_GNU_PROPERTY dependent
on ARCH_BINFMT_ELF_STATE. It would be ok as-is too. ARM people might
have other plans in mind.

[...]

>
>> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
>> index 30f68b42eeb5..24ba55ba8278 100644
>> --- a/include/uapi/linux/elf.h
>> +++ b/include/uapi/linux/elf.h
>> @@ -455,4 +455,13 @@ typedef struct elf64_note {
>> /* Bits for GNU_PROPERTY_AARCH64_FEATURE_1_BTI */
>> #define GNU_PROPERTY_AARCH64_FEATURE_1_BTI (1U << 0)
>>
>> +/* .note.gnu.property types for x86: */
>> +#define GNU_PROPERTY_X86_FEATURE_1_AND 0xc0000002
>
> Why not 0xc0000001? ARM64 is 0xc0000000...
>

I just looked at the ABI document.

ARM has GNU_PROPERTY_AARCH64_FEATURE_1_AND 0xc0000000

X86 has:
GNU_PROPERTY_X86_ISA_1_USED 0xc0000000
GNU_PROPERTY_X86_ISA_1_NEEDED 0xc0000001
GNU_PROPERTY_X86_FEATURE_1_AND 0xc0000002

Yu-cheng