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

[Yu, Yu-cheng]

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