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

Borislav Petkov
2021-05-19T18:10:22Z

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?

> +int arch_setup_elf_property(struct arch_elf_state *state)
> +{
> + int r = 0;
> +
> + if (!IS_ENABLED(CONFIG_X86_SHADOW_STACK))
> + return r;
> +
> + memset(&current->thread.cet, 0, sizeof(struct cet_status));
> +
> + if (static_cpu_has(X86_FEATURE_SHSTK)) {

cpu_feature_enabled

> + if (state->gnu_property & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
> + r = shstk_setup();
> + }
> +
> + return r;
> +}
> +#endif

...

> 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...

--
Regards/Gruss,
Boris.