[PATCH v2] arm64: errata: Fix exec handling in erratum 1418040 workaround

[Catalin Marinas]

On Thu, Dec 16, 2021 at 11:16:18AM -0800, D Scott Phillips wrote:
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 97932fbf973d..24036b914226 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -160,8 +160,16 @@ typedef struct user_fpsimd_state elf_fpregset_t;
>  
>  #define SET_PERSONALITY(ex)						\
>  ({									\
> +	if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040))			\
> +		preempt_disable();					\
>  	clear_thread_flag(TIF_32BIT);					\
>  	current->personality &= ~READ_IMPLIES_EXEC;			\
> +	if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) {			\
> +		if (this_cpu_has_cap(ARM64_WORKAROUND_1418040))		\
> +			sysreg_clear_set(cntkctl_el1, 0,		\
> +					 ARCH_TIMER_USR_VCT_ACCESS_EN);	\
> +		preempt_enable();					\
> +	}								\
>  })
>  
>  /* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */
> @@ -223,7 +231,16 @@ int compat_elf_check_arch(const struct elf32_hdr *);
>   */
>  #define COMPAT_SET_PERSONALITY(ex)					\
>  ({									\
> +	if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040))			\
> +		preempt_disable();					\
>  	set_thread_flag(TIF_32BIT);					\
> +	if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) {			\
> +		if (this_cpu_has_cap(ARM64_WORKAROUND_1418040))		\
> +			sysreg_clear_set(cntkctl_el1,			\
> +					 ARCH_TIMER_USR_VCT_ACCESS_EN,	\
> +					 0);				\
> +		preempt_enable();					\
> +	}								\

I don't particularly like adding more to these macros. There's
arch_setup_new_exec() that gets called after SET_PERSONALITY, so you can
check whether the task is compat or not.

Thanks.

-- 
Catalin