Re: [PATCH] x86: predict __access_ok() returning true

Ingo Molnar
2025-04-01T20:43:52Z

* Ingo Molnar <mingo@kernel.org> wrote:

> It's also the right place to have the hint: that user addresses are
> valid is the common case we optimize for.
>
> Thanks,
>
> Ingo
>
> arch/x86/include/asm/uaccess_64.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
> index c52f0133425b..4c13883371aa 100644
> --- a/arch/x86/include/asm/uaccess_64.h
> +++ b/arch/x86/include/asm/uaccess_64.h
> @@ -54,7 +54,7 @@ static inline unsigned long __untagged_addr_remote(struct mm_struct *mm,
> #endif
>
> #define valid_user_address(x) \
> - ((__force unsigned long)(x) <= runtime_const_ptr(USER_PTR_MAX))
> + likely((__force unsigned long)(x) <= runtime_const_ptr(USER_PTR_MAX))

Should we go this way, this is the safe macro variant:

#define valid_user_address(x) \
(likely((__force unsigned long)(x) <= runtime_const_ptr(USER_PTR_MAX)))

But this compiler bug sounds weird ...

Thanks,

Ingo