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SubjectRe: [PATCH v2 02/36] x86/uaccess: __chk_range_not_ok is unlikely to return true
On Mon, Oct 05, 2015 at 05:47:50PM -0700, Andy Lutomirski wrote:
> This should improve code quality a bit. It also shrinks the kernel
> text.
>
> Before:
> text data bss dec hex filename
> 21828379 5194760 1277952 28301091 1afd723 vmlinux
> text data bss dec hex filename
> 21827997 5194760 1277952 28300709 1afd5a5 vmlinux
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/include/asm/uaccess.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 3e911c68876e..09b1b0ab94b7 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -51,13 +51,13 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
> * limit, not add it to the address).
> */
> if (__builtin_constant_p(size))
> - return addr > limit - size;
> + return unlikely(addr > limit - size);
>
> /* Arbitrary sizes? Be careful about overflow */
> addr += size;
> - if (addr < size)
> + if (unlikely(addr < size))
> return true;
> - return addr > limit;
> + return unlikely(addr > limit);

It certainly uglifies it though. Are the wins worth the (un-)readability
hit?

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--


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