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Message-ID: <20151007162323.GB8738@gmail.com> Date: Wed, 7 Oct 2015 18:23:23 +0200 From: Ingo Molnar <mingo@...nel.org> To: Borislav Petkov <bp@...en8.de> Cc: Andy Lutomirski <luto@...nel.org>, x86@...nel.org, linux-kernel@...r.kernel.org, Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH v2 02/36] x86/uaccess: __chk_range_not_ok is unlikely to return true * Borislav Petkov <bp@...en8.de> wrote: > 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@...nel.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? Well, adding likely/unlikely hints in headers is OK I think, especially since these are performance sensitive user-access routines. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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