lkml.org 
[lkml]   [2008]   [Jul]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Fw: asm-x86/byteorder.h, CONFIG_X86_BSWAP leaks to userland
    Harvey Harrison wrote:
    >>
    >> An undefined CONFIG_foo defaults to 0 (I think), so bswap is never used.
    >> Is this done on purpose, or can the CONFIG_ foo be moved inside
    >> __KERNEL__ somehow?
    >
    > I believe it's there to prevent the bswap instruction from being used on
    > early x86_32 models (i386/i486). As this will be 0 in userspace it is
    > effectively never using the bswap instruction for these routines.
    >

    i386, specifically.

    However, you shouldn't leak these symbols to userspace; there is a
    warning option in gcc for undefined macros, and it's a *good thing* to
    use it. Causing warnings in user space is not nice.

    > I'm not sure if it's time yet to make the bswap ones be exported, as they
    > would no longer be usable for those early machines. X86 guys CC:d.

    On i386 we still default to i386-compatible binaries; I *think* gcc has
    macros telling you if the user has used -march=i486 etc.

    -hpa


    \
     
     \ /
      Last update: 2008-07-26 18:53    [W:3.325 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site