[lkml]   [2011]   [Sep]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH] ARM: alignment: setup alignment handler earlier
    On Wed, Sep 07, 2011 at 06:04:52PM +0100, Russell King - ARM Linux wrote:
    > On Wed, Sep 07, 2011 at 05:42:19PM +0100, Måns Rullgård wrote:
    > > There are such instructions (ldrd, ldm), but gcc will not emit those
    > > unless the address is known to be aligned. For ARMv6 and later, gcc 4.6
    > > *will* emit potentially unaligned ldr and ldrh since these very clearly
    > > allow an unaligned address and are faster than the alternatives in all
    > > implementations to date. This is unless strict alignment checking is
    > > explicitly enabled, which unfortunately the Linux kernel does for no
    > > apparent reason at all.
    > "no apparant reason at all" heh. The reason is to keep the code
    > simple and free from bugs. To do otherwise means that each of the
    > CPU files needs to be littered with ifdefs to deal with the alignment
    > fault configuration, of which there are 16 of them (ignoring v6 and v7.)
    > If you think code maintanence of the same thing in 16 places is efficient
    > then I guess there is "no apparant reason". I beg to differ, being one
    > of those folk who have had to edit 18 different places several times.
    > So no, I do not intend to move this:
    > orr r0, r0, #CR_A
    > #else
    > bic r0, r0, #CR_A
    > #endif
    > into 16 separate places in the kernel.

    What about something like this (untested):

    #if defined(CONFIG_ALIGNMENT_TRAP) && __LINUX_ARM_ARCH__ < 6
    orr r0, r0, #CR_A
    bic r0, r0, #CR_A

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2011-09-07 19:27    [W:0.021 / U:6.868 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site