Messages in this thread | | | From | Måns Rullgård <> | Subject | Re: [PATCH] ARM: alignment: setup alignment handler earlier | Date | Wed, 07 Sep 2011 18:40:11 +0100 |
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Russell King - ARM Linux <linux@arm.linux.org.uk> writes:
> 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.
Some people, myself included, consider the current behaviour a bug.
> 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: > > #ifdef CONFIG_ALIGNMENT_TRAP > orr r0, r0, #CR_A > #else > bic r0, r0, #CR_A > #endif > > into 16 separate places in the kernel.
So change that condition to also depend on !CPU_V6 && !CPU_V7 or something equivalent.
-- Måns Rullgård mans@mansr.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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