On Fri, 2011-01-07 at 20:23 +0000, Andy Green wrote: > On 01/07/11 19:46, Somebody in the thread at some point said: > > ..snip.. > > > >>> > >>> This must be a bug in sha512sum -- it shouldn't be affected by alignment. > >> > >> I am inclined to think it might be compiler related. Andy's package is > >> the same version as mine, his works, mine does not. The only thing that > >> is likely to be different is the build environment. > > > > That and the development board. You are using a sheevaplug. > > It is also likely that Andy's hardware does fixups for misaligned accesses. > > It's an NXP LPC3250, ARM926EJ-S. I have no idea if the hardware is > handling the alignment issue but that would explain why everything is > exactly zero on that box's alignment error stats. Searching the > datasheet for 'alignment' doesn't tell anything relevant. As I understant it, the 'A' profile for armv7 includes mandatory alignment fixup. Thus, if your CPU is armv7 it should do fixups in hardware -- with cost, but transparent. Most armv5 does not appear to do this. (Did the PHP 2.5*5 bug come up in this discussion? On a machine without hardware fixup, PHP prints 5.3114652946464E-315 as the answer for 2.5*5 with 0 in /proc/cpu/alignment, but prints 5 when fixups are enabled. This seems to be a useful quick test). Related proposal: I think we should have the startup scripts set /proc/cpu/alignment to 3 (warn+fixup) by default in Fedora-ARM (we do this on the Koji builder image). I don't see a downside, and there's a definite upside on armv5 systems. -Chris _______________________________________________ arm mailing list arm@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/arm
