On 08.07.2018 15:56, Christos Zoulas wrote: > In article <20180708092413.GB8981%mail.duskware.de@localhost>, > Martin Husemann <martin%duskware.de@localhost> wrote: >> On Sun, Jul 08, 2018 at 10:49:53AM +0200, Jaromír Dole?ek wrote: >>>> Module Name: src >>>> Committed By: kamil >>>> Date: Sat Jul 7 23:05:50 UTC 2018 >>>> >>>> Modified Files: >>>> src/sys/arch/x86/x86: mpbios.c >>>> >>>> Log Message: >>>> Remove unaligned access to mpbios_page[] >>>> >>>> Replace unaligned pointer dereference with a more portable construct that >>>> is free from Undefined Behavior semantics. >>>> >>>> sys/arch/x86/x86/mpbios.c:308:11, load of misaligned address 0xffff800031c7a413 for type 'const >> __uint16_t' which requires 2 byte alignment >> >> >> Can we please do NOT do such stupid changes? >> >> This is a bogus error message, please restore the original code! > > These changes are pointless; how much code will we need to change > to silence mis-aligned warnings? These changes are also dangerous > when it comes to reading from devices (where multiple reads can > behave differently). If you want to silence the warnings, use > __attribute__, but even that is of questionable use. I'd venture > to say, misaligned warnings on cpus where aligned access (to do > the aligning) is costlier than direct misaligned accesses (like > x86) are useless. In addition, it is not like we would ever turn > on the force alignment bit on an x86 cpu and have things work! > > So my preference would be to revert the change and take this up > to tech-kern first (how misaligned accesses should be treated), > because the situation is not that simple (when it comes to things > like SSE operations etc.) > http://pzemtsov.github.io/2016/11/06/bug-story-alignment-on-x86.html > > > Best, > > christos > I've started a tech-kern discussion on the request. Regarding the number of assignment issues to address: - acpica - mpbios.c [this one] - arch/x86/x86/patch.c [load of address with insufficient space] - sys/kern/subr_disk_mbr.c disklabel struct misaligned - IPv6, TCP - amd64/amd64/kobj_machdep.c (ELF) - XHCI http://netbsd.org/~kamil/kubsan/0007-boot-real-hardware.txt I'm going to revert it for a while, until there will be a conclusion.
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