On Mon, 2018-04-16 at 14:39:01 UTC, Michael Ellerman wrote:
> When we patch an alternate feature section, we have to adjust any
> relative branches that branch out of the alternate section.
>
> But currently we have a bug if we have a branch that points to past
> the last instruction of the alternate section, eg:
>
> FTR_SECTION_ELSE
> 1: b 2f
> or 6,6,6
> 2:
> ALT_FTR_SECTION_END(...)
> nop
>
> This will result in a relative branch at 1 with a target that equals
> the end of the alternate section.
>
> That branch does not need adjusting when it's moved to the non-else
> location. Currently we do adjust it, resulting in a branch that goes
> off into the link-time location of the else section, which is junk.
>
> The fix is to not patch branches that have a target == end of the
> alternate section.
>
> Fixes: d20fe50a7b3c ("KVM: PPC: Book3S HV: Branch inside feature section")
> Fixes: 9b1a735de64c ("powerpc: Add logic to patch alternative feature
> sections")
> Cc: sta...@vger.kernel.org # v2.6.27+
> Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Applied to powerpc fixes.
https://git.kernel.org/powerpc/c/b8858581febb050688e276b956796b
cheers
