4.9-stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman mpe@ellerman.id.au
commit b8858581febb050688e276b956796bc4a78299ed upstream.
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: stable@vger.kernel.org # v2.6.27+ Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/lib/feature-fixups.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -55,7 +55,7 @@ static int patch_alt_instruction(unsigne unsigned int *target = (unsigned int *)branch_target(src);
/* Branch within the section doesn't need translating */ - if (target < alt_start || target >= alt_end) { + if (target < alt_start || target > alt_end) { instr = translate_branch(dest, src); if (!instr) return 1;