[PATCH] selftests/powerpc: Fix prefixes in alignment_handler signal handler

The signal handler in the alignment handler self test has the ability to
jump over the instruction that triggered the signal. It does this by
incrementing the PT_NIP in the user context by 4. If it were a prefixed
instruction this will mean that the suffix is then executed which is
incorrect. Instead check if the major opcode indicates a prefixed
instruction (e.g. it is 1) and if so increment PT_NIP by 8.

If ISA v3.1 is not available treat it as a word instruction even if the
major opcode is 1.

Fixes: 620a6473df36 ("selftests/powerpc: Add prefixed loads/stores to
alignment_handler test")
Signed-off-by: Jordan Niethe <redacted>
---
 .../selftests/powerpc/alignment/alignment_handler.c   | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/powerpc/alignment/alignment_handler.c b/tools/testing/selftests/powerpc/alignment/alignment_handler.c
index 55ef15184057..c197ff828120 100644
--- a/tools/testing/selftests/powerpc/alignment/alignment_handler.c
+++ b/tools/testing/selftests/powerpc/alignment/alignment_handler.c

@@ -64,12 +64,14 @@ int bufsize;
 int debug;
 int testing;
 volatile int gotsig;
+bool haveprefixes;
 char *cipath = "/dev/fb0";
 long cioffset;

 void sighandler(int sig, siginfo_t *info, void *ctx)
 {
        ucontext_t *ucp = ctx;
+       u32 inst;

        if (!testing) {
                signal(sig, SIG_DFL);

@@ -77,7 +79,12 @@ void sighandler(int sig, siginfo_t *info, void *ctx)
        }
        gotsig = sig;
 #ifdef __powerpc64__
-       ucp->uc_mcontext.gp_regs[PT_NIP] += 4;
+       if (haveprefixes) {
+               inst = *(u32 *)ucp->uc_mcontext.gp_regs[PT_NIP];
+               ucp->uc_mcontext.gp_regs[PT_NIP] += ((inst >> 26 == 1) ? 8 : 4);
+       } else {
+               ucp->uc_mcontext.gp_regs[PT_NIP] += 4;
+       }
 #else
        ucp->uc_mcontext.uc_regs->gregs[PT_NIP] += 4;
 #endif

@@ -648,6 +655,8 @@ int main(int argc, char *argv[])
                exit(1);
        }

+       haveprefixes = have_hwcap2(PPC_FEATURE2_ARCH_3_1);
+
        rc |= test_harness(test_alignment_handler_vsx_206,
                           "test_alignment_handler_vsx_206");
        rc |= test_harness(test_alignment_handler_vsx_207,
--

2.17.1