[PATCH 1/6] powerpc test_emulate_step: update nip with patched instruction address

[Balamuruhan S]

pt_regs are initialized to zero in the test infrastructure, R bit
in prefixed instruction form is used to specify whether the effective
address of the storage operand is computed relative to the address
of the instruction.

If R = 1 and RA = R0|0, the sum of the address of the instruction
and the value SI is placed into register RT. So to assert the emulated
instruction with executed instruction, update nip of emulated pt_regs.

Signed-off-by: Balamuruhan S <bal...@linux.ibm.com>
---
 arch/powerpc/lib/test_emulate_step.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/test_emulate_step.c 
b/arch/powerpc/lib/test_emulate_step.c
index 33a72b7d2764..d5902b7b4e5c 100644
--- a/arch/powerpc/lib/test_emulate_step.c
+++ b/arch/powerpc/lib/test_emulate_step.c
@@ -1204,13 +1204,24 @@ static struct compute_test compute_tests[] = {
 static int __init emulate_compute_instr(struct pt_regs *regs,
                                        struct ppc_inst instr)
 {
+       int prefix_r, ra;
        extern s32 patch__exec_instr;
        struct instruction_op op;
 
        if (!regs || !ppc_inst_val(instr))
                return -EINVAL;
 
-       regs->nip = patch_site_addr(&patch__exec_instr);
+       /*
+        * If R=1 and RA=0 in Prefixed instruction form, calculate the address
+        * of the instruction and update nip to assert with executed
+        * instruction
+        */
+       if (ppc_inst_prefixed(instr)) {
+               prefix_r = ppc_inst_val(instr) & (1UL << 20);
+               ra = (ppc_inst_suffix(instr) >> 16) & 0x1f;
+               if (prefix_r && !ra)
+                       regs->nip = patch_site_addr(&patch__exec_instr);
+       }
 
        if (analyse_instr(&op, regs, instr) != 1 ||
            GETTYPE(op.type) != COMPUTE) {
-- 
2.24.1