[Stable-7.2.15,30/33] target/ppc: Set ctx->opcode for decode_insn32()

Commit Message

Michael Tokarev Nov. 9, 2024, 6:38 a.m. UTC

From: Ilya Leoshkevich <[e-mail]>

divdu (without a dot) sometimes updates cr0, even though it shouldn't.
The reason is that gen_op_arith_divd() checks Rc(ctx->opcode), which is
not initialized. This field is initialized only for instructions that
go through decode_legacy(), and not decodetree.

There already was a similar issue fixed in commit 86e6202a57b1
("target/ppc: Make divw[u] handler method decodetree compatible.").

It's not immediately clear what else may access the uninitialized
ctx->opcode, so instead of playing whack-a-mole and changing the check
to compute_rc0, simply initialize ctx->opcode.

Cc: [e-mail]
Fixes: 99082815f17f ("target/ppc: Add infrastructure for prefixed insns")
Reviewed-by: Richard Henderson <[e-mail]>
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Signed-off-by: Ilya Leoshkevich <[e-mail]>
Signed-off-by: Nicholas Piggin <[e-mail]>
(cherry picked from commit c9b8a13a8841e0e23901e57e24ea98eeef16cf91)
Signed-off-by: Michael Tokarev <[e-mail]>

Patch

diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 90f749a728..5ab6c5c861 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -7455,8 +7455,6 @@  static bool decode_legacy(PowerPCCPU *cpu, DisasContext *ctx, uint32_t insn)
     opc_handler_t **table, *handler;
     uint32_t inval;
 
-    ctx->opcode = insn;
-
     LOG_DISAS("translate opcode %08x (%02x %02x %02x %02x) (%s)\n",
               insn, opc1(insn), opc2(insn), opc3(insn), opc4(insn),
               ctx->le_mode ? "little" : "big");
@@ -7587,6 +7585,7 @@  static void ppc_tr_translate_insn(DisasContextBase *dcbase, CPUState *cs)
     ctx->base.pc_next = pc += 4;
 
     if (!is_prefix_insn(ctx, insn)) {
+        ctx->opcode = insn;
         ok = (decode_insn32(ctx, insn) ||
               decode_legacy(cpu, ctx, insn));
     } else if ((pc & 63) == 0) {