From bc63102e5041595cc8da3b843b0e54d970166b2c Mon Sep 17 00:00:00 2001
From: Nguyen Anh Quynh <aquynh@gmail.com>
Date: Sun, 13 Dec 2015 13:11:40 +0800
Subject: [PATCH] mips: only patch instruction size when there is a callback on
 the instruction. this fixes issue #282

---
 qemu/target-mips/translate.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/qemu/target-mips/translate.c b/qemu/target-mips/translate.c
index c1941505..ccf11255 100644
--- a/qemu/target-mips/translate.c
+++ b/qemu/target-mips/translate.c
@@ -11322,7 +11322,7 @@ static int decode_extended_mips16_opc (CPUMIPSState *env, DisasContext *ctx)
     return 4;
 }
 
-static int decode_mips16_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot)
+static int decode_mips16_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot, bool *insn_need_patch)
 {
     TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
     TCGv **cpu_gpr = (TCGv **)tcg_ctx->cpu_gpr;
@@ -11345,8 +11345,10 @@ static int decode_mips16_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_s
     // Unicorn: trace this instruction on request
     if (!is_bc_slot && env->uc->hook_insn) {
         struct hook_struct *trace = hook_find(env->uc, UC_HOOK_CODE, ctx->pc);
-        if (trace)
+        if (trace) {
             gen_uc_tracecode(tcg_ctx, 0xf8f8f8f8, trace->callback, env->uc, ctx->pc, trace->user_data);
+            *insn_need_patch = true;
+        }
         // if requested to emulate only some instructions, check if
         // we need to exit immediately
         if (env->uc->emu_count > 0) {
@@ -13928,7 +13930,7 @@ static void decode_micromips32_opc (CPUMIPSState *env, DisasContext *ctx,
     }
 }
 
-static int decode_micromips_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot)
+static int decode_micromips_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot, bool *insn_need_patch)
 {
     TCGContext *tcg_ctx = env->uc->tcg_ctx;
     TCGv **cpu_gpr = (TCGv **)tcg_ctx->cpu_gpr;
@@ -13945,8 +13947,10 @@ static int decode_micromips_opc (CPUMIPSState *env, DisasContext *ctx, bool is_b
     // Unicorn: trace this instruction on request
     if (!is_bc_slot && env->uc->hook_insn) {
         struct hook_struct *trace = hook_find(env->uc, UC_HOOK_CODE, ctx->pc);
-        if (trace)
+        if (trace) {
             gen_uc_tracecode(tcg_ctx, 0xf8f8f8f8, trace->callback, env->uc, ctx->pc, trace->user_data);
+            *insn_need_patch = true;
+        }
         // if requested to emulate only some instructions, check if
         // we need to exit immediately
         if (env->uc->emu_count > 0) {
@@ -18503,7 +18507,7 @@ static void gen_msa(CPUMIPSState *env, DisasContext *ctx)
     }
 }
 
-static void decode_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot)
+static void decode_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot, bool *insn_need_patch)
 {
     TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
 #if defined(TARGET_MIPS64)
@@ -18514,7 +18518,6 @@ static void decode_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot)
     uint32_t op, op1;
     int16_t imm;
 
-
     /* make sure instructions are on a word boundary */
     if (ctx->pc & 0x3) {
         env->CP0_BadVAddr = ctx->pc;
@@ -18525,8 +18528,10 @@ static void decode_opc (CPUMIPSState *env, DisasContext *ctx, bool is_bc_slot)
     // Unicorn: trace this instruction on request
     if (!is_bc_slot && env->uc->hook_insn) {
         struct hook_struct *trace = hook_find(env->uc, UC_HOOK_CODE, ctx->pc);
-        if (trace)
+        if (trace) {
             gen_uc_tracecode(tcg_ctx, 0xf8f8f8f8, trace->callback, env->uc, ctx->pc, trace->user_data);
+            *insn_need_patch = true;
+        }
         // if requested to emulate only some instructions, check if
         // we need to exit immediately
         if (env->uc->emu_count > 0) {
@@ -19268,6 +19273,7 @@ gen_intermediate_code_internal(MIPSCPU *cpu, TranslationBlock *tb,
             ctx.bstate = BS_EXCP;
             break;
         } else {
+            bool insn_need_patch = false;
             // Unicorn: save param buffer
             if (env->uc->hook_insn)
                 save_opparam_ptr = tcg_ctx->gen_opparam_ptr;
@@ -19278,13 +19284,13 @@ gen_intermediate_code_internal(MIPSCPU *cpu, TranslationBlock *tb,
             if (!(ctx.hflags & MIPS_HFLAG_M16)) {
                 ctx.opcode = cpu_ldl_code(env, ctx.pc);
                 insn_bytes = 4;
-                decode_opc(env, &ctx, is_bc_slot);
+                decode_opc(env, &ctx, is_bc_slot, &insn_need_patch);
             } else if (ctx.insn_flags & ASE_MICROMIPS) {
                 ctx.opcode = cpu_lduw_code(env, ctx.pc);
-                insn_bytes = decode_micromips_opc(env, &ctx, is_bc_slot);
+                insn_bytes = decode_micromips_opc(env, &ctx, is_bc_slot, &insn_need_patch);
             } else if (ctx.insn_flags & ASE_MIPS16) {
                 ctx.opcode = cpu_lduw_code(env, ctx.pc);
-                insn_bytes = decode_mips16_opc(env, &ctx, is_bc_slot);
+                insn_bytes = decode_mips16_opc(env, &ctx, is_bc_slot, &insn_need_patch);
             } else {
                 generate_exception(&ctx, EXCP_RI);
                 ctx.bstate = BS_STOP;
@@ -19292,7 +19298,7 @@ gen_intermediate_code_internal(MIPSCPU *cpu, TranslationBlock *tb,
             }
 
             // Unicorn: patch the callback for the instruction size
-            if (!is_bc_slot && env->uc->hook_insn)
+            if (insn_need_patch)
                 *(save_opparam_ptr + 1) = insn_bytes;
         }