5 files changed, 53 insertions, 21 deletions

diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c
index df49ff1880..efd6bbded8 100644
--- a/target/m68k/cpu.c
+++ b/target/m68k/cpu.c
@@ -71,7 +71,7 @@ static void m68k_unset_feature(CPUM68KState *env, int feature)
     env->features &= ~BIT_ULL(feature);
 }
 
-static void m68k_cpu_reset_hold(Object *obj)
+static void m68k_cpu_reset_hold(Object *obj, ResetType type)
 {
     CPUState *cs = CPU(obj);
     M68kCPUClass *mcc = M68K_CPU_GET_CLASS(obj);
@@ -80,7 +80,7 @@ static void m68k_cpu_reset_hold(Object *obj)
     int i;
 
     if (mcc->parent_phases.hold) {
-        mcc->parent_phases.hold(obj);
+        mcc->parent_phases.hold(obj, type);
     }
 
     memset(env, 0, offsetof(CPUM68KState, end_reset_fields));
diff --git a/target/m68k/cpu.h b/target/m68k/cpu.h
index e184239a81..b5bbeedb7a 100644
--- a/target/m68k/cpu.h
+++ b/target/m68k/cpu.h
@@ -66,7 +66,7 @@
 #define EXCP_MMU_ACCESS     58  /* MMU Access Level Violation Error */
 
 #define EXCP_RTE            0x100
-#define EXCP_HALT_INSN      0x101
+#define EXCP_SEMIHOSTING    0x101
 
 #define M68K_DTTR0   0
 #define M68K_DTTR1   1
diff --git a/target/m68k/m68k-semi.c b/target/m68k/m68k-semi.c
index 546cff2246..6fbbd140f3 100644
--- a/target/m68k/m68k-semi.c
+++ b/target/m68k/m68k-semi.c
@@ -132,8 +132,8 @@ void do_m68k_semihosting(CPUM68KState *env, int nr)
     args = env->dregs[1];
     switch (nr) {
     case HOSTED_EXIT:
-        gdb_exit(env->dregs[0]);
-        exit(env->dregs[0]);
+        gdb_exit(env->dregs[1]);
+        exit(env->dregs[1]);
 
     case HOSTED_OPEN:
         GET_ARG(0);
diff --git a/target/m68k/op_helper.c b/target/m68k/op_helper.c
index 125f6c1b08..15bad5dd46 100644
--- a/target/m68k/op_helper.c
+++ b/target/m68k/op_helper.c
@@ -202,18 +202,8 @@ static void cf_interrupt_all(CPUM68KState *env, int is_hw)
             /* Return from an exception.  */
             cf_rte(env);
             return;
-        case EXCP_HALT_INSN:
-            if (semihosting_enabled((env->sr & SR_S) == 0)
-                    && (env->pc & 3) == 0
-                    && cpu_lduw_code(env, env->pc - 4) == 0x4e71
-                    && cpu_ldl_code(env, env->pc) == 0x4e7bf000) {
-                env->pc += 4;
-                do_m68k_semihosting(env, env->dregs[0]);
-                return;
-            }
-            cs->halted = 1;
-            cs->exception_index = EXCP_HLT;
-            cpu_loop_exit(cs);
+        case EXCP_SEMIHOSTING:
+            do_m68k_semihosting(env, env->dregs[0]);
             return;
         }
     }
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index 8a194f2f21..169927552a 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -26,12 +26,11 @@
 #include "qemu/log.h"
 #include "qemu/qemu-print.h"
 #include "exec/translator.h"
-
 #include "exec/helper-proto.h"
 #include "exec/helper-gen.h"
-
 #include "exec/log.h"
 #include "fpu/softfloat.h"
+#include "semihosting/semihost.h"
 
 #define HELPER_H "helper.h"
 #include "exec/helper-info.c.inc"
@@ -1401,6 +1400,40 @@ static void gen_jmp_tb(DisasContext *s, int n, target_ulong dest,
     s->base.is_jmp = DISAS_NORETURN;
 }
 
+#ifndef CONFIG_USER_ONLY
+static bool semihosting_test(DisasContext *s)
+{
+    uint32_t test;
+
+    if (!semihosting_enabled(IS_USER(s))) {
+        return false;
+    }
+
+    /*
+     * "The semihosting instruction is immediately preceded by a
+     * nop aligned to a 4-byte boundary..."
+     * The preceding 2-byte (aligned) nop plus the 2-byte halt/bkpt
+     * means that we have advanced 4 bytes from the required nop.
+     */
+    if (s->pc % 4 != 0) {
+        return false;
+    }
+    test = translator_lduw(s->env, &s->base, s->pc - 4);
+    if (test != 0x4e71) {
+        return false;
+    }
+    /* "... and followed by an invalid sentinel instruction movec %sp,0." */
+    test = translator_ldl(s->env, &s->base, s->pc);
+    if (test != 0x4e7bf000) {
+        return false;
+    }
+
+    /* Consume the sentinel. */
+    s->pc += 4;
+    return true;
+}
+#endif /* !CONFIG_USER_ONLY */
+
 DISAS_INSN(scc)
 {
     DisasCompare c;
@@ -2613,6 +2646,11 @@ DISAS_INSN(bkpt)
 #if defined(CONFIG_USER_ONLY)
     gen_exception(s, s->base.pc_next, EXCP_DEBUG);
 #else
+    /* BKPT #0 is the alternate semihosting instruction. */
+    if ((insn & 7) == 0 && semihosting_test(s)) {
+        gen_exception(s, s->pc, EXCP_SEMIHOSTING);
+        return;
+    }
     gen_exception(s, s->base.pc_next, EXCP_ILLEGAL);
 #endif
 }
@@ -4465,8 +4503,12 @@ DISAS_INSN(halt)
         gen_exception(s, s->base.pc_next, EXCP_PRIVILEGE);
         return;
     }
-
-    gen_exception(s, s->pc, EXCP_HALT_INSN);
+    if (semihosting_test(s)) {
+        gen_exception(s, s->pc, EXCP_SEMIHOSTING);
+        return;
+    }
+    tcg_gen_movi_i32(cpu_halted, 1);
+    gen_exception(s, s->pc, EXCP_HLT);
 }
 
 DISAS_INSN(stop)