From 7fc357f3585280325909e87acabcfc054d7076b6 Mon Sep 17 00:00:00 2001
From: Christian Vogelgsang <chris@vogelgsang.org>
Date: Mon, 3 Jan 2022 13:44:53 +0100
Subject: [PATCH] added aline hooks

---
 m68k.h     | 18 +++++++++++++++++-
 m68kconf.h |  3 +++
 m68kcpu.c  | 11 +++++++++++
 m68kcpu.h  | 23 ++++++++++++++++++++++-
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/m68k.h b/m68k.h
index 555b314..d3e14d9 100644
--- a/m68k.h
+++ b/m68k.h
@@ -293,7 +293,23 @@ void m68k_set_fc_callback(void  (*callback)(unsigned int new_fc));
  */
 void m68k_set_instr_hook_callback(void  (*callback)(unsigned int pc));
 
-
+/* Operation done after aline callback.
+ * Normal behaviour is triggering a CPU exception.
+ * If you use the aline hook for own emulator traps
+ * then you can decide to do nothing in CPU emulation
+ * or perform an automatic RTS instruction afterwards.
+ */
+#define M68K_ALINE_NONE   0
+#define M68K_ALINE_EXCEPT 1
+#define M68K_ALINE_RTS    2
+
+/* Set the aline callback. It will be executed every
+ * time an 0xaxxx opcode is encountered. Parameters are
+ * (opcode, current_pc). The return value is one of
+ * M68K_ALINE_* (see above).
+ * Default behaviour: CPU exception.
+ */
+void m68k_set_aline_hook_callback(int (*callback)(unsigned int, unsigned int));
 
 /* ======================================================================== */
 /* ====================== FUNCTIONS TO ACCESS THE CPU ===================== */
diff --git a/m68kconf.h b/m68kconf.h
index 8844952..10f93fc 100644
--- a/m68kconf.h
+++ b/m68kconf.h
@@ -175,6 +175,9 @@
  */
 #define M68K_EMULATE_ADDRESS_ERROR  OPT_OFF
 
+/* Intercept A-Line opcodes and call an own hook. */
+#define M68K_ALINE_HOOK             OPT_OFF
+#define M68K_ALINE_CALLBACK()       your_aline_hook_function()
 
 /* Turn ON to enable logging of illegal instruction calls.
  * M68K_LOG_FILEHANDLE must be #defined to a stdio file stream.
diff --git a/m68kcpu.c b/m68kcpu.c
index fc43122..b5b8a43 100644
--- a/m68kcpu.c
+++ b/m68kcpu.c
@@ -599,6 +599,11 @@ static void default_instr_hook_callback(unsigned int pc)
 	(void)pc;
 }
 
+/* Called every time an 0xaxxx opcode is encountered */
+static int default_aline_hook_callback(unsigned int opcode, unsigned int pc)
+{
+  return M68K_ALINE_EXCEPT;
+}
 
 #if M68K_EMULATE_ADDRESS_ERROR
 	#include <setjmp.h>
@@ -776,6 +781,11 @@ void m68k_set_instr_hook_callback(void  (*callback)(unsigned int pc))
 	CALLBACK_INSTR_HOOK = callback ? callback : default_instr_hook_callback;
 }
 
+void m68k_set_aline_hook_callback(int (*callback)(unsigned int, unsigned int))
+{
+  CALLBACK_ALINE_HOOK = callback ? callback : default_aline_hook_callback;
+}
+
 /* Set the CPU type. */
 void m68k_set_cpu_type(unsigned int cpu_type)
 {
@@ -1097,6 +1107,7 @@ void m68k_init(void)
 	m68k_set_pc_changed_callback(NULL);
 	m68k_set_fc_callback(NULL);
 	m68k_set_instr_hook_callback(NULL);
+	m68k_set_aline_hook_callback(NULL);
 }
 
 /* Trigger a Bus Error exception */
diff --git a/m68kcpu.h b/m68kcpu.h
index be88bf8..3894ce1 100644
--- a/m68kcpu.h
+++ b/m68kcpu.h
@@ -396,6 +396,7 @@ typedef uint32 uint64;
 #define CALLBACK_PC_CHANGED  m68ki_cpu.pc_changed_callback
 #define CALLBACK_SET_FC      m68ki_cpu.set_fc_callback
 #define CALLBACK_INSTR_HOOK  m68ki_cpu.instr_hook_callback
+#define CALLBACK_ALINE_HOOK  m68ki_cpu.aline_hook_callback
 
 
 
@@ -684,6 +685,16 @@ extern jmp_buf m68ki_aerr_trap;
 	#define M68K_DO_LOG_EMU(A)
 #endif
 
+/* Aline hook */
+#if M68K_ALINE_HOOK
+       #if M68K_ALINE_HOOK == OPT_SPECIFY_HANDLER
+               #define m68ki_aline_hook() M68K_ALINE_CALLBACK()
+       #else
+               #define m68ki_aline_hook() CALLBACK_ALINE_HOOK()
+       #endif
+#else
+       #define m68ki_aline_hook()  M68K_ALINE_EXCEPT
+#endif /* M68K_ALINE_HOOK */
 
 
 /* -------------------------- EA / Operand Access ------------------------- */
@@ -1000,7 +1011,7 @@ typedef struct
 	void (*pc_changed_callback)(unsigned int new_pc); /* Called when the PC changes by a large amount */
 	void (*set_fc_callback)(unsigned int new_fc);     /* Called when the CPU function code changes */
 	void (*instr_hook_callback)(unsigned int pc);     /* Called every instruction cycle prior to execution */
-
+	int  (*aline_hook_callback)(unsigned int opcode, unsigned int pc); /* Called if invalid a-line opcode occurred */
 } m68ki_cpu_core;
 
 
@@ -1952,6 +1963,10 @@ extern int cpu_log_enabled;
 /* Exception for A-Line instructions */
 static inline void m68ki_exception_1010(void)
 {
+#if M68K_ALINE_HOOK
+	int res = CALLBACK_ALINE_HOOK(REG_IR,ADDRESS_68K(REG_PPC));
+	if(res == M68K_ALINE_EXCEPT) {
+#endif
 	uint sr;
 #if M68K_LOG_1010_1111 == OPT_ON
 	M68K_DO_LOG_EMU((M68K_LOG_FILEHANDLE "%s at %08x: called 1010 instruction %04x (%s)\n",
@@ -1965,6 +1980,12 @@ static inline void m68ki_exception_1010(void)
 
 	/* Use up some clock cycles and undo the instruction's cycles */
 	USE_CYCLES(CYC_EXCEPTION[EXCEPTION_1010] - CYC_INSTRUCTION[REG_IR]);
+#if M68K_ALINE_HOOK
+	} else if(res == M68K_ALINE_RTS) {
+		m68ki_trace_t0();                             /* auto-disable (see m68kcpu.h) */
+		m68ki_jump(m68ki_pull_32());
+	}
+#endif
 }
 
 /* Exception for F-Line instructions */