tuxedo: readd default system call exception handler

Author: fincs

gc/tuxedo/ppc/exception.h

@@ -29,6 +29,7 @@ extern PPCExcptHandlerFn __ppc_excpt_table[];
 extern PPCExcptPanicFn PPCExcptCurPanicFn;
 
 void PPCExcptDefaultHandler(void);
+void PPCExcptDefaultScHandler(void);
 
 MK_INLINE void PPCExcptSetHandler(unsigned exid, PPCExcptHandlerFn handler)
 {

tuxedo/exception.c

@@ -14,9 +14,14 @@ void PPCExcptInit(void)
 		u32* target = (u32*)(0x80000000 + i*0x100);
 		__builtin_memcpy(target, impl, impl[-1]);
 
+		PPCExcptHandlerFn fn = PPCExcptDefaultHandler;
+		if (i == PPC_EXCPT_SYSCALL) {
+			fn = PPCExcptDefaultScHandler;
+		}
+
 		if (i != PPC_EXCPT_FPU) {
 			target[11] |= i;
-			PPCExcptSetHandler(i, PPCExcptDefaultHandler);
+			PPCExcptSetHandler(i, fn);
 		}
 	}
 

tuxedo/exception_asm.S

@@ -164,6 +164,31 @@ FUNC_START PPCExcptFpuHandler, text, local
 
 FUNC_END
 
+FUNC_START PPCExcptDefaultScHandler
+
+	// Restore saved PC/MSR
+	lis     r11, __ppc_excpt_buf@ha
+	lwz     r12, __ppc_excpt_buf@l+PPC_CONTEXT_PC(r11)
+	mtsrr0  r12
+	lwz     r12, __ppc_excpt_buf@l+PPC_CONTEXT_MSR(r11)
+	mtsrr1  r12
+
+	// Perform PPCSync()
+	mfspr   r11, HID0
+	ori     r12, r11, HID0_ABE
+	mtspr   HID0, r12
+	isync
+	sync
+	mtspr   HID0, r11
+	isync
+
+	// Restore saved GPR11/GPR12 and return
+	mfsprg0 r11
+	mfsprg1 r12
+	rfi
+
+FUNC_END
+
 FUNC_START PPCExcptDefaultHandler
 
 	// Set up exception stack if needed