GB Serialize: Fix loading non-BIOS state from BIOS (fixes #1280)

CHANGES

@@ -30,6 +30,7 @@ Other fixes:
  - Qt: Fix FPS target maxing out at 59.727 (fixes mgba.io/i/1421)
  - Core: Fix crashes if core directories aren't set
  - Qt: Cap audio buffer size to 8192 (fixes mgba.io/i/1433)
+ - GB Serialize: Fix loading non-BIOS state from BIOS (fixes mgba.io/i/1280)
 Misc:
  - GBA Savedata: EEPROM performance fixes
  - GBA Savedata: Automatically map 1Mbit Flash files as 1Mbit Flash

include/mgba/internal/gb/gb.h

@@ -150,6 +150,7 @@ void GBDestroy(struct GB* gb);
 
 void GBReset(struct LR35902Core* cpu);
 void GBSkipBIOS(struct GB* gb);
+void GBMapBIOS(struct GB* gb);
 void GBUnmapBIOS(struct GB* gb);
 void GBDetectModel(struct GB* gb);
 

src/gb/gb.c

@@ -419,14 +419,7 @@ void GBReset(struct LR35902Core* cpu) {
 			gb->biosVf->close(gb->biosVf);
 			gb->biosVf = NULL;
 		} else {
-			gb->biosVf->seek(gb->biosVf, 0, SEEK_SET);
+			GBMapBIOS(gb);
-			gb->memory.romBase = malloc(GB_SIZE_CART_BANK0);
-			ssize_t size = gb->biosVf->read(gb->biosVf, gb->memory.romBase, GB_SIZE_CART_BANK0);
-			memcpy(&gb->memory.romBase[size], &gb->memory.rom[size], GB_SIZE_CART_BANK0 - size);
-			if (size > 0x100) {
-				memcpy(&gb->memory.romBase[0x100], &gb->memory.rom[0x100], sizeof(struct GBCartridge));
-			}
-
 			cpu->a = 0;
 			cpu->f.packed = 0;
 			cpu->c = 0;
@@ -563,6 +556,16 @@ void GBSkipBIOS(struct GB* gb) {
 	}
 }
 
+void GBMapBIOS(struct GB* gb) {
+	gb->biosVf->seek(gb->biosVf, 0, SEEK_SET);
+	gb->memory.romBase = malloc(GB_SIZE_CART_BANK0);
+	ssize_t size = gb->biosVf->read(gb->biosVf, gb->memory.romBase, GB_SIZE_CART_BANK0);
+	memcpy(&gb->memory.romBase[size], &gb->memory.rom[size], GB_SIZE_CART_BANK0 - size);
+	if (size > 0x100) {
+		memcpy(&gb->memory.romBase[0x100], &gb->memory.rom[0x100], sizeof(struct GBCartridge));
+	}
+}
+
 void GBUnmapBIOS(struct GB* gb) {
 	if (gb->memory.romBase < gb->memory.rom || gb->memory.romBase > &gb->memory.rom[gb->memory.romSize - 1]) {
 		free(gb->memory.romBase);

src/gb/io.c

@@ -185,8 +185,10 @@ void GBIOReset(struct GB* gb) {
 	GBIOWrite(gb, REG_NR51, 0xF3);
 	if (!gb->biosVf) {
 		GBIOWrite(gb, REG_LCDC, 0x91);
+		gb->memory.io[0x50] = 1;
 	} else {
 		GBIOWrite(gb, REG_LCDC, 0x00);
+		gb->memory.io[0x50] = 0xFF;
 	}
 	GBIOWrite(gb, REG_SCY, 0x00);
 	GBIOWrite(gb, REG_SCX, 0x00);

src/gb/serialize.c

@@ -135,6 +135,16 @@ bool GBDeserialize(struct GB* gb, const struct GBSerializedState* state) {
 	if (ucheck16 >= 0x40) {
 		mLOG(GB_STATE, WARN, "Savestate is corrupted: OCPS is out of range");
 	}
+	bool differentBios = !gb->biosVf || gb->model != state->model;
+	if (state->io[0x50] == 0xFF) {
+		if (differentBios) {
+			mLOG(GB_STATE, WARN, "Incompatible savestate, please restart with correct BIOS in %s mode", GBModelToName(state->model));
+			error = true;
+		} else {
+			// TODO: Make it work correctly
+			mLOG(GB_STATE, WARN, "ILoading savestate in BIOS. This may not work correctly");
+		}
+	}
 	if (error) {
 		return false;
 	}
@@ -187,6 +197,12 @@ bool GBDeserialize(struct GB* gb, const struct GBSerializedState* state) {
 	GBTimerDeserialize(&gb->timer, state);
 	GBAudioDeserialize(&gb->audio, state);
 
+	if (gb->memory.io[0x50] == 0xFF) {
+		GBMapBIOS(gb);
+	} else {
+		GBUnmapBIOS(gb);
+	}
+
 	if (gb->model & GB_MODEL_SGB && canSgb) {
 		GBSGBDeserialize(gb, state);
 	}