GBA BIOS: Fix undefined instruction HLE behavior

CHANGES

@@ -5,6 +5,7 @@ Emulation fixes:
  - ARM: Fix ALU reading PC after shifting
  - ARM: Fix STR storing PC after address calculation
  - GB Serialize: Fix timing bug loading channel 4 timing
+ - GBA BIOS: Fix undefined instruction HLE behavior
  - GBA DMA: Linger last DMA on bus (fixes mgba.io/i/301 and mgba.io/i/1320)
  - GBA Memory: Misaligned SRAM writes are ignored
  - GBA Memory: Improve gamepak prefetch timing

src/gba/hle-bios.c

@@ -3,10 +3,10 @@
 #include <mgba/internal/gba/memory.h>
 
 const uint8_t hleBios[SIZE_BIOS] = {
-	0x06, 0x00, 0x00, 0xea, 0xfe, 0xff, 0xff, 0xea, 0x0b, 0x00, 0x00, 0xea,
+	0x06, 0x00, 0x00, 0xea, 0x88, 0x00, 0x00, 0xea, 0x0b, 0x00, 0x00, 0xea,
 	0xfe, 0xff, 0xff, 0xea, 0xfe, 0xff, 0xff, 0xea, 0x00, 0x00, 0xa0, 0xe1,
 	0x2c, 0x00, 0x00, 0xea, 0xfe, 0xff, 0xff, 0xea, 0x02, 0x03, 0xa0, 0xe3,
-	0x03, 0x10, 0xd0, 0xe5, 0xea, 0x00, 0x51, 0xe3, 0xf8, 0x01, 0x9f, 0x15,
+	0x03, 0x10, 0xd0, 0xe5, 0xea, 0x00, 0x51, 0xe3, 0x04, 0x02, 0x9f, 0x15,
 	0x10, 0xff, 0x2f, 0xe1, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0, 0x29, 0xe1,
 	0x00, 0x00, 0x5d, 0xe3, 0x01, 0xd3, 0xa0, 0x03, 0x20, 0xd0, 0x4d, 0x02,
 	0x00, 0x58, 0x2d, 0xe9, 0x02, 0xb0, 0x5e, 0xe5, 0x9c, 0xc0, 0xa0, 0xe3,
@@ -49,5 +49,6 @@ const uint8_t hleBios[SIZE_BIOS] = {
 	0x03, 0xa0, 0xa0, 0xe1, 0x02, 0x00, 0x51, 0xe1, 0xf8, 0x07, 0xa1, 0xb8,
 	0xfc, 0xff, 0xff, 0xba, 0x03, 0x00, 0x00, 0xea, 0x02, 0x00, 0x51, 0xe1,
 	0xf8, 0x07, 0xb0, 0xb8, 0xf8, 0x07, 0xa1, 0xb8, 0xfb, 0xff, 0xff, 0xba,
-	0xf0, 0x87, 0xbd, 0xe8, 0xc0, 0x00, 0x00, 0x02
+	0xf0, 0x87, 0xbd, 0xe8, 0x04, 0xf0, 0x5e, 0xe2, 0x00, 0x00, 0x00, 0x00,
+	0x04, 0xe0, 0xa0, 0x03, 0xc0, 0x00, 0x00, 0x02
 };

src/gba/hle-bios.s

@@ -187,4 +187,9 @@ blt    0b
 2:
 ldmfd  sp!, {r4-r10, pc}
 
+undefBase:
+subs   pc, lr, #4
+.word 0
+.word 0x03A0E004
+
 .ltorg