From 4f94849728227e028564cbd72ef4605edbb56707 Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Thu, 10 Feb 2022 18:26:08 -0800
Subject: [PATCH] GBA: Automatically skip BIOS if ROM has invalid logo

---
 CHANGES        |  1 +
 src/gba/core.c | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index dc8ad9aa0..7a7285bd5 100644
--- a/CHANGES
+++ b/CHANGES
@@ -41,6 +41,7 @@ Other fixes:
 Misc:
  - Core: Suspend runloop when a core crashes
  - GB Video: Add default SGB border
+ - GBA: Automatically skip BIOS if ROM has invalid logo
  - mGUI: Add margin to right-aligned menu text (fixes mgba.io/i/871)
  - Qt: Rearrange menus some
  - Qt: Clean up cheats dialog
diff --git a/src/gba/core.c b/src/gba/core.c
index 8515fa9c1..633572249 100644
--- a/src/gba/core.c
+++ b/src/gba/core.c
@@ -25,6 +25,7 @@
 #include <mgba/internal/gba/renderers/video-software.h>
 #include <mgba/internal/gba/savedata.h>
 #include <mgba/internal/gba/serialize.h>
+#include <mgba-util/crc32.h>
 #ifdef USE_ELF
 #include <mgba-util/elf-read.h>
 #endif
@@ -129,6 +130,7 @@ static const struct mCoreMemoryBlock _GBAMemoryBlocksEEPROM[] = {
 struct mVideoLogContext;
 
 #define CPU_COMPONENT_AUDIO_MIXER CPU_COMPONENT_MISC_1
+#define LOGO_CRC32 0xD0BEB55E
 
 struct GBACore {
 	struct mCore d;
@@ -658,7 +660,16 @@ static void _GBACoreReset(struct mCore* core) {
 #endif
 
 	ARMReset(core->cpu);
-	if ((core->opts.skipBios && (gba->romVf || gba->memory.rom)) || (gba->romVf && GBAIsMB(gba->romVf))) {
+	bool forceSkip = gba->romVf && GBAIsMB(gba->romVf);
+	if (!(forceSkip || core->opts.skipBios) && (gba->romVf || gba->memory.rom) && gba->pristineRomSize >= 0xA0 && gba->biosVf) {
+		uint32_t crc = doCrc32(&gba->memory.rom[1], 0x9C);
+		if (crc != LOGO_CRC32) {
+			mLOG(STATUS, WARN, "Invalid logo, skipping BIOS");
+			forceSkip = true;
+		}
+	}
+
+	if (forceSkip || (core->opts.skipBios && (gba->romVf || gba->memory.rom))) {
 		GBASkipBIOS(core->board);
 	}
 }