Fix detection of native NDS ARM BIOS images (#1910)

* Fix detection of native NDS ARM BIOS images

- Instead of checking for built-in BIOS images, now the altered methods check for native ones
- The CRC32 must match exactly; patched BIOS images will result in `false`

* Encapsulate `NDS::ARM9BIOS` and `ARM7BIOS`

- Also compute the checksum only when setting the BIOS

src/ARMJIT.cpp

@@ -63,12 +63,12 @@ const u32 CodeRegionSizes[ARMJIT_Memory::memregions_Count] =
     0,
     ITCMPhysicalSize,
     0,
-    sizeof(NDS::ARM9BIOS),
+    ARM9BIOSSize,
     MainRAMMaxSize,
     SharedWRAMSize,
     0,
     0x100000,
-    sizeof(NDS::ARM7BIOS),
+    ARM7BIOSSize,
     ARM7WRAMSize,
     0,
     0,

src/MemConstants.h

@@ -32,6 +32,8 @@ constexpr u32 ARM7BIOSSize = 0x4000;
 constexpr u32 DSiBIOSSize = 0x10000;
 constexpr u32 ITCMPhysicalSize = 0x8000;
 constexpr u32 DTCMPhysicalSize = 0x4000;
+constexpr u32 ARM7BIOSCRC32 = 0x1280f0d5;
+constexpr u32 ARM9BIOSCRC32 = 0x2ab23573;
 }
 
 #endif // MELONDS_MEMCONSTANTS_H

src/NDS.cpp

@@ -92,6 +92,8 @@ NDS::NDS(NDSArgs&& args, int type) noexcept :
     ConsoleType(type),
     ARM7BIOS(args.ARM7BIOS),
     ARM9BIOS(args.ARM9BIOS),
+    ARM7BIOSNative(CRC32(ARM7BIOS.data(), ARM7BIOS.size()) == ARM7BIOSCRC32),
+    ARM9BIOSNative(CRC32(ARM9BIOS.data(), ARM9BIOS.size()) == ARM9BIOSCRC32),
     JIT(*this, args.JIT),
     SPU(*this, args.BitDepth, args.Interpolation),
     GPU(*this, std::move(args.Renderer3D)),
@@ -270,7 +272,7 @@ bool NDS::NeedsDirectBoot() const
             return true;
 
         // FreeBIOS requires direct boot (it can't boot firmware)
-        if (IsLoadedARM7BIOSBuiltIn() || IsLoadedARM9BIOSBuiltIn())
+        if (!IsLoadedARM9BIOSKnownNative() || !IsLoadedARM7BIOSKnownNative())
             return true;
 
         return false;
@@ -286,7 +288,7 @@ void NDS::SetupDirectBoot()
 
     // Copy the Nintendo logo from the NDS ROM header to the ARM9 BIOS if using FreeBIOS
     // Games need this for DS<->GBA comm to work
-    if (IsLoadedARM9BIOSBuiltIn())
+    if (!IsLoadedARM9BIOSKnownNative())
     {
         memcpy(ARM9BIOS.data() + 0x20, header.NintendoLogo, 0x9C);
     }
@@ -756,6 +758,18 @@ void NDS::LoadBIOS()
     Reset();
 }
 
+void NDS::SetARM7BIOS(const std::array<u8, ARM7BIOSSize>& bios) noexcept
+{
+    ARM7BIOS = bios;
+    ARM7BIOSNative = CRC32(ARM7BIOS.data(), ARM7BIOS.size()) == ARM7BIOSCRC32;
+}
+
+void NDS::SetARM9BIOS(const std::array<u8, ARM9BIOSSize>& bios) noexcept
+{
+    ARM9BIOS = bios;
+    ARM9BIOSNative = CRC32(ARM9BIOS.data(), ARM9BIOS.size()) == ARM9BIOSCRC32;
+}
+
 u64 NDS::NextTarget()
 {
     u64 minEvent = UINT64_MAX;

src/NDS.h

@@ -39,6 +39,7 @@
 #include "MemRegion.h"
 #include "ARMJIT_Memory.h"
 #include "ARM.h"
+#include "CRC32.h"
 #include "DMA.h"
 #include "FreeBIOS.h"
 
@@ -227,7 +228,7 @@ private:
     bool EnableJIT;
 #endif
 
-public:
+public: // TODO: Encapsulate the rest of these members
     int ConsoleType;
     int CurCPU;
 
@@ -261,8 +262,14 @@ public:
     u8 ROMSeed0[2*8];
     u8 ROMSeed1[2*8];
 
+protected:
+    // These BIOS arrays should be declared *before* the component objects (JIT, SPI, etc.)
+    // so that they're initialized before the component objects' constructors run.
     std::array<u8, ARM9BIOSSize> ARM9BIOS;
     std::array<u8, ARM7BIOSSize> ARM7BIOS;
+    bool ARM9BIOSNative;
+    bool ARM7BIOSNative;
+public: // TODO: Encapsulate the rest of these members
     u16 ARM7BIOSProt;
 
     u8* MainRAM;
@@ -310,8 +317,19 @@ public:
     void SetARM7RegionTimings(u32 addrstart, u32 addrend, u32 region, int buswidth, int nonseq, int seq);
 
     void LoadBIOS();
-    [[nodiscard]] bool IsLoadedARM9BIOSBuiltIn() const noexcept { return ARM9BIOS == bios_arm9_bin; }
+
-    [[nodiscard]] bool IsLoadedARM7BIOSBuiltIn() const noexcept { return ARM7BIOS == bios_arm7_bin; }
+    /// @return \c true if the loaded ARM9 BIOS image is a known dump
+    /// of a native DS-compatible ARM9 BIOS.
+    [[nodiscard]] bool IsLoadedARM9BIOSKnownNative() const noexcept { return ARM9BIOSNative; }
+    [[nodiscard]] const std::array<u8, ARM9BIOSSize>& GetARM9BIOS() const noexcept { return ARM9BIOS; }
+    void SetARM9BIOS(const std::array<u8, ARM9BIOSSize>& bios) noexcept;
+
+    [[nodiscard]] const std::array<u8, ARM7BIOSSize>& GetARM7BIOS() const noexcept { return ARM7BIOS; }
+    void SetARM7BIOS(const std::array<u8, ARM7BIOSSize>& bios) noexcept;
+
+    /// @return \c true if the loaded ARM7 BIOS image is a known dump
+    /// of a native DS-compatible ARM9 BIOS.
+    [[nodiscard]] bool IsLoadedARM7BIOSKnownNative() const noexcept { return ARM7BIOSNative; }
 
     [[nodiscard]] NDSCart::CartCommon* GetNDSCart() { return NDSCartSlot.GetCart(); }
     [[nodiscard]] const NDSCart::CartCommon* GetNDSCart() const { return NDSCartSlot.GetCart(); }

src/NDSCart.cpp

@@ -111,7 +111,7 @@ void NDSCartSlot::Key1_ApplyKeycode(u32* keycode, u32 mod) noexcept
 
 void NDSCartSlot::Key1_LoadKeyBuf(bool dsi, const u8 *bios, u32 biosLength) noexcept
 {
-    if (!NDS.IsLoadedARM7BIOSBuiltIn())
+    if (NDS.IsLoadedARM7BIOSKnownNative())
     {
         u32 expected_bios_length = dsi ? 0x10000 : 0x4000;
         if (biosLength != expected_bios_length)
@@ -261,7 +261,7 @@ int CartCommon::ROMCommandStart(NDS& nds, NDSCartSlot& cartslot, const u8* cmd,
 
         case 0x3C:
             CmdEncMode = 1;
-            cartslot.Key1_InitKeycode(false, *(u32*)&ROM[0xC], 2, 2, &nds.ARM7BIOS[0], sizeof(NDS::ARM7BIOS));
+            cartslot.Key1_InitKeycode(false, *(u32*)&ROM[0xC], 2, 2, nds.GetARM7BIOS().data(), ARM7BIOSSize);
             DSiMode = false;
             return 0;
 
@@ -1540,10 +1540,10 @@ void NDSCartSlot::DecryptSecureArea(u8* out) noexcept
 
     memcpy(out, &cartrom[arm9base], 0x800);
 
-    Key1_InitKeycode(false, gamecode, 2, 2, &NDS.ARM7BIOS[0], sizeof(NDS::ARM7BIOS));
+    Key1_InitKeycode(false, gamecode, 2, 2, NDS.GetARM7BIOS().data(), ARM7BIOSSize);
     Key1_Decrypt((u32*)&out[0]);
 
-    Key1_InitKeycode(false, gamecode, 3, 2, &NDS.ARM7BIOS[0], sizeof(NDS::ARM7BIOS));
+    Key1_InitKeycode(false, gamecode, 3, 2, NDS.GetARM7BIOS().data(), ARM7BIOSSize);
     for (u32 i = 0; i < 0x800; i += 8)
         Key1_Decrypt((u32*)&out[i]);
 
@@ -1695,11 +1695,11 @@ void NDSCartSlot::SetCart(std::unique_ptr<CartCommon>&& cart) noexcept
 
             strncpy((char*)&cartrom[header.ARM9ROMOffset], "encryObj", 8);
 
-            Key1_InitKeycode(false, romparams.GameCode, 3, 2, &NDS.ARM7BIOS[0], sizeof(NDS::ARM7BIOS));
+            Key1_InitKeycode(false, romparams.GameCode, 3, 2, NDS.GetARM7BIOS().data(), ARM7BIOSSize);
             for (u32 i = 0; i < 0x800; i += 8)
                 Key1_Encrypt((u32*)&cartrom[header.ARM9ROMOffset + i]);
 
-            Key1_InitKeycode(false, romparams.GameCode, 2, 2, &NDS.ARM7BIOS[0], sizeof(NDS::ARM7BIOS));
+            Key1_InitKeycode(false, romparams.GameCode, 2, 2, NDS.GetARM7BIOS().data(), ARM7BIOSSize);
             Key1_Encrypt((u32*)&cartrom[header.ARM9ROMOffset]);
 
             Log(LogLevel::Debug, "Re-encrypted cart secure area\n");

src/frontend/qt_sdl/main.cpp

@@ -395,8 +395,8 @@ bool EmuThread::UpdateConsole(UpdateConsoleNDSArgs&& ndsargs, UpdateConsoleGBAAr
     };
     NDS->SetJITArgs(Config::JIT_Enable ? std::make_optional(jitargs) : std::nullopt);
 #endif
-    NDS->ARM7BIOS = *arm7bios;
+    NDS->SetARM7BIOS(*arm7bios);
-    NDS->ARM9BIOS = *arm9bios;
+    NDS->SetARM9BIOS(*arm9bios);
     NDS->SetFirmware(std::move(*firmware));
     NDS->SetNDSCart(std::move(nextndscart));
     NDS->SPU.SetInterpolation(static_cast<AudioInterpolation>(Config::AudioInterp));