feat: 3dsx loading

romFS works too, pretty neat

CMakeLists.txt

@@ -144,7 +144,7 @@ set(PICA_SOURCE_FILES src/core/PICA/gpu.cpp src/core/PICA/regs.cpp src/core/PICA
                       src/core/PICA/dynapica/shader_rec_emitter_x64.cpp src/core/PICA/pica_hash.cpp
 )
 
-set(LOADER_SOURCE_FILES src/core/loader/elf.cpp src/core/loader/ncsd.cpp src/core/loader/ncch.cpp src/core/loader/lz77.cpp)
+set(LOADER_SOURCE_FILES src/core/loader/elf.cpp src/core/loader/ncsd.cpp src/core/loader/ncch.cpp src/core/loader/3dsx.cpp src/core/loader/lz77.cpp)
 set(FS_SOURCE_FILES src/core/fs/archive_self_ncch.cpp src/core/fs/archive_save_data.cpp src/core/fs/archive_sdmc.cpp
                     src/core/fs/archive_ext_save_data.cpp src/core/fs/archive_ncch.cpp src/core/fs/romfs.cpp
                     src/core/fs/ivfc.cpp src/core/fs/archive_user_save_data.cpp
@@ -161,7 +161,7 @@ set(HEADER_FILES include/emulator.hpp include/helpers.hpp include/termcolor.hpp
                  include/services/gsp_gpu.hpp include/services/gsp_lcd.hpp include/arm_defs.hpp include/renderer_null/renderer_null.hpp
                  include/PICA/gpu.hpp include/PICA/regs.hpp include/services/ndm.hpp
                  include/PICA/shader.hpp include/PICA/shader_unit.hpp include/PICA/float_types.hpp
-                 include/logger.hpp include/loader/ncch.hpp include/loader/ncsd.hpp include/io_file.hpp
+                 include/logger.hpp include/loader/ncch.hpp include/loader/ncsd.hpp include/loader/3dsx.hpp include/io_file.hpp
                  include/loader/lz77.hpp include/fs/archive_base.hpp include/fs/archive_self_ncch.hpp
                  include/services/dsp.hpp include/services/cfg.hpp include/services/region_codes.hpp
                  include/fs/archive_save_data.hpp include/fs/archive_sdmc.hpp include/services/ptm.hpp

include/emulator.hpp

@@ -24,6 +24,7 @@ enum class ROMType {
 	ELF,
 	NCSD,
 	CXI,
+	HB_3DSX,
 };
 
 class Emulator {
@@ -99,6 +100,7 @@ class Emulator {
 
 	bool loadROM(const std::filesystem::path& path);
 	bool loadNCSD(const std::filesystem::path& path, ROMType type);
+	bool load3DSX(const std::filesystem::path& path);
 	bool loadELF(const std::filesystem::path& path);
 	bool loadELF(std::ifstream& file);
 	void initGraphicsContext();

include/fs/archive_self_ncch.hpp

@@ -18,7 +18,8 @@ public:
 	// Returns whether the cart has a RomFS
 	bool hasRomFS() {
 		auto cxi = mem.getCXI();
-		return (cxi != nullptr && cxi->hasRomFS());
+		auto hb3dsx = mem.get3DSX();
+		return (cxi != nullptr && cxi->hasRomFS()) | (hb3dsx != nullptr && hb3dsx->hasRomFs());
 	}
 
 	// Returns whether the cart has an ExeFS (All executable carts should have an ExeFS. This is just here to be safe)

include/loader/3dsx.hpp

@@ -0,0 +1,79 @@
+#pragma once
+#include <array>
+#include "helpers.hpp"
+#include "io_file.hpp"
+#include "loader/ncch.hpp"
+
+struct HB3DSX {
+    // File layout:
+    // - File header
+    // - Code, rodata and data relocation table headers
+    // - Code segment
+    // - Rodata segment
+    // - Loadable (non-BSS) part of the data segment
+    // - Code relocation table
+    // - Rodata relocation table
+    // - Data relocation table
+
+    // Memory layout before relocations are applied:
+    // [0..codeSegSize)             -> code segment
+    // [codeSegSize..rodataSegSize) -> rodata segment
+    // [rodataSegSize..dataSegSize) -> data segment
+
+    // Memory layout after relocations are applied: well, however the loader sets it up :)
+    // The entrypoint is always the start of the code segment.
+    // The BSS section must be cleared manually by the application.
+
+    // File header
+    struct Header {
+        // minus char magic[4]
+        u16 headerSize;
+        u16 relocHdrSize;
+        u32 formatVer;
+        u32 flags;
+
+        // Sizes of the code, rodata and data segments +
+        // size of the BSS section (uninitialized latter half of the data segment)
+        u32 codeSegSize, rodataSegSize, dataSegSize, bssSize;
+    };
+
+    // Relocation header: all fields (even extra unknown fields) are guaranteed to be relocation counts.
+    struct RelocHdr {
+        u32 cAbsolute; // # of absolute relocations (that is, fix address to post-relocation memory layout)
+        u32 cRelative; // # of cross-segment relative relocations (that is, 32bit signed offsets that need to be patched)
+        // more?
+
+        // Relocations are written in this order:
+        // - Absolute relocs
+        // - Relative relocs
+    };
+    enum class RelocKind {
+        Absolute,
+        Relative,
+    };
+
+    // Relocation entry: from the current pointer, skip X words and patch Y words
+    struct Reloc {
+        u16 skip, patch;
+    };
+
+    // _prm structure
+    static constexpr std::array<char, 4> PRM_MAGIC = {'_', 'P', 'R', 'M'};
+    struct PrmStruct {
+        char magic[4];
+        u32 pSrvOverride;
+        u32 aptAppId;
+        u32 heapSize, linearHeapSize;
+        u32 pArgList;
+        u32 runFlags;
+    };
+
+    IOFile file;
+
+    static constexpr u32 ENTRYPOINT = 0x00100000; // Initial ARM11 PC
+    u32 romFSSize = 0;
+    u32 romFSOffset = 0;
+
+    bool hasRomFs() const;
+    std::pair<bool, std::size_t> readRomFSBytes(void *dst, std::size_t offset, std::size_t size);
+};

include/memory.hpp

@@ -11,6 +11,7 @@
 #include "handles.hpp"
 #include "helpers.hpp"
 #include "loader/ncsd.hpp"
+#include "loader/3dsx.hpp"
 #include "services/region_codes.hpp"
 
 namespace PhysicalAddrs {
@@ -167,10 +168,12 @@ public:
 	void* getReadPointer(u32 address);
 	void* getWritePointer(u32 address);
 	std::optional<u32> loadELF(std::ifstream& file);
+	std::optional<u32> load3DSX(const std::filesystem::path& path);
 	std::optional<NCSD> loadNCSD(Crypto::AESEngine& aesEngine, const std::filesystem::path& path);
 	std::optional<NCSD> loadCXI(Crypto::AESEngine& aesEngine, const std::filesystem::path& path);
 
 	bool mapCXI(NCSD& ncsd, NCCH& cxi);
+	bool map3DSX(HB3DSX& hb3dsx, const HB3DSX::Header& header);
 
 	u8 read8(u32 vaddr);
 	u16 read16(u32 vaddr);
@@ -221,6 +224,14 @@ public:
 		}
 	}
 
+	HB3DSX* get3DSX() {
+		if (loaded3DSX.has_value()) {
+			return &loaded3DSX.value();
+		} else {
+			return nullptr;
+		}
+	}
+
 	// Returns whether "addr" is aligned to a page (4096 byte) boundary
 	static constexpr bool isAligned(u32 addr) {
 		return (addr & pageMask) == 0;
@@ -256,6 +267,7 @@ public:
 
 	// Backup of the game's CXI partition info, if any
 	std::optional<NCCH> loadedCXI = std::nullopt;
+	std::optional<HB3DSX> loaded3DSX = std::nullopt;
 	// File handle for reading the loaded ncch
 	IOFile CXIFile;
 

src/core/fs/archive_self_ncch.cpp

@@ -69,57 +69,78 @@ std::optional<u32> SelfNCCHArchive::readFile(FileSession* file, u64 offset, u32
 		return std::nullopt;
 	}
 
-	auto cxi = mem.getCXI();
-	IOFile& ioFile = mem.CXIFile;
+	bool success = false;
+	std::size_t bytesRead = 0;
+	std::vector<u8> data;
 
-	NCCH::FSInfo fsInfo;
+	if (auto cxi = mem.getCXI(); cxi != nullptr) {
+		IOFile& ioFile = mem.CXIFile;
 
-	// Seek to file offset depending on if we're reading from RomFS, ExeFS, etc
-	switch (type) {
-		case PathType::RomFS: {
-			const u64 romFSSize = cxi->romFS.size;
-			const u64 romFSOffset = cxi->romFS.offset;
-			if ((offset >> 32) || (offset >= romFSSize) || (offset + size >= romFSSize)) {
-				Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+		NCCH::FSInfo fsInfo;
+
+		// Seek to file offset depending on if we're reading from RomFS, ExeFS, etc
+		switch (type) {
+			case PathType::RomFS: {
+				const u64 romFSSize = cxi->romFS.size;
+				const u64 romFSOffset = cxi->romFS.offset;
+				if ((offset >> 32) || (offset >= romFSSize) || (offset + size >= romFSSize)) {
+					Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+				}
+
+				fsInfo = cxi->romFS;
+				offset += 0x1000;
+				break;
 			}
 
-			fsInfo = cxi->romFS;
-			offset += 0x1000;
-			break;
-		}
+			case PathType::ExeFS: {
+				const u64 exeFSSize = cxi->exeFS.size;
+				const u64 exeFSOffset = cxi->exeFS.offset;
+				if ((offset >> 32) || (offset >= exeFSSize) || (offset + size >= exeFSSize)) {
+					Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+				}
 
-		case PathType::ExeFS: {
-			const u64 exeFSSize = cxi->exeFS.size;
-			const u64 exeFSOffset = cxi->exeFS.offset;
-			if ((offset >> 32) || (offset >= exeFSSize) || (offset + size >= exeFSSize)) {
-				Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+				fsInfo = cxi->exeFS;
+				break;
 			}
 
-			fsInfo = cxi->exeFS;
-			break;
-		}
+			// Normally, the update RomFS should overlay the cartridge RomFS when reading from this and an update is installed.
+			// So to support updates, we need to perform this overlaying. For now, read from the cartridge RomFS.
+			case PathType::UpdateRomFS: {
+				Helpers::warn("Reading from update RomFS but updates are currently not supported! Reading from regular RomFS instead\n");
 
-		// Normally, the update RomFS should overlay the cartridge RomFS when reading from this and an update is installed.
-		// So to support updates, we need to perform this overlaying. For now, read from the cartridge RomFS.
-		case PathType::UpdateRomFS: {
-			Helpers::warn("Reading from update RomFS but updates are currently not supported! Reading from regular RomFS instead\n");
+				const u64 romFSSize = cxi->romFS.size;
+				const u64 romFSOffset = cxi->romFS.offset;
+				if ((offset >> 32) || (offset >= romFSSize) || (offset + size >= romFSSize)) {
+					Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+				}
 
-			const u64 romFSSize = cxi->romFS.size;
-			const u64 romFSOffset = cxi->romFS.offset;
-			if ((offset >> 32) || (offset >= romFSSize) || (offset + size >= romFSSize)) {
-				Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+				fsInfo = cxi->romFS;
+				offset += 0x1000;
+				break;
 			}
 
-			fsInfo = cxi->romFS;
-			offset += 0x1000;
-			break;
+			default: Helpers::panic("Unimplemented file path type for SelfNCCH archive");
 		}
 
-		default: Helpers::panic("Unimplemented file path type for SelfNCCH archive");
+		data.resize(size);
+		std::tie(success, bytesRead) = cxi->readFromFile(ioFile, fsInfo, &data[0], offset, size);
 	}
+	else if (auto hb3dsx = mem.get3DSX(); hb3dsx != nullptr) {
+		switch (type) {
+			case PathType::RomFS: {
+				const u64 romFSSize = hb3dsx->romFSSize;
+				if ((offset >> 32) || (offset >= romFSSize) || (offset + size >= romFSSize)) {
+					Helpers::panic("Tried to read from SelfNCCH with too big of an offset");
+				}
+				break;
+			}
 
-	std::unique_ptr<u8[]> data(new u8[size]);
-	auto [success, bytesRead] = cxi->readFromFile(ioFile, fsInfo, &data[0], offset, size);
+			default: Helpers::panic("Unimplemented file path type for 3DSX SelfNCCH archive");
+		}
+
+		data.resize(size);
+		std::tie(success, bytesRead) = hb3dsx->readRomFSBytes(&data[0], offset, size);
+	}
 
 	if (!success) {
 		Helpers::panic("Failed to read from SelfNCCH archive");

src/core/loader/3dsx.cpp

@@ -0,0 +1,300 @@
+#include "loader/3dsx.hpp"
+
+#include <cstring>
+#include <optional>
+#include <span>
+
+#include "memory.hpp"
+
+namespace {
+
+struct LoadInfo {
+	u32 codeSegSizeAligned;
+	u32 rodataSegSizeAligned;
+	u32 dataSegSizeAligned;
+};
+
+static inline u32 TranslateAddr(const u32 off, const u32* addrs, const u32* offsets)
+{
+    if (off < offsets[1])
+        return addrs[0] + off;
+    if (off < offsets[2])
+        return addrs[1] + off - offsets[1];
+    return addrs[2] + off - offsets[2];
+}
+
+}
+
+bool Memory::map3DSX(HB3DSX& hb3dsx, const HB3DSX::Header& header) {
+	const LoadInfo hbInfo = {
+		(header.codeSegSize+0xFFF) &~ 0xFFF,
+		(header.rodataSegSize+0xFFF) &~ 0xFFF,
+		(header.dataSegSize+0xFFF) &~ 0xFFF,
+	};
+
+	const u32 textSegAddr = HB3DSX::ENTRYPOINT;
+	const u32 rodataSegAddr = textSegAddr + hbInfo.codeSegSizeAligned;
+	const u32 dataSegAddr = rodataSegAddr + hbInfo.rodataSegSizeAligned;
+	const u32 extraPageAddr = dataSegAddr + hbInfo.dataSegSizeAligned;
+
+	printf("Text address = %08X, size = %08X\n", textSegAddr, hbInfo.codeSegSizeAligned);
+	printf("Rodata address = %08X, size = %08X\n", rodataSegAddr, hbInfo.rodataSegSizeAligned);
+	printf("Data address = %08X, size = %08X\n", dataSegAddr, hbInfo.dataSegSizeAligned);
+
+	// Allocate stack, 3dsx/libctru don't require anymore than this
+	if (!allocateMainThreadStack(0x1000)) {
+		// Should be unreachable
+		printf("Failed to allocate stack for 3DSX.\n");
+		return false;
+	}
+
+	// Map code file to memory
+	// Total memory to allocate for loading
+	// suum of aligned values is always aligned, have an extra RW page for libctru
+	const u32 totalSize = hbInfo.codeSegSizeAligned + hbInfo.rodataSegSizeAligned + hbInfo.dataSegSizeAligned + 0x1000;
+
+	const auto opt = findPaddr(totalSize);
+	if (!opt.has_value()) {
+		Helpers::panic("Failed to find paddr to map 3DSX file's code to");
+		return false;
+	}
+
+	// Map the ROM on the kernel side
+	const u32 textOffset = 0;
+	const u32 rodataOffset = textOffset + hbInfo.codeSegSizeAligned;
+	const u32 dataOffset = rodataOffset + hbInfo.rodataSegSizeAligned;
+	const u32 extraPageOffset = dataOffset + hbInfo.dataSegSizeAligned;
+
+	std::array<HB3DSX::RelocHdr, 3> relocHdrs;
+	auto [success, count] = hb3dsx.file.read(&relocHdrs[0], relocHdrs.size(), sizeof(HB3DSX::RelocHdr));
+	if (!success || count != relocHdrs.size()) {
+		Helpers::panic("Failed to read 3DSX relocation headers");
+		return false;
+	}
+
+	const u32 dataLoadsize = header.dataSegSize - header.bssSize; // 3DSX data size in header includes bss
+	std::vector<u8> code(totalSize, 0);
+
+	std::tie(success, count) = hb3dsx.file.readBytes(&code[textOffset], header.codeSegSize);
+	if (!success || count != header.codeSegSize) {
+		Helpers::panic("Failed to read 3DSX text segment");
+		return false;
+	}
+
+	std::tie(success, count) = hb3dsx.file.readBytes(&code[rodataOffset], header.rodataSegSize);
+	if (!success || count != header.rodataSegSize) {
+		Helpers::panic("Failed to read 3DSX rodata segment");
+		return false;
+	}
+
+	std::tie(success, count) = hb3dsx.file.readBytes(&code[dataOffset], dataLoadsize);
+	if (!success || count !=  dataLoadsize) {
+		Helpers::panic("Failed to read 3DSX data segment");
+		return false;
+	}
+
+	std::vector<HB3DSX::Reloc> currentRelocs;
+	const u32 segAddrs[] = {
+		textSegAddr,
+		rodataSegAddr,
+		dataSegAddr,
+		extraPageAddr,
+	};
+	const u32 segOffs[] = {
+		textOffset,
+		rodataOffset,
+		dataOffset,
+		extraPageOffset,
+	};
+	const u32 segSizes[] = {
+		header.codeSegSize,
+		header.rodataSegSize,
+		dataLoadsize,
+		0x1000,
+	};
+
+	for (const auto& relocHdr : relocHdrs) {
+		currentRelocs.resize(relocHdr.cAbsolute + relocHdr.cRelative);
+		std::tie(success, count) = hb3dsx.file.read(&currentRelocs[0], currentRelocs.size(), sizeof(HB3DSX::Reloc));
+		if (!success || count !=  currentRelocs.size()) {
+			Helpers::panic("Failed to read 3DSX relocations");
+			return false;
+		}
+
+		const auto allRelocs = std::span(currentRelocs);
+		const auto absoluteRelocs = allRelocs.subspan(0, relocHdr.cAbsolute);
+		const auto relativeRelocs = allRelocs.subspan(relocHdr.cAbsolute, relocHdr.cRelative);
+
+		const auto currentSeg = &relocHdr - &relocHdrs[0];
+		const auto sectionDataStartAs = std::span(code).subspan(segOffs[currentSeg], segSizes[currentSeg]);
+
+		auto sectionData = sectionDataStartAs;
+		const auto RelocationAction = [&](const HB3DSX::Reloc& reloc, const HB3DSX::RelocKind relocKind) -> bool {
+			if(reloc.skip) {
+				sectionData = sectionData.subspan(reloc.skip * sizeof(u32)); // advance by `skip` words (32-bit values)
+			}
+
+			for (u32 m = 0; m < reloc.patch && !sectionData.empty(); ++m) {
+				const u32 inAddr = textSegAddr + (sectionData.data() - code.data()); // byte offset -> word count
+				u32 origData = 0;
+				std::memcpy(&origData, &sectionData[0], sizeof(u32));
+				const u32 subType = origData >> (32-4);
+				const u32 addr = TranslateAddr(origData &~ 0xF0000000, segAddrs, segOffs);
+
+				switch (relocKind) {
+					case HB3DSX::RelocKind::Absolute: {
+						if (subType != 0) {
+							Helpers::panic("Unsupported absolute reloc subtype");
+							return false;
+						}
+						std::memcpy(&sectionData[0], &addr, sizeof(u32));
+						break;
+					}
+					case HB3DSX::RelocKind::Relative: {
+						u32 data = addr - inAddr;
+						switch (subType) {
+							case 1: // 31-bit signed offset
+								data &= ~(1u << 31);
+							case 0: // 32-bit signed offset
+								std::memcpy(&sectionData[0], &data, sizeof(u32));
+								break;
+							default:
+								Helpers::panic("Unsupported relative reloc subtype");
+								return false;
+						}
+						break;
+					}
+				}
+				sectionData = sectionData.subspan(sizeof(u32));
+			}
+
+			return true;
+		};
+
+		for (const auto& reloc : absoluteRelocs) {
+			if(!RelocationAction(reloc, HB3DSX::RelocKind::Absolute)) {
+				return false;
+			}
+		}
+
+		sectionData = sectionDataStartAs; // restart from the beginning for the next part
+		for (const auto& reloc : relativeRelocs) {
+			if(!RelocationAction(reloc, HB3DSX::RelocKind::Relative)) {
+				return false;
+			}
+		}
+	}
+
+	// Detect and fill _prm structure
+	HB3DSX::PrmStruct pst;
+	std::memcpy(&pst, &code[4], sizeof(pst));
+	if (pst.magic[0] == '_' && pst.magic[1] == 'p' && pst.magic[2] == 'r' && pst.magic[3] == 'm' ) {
+		// if there was any argv to put, it would go there
+		// first u32: argc
+		// remaining: continuous argv string (NUL-char separated, ofc)
+		// std::memcpy(&code[extraPageOffset], argvBuffer, ...);
+		
+		// setting to NULL (default) = run from system. load romfs from process.
+		// non-NULL = homebrew launcher. load romfs from 3dsx @ argv[0]
+		// pst.pSrvOverride = extraPageAddr + 0xFFC;
+		
+		pst.pArgList = extraPageAddr;
+		
+		// RUNFLAG_APTREINIT: Reinitialize APT.
+		// From libctru. Because there's no previously running software here
+		pst.runFlags |= 1 << 1;
+		
+		/* s64 dummy;
+		bool isN3DS = svcGetSystemInfo(&dummy, 0x10001, 0) == 0;
+		if (isN3DS)
+		{
+			pst->heapSize = 48*1024*1024;
+			pst->linearHeapSize = 64*1024*1024;
+		} else */ {
+			pst.heapSize = 24*1024*1024;
+			pst.linearHeapSize = 32*1024*1024;
+		}
+
+		std::memcpy(&code[4], &pst, sizeof(pst));
+	}
+
+	const auto paddr = opt.value();
+	std::memcpy(&fcram[paddr], &code[0], totalSize);  // Copy the 3 segments + BSS to FCRAM
+
+	allocateMemory(textSegAddr, paddr + textOffset, hbInfo.codeSegSizeAligned, true, true, false, true);         // Text is R-X
+	allocateMemory(rodataSegAddr, paddr + rodataOffset, hbInfo.rodataSegSizeAligned, true, true, false, false);  // Rodata is R--
+	allocateMemory(dataSegAddr, paddr + dataOffset, hbInfo.dataSegSizeAligned + 0x1000, true, true, true, false);         // Data+BSS+Extra is RW-
+
+	return true;
+}
+
+std::optional<u32> Memory::load3DSX(const std::filesystem::path& path) {
+	HB3DSX hb3dsx;
+	if (!hb3dsx.file.open(path, "rb")) return std::nullopt;
+
+	u8 magic[4];  // Must be "3DSX"
+	auto [success, bytes] = hb3dsx.file.readBytes(magic, 4);
+
+	if (!success || bytes != 4) {
+		printf("Failed to read 3DSX magic\n");
+		return std::nullopt;
+	}
+
+	if (magic[0] != '3' || magic[1] != 'D' || magic[2] != 'S' || magic[3] != 'X') {
+		printf("3DSX with wrong magic value\n");
+		return std::nullopt;
+	}
+
+	HB3DSX::Header hbHeader;
+	std::tie(success, bytes) = hb3dsx.file.readBytes(&hbHeader, sizeof(hbHeader));
+	if (!success || bytes != sizeof(hbHeader)) {
+		printf("Failed to read 3DSX header\n");
+		return std::nullopt;
+	}
+
+	if (hbHeader.headerSize == 0x20 || hbHeader.headerSize == 0x2C) {
+		if (hbHeader.headerSize == 0x2C)
+		{
+			hb3dsx.file.seek(8, SEEK_CUR); // skip SMDH info
+			std::tie(success, bytes) = hb3dsx.file.readBytes(&hb3dsx.romFSOffset, 4);
+			if (!success || bytes != 4) {
+				printf("Failed to read 3DSX romFS offset\n");
+				return std::nullopt;
+			}
+			const auto fileSize = hb3dsx.file.size();
+			if (!fileSize) {
+				printf("Failed to get 3DSX size\n");
+				return std::nullopt;
+			}
+			hb3dsx.romFSSize = *fileSize - hb3dsx.romFSOffset;
+		}
+	}
+	else {
+		printf("Invalid 3DSX header size\n");
+		return std::nullopt;
+	}
+
+	if (!map3DSX(hb3dsx, hbHeader)) {
+		printf("Failed to map 3DSX\n");
+		return std::nullopt;
+	}
+
+	loaded3DSX = std::move(hb3dsx);
+	return HB3DSX::ENTRYPOINT;
+}
+
+bool HB3DSX::hasRomFs() const {
+	return romFSSize != 0 && romFSOffset != 0;
+}
+
+std::pair<bool, std::size_t> HB3DSX::readRomFSBytes(void *dst, std::size_t offset, std::size_t size) {
+	if (!hasRomFs()) {
+		return { false, 0 };
+	}
+
+	if (!file.seek(romFSOffset + offset)) {
+		return { false, 0 };
+	}
+
+	return file.readBytes(dst, size);
+}

src/emulator.cpp

@@ -453,6 +453,8 @@ bool Emulator::loadROM(const std::filesystem::path& path) {
 		success = loadNCSD(path, ROMType::NCSD);
 	else if (extension == ".cxi" || extension == ".app")
 		success = loadNCSD(path, ROMType::CXI);
+	else if (extension == ".3dsx")
+		success = load3DSX(path);
 	else {
 		printf("Unknown file type\n");
 		success = false;
@@ -492,6 +494,19 @@ bool Emulator::loadNCSD(const std::filesystem::path& path, ROMType type) {
 	return true;
 }
 
+bool Emulator::load3DSX(const std::filesystem::path& path) {
+	std::optional<u32> entrypoint = memory.load3DSX(path);
+	romType = ROMType::HB_3DSX;
+
+	if (!entrypoint.has_value()) {
+		return false;
+	}
+
+	cpu.setReg(15, entrypoint.value());  // Set initial PC
+
+	return true;
+}
+
 bool Emulator::loadELF(const std::filesystem::path& path) {
 	loadedELF.open(path, std::ios_base::binary);  // Open ROM in binary mode
 	romType = ROMType::ELF;