feat: 3dsx loading

romFS works too, pretty neat

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);
+};