load_obfuscation_shims.c

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#include "common.h"
#include "nu/nusys.h"
#include "ld_addrs.h"
#include "mips.h"
 
extern s8 obfuscated_obfuscation_shims_ROM_START[];
extern s8 obfuscated_obfuscation_shims_VRAM[];
 
#if VERSION_JP
// TODO: split these segments
extern Addr battle_heap_create_obfuscated_ROM_START;
extern Addr battle_heap_create_obfuscated_ROM_END;
extern Addr obfuscation_shims_ROM_START;
extern Addr obfuscation_shims_ROM_END;
#endif
 
#ifdef SHIFT
void load_obfuscation_shims(void) {
    // no-op since in shiftable builds, we bypass the obfuscation
}
#else
void load_obfuscation_shims(void) {
    s32 (*readFunc)(OSPiHandle*, u32, u32*);
    s32 (*readFunc2)(OSPiHandle*, u32, u32*);
    s8* vramDest = obfuscated_obfuscation_shims_VRAM;
    s8* romStart = obfuscated_obfuscation_shims_ROM_START;
    s32 seed;
    u32 hash;
    u32 thisInsn;
    u32 thisInsn2;
    u32 prevInsn;
    u8* it;
 
    // vramDest
    readFunc = osEPiReadIo;
    seed = 0x0B112D28;
    hash = 0;
    readFunc(nuPiCartHandle, 0xB0000D10, &thisInsn);
    seed -= thisInsn;
    prevInsn = 0;
 
    for (it = battle_heap_create_obfuscated_ROM_START; it < battle_heap_create_obfuscated_ROM_END; it += 4) {
        readFunc(nuPiCartHandle, (u32)it, &thisInsn);
        hash += LOWER(thisInsn) + UPPER(thisInsn);
 
        if (OPCODE(prevInsn) == LUI && (OPCODE(thisInsn) == ADDIU || OPCODE(thisInsn) == LW)) {
            if (GET_RS(thisInsn) == GET_RT(prevInsn) && GET_RS(thisInsn) == GET_RT(thisInsn)) {
                hash -= LOWER(thisInsn);
                hash -= LOWER(prevInsn);
            }
        }
 
        if (OPCODE(thisInsn) == JAL) {
            hash -= LOWER(thisInsn) + (UPPER(thisInsn) & 0xFC00);
        }
 
        prevInsn = thisInsn;
    }
    vramDest += seed + 0x2A4EB6 - hash;
 
    // romStart
    readFunc2 = osEPiReadIo;
    seed = 0x18F414AB;
    hash = 0;
    readFunc2(nuPiCartHandle, 0xB0000E38, &thisInsn2);
    seed -= thisInsn2;
    prevInsn = 0;
 
    for (it = obfuscation_shims_ROM_START; it < obfuscation_shims_ROM_END; it += 4) {
        readFunc2(nuPiCartHandle, (u32)it, &thisInsn2);
        hash += LOWER(thisInsn2) + UPPER(thisInsn2);
 
        if (OPCODE(prevInsn) == LUI && (OPCODE(thisInsn2) == ADDIU || OPCODE(thisInsn2) == LW)) {
            if (GET_RS(thisInsn2) == GET_RT(prevInsn) && GET_RS(thisInsn2) == GET_RT(thisInsn2)) {
                hash -= LOWER(thisInsn2);
                hash -= LOWER(prevInsn);
            }
        }
 
        if (OPCODE(thisInsn2) == JAL) {
            hash -= LOWER(thisInsn2) + (UPPER(thisInsn2) & 0xFC00);
        }
        prevInsn = thisInsn2;
    }
    romStart += seed + 0xED41C - hash;
 
    dma_copy(romStart, obfuscation_shims_ROM_END, vramDest);
}
#endif