pico-loader/arm9/source/ModuleParamsLocator.cpp

#include "common.h"
#include "ModuleParamsLocator.h"

static bool isValidArm9Address(const nds_header_ntr_t* romHeader, const void* address)
{
    return romHeader->arm9LoadAddress <= (u32)address && (u32)address < romHeader->arm9LoadAddress + romHeader->arm9Size;
}

module_params_ntr_t* ModuleParamsLocator::FindModuleParams(const nds_header_ntr_t* romHeader) const
{
    //todo: static footer
    module_params_ntr_t* moduleParams = nullptr;
    if (romHeader->arm9ModuleParamsAddress != 0)
    {
        moduleParams = (module_params_ntr_t*)(romHeader->arm9LoadAddress + romHeader->arm9ModuleParamsAddress);
        if (!isValidArm9Address(romHeader, &moduleParams->magicLittleEndian) ||
            moduleParams->magicBigEndian != MODULE_PARAMS_NTR_MAGIC_BE ||
            moduleParams->magicLittleEndian != MODULE_PARAMS_NTR_MAGIC_LE)
        {
            // try again by subtracting arm9 rom address
            moduleParams = (module_params_ntr_t*)((u8*)moduleParams - romHeader->arm9RomOffset);
            if (!isValidArm9Address(romHeader, &moduleParams->magicLittleEndian) ||
                moduleParams->magicBigEndian != MODULE_PARAMS_NTR_MAGIC_BE ||
                moduleParams->magicLittleEndian != MODULE_PARAMS_NTR_MAGIC_LE)
            {
                LOG_DEBUG("Module params not found at header specified offset 0x%x\n", romHeader->arm9ModuleParamsAddress);
                moduleParams = nullptr;
            }
        }
    }
    else
    {
        LOG_DEBUG("Header specifies no module params address\n");
    }

    if (!moduleParams)
    {
        // try searching for the module params as not all roms have the address in the header
        for (u32 i = 0; i < romHeader->arm9Size; i += 4)
        {
            u32* ptr = (u32*)(romHeader->arm9LoadAddress + i);
            if (ptr[0] == MODULE_PARAMS_NTR_MAGIC_BE && ptr[1] == MODULE_PARAMS_NTR_MAGIC_LE)
            {
                moduleParams = (module_params_ntr_t*)((u8*)ptr + 8 - sizeof(module_params_ntr_t));
                break;
            }
        }

        if (moduleParams != nullptr && (u32)moduleParams - romHeader->arm9LoadAddress > 0x1000)
        {
            LOG_WARNING("Module params not found in first 0x1000 bytes of arm9\n");
        }
    }

    return moduleParams;
}