gdbstub_plugin/src/patches.cpp

#include "cafe/coreinit.h"
#include "kernel.h"

#include <cstdint>

int OSSetExceptionCallback_Patch() {
    return 0;
}

int OSSetExceptionCallbackEx_Patch() {
    return 0;
}

bool OSIsDebuggerInitialized_Patch() {
    return true;
}

void Patch(void *funcPtr, void *patchPtr) {
    OSDynLoad_NotifyData *sectionInfo = MainRPL->notifyData;

    uint32_t func  = (uint32_t) funcPtr;
    uint32_t patch = (uint32_t) patchPtr;
    if (func < 0x01800000) { //OS function (with trampoline)
        for (uint32_t addr = sectionInfo->textAddr; addr < 0x10000000; addr += 4) {
            uint32_t *instrs = (uint32_t *) addr;
            if (instrs[0] == (0x3D600000 | (func >> 16)) &&    //lis   r11, func@h
                instrs[1] == (0x616B0000 | (func & 0xFFFF)) && //ori   r11, r11, func@l
                instrs[2] == 0x7D6903A6 &&                     //mtctr r11
                instrs[3] == 0x4E800420)                       //bctr
            {
                KernelWriteU32(addr, 0x3D600000 | (patch >> 16));        //lis r11, patch@h
                KernelWriteU32(addr + 4, 0x616B0000 | (patch & 0xFFFF)); //ori r11, r11, patch@l
            }
        }
    } else { //Dynamic function
        for (uint32_t addr = sectionInfo->textAddr; addr < 0x10000000; addr += 4) {
            uint32_t instr = *(uint32_t *) addr;
            if ((instr & 0xFC000002) == 0x48000000) { //b or bl
                if ((instr & 0x03FFFFFC) == func - addr) {
                    instr = instr & ~0x03FFFFFC;
                    instr |= patch;
                    instr |= 2; //Turn b/bl into ba/bla
                    KernelWriteU32(addr, instr);
                }
            }
        }
    }
}

void ApplyPatches() {
    Patch((void *) OSSetExceptionCallback, (void *) OSSetExceptionCallback_Patch);
    Patch((void *) OSSetExceptionCallbackEx, (void *) OSSetExceptionCallbackEx_Patch);

    Patch((void *) OSIsDebuggerInitialized, (void *) OSIsDebuggerInitialized_Patch);
}