Method _callFunctionFrom

KittyMemoryEx/KittyTrace.cpp:375–661

// https://github.com/topjohnwu/Magisk/blob/master/native/src/zygisk/ptrace.cpp

kitty_rp_call_t KittyTraceMgr::_callFunctionFrom(uintptr_t callerAddress, uintptr_t functionAddress, int nargs, ...)
{
    if (!_attached || _pid <= 0 || functionAddress == 0)
        return {KT_RP_CALL_FAILED, {0}};

    user_regs_struct backup_regs, return_regs, tmp_regs;
    memset(&backup_regs, 0, sizeof(backup_regs));
    memset(&return_regs, 0, sizeof(return_regs));
    memset(&tmp_regs, 0, sizeof(tmp_regs));

    // backup current regs
    if (!getRegs(&backup_regs))
    {
        KITTY_LOGE("callFunction(%p): Failed, couldn't get regs.", (void *)functionAddress);
        return {KT_RP_CALL_REGS_FAILED, {0}};
    }

    memcpy(&tmp_regs, &backup_regs, sizeof(backup_regs));

    KT_REGS_ALIGN_STACK(backup_regs);
    KT_REGS_ALIGN_STACK(tmp_regs);
    KT_REGS_ALIGN_STACK(return_regs);

    KITTY_LOGD("callFunction(%p): Calling with %d args.", (void *)functionAddress, nargs);

    std::vector<uintptr_t> vargs(nargs, 0);
    if (nargs > 0)
    {
        va_list vl;
        va_start(vl, nargs);
        for (int i = 0; i < nargs; i++)
        {
            vargs[i] = va_arg(vl, uintptr_t);
        }
        va_end(vl);
    }

    // cleanup failure return
    auto failure_return = [&](KT_RP_CALL_STATUS s = KT_RP_CALL_FAILED) -> kitty_rp_call_t {
        KITTY_LOGE("callFunction(%p): Failed.", (void *)functionAddress);
        if (_autoRestoreRegs)
            setRegs(&backup_regs);
        return {s, {0}};
    };

    auto validate_ret = [this](const user_regs_struct &regs, uintptr_t return_addr) -> bool {
        uintptr_t pc = regs.KT_REG_PC;
        if (pc != return_addr)
        {
#if defined(__arm__)
            if (uintptr_t((intptr_t(pc) & ~1)) != uintptr_t((intptr_t(return_addr) & ~1)))
#elif defined(__i386__) || defined(__x86_64__)
            if (pc < return_addr || pc > (return_addr + 7))
#endif
            {
                siginfo_t si = {};
                getSignalInfo(&si);
                return uintptr_t(si.si_addr) == return_addr;