[Bug 48988] Riot Vanguard (Riot Games) 'vgk.sys' needs KSHARED_USER_DATA access instruction emulation for 'CMP r/m16/32/64, r16/32/64'

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=48988

--- Comment #10 from Etaash Mathamsetty  ---
I made a probably terrible implementation of this instruction, feedback is
appreciated!

case 0x38:
case 0x39:
    {

BYTE *data = INSTR_GetOperandAddr(context, instr + 1, prefixlen + 1,
long_addr, rex, segprefix, &len);
        BYTE* data2 = INSTR_GetOperandAddr(context, instr + 2, prefixlen + 2,
long_addr, rex, segprefix, &len);
        SIZE_T offset = data - user_shared_data;
        SIZE_T data_size = get_op_size( long_op, rex );

if(offset <= KSHARED_USER_DATA_PAGE_SIZE - data_size)
        {

FIXME("data 1 = %llx data 2 = %llx\n", data, data2);
             //clear ZF and CF
             context->EFlags &= ~(1UL << 6);
             context->EFlags &= ~(1UL);

if( *(wine_user_shared_data + offset) == *data2)
                context->EFlags |= (1 << 6);
             else if(*(wine_user_shared_data + offset) < *data2)
                context->EFlags |= (1);

context->Rip += prefixlen + len + 1;
            return ExceptionContinueExecution;
        }
        break;
    }