vmprofiler/src/calc_jmp.cpp

#include <vmprofiler.hpp>

namespace vm
{
    namespace calc_jmp
    {
        bool get( zydis_routine_t &vm_entry, zydis_routine_t &calc_jmp )
        {
            auto result = vm::util::get_fetch_operand( vm_entry );

            if ( !result.has_value() )
                return false;

            calc_jmp.insert( calc_jmp.end(), result.value(), vm_entry.end() );
            return true;
        }

        std::optional< vmp2::exec_type_t > get_advancement( const zydis_routine_t &calc_jmp )
        {
            auto result =
                std::find_if( calc_jmp.begin(), calc_jmp.end(), []( const zydis_instr_t &instr_data ) -> bool {
                    // look for any instruction with RSI being the first operand and its being written too..
                    return instr_data.instr.operands[ 0 ].actions & ZYDIS_OPERAND_ACTION_WRITE &&
                           instr_data.instr.operands[ 0 ].type == ZYDIS_OPERAND_TYPE_REGISTER &&
                           instr_data.instr.operands[ 0 ].reg.value == ZYDIS_REGISTER_RSI;
                } );

            if ( result == calc_jmp.end() )
                return {};

            const auto &instr = result->instr;

            switch ( instr.mnemonic )
            {
            case ZYDIS_MNEMONIC_LEA:
                // if operand type is memory, then return advancement type
                // based off of the disposition value... (neg == backward, pos == forward)
                if ( instr.operands[ 1 ].type == ZYDIS_OPERAND_TYPE_MEMORY )
                    return instr.operands[ 1 ].mem.disp.value > 0 ? vmp2::exec_type_t::forward
                                                                  : vmp2::exec_type_t::backward;
                break;
            case ZYDIS_MNEMONIC_ADD:
                if ( instr.operands[ 1 ].type == ZYDIS_OPERAND_TYPE_IMMEDIATE )
                    return instr.operands[ 1 ].imm.value.s > 0 ? vmp2::exec_type_t::forward
                                                               : vmp2::exec_type_t::backward;
                break;
            case ZYDIS_MNEMONIC_SUB:
                if ( instr.operands[ 1 ].type == ZYDIS_OPERAND_TYPE_IMMEDIATE )
                    return instr.operands[ 1 ].imm.value.s > 0 ? vmp2::exec_type_t::backward
                                                               : vmp2::exec_type_t::forward;
                break;
            case ZYDIS_MNEMONIC_INC:
                return vmp2::exec_type_t::forward;
            case ZYDIS_MNEMONIC_DEC:
                return vmp2::exec_type_t::backward;
            default:
                break;
            }
            return {};
        }
    } // namespace calc_jmp
} // namespace vm