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202 lines
9.2 KiB
C++
202 lines
9.2 KiB
C++
//
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// StaticAnalyser.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 15/09/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#include "StaticAnalyser.hpp"
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#include "../Disassembler/6502.hpp"
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using namespace StaticAnalyser::Atari;
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static void DeterminePagingFor2kCartridge(StaticAnalyser::Target &target, const Storage::Cartridge::Cartridge::Segment &segment) {
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// if this is a 2kb cartridge then it's definitely either unpaged or a CommaVid
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uint16_t entry_address, break_address;
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entry_address = (static_cast<uint16_t>(segment.data[0x7fc] | (segment.data[0x7fd] << 8))) & 0x1fff;
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break_address = (static_cast<uint16_t>(segment.data[0x7fe] | (segment.data[0x7ff] << 8))) & 0x1fff;
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// a CommaVid start address needs to be outside of its RAM
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if(entry_address < 0x1800 || break_address < 0x1800) return;
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std::function<std::size_t(uint16_t address)> high_location_mapper = [](uint16_t address) {
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address &= 0x1fff;
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return static_cast<std::size_t>(address - 0x1800);
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};
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StaticAnalyser::MOS6502::Disassembly high_location_disassembly =
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StaticAnalyser::MOS6502::Disassemble(segment.data, high_location_mapper, {entry_address, break_address});
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// assume that any kind of store that looks likely to be intended for large amounts of memory implies
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// large amounts of memory
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bool has_wide_area_store = false;
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for(std::map<uint16_t, StaticAnalyser::MOS6502::Instruction>::value_type &entry : high_location_disassembly.instructions_by_address) {
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if(entry.second.operation == StaticAnalyser::MOS6502::Instruction::STA) {
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has_wide_area_store |= entry.second.addressing_mode == StaticAnalyser::MOS6502::Instruction::Indirect;
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has_wide_area_store |= entry.second.addressing_mode == StaticAnalyser::MOS6502::Instruction::IndexedIndirectX;
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has_wide_area_store |= entry.second.addressing_mode == StaticAnalyser::MOS6502::Instruction::IndirectIndexedY;
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if(has_wide_area_store) break;
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}
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}
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// conclude that this is a CommaVid if it attempted to write something to the CommaVid RAM locations;
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// caveat: false positives aren't likely to be problematic; a false positive is a 2KB ROM that always addresses
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// itself so as to land in ROM even if mapped as a CommaVid and this code is on the fence as to whether it
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// attempts to modify itself but it probably doesn't
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if(has_wide_area_store) target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::CommaVid;
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}
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static void DeterminePagingFor8kCartridge(StaticAnalyser::Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const StaticAnalyser::MOS6502::Disassembly &disassembly) {
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// Activision stack titles have their vectors at the top of the low 4k, not the top, and
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// always list 0xf000 as both vectors; they do not repeat them, and, inexplicably, they all
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// issue an SEI as their first instruction (maybe some sort of relic of the development environment?)
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if(
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segment.data[4095] == 0xf0 && segment.data[4093] == 0xf0 && segment.data[4094] == 0x00 && segment.data[4092] == 0x00 &&
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(segment.data[8191] != 0xf0 || segment.data[8189] != 0xf0 || segment.data[8190] != 0x00 || segment.data[8188] != 0x00) &&
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segment.data[0] == 0x78
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) {
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target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::ActivisionStack;
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return;
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}
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// make an assumption that this is the Atari paging model
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target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::Atari8k;
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std::set<uint16_t> internal_accesses;
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internal_accesses.insert(disassembly.internal_stores.begin(), disassembly.internal_stores.end());
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internal_accesses.insert(disassembly.internal_modifies.begin(), disassembly.internal_modifies.end());
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internal_accesses.insert(disassembly.internal_loads.begin(), disassembly.internal_loads.end());
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int atari_access_count = 0;
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int parker_access_count = 0;
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int tigervision_access_count = 0;
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for(uint16_t address : internal_accesses) {
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uint16_t masked_address = address & 0x1fff;
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atari_access_count += masked_address >= 0x1ff8 && masked_address < 0x1ffa;
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parker_access_count += masked_address >= 0x1fe0 && masked_address < 0x1ff8;
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}
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for(uint16_t address: disassembly.external_stores) {
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uint16_t masked_address = address & 0x1fff;
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tigervision_access_count += masked_address == 0x3f;
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}
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if(parker_access_count > atari_access_count) target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::ParkerBros;
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else if(tigervision_access_count > atari_access_count) target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::Tigervision;
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}
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static void DeterminePagingFor16kCartridge(StaticAnalyser::Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const StaticAnalyser::MOS6502::Disassembly &disassembly) {
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// make an assumption that this is the Atari paging model
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target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::Atari16k;
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std::set<uint16_t> internal_accesses;
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internal_accesses.insert(disassembly.internal_stores.begin(), disassembly.internal_stores.end());
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internal_accesses.insert(disassembly.internal_modifies.begin(), disassembly.internal_modifies.end());
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internal_accesses.insert(disassembly.internal_loads.begin(), disassembly.internal_loads.end());
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int atari_access_count = 0;
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int mnetwork_access_count = 0;
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for(uint16_t address : internal_accesses) {
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uint16_t masked_address = address & 0x1fff;
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atari_access_count += masked_address >= 0x1ff6 && masked_address < 0x1ffa;
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mnetwork_access_count += masked_address >= 0x1fe0 && masked_address < 0x1ffb;
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}
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if(mnetwork_access_count > atari_access_count) target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::MNetwork;
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}
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static void DeterminePagingFor64kCartridge(StaticAnalyser::Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const StaticAnalyser::MOS6502::Disassembly &disassembly) {
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// make an assumption that this is a Tigervision if there is a write to 3F
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target.atari.paging_model =
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(disassembly.external_stores.find(0x3f) != disassembly.external_stores.end()) ?
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StaticAnalyser::Atari2600PagingModel::Tigervision : StaticAnalyser::Atari2600PagingModel::MegaBoy;
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}
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static void DeterminePagingForCartridge(StaticAnalyser::Target &target, const Storage::Cartridge::Cartridge::Segment &segment) {
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if(segment.data.size() == 2048) {
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DeterminePagingFor2kCartridge(target, segment);
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return;
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}
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uint16_t entry_address, break_address;
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entry_address = static_cast<uint16_t>(segment.data[segment.data.size() - 4] | (segment.data[segment.data.size() - 3] << 8));
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break_address = static_cast<uint16_t>(segment.data[segment.data.size() - 2] | (segment.data[segment.data.size() - 1] << 8));
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std::function<std::size_t(uint16_t address)> address_mapper = [](uint16_t address) {
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if(!(address & 0x1000)) return static_cast<std::size_t>(-1);
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return static_cast<std::size_t>(address & 0xfff);
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};
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std::vector<uint8_t> final_4k(segment.data.end() - 4096, segment.data.end());
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StaticAnalyser::MOS6502::Disassembly disassembly = StaticAnalyser::MOS6502::Disassemble(final_4k, address_mapper, {entry_address, break_address});
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switch(segment.data.size()) {
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case 8192:
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DeterminePagingFor8kCartridge(target, segment, disassembly);
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break;
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case 10495:
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target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::Pitfall2;
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break;
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case 12288:
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target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::CBSRamPlus;
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break;
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case 16384:
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DeterminePagingFor16kCartridge(target, segment, disassembly);
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break;
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case 32768:
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target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::Atari32k;
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break;
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case 65536:
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DeterminePagingFor64kCartridge(target, segment, disassembly);
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break;
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default:
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break;
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}
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// check for a Super Chip. Atari ROM images [almost] always have the same value stored over RAM
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// regions; when they don't they at least seem to have the first 128 bytes be the same as the
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// next 128 bytes. So check for that.
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if( target.atari.paging_model != StaticAnalyser::Atari2600PagingModel::CBSRamPlus &&
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target.atari.paging_model != StaticAnalyser::Atari2600PagingModel::MNetwork) {
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bool has_superchip = true;
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for(std::size_t address = 0; address < 128; address++) {
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if(segment.data[address] != segment.data[address+128]) {
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has_superchip = false;
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break;
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}
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}
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target.atari.uses_superchip = has_superchip;
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}
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// check for a Tigervision or Tigervision-esque scheme
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if(target.atari.paging_model == StaticAnalyser::Atari2600PagingModel::None && segment.data.size() > 4096) {
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bool looks_like_tigervision = disassembly.external_stores.find(0x3f) != disassembly.external_stores.end();
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if(looks_like_tigervision) target.atari.paging_model = StaticAnalyser::Atari2600PagingModel::Tigervision;
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}
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}
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void StaticAnalyser::Atari::AddTargets(const Media &media, std::list<Target> &destination) {
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// TODO: sanity checking; is this image really for an Atari 2600.
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Target target;
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target.machine = Target::Atari2600;
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target.probability = 1.0;
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target.media.cartridges = media.cartridges;
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target.atari.paging_model = Atari2600PagingModel::None;
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target.atari.uses_superchip = false;
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// try to figure out the paging scheme
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if(!media.cartridges.empty()) {
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const auto &segments = media.cartridges.front()->get_segments();
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if(segments.size() == 1) {
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const Storage::Cartridge::Cartridge::Segment &segment = segments.front();
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DeterminePagingForCartridge(target, segment);
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}
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}
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destination.push_back(target);
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}
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