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Fix trans; take further crack at MEMC permissions.

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This commit is contained in:
Thomas Harte 2024-03-25 15:50:59 -04:00
parent 1154ffd072
commit 72a645ec1e
3 changed files with 36 additions and 26 deletions
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12
InstructionSets/ARM/Executor.hpp
View File

@ -295,7 +295,10 @@ struct Executor {
return;
}
constexpr bool trans = !flags.pre_index() && flags.write_back_address();
// "... post-indexed data transfers always write back the modified base. The only use of the [write-back address]
// bit in a post-indexed data transfer is in non-user mode code, where setting the W bit forces the /TRANS pin
// to go LOW for the transfer"
const bool trans = (registers_.mode() == Mode::User) || (!flags.pre_index() && flags.write_back_address());
if constexpr (flags.operation() == SingleDataTransferFlags::Operation::STR) {
const uint32_t source =
transfer.source() == 15 ?
@ -430,6 +433,7 @@ struct Executor {
}
bool address_error = false;
const bool trans = registers_.mode() == Mode::User;
// Keep track of whether all accesses succeeded in order potentially to
// throw a data abort later.
@ -447,7 +451,7 @@ struct Executor {
// "If the abort occurs during a store multiple instruction, ARM takes little action until
// the instruction completes, whereupon it enters the data abort trap. The memory manager is
// responsible for preventing erroneous writes to the memory."
accesses_succeeded &= bus.template write<uint32_t>(address, value, registers_.mode(), false);
accesses_succeeded &= bus.template write<uint32_t>(address, value, registers_.mode(), trans);
}
} else {
// When ARM detects a data abort during a load multiple instruction, it modifies the operation of
@ -458,7 +462,7 @@ struct Executor {
// * The base register is restored, to its modified value if write-back was requested.
if(accesses_succeeded) {
const uint32_t replaced = value;
accesses_succeeded &= bus.template read<uint32_t>(address, value, registers_.mode(), false);
accesses_succeeded &= bus.template read<uint32_t>(address, value, registers_.mode(), trans);
// Update the last-modified slot if the access succeeded; otherwise
// undo the last modification if there was one, and undo the base
@ -483,7 +487,7 @@ struct Executor {
} else {
// Implicitly: do the access anyway, but don't store the value. I think.
uint32_t throwaway;
bus.template read<uint32_t>(address, throwaway, registers_.mode(), false);
bus.template read<uint32_t>(address, throwaway, registers_.mode(), trans);
}
}

7
Machines/Acorn/Archimedes/Archimedes.cpp
View File

@ -90,10 +90,15 @@ class ConcreteMachine:
template <int offset, int video_divider>
void tick_cpu_video() {
tick_cpu();
if constexpr (!(offset % video_divider)) {
tick_video();
}
#ifndef NDEBUG
// Debug mode: run CPU a lot slower.
if constexpr (offset & 15) return;
#endif
tick_cpu();
}
public:

43
Machines/Acorn/Archimedes/MemoryController.hpp
View File

@ -60,7 +60,7 @@ struct MemoryController {
}
template <typename IntT>
bool write(uint32_t address, IntT source, InstructionSet::ARM::Mode mode, bool) {
bool write(uint32_t address, IntT source, InstructionSet::ARM::Mode mode, bool trans) {
// User mode may only _write_ to logically-mapped RAM (subject to further testing below).
if(mode == InstructionSet::ARM::Mode::User && address >= 0x200'0000) {
return false;
@ -107,7 +107,7 @@ struct MemoryController {
} break;
case Zone::LogicallyMappedRAM: {
const auto item = logical_ram<IntT, false>(address, mode);
const auto item = logical_ram<IntT, false>(address, trans);
if(!item) {
return false;
}
@ -142,7 +142,7 @@ struct MemoryController {
}
template <typename IntT>
bool read(uint32_t address, IntT &source, InstructionSet::ARM::Mode mode, bool) {
bool read(uint32_t address, IntT &source, InstructionSet::ARM::Mode mode, bool trans) {
// User mode may only read logically-maped RAM and ROM.
if(mode == InstructionSet::ARM::Mode::User && address >= 0x200'0000 && address < 0x380'0000) {
return false;
@ -154,7 +154,7 @@ struct MemoryController {
break;
case Zone::LogicallyMappedRAM: {
const auto item = logical_ram<IntT, true>(address, mode);
const auto item = logical_ram<IntT, true>(address, trans);
if(!item) {
return false;
}
@ -303,7 +303,7 @@ struct MemoryController {
bool map_dirty_ = true;
template <typename IntT, bool is_read>
IntT *logical_ram(uint32_t address, InstructionSet::ARM::Mode mode) {
IntT *logical_ram(uint32_t address, bool trans) {
// Possibly TODO: this recompute-if-dirty flag is supposed to ameliorate for an expensive
// mapping process. It can be eliminated when the process is improved.
if(map_dirty_) {
@ -341,24 +341,25 @@ struct MemoryController {
}
// TODO: eliminate switch here.
// Top of my head idea: is_read, is_user and is_os_mode make three bits, so
// Top of my head idea: is_read, trans and os_mode_ make three bits, so
// keep a one-byte bitmap of permitted accesses rather than the raw protection
// level?
switch(mapping_[page].protection_level) {
case 0b00: break;
case 0b01:
if(!is_read && mode == InstructionSet::ARM::Mode::User) {
return nullptr;
}
break;
default:
if(mode == InstructionSet::ARM::Mode::User) {
return nullptr;
}
if(!is_read && !os_mode_) {
return nullptr;
}
break;
if(trans) {
switch(mapping_[page].protection_level) {
case 0b00: break;
case 0b01:
// Reject: writes, in user mode.
if(!is_read && !os_mode_) {
return nullptr;
}
break;
default:
// Reject: writes, and user mode.
if(!is_read || !os_mode_) {
return nullptr;
}
break;
}
}
return reinterpret_cast<IntT *>(mapping_[page].target + address);