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Rework the paging system a little bit, add FLP instr., bump ver to 0.5.0
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@ry755
ry755 committed Sep 14, 2022
1 parent 9970a04 commit 3df3a98
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Showing 5 changed files with 89 additions and 54 deletions.
2 changes: 1 addition & 1 deletion Cargo.lock
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2 changes: 1 addition & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
[package]
name = "fox32"
version = "0.4.0"
version = "0.5.0"
authors = ["ry"]
edition = "2021"
build = "build.rs"
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2 changes: 1 addition & 1 deletion docs/encoding.md
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ If the instruction doesn't allow variable sizes or a size was not specified, set
| 0- | NOP | ADD[.8,16,32] | MUL[.8,16,32] | AND[.8,16,32] | SLA[.8,16,32] | SRA[.8,16,32] | BSE[.8,16,32] | CMP[.8,16,32] | JMP | RJMP | PUSH[.8,16,32] | IN | ISE | MSE | | |
| 1- | HALT | INC[.8,16,32] | | OR[.8,16,32] | | SRL[.8,16,32] | BCL[.8,16,32] | MOV[.8,16,32] | CALL | RCALL | POP[.8,16,32] | OUT | ICL | MCL | | |
| 2- | BRK | SUB[.8,16,32] | DIV[.8,16,32] | XOR[.8,16,32] | ROL[.8,16,32] | ROR[.8,16,32] | BTS[.8,16,32] | MOVZ[.8,16,32] | LOOP | RLOOP | RET | | INT | TLB | | |
| 3- | | DEC[.8,16,32] | REM[.8,16,32] | NOT[.8,16,32] | | | | | | RTA | RETI | | | | | |
| 3- | | DEC[.8,16,32] | REM[.8,16,32] | NOT[.8,16,32] | | | | | | RTA | RETI | | | FLP | | |

# Condition table
| | | |
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21 changes: 17 additions & 4 deletions src/cpu.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,7 @@ impl Cpu {
fn relative_to_absolute(&self, relative_address: u32) -> u32 {
self.instruction_pointer.wrapping_add(relative_address)
}
fn read_source(&self, source: Operand) -> (u32, u32) {
fn read_source(&mut self, source: Operand) -> (u32, u32) {
let mut instruction_pointer_offset = 2; // increment past opcode half
let source_value = match source {
Operand::Register => {
Expand Down Expand Up @@ -2344,7 +2344,8 @@ impl Cpu {
instruction_pointer_offset += 1; // increment past 8 bit register number
}
Operand::ImmediatePtr(_) => {
let pointer = self.relative_to_absolute(self.bus.memory.read_32(self.instruction_pointer + instruction_pointer_offset));
let word = self.bus.memory.read_32(self.instruction_pointer + instruction_pointer_offset);
let pointer = self.relative_to_absolute(word);
if should_run {
self.bus.memory.write_32(pointer, self.relative_to_absolute(source_value));
}
Expand Down Expand Up @@ -2527,14 +2528,16 @@ impl Cpu {
let pointer = self.read_register(register);
instruction_pointer_offset += 1; // increment past 8 bit register number
if should_run {
self.bus.write_io(self.bus.memory.read_32(pointer), source_value);
let word = self.bus.memory.read_32(pointer);
self.bus.write_io(word, source_value);
}
}
Operand::ImmediatePtr(_) => {
let pointer = self.bus.memory.read_32(self.instruction_pointer + instruction_pointer_offset);
instruction_pointer_offset += 4; // increment past 32 bit pointer
if should_run {
self.bus.write_io(self.bus.memory.read_32(pointer), source_value);
let word = self.bus.memory.read_32(pointer);
self.bus.write_io(word, source_value);
}
}
_ => panic!("Attempting to use an immediate value as a destination"),
Expand Down Expand Up @@ -2594,6 +2597,14 @@ impl Cpu {
}
self.instruction_pointer + instruction_pointer_offset
}
Instruction::Flp(condition, source) => {
let (source_value, instruction_pointer_offset) = self.read_source(source);
let should_run = self.check_condition(condition);
if should_run {
self.bus.memory.flush_page(source_value);
}
self.instruction_pointer + instruction_pointer_offset
}
}
}
}
Expand Down Expand Up @@ -2688,6 +2699,7 @@ enum Instruction {
Mse(Condition),
Mcl(Condition),
Tlb(Condition, Operand),
Flp(Condition, Operand),
}

impl Instruction {
Expand Down Expand Up @@ -2787,6 +2799,7 @@ impl Instruction {
0x0D => Some(Instruction::Mse(condition)),
0x1D => Some(Instruction::Mcl(condition)),
0x2D => Some(Instruction::Tlb(condition, source)),
0x3D => Some(Instruction::Flp(condition, source)),

_ => None,
}
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116 changes: 69 additions & 47 deletions src/memory.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,5 @@
// memory.rs

const DEBUG: bool = false;

use crate::error;
use crate::cpu::Exception;

Expand Down Expand Up @@ -84,54 +82,58 @@ impl Memory {
file.write_all(self.ram()).expect("failed to write memory dump file");
}

// each table contains 1024 entries
// the paging directory contains pointers to paging tables with the following format:
// bit 0: present
// remaining bits are ignored, should be zero
// bits 12-31: physical address of paging table

// the paging table contains pointers to physical memory pages with the following format:
// bit 0: present
// bit 1: r/w
// remaining bits are ignored, should be zero
// bits 12-31: physical address

pub fn flush_tlb(&self, paging_directory_address: Option<u32>) {
let directory_address = if let Some(address) = paging_directory_address {
if let Some(address) = paging_directory_address {
*self.paging_directory_address() = address;
address
} else {
*self.paging_directory_address()
};

self.tlb().clear();
}

// each table contains 1024 entries
// the paging directory contains pointers to paging tables with the following format:
// bit 0: present
// remaining bits are ignored, should be zero
// bits 12-31: physical address of paging table

// the paging table contains pointers to physical memory pages with the following format:
// bit 0: present
// bit 1: r/w
// remaining bits are ignored, should be zero
// bits 12-31: physical address

for directory_index in 0..1024 {
let directory = self.read_32(directory_address + (directory_index * 4));
let dir_present = directory & 0b1 != 0;
let dir_address = directory & 0xFFFFF000;
if dir_present {
for table_index in 0..1024 {
let table = self.read_32(dir_address + (table_index * 4));
let table_present = table & 0b01 != 0;
let table_rw = table & 0b10 != 0;
let table_address = table & 0xFFFFF000;

if table_present {
let tlb_entry = MemoryPage {
physical_address: table_address,
present: table_present,
rw: table_rw,
};
self.tlb().entry((directory_index << 22) | (table_index << 12)).or_insert(tlb_entry);
}
}
pub fn flush_page(&self, virtual_address: u32) {
let virtual_page = virtual_address & 0xFFFFF000;
self.tlb().remove(&virtual_page);
}

pub fn insert_tlb_entry_from_tables(&mut self, page_directory_index: u32, page_table_index: u32) -> bool {
let old_state = *self.mmu_enabled();
*self.mmu_enabled() = false;
let directory_address = *self.paging_directory_address();
let directory = self.read_32(directory_address + (page_directory_index * 4));
let dir_present = directory & 0b1 != 0;
let dir_address = directory & 0xFFFFF000;
if dir_present {
let table = self.read_32(dir_address + (page_table_index * 4));
let table_present = table & 0b01 != 0;
let table_rw = table & 0b10 != 0;
let table_address = table & 0xFFFFF000;

if table_present {
let tlb_entry = MemoryPage {
physical_address: table_address,
present: table_present,
rw: table_rw,
};
self.tlb().entry((page_directory_index << 22) | (page_table_index << 12)).or_insert(tlb_entry);
}
}
if DEBUG { println!("{:#X?}", self.tlb()); }
*self.mmu_enabled() = old_state;
dir_present
}

pub fn virtual_to_physical(&self, virtual_address: u32) -> Option<(u32, bool)> {
pub fn virtual_to_physical(&mut self, virtual_address: u32) -> Option<(u32, bool)> {
let virtual_page = virtual_address & 0xFFFFF000;
let offset = virtual_address & 0x00000FFF;
let physical_page = self.tlb().get(&virtual_page);
Expand All @@ -143,12 +145,32 @@ impl Memory {
None
}
},
None => None,
None => {
let page_directory_index = virtual_address >> 22;
let page_table_index = (virtual_address >> 12) & 0x03FF;
let dir_present = self.insert_tlb_entry_from_tables(page_directory_index, page_table_index);
if !dir_present {
return None;
}
// try again after inserting the TLB entry
let physical_page = self.tlb().get(&virtual_page);
let physical_address = match physical_page {
Some(page) => {
if page.present {
Some((page.physical_address | offset, page.rw))
} else {
None
}
},
None => None,
};
physical_address
},
};
physical_address
}

pub fn read_8(&self, mut address: u32) -> u8 {
pub fn read_8(&mut self, mut address: u32) -> u8 {
if *self.mmu_enabled() {
(address, _) = self.virtual_to_physical(address as u32).unwrap_or_else(|| {
self.exception_sender().send(Exception::PageFault(address)).unwrap();
Expand All @@ -173,18 +195,18 @@ impl Memory {
}
}
}
pub fn read_16(&self, address: u32) -> u16 {
pub fn read_16(&mut self, address: u32) -> u16 {
(self.read_8(address) as u16) |
(self.read_8(address + 1) as u16) << 8
}
pub fn read_32(&self, address: u32) -> u32 {
pub fn read_32(&mut self, address: u32) -> u32 {
(self.read_8(address) as u32) |
(self.read_8(address + 1) as u32) << 8 |
(self.read_8(address + 2) as u32) << 16 |
(self.read_8(address + 3) as u32) << 24
}

pub fn write_8(&self, mut address: u32, byte: u8) {
pub fn write_8(&mut self, mut address: u32, byte: u8) {
let mut writable = true;
if *self.mmu_enabled() {
(address, writable) = self.virtual_to_physical(address as u32).unwrap_or_else(|| {
Expand Down Expand Up @@ -212,11 +234,11 @@ impl Memory {
self.exception_sender().send(Exception::PageFault(address)).unwrap();
}
}
pub fn write_16(&self, address: u32, half: u16) {
pub fn write_16(&mut self, address: u32, half: u16) {
self.write_8(address, (half & 0x00FF) as u8);
self.write_8(address + 1, (half >> 8) as u8);
}
pub fn write_32(&self, address: u32, word: u32) {
pub fn write_32(&mut self, address: u32, word: u32) {
self.write_8(address, (word & 0x000000FF) as u8);
self.write_8(address + 1, ((word & 0x0000FF00) >> 8) as u8);
self.write_8(address + 2, ((word & 0x00FF0000) >> 16) as u8);
Expand Down

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