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Implement paging, bump version to 0.3.0

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This works in a similar way to x86's paging, by using page directories
which point to page tables, which point to physical addresses.
This commit is contained in:
Ry 2022-08-15 17:40:04 -07:00
parent 6edcda5b18
commit 82edb1d8da
6 changed files with 170 additions and 41 deletions
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2
Cargo.lock generated
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@ -865,7 +865,7 @@ dependencies = [
[[package]]
name = "fox32"
version = "0.2.1"
version = "0.3.0"
dependencies = [
"anyhow",
"image",

2
Cargo.toml
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@ -1,6 +1,6 @@
[package]
name = "fox32"
version = "0.2.1"
version = "0.3.0"
authors = ["ry"]
edition = "2021"
build = "build.rs"

6
docs/encoding.md
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@ -16,9 +16,9 @@ If the instruction doesn't allow variable sizes or a size was not specified, set
# Instruction table
| 0x | -0 | -1 | -2 | -3 | -4 | -5 | -6 | -7 | -8 | -9 | -A | -B | -C | -D | -E | -F |
| :-: | ---- | ------------- | ------------- | ------------- | ------------- | ------------- | ------------- | -------------- | ---- | ----- | -------------- | --- | --- | --- | --- | --- |
| 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 | | | |
| 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 | | | |
| 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 | | | |
| 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 | | | | | |
# Condition table

56
src/cpu.rs
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@ -35,6 +35,7 @@ impl std::convert::From<u8> for Flag {
pub enum Exception {
DivideByZero,
InvalidOpcode(u32),
PageFault(u32),
}
#[derive(Debug)]
@ -159,52 +160,34 @@ impl Cpu {
pub fn push_stack_8(&mut self, byte: u8) {
let decremented_stack_pointer = self.stack_pointer.overflowing_sub(1);
self.stack_pointer = decremented_stack_pointer.0;
if decremented_stack_pointer.1 {
// TODO: stack overflow exception
}
self.bus.memory.write_8(self.stack_pointer, byte);
}
pub fn pop_stack_8(&mut self) -> u8 {
let byte = self.bus.memory.read_8(self.stack_pointer);
let incremented_stack_pointer = self.stack_pointer.overflowing_add(1);
self.stack_pointer = incremented_stack_pointer.0;
if incremented_stack_pointer.1 {
// TODO: stack overflow exception
}
byte
}
pub fn push_stack_16(&mut self, half: u16) {
let decremented_stack_pointer = self.stack_pointer.overflowing_sub(2);
self.stack_pointer = decremented_stack_pointer.0;
if decremented_stack_pointer.1 {
// TODO: stack overflow exception
}
self.bus.memory.write_16(self.stack_pointer, half);
}
pub fn pop_stack_16(&mut self) -> u16 {
let half = self.bus.memory.read_16(self.stack_pointer);
let incremented_stack_pointer = self.stack_pointer.overflowing_add(2);
self.stack_pointer = incremented_stack_pointer.0;
if incremented_stack_pointer.1 {
// TODO: stack overflow exception
}
half
}
pub fn push_stack_32(&mut self, word: u32) {
let decremented_stack_pointer = self.stack_pointer.overflowing_sub(4);
self.stack_pointer = decremented_stack_pointer.0;
if decremented_stack_pointer.1 {
// TODO: stack overflow exception
}
self.bus.memory.write_32(self.stack_pointer, word);
}
pub fn pop_stack_32(&mut self) -> u32 {
let word = self.bus.memory.read_32(self.stack_pointer);
let incremented_stack_pointer = self.stack_pointer.overflowing_add(4);
self.stack_pointer = incremented_stack_pointer.0;
if incremented_stack_pointer.1 {
// TODO: stack overflow exception
}
word
}
pub fn interrupt(&mut self, interrupt: Interrupt) {
@ -224,6 +207,10 @@ impl Cpu {
let vector: u16 = 1;
self.handle_exception(vector, Some(opcode));
}
Exception::PageFault(virtual_address) => {
let vector: u16 = 2;
self.handle_exception(vector, Some(virtual_address));
}
}
}
}
@ -2582,6 +2569,31 @@ impl Cpu {
self.instruction_pointer + instruction_pointer_offset
}
}
Instruction::Mse(condition) => {
let instruction_pointer_offset = 2; // increment past opcode half
let should_run = self.check_condition(condition);
if should_run {
*self.bus.memory.mmu_enabled() = true;
}
self.instruction_pointer + instruction_pointer_offset
}
Instruction::Mcl(condition) => {
let instruction_pointer_offset = 2; // increment past opcode half
let should_run = self.check_condition(condition);
if should_run {
*self.bus.memory.mmu_enabled() = false;
}
self.instruction_pointer + instruction_pointer_offset
}
Instruction::Tlb(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_tlb(Some(source_value));
}
self.instruction_pointer + instruction_pointer_offset
}
}
}
}
@ -2672,6 +2684,10 @@ enum Instruction {
Ise(Condition),
Icl(Condition),
Int(Condition, Operand),
Mse(Condition),
Mcl(Condition),
Tlb(Condition, Operand),
}
impl Instruction {
@ -2768,6 +2784,10 @@ impl Instruction {
0x1C => Some(Instruction::Icl(condition)),
0x2C => Some(Instruction::Int(condition, source)),
0x0D => Some(Instruction::Mse(condition)),
0x1D => Some(Instruction::Mcl(condition)),
0x2D => Some(Instruction::Tlb(condition, source)),
_ => None,
}
}

9
src/main.rs
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@ -10,7 +10,7 @@ pub mod disk;
use audio::AudioChannel;
use bus::Bus;
use cpu::{Cpu, Interrupt};
use cpu::{Cpu, Exception, Interrupt};
use keyboard::Keyboard;
use mouse::Mouse;
use disk::DiskController;
@ -84,7 +84,9 @@ fn main() {
let audio_channel_2 = Arc::new(Mutex::new(AudioChannel::new(2)));
let audio_channel_3 = Arc::new(Mutex::new(AudioChannel::new(3)));
let memory = Memory::new(read_rom().as_slice());
let (exception_sender, exception_receiver) = mpsc::channel::<Exception>();
let memory = Memory::new(read_rom().as_slice(), exception_sender);
let mut bus = Bus {
memory: memory.clone(),
audio_channel_0: audio_channel_0.clone(),
@ -155,6 +157,9 @@ fn main() {
move || {
loop {
while !cpu.halted {
if let Ok(exception) = exception_receiver.try_recv() {
cpu.interrupt(Interrupt::Exception(exception));
}
if let Ok(interrupt) = interrupt_receiver.try_recv() {
cpu.interrupt(interrupt);
}

118
src/memory.rs
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@ -1,9 +1,12 @@
// memory.rs
use crate::error;
use crate::cpu::Exception;
use std::cell::UnsafeCell;
use std::collections::HashMap;
use std::sync::Arc;
use std::sync::mpsc::Sender;
use std::io::Write;
use std::fs::File;
@ -16,18 +19,33 @@ pub const MEMORY_ROM_START: usize = 0xF0000000;
pub type MemoryRam = [u8; MEMORY_RAM_SIZE];
pub type MemoryRom = [u8; MEMORY_ROM_SIZE];
#[derive(Debug)]
pub struct MemoryPage {
physical_address: u32,
present: bool,
rw: bool,
}
struct MemoryInner {
ram: Box<MemoryRam>,
rom: Box<MemoryRom>,
mmu_enabled: Box<bool>,
tlb: Box<HashMap<u32, MemoryPage>>,
paging_directory_address: Box<u32>,
exception_sender: Sender<Exception>,
}
impl MemoryInner {
pub fn new(rom: &[u8]) -> Self {
pub fn new(rom: &[u8], exception_sender: Sender<Exception>) -> Self {
let mut this = Self {
// HACK: allocate directly on the heap to avoid a stack overflow
// at runtime while trying to move around a 64MB array
ram: unsafe { Box::from_raw(Box::into_raw(vec![0u8; MEMORY_RAM_SIZE].into_boxed_slice()) as *mut MemoryRam) },
rom: unsafe { Box::from_raw(Box::into_raw(vec![0u8; MEMORY_ROM_SIZE].into_boxed_slice()) as *mut MemoryRom) },
mmu_enabled: Box::from(false),
tlb: Box::from(HashMap::with_capacity(1024)),
paging_directory_address: Box::from(0x00000000),
exception_sender,
};
this.rom.as_mut_slice().write(rom).expect("failed to copy ROM to memory");
this
@ -44,8 +62,8 @@ unsafe impl Send for Memory {}
unsafe impl Sync for Memory {}
impl Memory {
pub fn new(rom: &[u8]) -> Self {
Self(Arc::new(UnsafeCell::new(MemoryInner::new(rom))))
pub fn new(rom: &[u8], exception_sender: Sender<Exception>) -> Self {
Self(Arc::new(UnsafeCell::new(MemoryInner::new(rom, exception_sender))))
}
fn inner(&self) -> &mut MemoryInner {
@ -54,13 +72,87 @@ impl Memory {
pub fn ram(&self) -> &mut MemoryRam { &mut self.inner().ram }
pub fn rom(&self) -> &mut MemoryRom { &mut self.inner().rom }
pub fn mmu_enabled(&self) -> &mut bool { &mut self.inner().mmu_enabled }
pub fn tlb(&self) -> &mut HashMap<u32, MemoryPage> { &mut self.inner().tlb }
pub fn paging_directory_address(&self) -> &mut u32 { &mut self.inner().paging_directory_address }
pub fn exception_sender(&self) -> &mut Sender<Exception> { &mut self.inner().exception_sender }
pub fn dump(&self) {
let mut file = File::create("memory.dump").expect("failed to open memory dump file");
file.write_all(self.ram()).expect("failed to write memory dump file");
}
pub fn read_8(&self, address: u32) -> u8 {
pub fn flush_tlb(&self, paging_directory_address: Option<u32>) {
let 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;
let tlb_entry = MemoryPage {
//physical_address: (((directory_index + 1) * (table_index + 1) * 4096) - 4096),
physical_address: (directory_index << 22) | (table_index << 12),
present: table_present,
rw: table_rw,
};
self.tlb().entry(table_address).or_insert(tlb_entry);
}
}
}
println!("{:#X?}", self.tlb());
}
pub fn virtual_to_physical(&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);
let physical_address = match physical_page {
Some(page) => {
if page.present {
Some((page.physical_address | offset, page.rw))
} else {
None
}
},
None => None,
};
physical_address
}
pub fn read_8(&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();
(0, false)
});
}
let address = address as usize;
let result = if address >= MEMORY_ROM_START && address < MEMORY_ROM_START + MEMORY_ROM_SIZE {
@ -74,7 +166,7 @@ impl Memory {
*value
}
None => {
error(&format!("attempting to read from unmapped memory address: {:#010X}", address));
error(&format!("attempting to read from unmapped physical memory address: {:#010X}", address));
}
}
}
@ -89,7 +181,16 @@ impl Memory {
(self.read_8(address + 3) as u32) << 24
}
pub fn write_8(&self, address: u32, byte: u8) {
pub fn write_8(&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(|| {
self.exception_sender().send(Exception::PageFault(address)).unwrap();
(0, false)
});
}
if writable {
let address = address as usize;
if address >= MEMORY_ROM_START && address < MEMORY_ROM_START + MEMORY_ROM_SIZE {
@ -101,9 +202,12 @@ impl Memory {
*value = byte;
}
None => {
error(&format!("attempting to write to unmapped memory address: {:#010X}", address));
error(&format!("attempting to write to unmapped physical memory address: {:#010X}", address));
}
}
} else {
self.exception_sender().send(Exception::PageFault(address)).unwrap();
}
}
pub fn write_16(&self, address: u32, half: u16) {
self.write_8(address, (half & 0x00FF) as u8);