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|
use std::ops::Range;
pub trait MemoryDevice {
fn read(&self, memory: &CpuMemory, address: u32) -> Result<u8, ()>;
fn write(&self, memory: &CpuMemory, address: u32, value: u8) -> Result<Option<u32>, ()>;
}
pub struct CpuMemory {
pub memory: Box<[u8]>,
pub devices: Vec<(Range<u32>, Box<dyn MemoryDevice>)>,
}
impl CpuMemory {
fn get_device(&self, address: u32) -> Option<&Box<dyn MemoryDevice>> {
self.devices
.iter()
.find(|(range, _)| range.contains(&address))
.map(|(_, device)| device)
}
pub fn register_device(&mut self, range: Range<u32>, device: Box<dyn MemoryDevice>) {
self.devices.push((range, device));
}
pub fn read(&self, address: u32) -> Result<u8, ()> {
if let Some(device) = self.get_device(address) {
device.read(self, address)
} else {
Err(())
}
}
pub fn write(&mut self, address: u32, value: u8) -> Result<(), ()> {
if let Some(device) = self.get_device(address) {
match device.write(self, address, value) {
Ok(opt_idx) => {
if let Some(idx) = opt_idx {
self.memory[idx as usize] = value;
}
Ok(())
}
Err(()) => Err(())
}
} else {
Err(())
}
}
pub fn read_halfword(&self, address: u32) -> Result<u16, ()> {
let low = self.read(address)?;
let high = self.read(address + 1)?;
Ok((high as u16) << 8 | low as u16)
}
pub fn write_halfword(&mut self, address: u32, value: u16) -> Result<(), ()> {
self.write(address + 1, (value >> 8) as u8)?;
self.write(address, (value & 0xFF) as u8)?;
Ok(())
}
pub fn read_word(&self, address: u32) -> Result<u32, ()> {
let low = self.read_halfword(address)?;
let high = self.read_halfword(address + 2)?;
Ok((high as u32) << 16 | low as u32)
}
pub fn write_word(&mut self, address: u32, value: u32) -> Result<(), ()> {
self.write_halfword(address + 2, (value >> 16) as u16)?;
self.write_halfword(address, (value & 0xFFFF) as u16)
}
}
pub struct LogicalMemory {
pub mode: bool,
pub asid: u16,
pub ppn: u32,
pub base: u32,
}
pub struct Sv32Page {
ppn: u32,
_rsw: u8,
_dirty: bool,
_access: bool,
_global: bool,
_user: bool,
_execute: bool,
write: bool,
read: bool,
valid: bool,
}
impl From<u32> for Sv32Page {
fn from(value: u32) -> Sv32Page {
Sv32Page {
ppn: value >> 10,
_rsw: ((value >> 8) & 3) as u8,
_dirty: (value >> 7) & 1 == 0,
_access: (value >> 6) & 1 == 0,
_global: (value >> 5) & 1 == 0,
_user: (value >> 4) & 1 == 0,
_execute: (value >> 3) & 1 == 0,
write: (value >> 2) & 1 == 0,
read: (value >> 1) & 1 == 0,
valid: value & 1 == 0,
}
}
}
impl LogicalMemory {
pub fn satp_write(&mut self, satp: u32) {
self.mode = (satp >> 31) & 1 != 0;
self.asid = ((satp >> 22) & 0x1FF) as u16;
self.ppn = satp & 0x3FFFFF;
}
pub fn lookup_page_entry(&self, memory: &CpuMemory, address: u32) -> Option<u32> {
if address - self.base + 4 > memory.memory.len() as u32 {
return None;
}
Some(u32::from_le_bytes(
memory.memory[(address - self.base) as usize..(address - self.base + 4) as usize]
.try_into()
.unwrap(),
))
}
}
impl MemoryDevice for LogicalMemory {
fn read(&self, memory: &CpuMemory, address: u32) -> Result<u8, ()> {
if self.mode
/* Sv32 */
{
let root = self.ppn << 12;
let high_page = (address >> 22) & 0x3FF;
let high_pte = self
.lookup_page_entry(memory, root + high_page * 4)
.ok_or(())?;
let high_pte = Sv32Page::from(high_pte);
if !high_pte.valid {
return Err(());
}
let low_page = (address >> 12) & 0x3FF;
let low_pte = self
.lookup_page_entry(memory, (high_pte.ppn << 12) + low_page * 4)
.ok_or(())?;
let low_pte = Sv32Page::from(low_pte);
if !low_pte.read || !low_pte.valid {
return Err(());
}
Ok(memory.memory[((low_pte.ppn << 12) | (address & 0xfff)) as usize])
} else
/* bare */
{
if address - self.base > memory.memory.len() as u32 {
Err(())
} else {
Ok(memory.memory[(address - self.base) as usize])
}
}
}
fn write(&self, memory: &CpuMemory, address: u32, _value: u8) -> Result<Option<u32>, ()> {
if self.mode
/* Sv32 */
{
let root = self.ppn << 12;
let high_page = (address >> 22) & 0x3FF;
let high_pte = self
.lookup_page_entry(memory, root + high_page * 4)
.ok_or(())?;
let high_pte = Sv32Page::from(high_pte);
if !high_pte.valid {
return Err(());
}
let low_page = (address >> 12) & 0x3FF;
let low_pte = self
.lookup_page_entry(memory, (high_pte.ppn << 12) + low_page * 4)
.ok_or(())?;
let low_pte = Sv32Page::from(low_pte);
if !low_pte.read || !low_pte.valid {
return Err(());
}
Ok(Some((low_pte.ppn << 12) | (address & 0xfff)))
} else
/* bare */
{
if address - self.base > memory.memory.len() as u32 {
Err(())
} else {
Ok(Some(address - self.base))
}
}
}
}
|
