Kernel library crate for xous
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xous-kernel/src/mem.rs

127 lines
4.1 KiB

use crate::syscalls::{XousError, XousPid};
use xous_riscv::register::mstatus;
const FLASH_START: usize = 0x20000000;
const FLASH_SIZE: usize = 16_777_216;
const FLASH_END: usize = FLASH_START + FLASH_SIZE;
const RAM_START: usize = 0x40000000;
const RAM_SIZE: usize = 16_777_216;
const RAM_END: usize = RAM_START + RAM_SIZE;
const IO_START: usize = 0xe0000000;
const IO_SIZE: usize = 65_536;
const IO_END: usize = IO_START + IO_SIZE;
const LCD_START: usize = 0xB0000000;
const LCD_SIZE: usize = 32_768;
const LCD_END: usize = LCD_START + LCD_SIZE;
const PAGE_SIZE: usize = 4096;
const FLASH_PAGE_COUNT: usize = FLASH_SIZE / PAGE_SIZE;
const RAM_PAGE_COUNT: usize = RAM_SIZE / PAGE_SIZE;
const IO_PAGE_COUNT: usize = IO_SIZE;
const LCD_PAGE_COUNT: usize = LCD_SIZE / PAGE_SIZE;
pub struct MemoryManager {
flash: [u8; FLASH_PAGE_COUNT],
ram: [u8; RAM_PAGE_COUNT],
io: [u8; IO_PAGE_COUNT],
lcd: [u8; LCD_PAGE_COUNT],
}
extern "C" {
// Boundaries of the .bss section
static mut _ebss: usize;
static mut _sbss: usize;
// Boundaries of the .data section
static mut _edata: usize;
static mut _sdata: usize;
// Boundaries of the stack
static mut _estack: usize;
static mut _sstack: usize;
// Boundaries of the heap
static _sheap: usize;
static _eheap: usize;
// Initial values of the .data section (stored in Flash)
static _sidata: usize;
}
use core::mem::transmute;
/// Initialzie the memory map.
/// This will go through memory and map anything that the kernel is
/// using to process 0xff, then allocate a pagetable for this process
/// and place it at the usual offset.
/// Finally, it will enable the MMU.
impl MemoryManager {
pub fn new() -> MemoryManager {
let mut mm = MemoryManager {
flash: [0; FLASH_PAGE_COUNT],
ram: [0; RAM_PAGE_COUNT],
io: [0; IO_PAGE_COUNT],
lcd: [0; LCD_PAGE_COUNT],
};
unsafe { mstatus::clear_mie() };
// Map the bss section
let start_bss = unsafe { transmute::<&usize, usize>(&_sbss) };
let end_bss = unsafe { transmute::<&usize, usize>(&_ebss) };
let bss_range = (start_bss..end_bss).step_by(PAGE_SIZE);
let start_data = unsafe { transmute::<&usize, usize>(&_sdata) };
let end_data = unsafe { transmute::<&usize, usize>(&_edata) };
let data_range = (start_data..end_data).step_by(PAGE_SIZE);
// Note: stack grows downwards so these are swapped.
let start_stack = unsafe { transmute::<&usize, usize>(&_estack) };
let end_stack = unsafe { transmute::<&usize, usize>(&_sstack) };
let stack_range = (start_stack..end_stack).step_by(PAGE_SIZE);
for region in bss_range {
mm.claim_page(region & !0xfff, 1).unwrap();
}
for region in data_range {
mm.claim_page(region & !0xfff, 1).unwrap();
}
for region in stack_range {
mm.claim_page(region & !0xfff, 1).unwrap();
}
unsafe { mstatus::set_mie() };
mm
}
fn claim_page(&mut self, addr: usize, pid: XousPid) -> Result<(), XousError> {
// Ensure the address lies on a page boundary
if addr & 0xfff != 0 {
return Err(XousError::BadAlignment);
}
match addr {
FLASH_START..=FLASH_END => {
Self::claim_page_inner(&mut self.flash, addr - FLASH_START, pid)
}
RAM_START..=RAM_END => Self::claim_page_inner(&mut self.ram, addr - RAM_START, pid),
IO_START..=IO_END => Self::claim_page_inner(&mut self.io, addr - IO_START, pid),
LCD_START..=LCD_END => Self::claim_page_inner(&mut self.lcd, addr - LCD_START, pid),
_ => Err(XousError::BadAddress),
}
}
fn claim_page_inner(tbl: &mut [u8], addr: usize, pid: XousPid) -> Result<(), XousError> {
let page = addr / PAGE_SIZE;
if page > tbl.len() {
return Err(XousError::BadAddress);
}
if tbl[page] != 0 {
return Err(XousError::OutOfMemory);
}
tbl[page] = pid;
Ok(())
}
}