mirror of https://github.com/barzamin/sparkle
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
241 lines
7.3 KiB
241 lines
7.3 KiB
//! Paging subsystem. *Note: uses recursive mapping.*
|
|
//!
|
|
//! Extremely ripped off from Phil Oppermann's tutorials, because I don't feel like writing
|
|
//! a paging system off the top of my head today.
|
|
|
|
use core::ops::{Deref, DerefMut};
|
|
use multiboot2::BootInformation;
|
|
use super::PAGE_SIZE;
|
|
use super::{Frame, FrameAllocator};
|
|
|
|
mod entry;
|
|
mod table;
|
|
mod mapper;
|
|
mod temporary_page;
|
|
|
|
pub use self::entry::*;
|
|
use self::table::{Table, Level4};
|
|
use self::temporary_page::TemporaryPage;
|
|
use self::mapper::Mapper;
|
|
|
|
/// Upper bound on entries per page table
|
|
const ENTRY_COUNT: usize = 512;
|
|
|
|
/// Helper type aliases used to make function signatures more expressive
|
|
pub type PhysicalAddress = usize;
|
|
pub type VirtualAddress = usize;
|
|
|
|
pub struct ActivePageTable {
|
|
mapper: Mapper
|
|
}
|
|
|
|
impl Deref for ActivePageTable {
|
|
type Target = Mapper;
|
|
fn deref(&self) -> &Mapper {&self.mapper}
|
|
}
|
|
|
|
impl DerefMut for ActivePageTable {
|
|
fn deref_mut(&mut self) -> &mut Mapper {&mut self.mapper}
|
|
}
|
|
|
|
impl ActivePageTable {
|
|
unsafe fn new() -> ActivePageTable {
|
|
ActivePageTable {
|
|
mapper: Mapper::new(),
|
|
}
|
|
}
|
|
|
|
/// Executes a closure, with a different page table recursively mapped
|
|
pub fn with<F>(&mut self, table: &mut InactivePageTable, scratch_page: &mut TemporaryPage, f: F)
|
|
where F: FnOnce(&mut Mapper) {
|
|
use x86::shared::{tlb, control_regs};
|
|
|
|
{
|
|
// Backup the original P4 pointer
|
|
let backup = Frame::containing_address(
|
|
unsafe {control_regs::cr3()}
|
|
);
|
|
|
|
// Map a scratch page to the current p4 table
|
|
let p4_table = scratch_page.map_table_frame(backup.clone(), self);
|
|
|
|
// Overwrite main P4 recursive mapping
|
|
self.p4_mut()[511].set(table.p4_frame.clone(), PRESENT | WRITABLE);
|
|
unsafe {tlb::flush_all();} // flush *all* TLBs to prevent fuckiness
|
|
|
|
// Execute f in context of the new page table
|
|
f(self);
|
|
|
|
// Restore the original pointer to P4
|
|
p4_table[511].set(backup, PRESENT | WRITABLE);
|
|
unsafe {tlb::flush_all();} // prevent fuckiness
|
|
}
|
|
|
|
scratch_page.unmap(self);
|
|
}
|
|
|
|
/// Switches to a new [`InactivePageTable`], making it active.
|
|
///
|
|
/// Note: We don't need to flush the TLB here, as the CPU automatically flushes
|
|
/// the TLB when the P4 table is switched.
|
|
pub fn switch(&mut self, new_table: InactivePageTable) -> InactivePageTable {
|
|
use x86::shared::{control_regs};
|
|
|
|
let old_table = InactivePageTable {
|
|
p4_frame: Frame::containing_address(unsafe {control_regs::cr3()}),
|
|
};
|
|
|
|
unsafe {
|
|
control_regs::cr3_write(new_table.p4_frame.start_address());
|
|
}
|
|
|
|
old_table
|
|
}
|
|
}
|
|
|
|
/// Owns an inactive P4 table.
|
|
pub struct InactivePageTable {
|
|
p4_frame: Frame,
|
|
}
|
|
|
|
impl InactivePageTable {
|
|
pub fn new(frame: Frame, active_table: &mut ActivePageTable, temporary_page: &mut TemporaryPage)
|
|
-> InactivePageTable {
|
|
{
|
|
let table = temporary_page.map_table_frame(frame.clone(), active_table);
|
|
|
|
// zero the new inactive page table
|
|
table.zero();
|
|
|
|
// set up a recursive mapping for this table
|
|
table[511].set(frame.clone(), PRESENT | WRITABLE);
|
|
}
|
|
temporary_page.unmap(active_table);
|
|
|
|
InactivePageTable { p4_frame: frame }
|
|
}
|
|
}
|
|
|
|
/// A representation of a virtual page.
|
|
|
|
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
|
|
pub struct Page {
|
|
index: usize,
|
|
}
|
|
|
|
impl Page {
|
|
/// Retrieves the page containing a given virtual address.
|
|
pub fn containing_address(address: VirtualAddress) -> Page {
|
|
assert!(address < 0x0000_8000_0000_0000 ||
|
|
address >= 0xffff_8000_0000_0000,
|
|
"invalid address: {:#x}", address);
|
|
|
|
Page { index: address / PAGE_SIZE }
|
|
}
|
|
|
|
/// Returns the start (virtual) address of a page
|
|
pub fn start_address(&self) -> VirtualAddress {
|
|
self.index * PAGE_SIZE
|
|
}
|
|
|
|
pub fn range_inclusive(start: Page, end: Page) -> PageIter {
|
|
PageIter {
|
|
start: start,
|
|
end: end,
|
|
}
|
|
}
|
|
|
|
fn p4_index(&self) -> usize {
|
|
(self.index >> 27) & 0o777
|
|
}
|
|
fn p3_index(&self) -> usize {
|
|
(self.index >> 18) & 0o777
|
|
}
|
|
fn p2_index(&self) -> usize {
|
|
(self.index >> 9) & 0o777
|
|
}
|
|
fn p1_index(&self) -> usize {
|
|
(self.index >> 0) & 0o777
|
|
}
|
|
}
|
|
|
|
pub struct PageIter {
|
|
start: Page,
|
|
end: Page,
|
|
}
|
|
|
|
impl Iterator for PageIter {
|
|
type Item = Page;
|
|
|
|
fn next(&mut self) -> Option<Page> {
|
|
if self.start <= self.end {
|
|
let frame = self.start.clone();
|
|
self.start.index += 1;
|
|
Some(frame)
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Remap the kernel
|
|
pub fn remap_kernel<A>(allocator: &mut A, boot_info: &BootInformation)
|
|
-> ActivePageTable
|
|
where A: FrameAllocator
|
|
{
|
|
|
|
let mut scratch_page = TemporaryPage::new(Page { index: 0xabadcafe },
|
|
allocator);
|
|
|
|
let mut active_table = unsafe {ActivePageTable::new()};
|
|
let mut new_table = {
|
|
let frame = allocator.alloc_frame()
|
|
.expect("Attempted to allocate a frame for a new page table, but no frames are available!");
|
|
InactivePageTable::new(frame, &mut active_table, &mut scratch_page)
|
|
};
|
|
|
|
active_table.with(&mut new_table, &mut scratch_page, |mapper| {
|
|
let elf_sections_tag = boot_info.elf_sections_tag()
|
|
.expect("ELF sections tag required!");
|
|
|
|
// -- Identity map the kernel sections
|
|
for section in elf_sections_tag.sections() {
|
|
if !section.is_allocated() {
|
|
// section is not loaded to memory
|
|
continue;
|
|
}
|
|
|
|
assert!(section.start_address() % PAGE_SIZE == 0, "ELF sections must be page-aligned!");
|
|
debug!("Mapping section at addr: {:#x}, size: {:#x}",
|
|
section.addr, section.size);
|
|
|
|
let flags = EntryFlags::from_elf_section_flags(section);
|
|
let start_frame = Frame::containing_address(section.start_address());
|
|
let end_frame = Frame::containing_address(section.end_address() - 1);
|
|
for frame in Frame::range_inclusive(start_frame, end_frame) {
|
|
mapper.identity_map(frame, flags, allocator);
|
|
}
|
|
}
|
|
|
|
// -- Identity map the VGA console buffer (it's only one frame long)
|
|
let vga_buffer_frame = Frame::containing_address(0xb8000);
|
|
mapper.identity_map(vga_buffer_frame, WRITABLE, allocator);
|
|
|
|
// -- Identity map the multiboot info structure
|
|
let multiboot_start = Frame::containing_address(boot_info.start_address());
|
|
let multiboot_end = Frame::containing_address(boot_info.end_address() - 1);
|
|
for frame in Frame::range_inclusive(multiboot_start, multiboot_end) {
|
|
mapper.identity_map(frame, PRESENT | WRITABLE, allocator);
|
|
}
|
|
});
|
|
|
|
let old_table = active_table.switch(new_table);
|
|
info!("successfully switched to new page table.");
|
|
|
|
// Create a guard page in place of the old P4 table's page
|
|
let old_p4_page = Page::containing_address(old_table.p4_frame.start_address());
|
|
active_table.unmap(old_p4_page, allocator);
|
|
info!("guard page established at {:#x}", old_p4_page.start_address());
|
|
|
|
active_table
|
|
}
|