Samuka007/asterinas
1
0
Fork 0
mirror of https://github.com/asterinas/asterinas.git synced 2025-06-21 00:06:34 +00:00
Code Issues Packages Projects Releases Wiki Activity

Introduce XArray and refactor the COW mechanism of Vmo

Browse Source
This commit is contained in:
Chen Chengjun
2024-04-08 14:26:36 +08:00
committed by Tate, Hongliang Tian
parent 233e1fac98
commit 33c8727a13
11 changed files with 575 additions and 310 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
kernel/aster-nix/src/vm/vmar/vm_mapping.rs
View File

@ -131,6 +131,22 @@ impl VmMapping {
&self.vmo
}
/// Set the entries in the page table associated with the current `VmMapping` to read-only.
pub(super) fn set_pt_read_only(&self, vm_space: &VmSpace) -> Result<()> {
let map_inner = self.inner.lock();
let mapped_addr = &map_inner.mapped_pages;
let perm = map_inner.perm;
if !perm.contains(VmPerm::W) {
return Ok(());
}
for page_idx in mapped_addr {
let map_addr = map_inner.page_map_addr(*page_idx);
vm_space.protect(&(map_addr..map_addr + PAGE_SIZE), perm - VmPerm::W)?;
}
Ok(())
}
/// Add a new committed page and map it to vmspace. If copy on write is set, it's allowed to unmap the page at the same address.
/// FIXME: This implementation based on the truth that we map one page at a time. If multiple pages are mapped together, this implementation may have problems
pub(super) fn map_one_page(
@ -167,6 +183,7 @@ impl VmMapping {
pub fn vmo_offset(&self) -> usize {
self.inner.lock().vmo_offset
}
pub fn read_bytes(&self, offset: usize, buf: &mut [u8]) -> Result<()> {
let vmo_read_offset = self.vmo_offset() + offset;
@ -186,8 +203,23 @@ impl VmMapping {
let page_idx_range = get_page_idx_range(&(vmo_write_offset..vmo_write_offset + buf.len()));
let write_perm = VmPerm::W;
let mut page_addr =
self.map_to_addr() - self.vmo_offset() + page_idx_range.start * PAGE_SIZE;
for page_idx in page_idx_range {
self.check_perm(&page_idx, &write_perm)?;
let parent = self.parent.upgrade().unwrap();
let vm_space = parent.vm_space();
// The `VmMapping` has the write permission but the corresponding PTE is present and is read-only.
// This means this PTE is set to read-only due to the COW mechanism. In this situation we need to trigger a
// page fault before writing at the VMO to guarantee the consistency between VMO and the page table.
let need_page_fault = vm_space.is_mapped(page_addr) && !vm_space.is_writable(page_addr);
if need_page_fault {
self.handle_page_fault(page_addr, false, true)?;
}
page_addr += PAGE_SIZE;
}
self.vmo.write_bytes(vmo_write_offset, buf)?;
@ -229,7 +261,7 @@ impl VmMapping {
// If read access to cow vmo triggers page fault, the map should be readonly.
// If user next tries to write to the frame, another page fault will be triggered.
let is_readonly = self.vmo.is_cow_child() && !write;
let is_readonly = self.vmo.is_cow_vmo() && !write;
self.map_one_page(page_idx, frame, is_readonly)
}
@ -429,7 +461,7 @@ impl VmMappingInner {
let vm_perm = {
let mut perm = self.perm;
if is_readonly {
debug_assert!(vmo.is_cow_child());
debug_assert!(vmo.is_cow_vmo());
perm -= VmPerm::W;
}
perm
@ -443,7 +475,7 @@ impl VmMappingInner {
};
// Cow child allows unmapping the mapped page.
if vmo.is_cow_child() && vm_space.is_mapped(map_addr) {
if vmo.is_cow_vmo() && vm_space.is_mapped(map_addr) {
vm_space.unmap(&(map_addr..(map_addr + PAGE_SIZE))).unwrap();
}