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

Allow overwriting PTEs in shared memory regions

Browse Source
This commit is contained in:
Ruihan Li
2024-06-20 19:06:44 +08:00
committed by Tate, Hongliang Tian
parent cb5b996274
commit 2beeedf7ed
4 changed files with 104 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
kernel/aster-nix/src/vm/vmar/vm_mapping.rs
View File

@ -143,21 +143,16 @@ impl VmMapping {
/// 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(
&self,
page_idx: usize,
frame: Frame,
is_readonly: bool,
) -> Result<()> {
fn map_one_page(&self, page_idx: usize, frame: Frame, is_readonly: bool) -> Result<()> {
let parent = self.parent.upgrade().unwrap();
let vm_space = parent.vm_space();
self.inner
.lock()
.map_one_page(&self.vmo, vm_space, page_idx, frame, is_readonly)
.map_one_page(vm_space, page_idx, frame, is_readonly)
}
/// unmap a page
pub(super) fn unmap_one_page(&self, page_idx: usize) -> Result<()> {
fn unmap_one_page(&self, page_idx: usize) -> Result<()> {
let parent = self.parent.upgrade().unwrap();
let vm_space = parent.vm_space();
self.inner.lock().unmap_one_page(vm_space, page_idx)
@ -458,7 +453,6 @@ impl VmMapping {
impl VmMappingInner {
fn map_one_page(
&mut self,
vmo: &Vmo<Rights>,
vm_space: &VmSpace,
page_idx: usize,
frame: Frame,
@ -469,7 +463,7 @@ impl VmMappingInner {
let vm_perms = {
let mut perms = self.perms;
if is_readonly {
debug_assert!(vmo.is_cow_vmo());
// COW pages are forced to be read-only.
perms -= VmPerms::WRITE;
}
perms
@ -479,14 +473,17 @@ impl VmMappingInner {
let mut options = VmMapOptions::new();
options.addr(Some(map_addr));
options.flags(vm_perms.into());
// After `fork()`, the entire memory space of the parent and child processes is
// protected as read-only. Therefore, whether the pages need to be COWed (if the memory
// region is private) or not (if the memory region is shared), it is necessary to
// overwrite the page table entry to make the page writable again when the parent or
// child process first tries to write to the memory region.
options.can_overwrite(true);
options
};
// Cow child allows unmapping the mapped page.
if vmo.is_cow_vmo() && vm_space.query(map_addr)?.is_some() {
vm_space.unmap(&(map_addr..(map_addr + PAGE_SIZE))).unwrap();
}
vm_space.map(FrameVec::from_one_frame(frame), &vm_map_options)?;
self.mapped_pages.insert(page_idx);
Ok(())