mm: rust: add VmaNew for f_ops->mmap() (dcb81aea) · Commits · git / linux-net

rust/kernel/mm/virt.rs

+185 −1

Original line number	Diff line number	Diff line
		@@ -16,7 +16,7 @@

		use crate::{
		bindings,
		error::{to_result, Result},
		error::{code::EINVAL, to_result, Result},
		mm::MmWithUser,
		page::Page,
		types::Opaque,
		@@ -198,6 +198,190 @@ pub fn vm_insert_page(&self, address: usize, page: &Page) -> Result {
		}
		}

		/// A configuration object for setting up a VMA in an `f_ops->mmap()` hook.
		///
		/// The `f_ops->mmap()` hook is called when a new VMA is being created, and the hook is able to
		/// configure the VMA in various ways to fit the driver that owns it. Using `VmaNew` indicates that
		/// you are allowed to perform operations on the VMA that can only be performed before the VMA is
		/// fully initialized.
		///
		/// # Invariants
		///
		/// For the duration of 'a, the referenced vma must be undergoing initialization in an
		/// `f_ops->mmap()` hook.
		pub struct VmaNew {
		vma: VmaRef,
		}

		// Make all `VmaRef` methods available on `VmaNew`.
		impl Deref for VmaNew {
		type Target = VmaRef;

		#[inline]
		fn deref(&self) -> &VmaRef {
		&self.vma
		}
		}

		impl VmaNew {
		/// Access a virtual memory area given a raw pointer.
		///
		/// # Safety
		///
		/// Callers must ensure that `vma` is undergoing initial vma setup for the duration of 'a.
		#[inline]
		pub unsafe fn from_raw<'a>(vma: *mut bindings::vm_area_struct) -> &'a Self {
		// SAFETY: The caller ensures that the invariants are satisfied for the duration of 'a.
		unsafe { &*vma.cast() }
		}

		/// Internal method for updating the vma flags.
		///
		/// # Safety
		///
		/// This must not be used to set the flags to an invalid value.
		#[inline]
		unsafe fn update_flags(&self, set: vm_flags_t, unset: vm_flags_t) {
		let mut flags = self.flags();
		flags \|= set;
		flags &= !unset;

		// SAFETY: This is not a data race: the vma is undergoing initial setup, so it's not yet
		// shared. Additionally, `VmaNew` is `!Sync`, so it cannot be used to write in parallel.
		// The caller promises that this does not set the flags to an invalid value.
		unsafe { (*self.as_ptr()).__bindgen_anon_2.__vm_flags = flags };
		}

		/// Set the `VM_MIXEDMAP` flag on this vma.
		///
		/// This enables the vma to contain both `struct page` and pure PFN pages. Returns a reference
		/// that can be used to call `vm_insert_page` on the vma.
		#[inline]
		pub fn set_mixedmap(&self) -> &VmaMixedMap {
		// SAFETY: We don't yet provide a way to set VM_PFNMAP, so this cannot put the flags in an
		// invalid state.
		unsafe { self.update_flags(flags::MIXEDMAP, 0) };

		// SAFETY: We just set `VM_MIXEDMAP` on the vma.
		unsafe { VmaMixedMap::from_raw(self.vma.as_ptr()) }
		}

		/// Set the `VM_IO` flag on this vma.
		///
		/// This is used for memory mapped IO and similar. The flag tells other parts of the kernel to
		/// avoid looking at the pages. For memory mapped IO this is useful as accesses to the pages
		/// could have side effects.
		#[inline]
		pub fn set_io(&self) {
		// SAFETY: Setting the VM_IO flag is always okay.
		unsafe { self.update_flags(flags::IO, 0) };
		}

		/// Set the `VM_DONTEXPAND` flag on this vma.
		///
		/// This prevents the vma from being expanded with `mremap()`.
		#[inline]
		pub fn set_dontexpand(&self) {
		// SAFETY: Setting the VM_DONTEXPAND flag is always okay.
		unsafe { self.update_flags(flags::DONTEXPAND, 0) };
		}

		/// Set the `VM_DONTCOPY` flag on this vma.
		///
		/// This prevents the vma from being copied on fork. This option is only permanent if `VM_IO`
		/// is set.
		#[inline]
		pub fn set_dontcopy(&self) {
		// SAFETY: Setting the VM_DONTCOPY flag is always okay.
		unsafe { self.update_flags(flags::DONTCOPY, 0) };
		}

		/// Set the `VM_DONTDUMP` flag on this vma.
		///
		/// This prevents the vma from being included in core dumps. This option is only permanent if
		/// `VM_IO` is set.
		#[inline]
		pub fn set_dontdump(&self) {
		// SAFETY: Setting the VM_DONTDUMP flag is always okay.
		unsafe { self.update_flags(flags::DONTDUMP, 0) };
		}

		/// Returns whether `VM_READ` is set.
		///
		/// This flag indicates whether userspace is mapping this vma as readable.
		#[inline]
		pub fn readable(&self) -> bool {
		(self.flags() & flags::READ) != 0
		}

		/// Try to clear the `VM_MAYREAD` flag, failing if `VM_READ` is set.
		///
		/// This flag indicates whether userspace is allowed to make this vma readable with
		/// `mprotect()`.
		///
		/// Note that this operation is irreversible. Once `VM_MAYREAD` has been cleared, it can never
		/// be set again.
		#[inline]
		pub fn try_clear_mayread(&self) -> Result {
		if self.readable() {
		return Err(EINVAL);
		}
		// SAFETY: Clearing `VM_MAYREAD` is okay when `VM_READ` is not set.
		unsafe { self.update_flags(0, flags::MAYREAD) };
		Ok(())
		}

		/// Returns whether `VM_WRITE` is set.
		///
		/// This flag indicates whether userspace is mapping this vma as writable.
		#[inline]
		pub fn writable(&self) -> bool {
		(self.flags() & flags::WRITE) != 0
		}

		/// Try to clear the `VM_MAYWRITE` flag, failing if `VM_WRITE` is set.
		///
		/// This flag indicates whether userspace is allowed to make this vma writable with
		/// `mprotect()`.
		///
		/// Note that this operation is irreversible. Once `VM_MAYWRITE` has been cleared, it can never
		/// be set again.
		#[inline]
		pub fn try_clear_maywrite(&self) -> Result {
		if self.writable() {
		return Err(EINVAL);
		}
		// SAFETY: Clearing `VM_MAYWRITE` is okay when `VM_WRITE` is not set.
		unsafe { self.update_flags(0, flags::MAYWRITE) };
		Ok(())
		}

		/// Returns whether `VM_EXEC` is set.
		///
		/// This flag indicates whether userspace is mapping this vma as executable.
		#[inline]
		pub fn executable(&self) -> bool {
		(self.flags() & flags::EXEC) != 0
		}

		/// Try to clear the `VM_MAYEXEC` flag, failing if `VM_EXEC` is set.
		///
		/// This flag indicates whether userspace is allowed to make this vma executable with
		/// `mprotect()`.
		///
		/// Note that this operation is irreversible. Once `VM_MAYEXEC` has been cleared, it can never
		/// be set again.
		#[inline]
		pub fn try_clear_mayexec(&self) -> Result {
		if self.executable() {
		return Err(EINVAL);
		}
		// SAFETY: Clearing `VM_MAYEXEC` is okay when `VM_EXEC` is not set.
		unsafe { self.update_flags(0, flags::MAYEXEC) };
		Ok(())
		}
		}

		/// The integer type used for vma flags.
		#[doc(inline)]
		pub use bindings::vm_flags_t;