Struct memory::PteFlags

pub struct PteFlags(/* private fields */);

Common, architecture-independent flags for a page table entry (PTE) that define how a page is mapped.

Note: items beginning with an underscore _ are not used in Theseus.

This contains only the flags that are common to both x86_64 and aarch64.

Converting to/from arch-specific flags

This type can be losslessly converted into PteFlagsX86_64 and PteFlagsAarch64 with the typical From and Into traits. This makes it easier to set general architecture-indepedent flags first, and then convert it in order to set more architecture-specific flags.

This type can also be converted from PteFlagsX86_64 and PteFlagsAarch64, but it may be lossy as only the bit flags defined herein are preserved.

Implementations

impl PteFlags

pub const VALID: PteFlags = _

• If set, this page is currently “present” in memory.
• If not set, this page is not in memory, which could mean one of several things:
  • The page is not mapped at all.
  • The page has been temporarily paged/swapped to disk.
  • The page is waiting to be mapped, i.e., for demand paging.

pub const WRITABLE: PteFlags = _

• If set, this page is writable.
• If not set, this page is read-only.

pub const _USER_ACCESSIBLE: PteFlags = _

• If set, userspace (unprivileged mode) can access this page.
• If not set, only kernelspace (privileged mode) can access this page.

This is not used in Theseus, because it has a single privilege level.

pub const DEVICE_MEMORY: PteFlags = _

• If set, this page maps device memory, which is non-cacheable.
• If not set, this page maps normal memory, which is cacheable by default.

pub const ACCESSED: PteFlags = _

• The hardware will set this bit when the page is accessed.
• The OS can then clear this bit once it has acknowledged that the page was accessed, if it cares at all about this information.

pub const DIRTY: PteFlags = _

• The hardware will set this bit when the page has been written to.
• The OS can then clear this bit once it has acknowledged that the page was written to, which is primarily useful for paging/swapping to disk.

pub const _GLOBAL: PteFlags = _

• If set, this page is mapped identically across all address spaces (all root page tables) and doesn’t need to be flushed out of the TLB when switching to another address space (page table).
• If not set, this page is mapped into only one or less than all address spaces, or is mapped differently across different address spaces, and thus be flushed out of the TLB when switching address spaces (page tables).

This is not used in Theseus, as it has a single address space.

pub const NOT_EXECUTABLE: PteFlags = _

• If set, this page is not executable.
• If not set, this page is executable.

pub const EXCLUSIVE: PteFlags = _

Note: code that invokes memory management functions in Theseus cannot actually set this flag. When flags are passed to those functions, this bit value is ignored and overridden as appropriate.

• If set, the frame mapped by this page table entry is owned exclusively by that page table entry. Currently, in Theseus, we only set the EXCLUSIVE bit for P1-level PTEs that we know are bijective (1-to-1 virtual-to-physical) mappings. This allows Theseus to safely deallocate the frame mapped by this page once this page table entry is unmapped.
• If not set, the frame mapped by this page is not owned exclusively and thus cannot be safely deallocated when this page is unmapped.

impl PteFlags

pub const fn empty() -> PteFlags

Get a flags value with all bits unset.

pub const fn all() -> PteFlags

Get a flags value with all known bits set.

pub const fn bits(&self) -> u64

Get the underlying bits value.

The returned value is exactly the bits set in this flags value.

pub const fn from_bits(bits: u64) -> Option<PteFlags>

Convert from a bits value.

This method will return None if any unknown bits are set.

pub const fn from_bits_truncate(bits: u64) -> PteFlags

Convert from a bits value, unsetting any unknown bits.

pub const fn from_bits_retain(bits: u64) -> PteFlags

Convert from a bits value exactly.

pub fn from_name(name: &str) -> Option<PteFlags>

Get a flags value with the bits of a flag with the given name set.

This method will return None if name is empty or doesn’t correspond to any named flag.

pub const fn is_empty(&self) -> bool

Whether all bits in this flags value are unset.

pub const fn is_all(&self) -> bool

Whether all known bits in this flags value are set.

pub const fn intersects(&self, other: PteFlags) -> bool

Whether any set bits in a source flags value are also set in a target flags value.

pub const fn contains(&self, other: PteFlags) -> bool

Whether all set bits in a source flags value are also set in a target flags value.

pub fn insert(&mut self, other: PteFlags)

The bitwise or (|) of the bits in two flags values.

pub fn remove(&mut self, other: PteFlags)

The intersection of a source flags value with the complement of a target flags value (&!).

This method is not equivalent to self & !other when other has unknown bits set. remove won’t truncate other, but the ! operator will.

pub fn toggle(&mut self, other: PteFlags)

The bitwise exclusive-or (^) of the bits in two flags values.

pub fn set(&mut self, other: PteFlags, value: bool)

Call insert when value is true or remove when value is false.

pub const fn intersection(self, other: PteFlags) -> PteFlags

The bitwise and (&) of the bits in two flags values.

pub const fn union(self, other: PteFlags) -> PteFlags

The bitwise or (|) of the bits in two flags values.

pub const fn difference(self, other: PteFlags) -> PteFlags

The intersection of a source flags value with the complement of a target flags value (&!).

This method is not equivalent to self & !other when other has unknown bits set. difference won’t truncate other, but the ! operator will.

pub const fn symmetric_difference(self, other: PteFlags) -> PteFlags

The bitwise exclusive-or (^) of the bits in two flags values.

pub const fn complement(self) -> PteFlags

The bitwise negation (!) of the bits in a flags value, truncating the result.

impl PteFlags

pub const fn iter(&self) -> Iter<PteFlags>

Yield a set of contained flags values.

Each yielded flags value will correspond to a defined named flag. Any unknown bits will be yielded together as a final flags value.

pub const fn iter_names(&self) -> IterNames<PteFlags>

Yield a set of contained named flags values.

This method is like iter, except only yields bits in contained named flags. Any unknown bits, or bits not corresponding to a contained flag will not be yielded.

impl PteFlags

pub const fn new() -> PteFlags

Returns a new PteFlags with the default value, in which:

• ACCESSED is set.
• the NOT_EXECUTABLE bit is set.

Note: the ACCESSED bit is set by default because Theseus currently doesn’t perform any paging/swapping of pages to disk, which is what this bit is typically used for. On aarch64, not setting this bit can cause an Access Flag Fault (which is useful only for software-managed LRU paging algorithms), so we just set that bit by default to avoid any faults that we don’t care about.

pub fn valid(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the VALID bit set or cleared.

• If enable is true, this PTE will be considered “present” and “valid”, meaning that the mapping from this page to a physical frame is valid and that the translation of a virtual address in this page should succeed.
• If enable is false, this PTE will be considered “invalid”, and any attempt to access it for translation purposes will cause a page fault.

pub fn writable(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the WRITABLE bit set or cleared.

• If enable is true, this will be writable.
• If enable is false, this will be read-only.

pub fn executable(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the NOT_EXECUTABLE bit cleared or set.

• If enable is true, this page will be executable (NOT_EXECUTABLE will be cleared).
• If enable is false, this page will be non-executable, which is the default (NOT_EXECUTABLE will be set).

pub fn device_memory(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the DEVICE_MEMORY bit set or cleared.

• If enable is true, this will be non-cacheable device memory.
• If enable is false, this will be “normal” memory, the default.

pub fn exclusive(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the EXCLUSIVE bit set or cleared.

• If enable is true, this page will exclusively map its frame.
• If enable is false, this page will NOT exclusively map its frame.

pub fn accessed(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the ACCESSED bit set or cleared.

Typically this is used to clear the ACCESSED bit, in order to indicate that the OS has “acknowledged” the fact that this page was accessed since the last time it checked.

• If enable is true, this page will be marked as accessed.
• If enable is false, this page will be marked as not accessed.

pub fn dirty(self, enable: bool) -> PteFlags

Returns a copy of this PteFlags with the DIRTY bit set or cleared.

Typically this is used to clear the DIRTY bit, in order to indicate that the OS has “acknowledged” the fact that this page was written to since the last time it checked. This bit is typically set by the hardware.

• If enable is true, this page will be marked as dirty.
• If enable is false, this page will be marked as clean.

pub const fn is_valid(&self) -> bool

pub const fn is_writable(&self) -> bool

pub const fn is_executable(&self) -> bool

pub const fn is_device_memory(&self) -> bool

pub const fn is_dirty(&self) -> bool

pub const fn is_accessed(&self) -> bool

pub const fn is_exclusive(&self) -> bool

Trait Implementations

impl Binary for PteFlags

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl BitAnd<PteFlags> for PteFlags

fn bitand(self, other: PteFlags) -> PteFlags

The bitwise and (&) of the bits in two flags values.

type Output = PteFlags

The resulting type after applying the & operator.

impl BitAndAssign<PteFlags> for PteFlags

fn bitand_assign(&mut self, other: PteFlags)

The bitwise and (&) of the bits in two flags values.

impl BitOr<PteFlags> for PteFlags

fn bitor(self, other: PteFlags) -> PteFlags

The bitwise or (|) of the bits in two flags values.

type Output = PteFlags

The resulting type after applying the | operator.

impl BitOrAssign<PteFlags> for PteFlags

fn bitor_assign(&mut self, other: PteFlags)

The bitwise or (|) of the bits in two flags values.

impl BitXor<PteFlags> for PteFlags

fn bitxor(self, other: PteFlags) -> PteFlags

The bitwise exclusive-or (^) of the bits in two flags values.

type Output = PteFlags

The resulting type after applying the ^ operator.

impl BitXorAssign<PteFlags> for PteFlags

fn bitxor_assign(&mut self, other: PteFlags)

The bitwise exclusive-or (^) of the bits in two flags values.

impl Clone for PteFlags

fn clone(&self) -> PteFlags

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PteFlags

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for PteFlags

See PteFlags::new() for what bits are set by default.

fn default() -> PteFlags

Returns the “default value” for a type.

impl Extend<PteFlags> for PteFlags

fn extend<T>(&mut self, iterator: T)where T: IntoIterator<Item = PteFlags>,

The bitwise or (|) of the bits in each flags value.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl Flags for PteFlags

const FLAGS: &'static [Flag<PteFlags>] = _

The set of defined flags.

type Bits = u64

The underlying bits type.

fn bits(&self) -> u64

Get the underlying bits value.

fn from_bits_retain(bits: u64) -> PteFlags

Convert from a bits value exactly.

fn empty() -> Self

Get a flags value with all bits unset.

fn all() -> Self

Get a flags value with all known bits set.

fn from_bits(bits: Self::Bits) -> Option<Self>

Convert from a bits value.

fn from_bits_truncate(bits: Self::Bits) -> Self

Convert from a bits value, unsetting any unknown bits.

fn from_name(name: &str) -> Option<Self>

Get a flags value with the bits of a flag with the given name set.

fn iter(&self) -> Iter<Self>

Yield a set of contained flags values.

fn iter_names(&self) -> IterNames<Self>

Yield a set of contained named flags values.

fn is_empty(&self) -> bool

Whether all bits in this flags value are unset.

fn is_all(&self) -> bool

Whether all known bits in this flags value are set.

fn intersects(&self, other: Self) -> boolwhere Self: Sized,

Whether any set bits in a source flags value are also set in a target flags value.

fn contains(&self, other: Self) -> boolwhere Self: Sized,

Whether all set bits in a source flags value are also set in a target flags value.

fn insert(&mut self, other: Self)where Self: Sized,

The bitwise or (|) of the bits in two flags values.

fn remove(&mut self, other: Self)where Self: Sized,

The intersection of a source flags value with the complement of a target flags value (&!).

fn toggle(&mut self, other: Self)where Self: Sized,

The bitwise exclusive-or (^) of the bits in two flags values.

fn set(&mut self, other: Self, value: bool)where Self: Sized,

Call [Flags::insert] when value is true or [Flags::remove] when value is false.

fn intersection(self, other: Self) -> Self

The bitwise and (&) of the bits in two flags values.

fn union(self, other: Self) -> Self

The bitwise or (|) of the bits in two flags values.

fn difference(self, other: Self) -> Self

The intersection of a source flags value with the complement of a target flags value (&!).

fn symmetric_difference(self, other: Self) -> Self

The bitwise exclusive-or (^) of the bits in two flags values.

fn complement(self) -> Self

The bitwise negation (!) of the bits in a flags value, truncating the result.

impl From<PteFlags> for PteFlagsX86_64

fn from(general: PteFlags) -> PteFlagsX86_64

Converts to this type from the input type.

impl From<PteFlagsX86_64> for PteFlags

fn from(specific: PteFlagsX86_64) -> PteFlags

Converts to this type from the input type.

impl FromIterator<PteFlags> for PteFlags

fn from_iter<T>(iterator: T) -> PteFlagswhere T: IntoIterator<Item = PteFlags>,

The bitwise or (|) of the bits in each flags value.

impl IntoIterator for PteFlags

type Item = PteFlags

The type of the elements being iterated over.

type IntoIter = Iter<PteFlags>

Which kind of iterator are we turning this into?

fn into_iter(self) -> <PteFlags as IntoIterator>::IntoIter

Creates an iterator from a value.

impl LowerHex for PteFlags

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Not for PteFlags

fn not(self) -> PteFlags

The bitwise negation (!) of the bits in a flags value, truncating the result.

type Output = PteFlags

The resulting type after applying the ! operator.

impl Octal for PteFlags

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl PartialEq<PteFlags> for PteFlags

fn eq(&self, other: &PteFlags) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Sub<PteFlags> for PteFlags

fn sub(self, other: PteFlags) -> PteFlags

The intersection of a source flags value with the complement of a target flags value (&!).

This method is not equivalent to self & !other when other has unknown bits set. difference won’t truncate other, but the ! operator will.

type Output = PteFlags

The resulting type after applying the - operator.

impl SubAssign<PteFlags> for PteFlags

fn sub_assign(&mut self, other: PteFlags)

The intersection of a source flags value with the complement of a target flags value (&!).

This method is not equivalent to self & !other when other has unknown bits set. difference won’t truncate other, but the ! operator will.

impl UpperHex for PteFlags

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Copy for PteFlags

impl Eq for PteFlags

impl StructuralEq for PteFlags

impl StructuralPartialEq for PteFlags