Struct framehop::aarch64::PtrAuthMask

pub struct PtrAuthMask(pub u64);

Aarch64 CPUs support special instructions which interpret pointers as pair of the pointer address and an encrypted hash: The address is stored in the lower bits and the hash in the high bits. These are called “authenticated” pointers. Special instructions exist to verify pointers before dereferencing them.

Return address can be such authenticated pointers. To return to an authenticated return address, the “retab” instruction is used instead of the regular “ret” instruction.

Stack walkers need to strip the encrypted hash from return addresses because they need the raw code address.

On macOS arm64, system libraries compiled with the arm64e target use pointer pointer authentication for return addresses.

Tuple Fields

0: u64

Implementations

impl PtrAuthMask

pub fn new_no_strip() -> Self

Create a no-op mask which treats all bits of the pointer as address bits, so no bits are stripped.

pub fn new_24_40() -> Self

Create a mask for 24 bits hash + 40 bits pointer. This appears to be what macOS arm64e uses. It is unclear whether we can rely on this or whether it can change.

On macOS arm64, this mask can be applied to both authenticated pointers and to non-authenticated pointers without data loss; non-authenticated don’t appear to use the top 24 bits (they’re always zero).

pub fn from_max_known_address(address: u64) -> Self

Deduce a mask based on the highest known address. The leading zero bits in this address will be reserved for the hash.

pub fn strip_ptr_auth(&self, ptr: u64) -> u64

Apply the mask to the given pointer.

Trait Implementations

impl Clone for PtrAuthMask

fn clone(&self) -> PtrAuthMask

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for PtrAuthMask

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

Formats the value using the given formatter.

impl Hash for PtrAuthMask

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for PtrAuthMask

fn cmp(&self, other: &PtrAuthMask) -> Ordering

This method returns an Ordering between self and other.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for PtrAuthMask

fn eq(&self, other: &PtrAuthMask) -> 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 PartialOrd for PtrAuthMask

fn partial_cmp(&self, other: &PtrAuthMask) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

This method tests less than (for self and other) and is used by the < operator.

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

This method tests less than or equal to (for self and other) and is used by the <= operator.

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

This method tests greater than (for self and other) and is used by the > operator.

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

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for PtrAuthMask

impl Eq for PtrAuthMask

impl StructuralEq for PtrAuthMask

impl StructuralPartialEq for PtrAuthMask