Enum Descriptor 

pub enum Descriptor {
    UserSegment(u64),
    SystemSegment(u64, u64),
}

A 64-bit mode segment descriptor.

Segmentation is no longer supported in 64-bit mode, so most of the descriptor contents are ignored.

Variants

UserSegment(u64)

Descriptor for a code or data segment.

Since segmentation is no longer supported in 64-bit mode, almost all of code and data descriptors is ignored. Only some flags are still used.

SystemSegment(u64, u64)

A system segment descriptor such as a LDT or TSS descriptor.

Implementations

impl Descriptor

pub const fn dpl(self) -> PrivilegeLevel

Returns the Descriptor Privilege Level (DPL). When using this descriptor via a SegmentSelector, the RPL and Current Privilege Level (CPL) must less than or equal to the DPL, except for stack segments where the RPL, CPL, and DPL must all be equal.

pub const fn kernel_code_segment() -> Descriptor

Creates a segment descriptor for a 64-bit kernel code segment. Suitable for use with syscall or 64-bit sysenter.

pub const fn kernel_data_segment() -> Descriptor

Creates a segment descriptor for a kernel data segment (32-bit or 64-bit). Suitable for use with syscall or sysenter.

pub const fn user_data_segment() -> Descriptor

Creates a segment descriptor for a ring 3 data segment (32-bit or 64-bit). Suitable for use with sysret or sysexit.

pub const fn user_code_segment() -> Descriptor

Creates a segment descriptor for a 64-bit ring 3 code segment. Suitable for use with sysret or sysexit.

pub fn tss_segment(tss: &'static TaskStateSegment) -> Descriptor

Creates a TSS system descriptor for the given TSS.

While it is possible to create multiple Descriptors that point to the same TSS, this generally isn’t recommended, as the TSS usually contains per-CPU information such as the RSP and IST pointers. Instead, there should be exactly one TSS and one corresponding TSS Descriptor per CPU. Then, each of these descriptors should be placed in a GDT (which can either be global or per-CPU).

pub unsafe fn tss_segment_unchecked(tss: *const TaskStateSegment) -> Descriptor

Similar to Descriptor::tss_segment, but unsafe since it does not enforce a lifetime constraint on the provided TSS.

Safety

The caller must ensure that the passed pointer is valid for as long as the descriptor is being used.

pub fn tss_segment_with_iomap( tss: &'static TaskStateSegment, iomap: &'static [u8], ) -> Result<Descriptor, InvalidIoMap>

Creates a TSS system descriptor for the given TSS, setting up the IO permissions bitmap.

Example

use x86_64::structures::gdt::Descriptor;
use x86_64::structures::tss::TaskStateSegment;

/// A helper that places some I/O map bytes behind a TSS.
#[repr(C)]
struct TssWithIOMap {
    tss: TaskStateSegment,
    iomap: [u8; 5],
}

static TSS: TssWithIOMap = TssWithIOMap {
    tss: TaskStateSegment::new(),
    iomap: [0xff, 0xff, 0x00, 0x80, 0xff],
};

let tss = Descriptor::tss_segment_with_iomap(&TSS.tss, &TSS.iomap).unwrap();

Trait Implementations

impl Clone for Descriptor

fn clone(&self) -> Descriptor

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Descriptor

impl Debug for Descriptor

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

Formats the value using the given formatter.