Struct SegmentDescriptor

#[repr(C)]
pub struct SegmentDescriptor {
    pub flags: SegmentDescriptorFlags,
    /* private fields */
}

Available on x86 or x86-64 only.

An entry in a segment descriptor table that defines a new segment. This includes code, data, task state (TSS), and local descriptor table (LDT) segments.

Notes on the size of this structure:

• In 32-bit mode, this structure is always 8 bytes and contains a 32-bit base address.
• In 64-bit mode:
  • Task state and local descriptor table segment descriptors are expanded to 16 bytes with 64-bit base addresses.
  • From the processor’s perspective, code and data segments remain 8 bytes and the address and limit are both ignored. However, this structure is still defined as 16 bytes. This is fine, since the first 8 bytes are compatible and the rest will be ignored.

Fields

flags: SegmentDescriptorFlags

Common segment descriptor settings.

Implementations

impl SegmentDescriptor

pub const LIMIT_MAX: u32 = 1_048_575u32

The maximum supported value of the limit field (20 bits).

pub const fn new() -> Self

Create a zero-initialized descriptor

pub fn address(self) -> usize

Base virtual address of the segment, to which offsets are added.

In 64-bit mode, this is ignored and assumed to be 0 for code and data segments, but it still applies to task state and local descriptor table segments.

pub fn set_address(&mut self, address: usize)

Update the base address.

pub fn limit(self) -> u32

The “limit” of the segment, which is a maximum or minimum offset from the base address.

If this is a stack-like data segment (data_expand_down), then this value is the exclusive minimum offset value. Otherwise, this is the inclusive maximum offset value (i.e., size - 1).

This value may be in bytes or in 4KB units, depending on flags.granularity.

In 64-bit mode, this is ignored (all limit checks are disabled) for code and data segments, but it still applies to task state and local descriptor table segments.

pub fn set_limit(&mut self, limit: u32)

Update the segment limit.

Panics

Panics if the limit is greater than LIMIT_MAX.

Trait Implementations

impl Clone for SegmentDescriptor

fn clone(&self) -> SegmentDescriptor

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for SegmentDescriptor

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

Formats the value using the given formatter.

impl Default for SegmentDescriptor

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for SegmentDescriptor

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl Copy for SegmentDescriptor

impl Eq for SegmentDescriptor

impl StructuralPartialEq for SegmentDescriptor