[−][src]Struct x86_64::structures::gdt::GlobalDescriptorTable
A 64-bit mode global descriptor table (GDT).
In 64-bit mode, segmentation is not supported. The GDT is used nonetheless, for example for switching between user and kernel mode or for loading a TSS.
The GDT has a fixed size of 8 entries, trying to add more entries will panic.
You do not need to add a null segment descriptor yourself - this is already done internally.
Data segment registers in ring 0 can be loaded with the null segment selector. When running in
ring 3, the ss
register must point to a valid data segment which can be obtained through the
Descriptor::user_data_segment()
function. Code segments must
be valid and non-null at all times and can be obtained through the
Descriptor::kernel_code_segment()
and
Descriptor::user_code_segment()
in rings 0 and 3
respectively.
For more info, see:
x86 Instruction Reference for mov
,
Intel Manual,
AMD Manual
Example
use x86_64::structures::gdt::{GlobalDescriptorTable, Descriptor}; let mut gdt = GlobalDescriptorTable::new(); gdt.add_entry(Descriptor::kernel_code_segment()); gdt.add_entry(Descriptor::user_code_segment()); gdt.add_entry(Descriptor::user_data_segment()); // Add entry for TSS, call gdt.load() then update segment registers
Methods
impl GlobalDescriptorTable
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pub const fn new() -> GlobalDescriptorTable
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Creates an empty GDT.
pub fn add_entry(&mut self, entry: Descriptor) -> SegmentSelector
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Adds the given segment descriptor to the GDT, returning the segment selector.
Panics if the GDT has no free entries left.
pub fn load(&'static self)
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Loads the GDT in the CPU using the lgdt
instruction. This does not alter any of the
segment registers; you must (re)load them yourself using the appropriate
functions:
load_ss,
set_cs.
Trait Implementations
impl Clone for GlobalDescriptorTable
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fn clone(&self) -> GlobalDescriptorTable
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fn clone_from(&mut self, source: &Self)
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impl Debug for GlobalDescriptorTable
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Auto Trait Implementations
impl Send for GlobalDescriptorTable
impl Sync for GlobalDescriptorTable
impl Unpin for GlobalDescriptorTable
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,