x86_64/instructions/
tables.rs

Help
1//! Functions to load GDT, IDT, and TSS structures.
2
3use crate::structures::gdt::SegmentSelector;
4use crate::VirtAddr;
5use core::arch::asm;
6
7pub use crate::structures::DescriptorTablePointer;
8
9/// Load a GDT.
10///
11/// Use the
12/// [`GlobalDescriptorTable`](crate::structures::gdt::GlobalDescriptorTable) struct for a high-level
13/// interface to loading a GDT.
14///
15/// ## Safety
16///
17/// This function is unsafe because the caller must ensure that the given
18/// `DescriptorTablePointer` points to a valid GDT and that loading this
19/// GDT is safe.
20#[inline]
21pub unsafe fn lgdt(gdt: &DescriptorTablePointer) {
22    unsafe {
23        asm!("lgdt [{}]", in(reg) gdt, options(readonly, nostack, preserves_flags));
24    }
25}
26
27/// Load an IDT.
28///
29/// Use the
30/// [`InterruptDescriptorTable`](crate::structures::idt::InterruptDescriptorTable) struct for a high-level
31/// interface to loading an IDT.
32///
33/// ## Safety
34///
35/// This function is unsafe because the caller must ensure that the given
36/// `DescriptorTablePointer` points to a valid IDT and that loading this
37/// IDT is safe.
38#[inline]
39pub unsafe fn lidt(idt: &DescriptorTablePointer) {
40    unsafe {
41        asm!("lidt [{}]", in(reg) idt, options(readonly, nostack, preserves_flags));
42    }
43}
44
45/// Get the address of the current GDT.
46#[inline]
47pub fn sgdt() -> DescriptorTablePointer {
48    let mut gdt: DescriptorTablePointer = DescriptorTablePointer {
49        limit: 0,
50        base: VirtAddr::new(0),
51    };
52    unsafe {
53        asm!("sgdt [{}]", in(reg) &mut gdt, options(nostack, preserves_flags));
54    }
55    gdt
56}
57
58/// Get the address of the current IDT.
59#[inline]
60pub fn sidt() -> DescriptorTablePointer {
61    let mut idt: DescriptorTablePointer = DescriptorTablePointer {
62        limit: 0,
63        base: VirtAddr::new(0),
64    };
65    unsafe {
66        asm!("sidt [{}]", in(reg) &mut idt, options(nostack, preserves_flags));
67    }
68    idt
69}
70
71/// Load the task state register using the `ltr` instruction.
72///
73/// Note that loading a TSS segment selector marks the corresponding TSS
74/// Descriptor in the GDT as "busy", preventing it from being loaded again
75/// (either on this CPU or another CPU). TSS structures (including Descriptors
76/// and Selectors) should generally be per-CPU. See
77/// [`tss_segment`](crate::structures::gdt::Descriptor::tss_segment)
78/// for more information.
79///
80/// Calling `load_tss` with a busy TSS selector results in a `#GP` exception.
81///
82/// ## Safety
83///
84/// This function is unsafe because the caller must ensure that the given
85/// `SegmentSelector` points to a valid TSS entry in the GDT and that the
86/// corresponding data in the TSS is valid.
87#[inline]
88pub unsafe fn load_tss(sel: SegmentSelector) {
89    unsafe {
90        asm!("ltr {0:x}", in(reg) sel.0, options(nostack, preserves_flags));
91    }
92}
x86_64/instructions/tables.rs

x86_64/instructions/
tables.rs
