//! Helpers to program the task state segment.
//! See Intel 3a, Chapter 7, Section 7
use segmentation;
/// In 64-bit mode the TSS holds information that is not
/// directly related to the task-switch mechanism,
/// but is used for finding kernel level stack
/// if interrupts arrive while in kernel mode.
#[derive(Debug)]
#[repr(C, packed)]
pub struct TaskStateSegment {
pub reserved: u32,
/// The full 64-bit canonical forms of the stack pointers (RSP) for privilege levels 0-2.
pub rsp: [u64; 3],
pub reserved2: u64,
/// The full 64-bit canonical forms of the interrupt stack table (IST) pointers.
pub ist: [u64; 7],
pub reserved3: u64,
pub reserved4: u16,
/// The 16-bit offset to the I/O permission bit map from the 64-bit TSS base.
pub iomap_base: u16,
}
impl TaskStateSegment {
pub const fn new() -> TaskStateSegment {
TaskStateSegment {
reserved: 0,
rsp: [0; 3],
reserved2: 0,
ist: [0; 7],
reserved3: 0,
reserved4: 0,
iomap_base: 0,
}
}
}
/// Load the task state register.
pub unsafe fn load_tr(sel: segmentation::SegmentSelector) {
asm!("ltr $0" :: "r" (sel));
}