An experimental microkernel OS
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use lazy_static::lazy_static;
use x86_64::structures::gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector};
use x86_64::structures::tss::TaskStateSegment;
use x86_64::VirtAddr;
pub const DOUBLE_FAULT_IST_INDEX: u16 = 0;
lazy_static! {
static ref TSS: TaskStateSegment = {
let mut tss = TaskStateSegment::new();
tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX as usize] = {
const STACK_SIZE: usize = 4096;
static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
let stack_end = stack_start + STACK_SIZE;
stack_end
};
tss
};
}
pub fn init() {
use x86_64::instructions::segmentation::set_cs;
use x86_64::instructions::tables::load_tss;
GDT.0.load();
unsafe {
set_cs(GDT.1.code_selector);
load_tss(GDT.1.tss_selector);
}
}
lazy_static! {
static ref GDT: (GlobalDescriptorTable, Selectors) = {
let mut gdt = GlobalDescriptorTable::new();
let code_selector = gdt.add_entry(Descriptor::kernel_code_segment());
let tss_selector = gdt.add_entry(Descriptor::tss_segment(&TSS));
(
gdt,
Selectors {
code_selector,
tss_selector,
},
)
};
}
struct Selectors {
code_selector: SegmentSelector,
tss_selector: SegmentSelector,
}