forked from AbleOS/ableos
77 lines
2.2 KiB
Rust
77 lines
2.2 KiB
Rust
use spin::Lazy;
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use x86_64::{
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structures::{
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gdt::{Descriptor, GlobalDescriptorTable, SegmentSelector},
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tss::TaskStateSegment,
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},
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VirtAddr,
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};
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pub const DOUBLE_FAULT_IX: u16 = 0;
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pub unsafe fn init() {
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use x86_64::instructions::segmentation::{Segment, CS, DS, ES, SS};
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use x86_64::instructions::tables::load_tss;
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log::info!("Initialising GDT");
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GDT.0.load();
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CS::set_reg(GDT.1.kcode);
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DS::set_reg(GDT.1.kdata);
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ES::set_reg(GDT.1.kdata);
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SS::set_reg(GDT.1.kdata);
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load_tss(GDT.1.tss);
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init_syscalls(&GDT.1);
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}
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struct Selectors {
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kcode: SegmentSelector,
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kdata: SegmentSelector,
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tss: SegmentSelector,
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udata: SegmentSelector,
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ucode: SegmentSelector,
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}
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static TSS: Lazy<TaskStateSegment> = Lazy::new(|| {
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let mut tss = TaskStateSegment::new();
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tss.interrupt_stack_table[usize::from(DOUBLE_FAULT_IX)] = {
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const SIZE: usize = 5 * 1024;
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let stack = unsafe {
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alloc::alloc::alloc_zeroed(
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alloc::alloc::Layout::from_size_align(SIZE, 1).expect("stack pointer"),
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)
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};
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VirtAddr::from_ptr(stack) + SIZE
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};
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tss
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});
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static GDT: Lazy<(GlobalDescriptorTable, Selectors)> = Lazy::new(|| {
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let mut gdt = GlobalDescriptorTable::new();
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let sels = Selectors {
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kcode: gdt.add_entry(Descriptor::kernel_code_segment()),
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kdata: gdt.add_entry(Descriptor::kernel_data_segment()),
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tss: gdt.add_entry(Descriptor::tss_segment(&TSS)),
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udata: gdt.add_entry(Descriptor::user_data_segment()),
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ucode: gdt.add_entry(Descriptor::user_code_segment()),
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};
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(gdt, sels)
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});
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/// Initialize syscalls
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unsafe fn init_syscalls(sls: &Selectors) {
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use x86_64::registers::{
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model_specific::{Efer, EferFlags, LStar, SFMask, Star},
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rflags::RFlags,
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};
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Star::write(sls.ucode, sls.udata, sls.kcode, sls.kdata);
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SFMask::write(RFlags::from_bits(0x200).expect("Invalid RFlags for SFMask"));
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LStar::write(VirtAddr::from_ptr(handle_syscall as *const ()));
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Efer::update(|x| *x |= EferFlags::SYSTEM_CALL_EXTENSIONS);
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}
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extern "C" fn handle_syscall(a: u64) -> ! {
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log::info!("called syscall {a}");
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todo!("Return from syscall");
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}
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