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use alloc::boxed::Box;
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use x86_64::registers::model_specific::Msr;
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use x86_64::structures::gdt::*;
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use x86_64::structures::tss::TaskStateSegment;
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use x86_64::{PrivilegeLevel, VirtAddr};
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use crate::consts::MAX_CPU_NUM;
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/// Init TSS & GDT.
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pub fn init() {
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unsafe {
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CPUS[super::cpu::id()] = Some(Cpu::new());
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CPUS[super::cpu::id()].as_mut().unwrap().init();
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}
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}
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static mut CPUS: [Option<Cpu>; MAX_CPU_NUM] = [
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// TODO: More elegant ?
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None, None, None, None, None, None, None, None,
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];
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pub struct Cpu {
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gdt: GlobalDescriptorTable,
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tss: TaskStateSegment,
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double_fault_stack: [u8; 0x100],
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}
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impl Cpu {
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pub fn current() -> &'static mut Self {
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unsafe { CPUS[super::cpu::id()].as_mut().unwrap() }
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}
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fn new() -> Self {
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Cpu {
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gdt: GlobalDescriptorTable::new(),
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tss: TaskStateSegment::new(),
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double_fault_stack: [0u8; 0x100],
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}
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}
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unsafe fn init(&'static mut self) {
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use x86_64::instructions::segmentation::{load_fs, set_cs};
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use x86_64::instructions::tables::load_tss;
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// Set the stack when DoubleFault occurs
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let stack_top = VirtAddr::new(self.double_fault_stack.as_ptr() as u64 + 0x100);
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self.tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX] = stack_top;
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// GDT
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self.gdt.add_entry(KCODE);
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self.gdt.add_entry(KDATA);
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self.gdt.add_entry(UCODE32);
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self.gdt.add_entry(UDATA32);
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self.gdt.add_entry(UCODE);
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self.gdt.add_entry(Descriptor::tss_segment(&self.tss));
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self.gdt.load();
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// reload code segment register
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set_cs(KCODE_SELECTOR);
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// load TSS
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load_tss(TSS_SELECTOR);
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// for fast syscall:
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// store address of TSS to kernel_gsbase
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let mut kernel_gsbase = Msr::new(0xC0000102);
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kernel_gsbase.write(&self.tss as *const _ as u64);
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}
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/// 设置从Ring3跳到Ring0时，自动切换栈的地址
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///
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/// 每次进入用户态前，都要调用此函数，才能保证正确返回内核态
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pub fn set_ring0_rsp(&mut self, rsp: usize) {
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trace!("gdt.set_ring0_rsp: {:#x}", rsp);
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self.tss.privilege_stack_table[0] = VirtAddr::new(rsp as u64);
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}
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}
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pub const DOUBLE_FAULT_IST_INDEX: usize = 0;
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// Copied from xv6 x86_64
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const KCODE: Descriptor = Descriptor::UserSegment(0x0020980000000000); // EXECUTABLE | USER_SEGMENT | PRESENT | LONG_MODE
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const UCODE: Descriptor = Descriptor::UserSegment(0x0020F80000000000); // EXECUTABLE | USER_SEGMENT | USER_MODE | PRESENT | LONG_MODE
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const KDATA: Descriptor = Descriptor::UserSegment(0x0000920000000000); // DATA_WRITABLE | USER_SEGMENT | PRESENT
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const UDATA: Descriptor = Descriptor::UserSegment(0x0000F20000000000); // DATA_WRITABLE | USER_SEGMENT | USER_MODE | PRESENT
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// Copied from xv6
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const UCODE32: Descriptor = Descriptor::UserSegment(0x00cffa00_0000ffff); // EXECUTABLE | USER_SEGMENT | USER_MODE | PRESENT
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const UDATA32: Descriptor = Descriptor::UserSegment(0x00cff200_0000ffff); // EXECUTABLE | USER_SEGMENT | USER_MODE | PRESENT
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// NOTICE: for fast syscall:
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// STAR[47:32] = K_CS = K_SS - 8
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// STAR[63:48] = U_CS32 = U_SS32 - 8 = U_CS - 16
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pub const KCODE_SELECTOR: SegmentSelector = SegmentSelector::new(1, PrivilegeLevel::Ring0);
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pub const KDATA_SELECTOR: SegmentSelector = SegmentSelector::new(2, PrivilegeLevel::Ring0);
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pub const UCODE32_SELECTOR: SegmentSelector = SegmentSelector::new(3, PrivilegeLevel::Ring3);
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pub const UDATA32_SELECTOR: SegmentSelector = SegmentSelector::new(4, PrivilegeLevel::Ring3);
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pub const UCODE_SELECTOR: SegmentSelector = SegmentSelector::new(5, PrivilegeLevel::Ring3);
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pub const TSS_SELECTOR: SegmentSelector = SegmentSelector::new(6, PrivilegeLevel::Ring0);
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