x86_64: enable interrupt during syscall. set TSS.sp0 through gs.

kernel/src/arch/x86_64/gdt.rs

@@ -39,10 +39,6 @@ pub struct Cpu {
 }
 
 impl Cpu {
-    pub fn current() -> &'static mut Self {
-        unsafe { CPUS[super::cpu::id()].as_mut().unwrap() }
-    }
-
     fn new() -> Self {
         Cpu {
             gdt: GlobalDescriptorTable::new(),
@@ -72,18 +68,9 @@ impl Cpu {
         set_cs(KCODE_SELECTOR);
         // load TSS
         load_tss(TSS_SELECTOR);
-        // for fast syscall:
+        // store address of TSS to GSBase
-        // store address of TSS to kernel_gsbase
+        let mut gsbase = Msr::new(0xC0000101);
-        let mut kernel_gsbase = Msr::new(0xC0000102);
+        gsbase.write(&self.tss as *const _ as u64);
-        kernel_gsbase.write(&self.tss as *const _ as u64);
-    }
-
-    /// 设置从Ring3跳到Ring0时，自动切换栈的地址
-    ///
-    /// 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
-    pub fn set_ring0_rsp(&mut self, rsp: usize) {
-        trace!("gdt.set_ring0_rsp: {:#x}", rsp);
-        self.tss.privilege_stack_table[0] = VirtAddr::new(rsp as u64);
     }
 }
 

kernel/src/arch/x86_64/interrupt/handler.rs

@@ -213,9 +213,3 @@ fn invalid_opcode(tf: &mut TrapFrame) {
 fn error(tf: &TrapFrame) {
     crate::trap::error(tf);
 }
-
-#[no_mangle]
-pub unsafe extern "C" fn set_return_rsp(tf: *const TrapFrame) {
-    use crate::arch::gdt::Cpu;
-    Cpu::current().set_ring0_rsp(tf.add(1) as usize);
-}

kernel/src/arch/x86_64/interrupt/trap.asm

@@ -49,8 +49,10 @@ __alltraps:
 .global trap_ret
 trap_ret:
 
+    # store kernel rsp -> TSS.sp0
     mov rdi, rsp
-    call set_return_rsp
+    add rdi, 720
+    mov gs:[4], rdi
 
     # pop fp state offset
     pop rcx
@@ -104,8 +106,6 @@ syscall_entry:
     # - store rip -> rcx
     # - load rip
 
-    # swap in kernel gs
-    swapgs
     # store user rsp -> scratch at TSS.sp1
     mov gs:[12], rsp
     # load kernel rsp <- TSS.sp0
@@ -119,11 +119,8 @@ syscall_entry:
     push 0          # error_code (dummy)
     push 0          # trap_num (dummy)
 
-    # swap out kernel gs
-    swapgs
-
     # enable interrupt
-    # sti
+    sti
 
     push rax
     push rcx
@@ -173,8 +170,10 @@ syscall_return:
     # disable interrupt
     cli
 
+    # store kernel rsp -> TSS.sp0
     mov rdi, rsp
-    call set_return_rsp
+    add rdi, 720
+    mov gs:[4], rdi
 
     # pop fp state offset
     pop rcx

kernel/src/arch/x86_64/mod.rs

@@ -15,7 +15,7 @@ pub mod rand;
 pub mod syscall;
 pub mod timer;
 
-static AP_CAN_INIT: AtomicBool = ATOMIC_BOOL_INIT;
+static AP_CAN_INIT: AtomicBool = AtomicBool::new(false);
 
 /// The entry point of kernel
 #[no_mangle] // don't mangle the name of this function