增加x87FPU支持 (#212)

* remove `ret_from_syscall`
*修复ps2键盘驱动程序inode在进程fork的时候导致死锁的问题.
*更新: VFS每次拷贝文件描述符的时候,都会去调用inode的open函数

---------

Co-authored-by: longjin <longjin@RinGoTek.cn>

kernel/src/arch/x86_64/context.rs

@@ -2,6 +2,8 @@ use crate::include::bindings::bindings::{process_control_block, switch_proc};
 
 use core::sync::atomic::compiler_fence;
 
+use super::fpu::{fp_state_save, fp_state_restore};
+
 /// @brief 切换进程的上下文（没有切换页表的动作）
 ///
 /// @param next 下一个进程的pcb
@@ -11,6 +13,8 @@ pub fn switch_process(
     prev: &'static mut process_control_block,
     next: &'static mut process_control_block,
 ) {
+    fp_state_save(prev);
+    fp_state_restore(next);
     compiler_fence(core::sync::atomic::Ordering::SeqCst);
     unsafe {
         switch_proc(prev, next);

kernel/src/arch/x86_64/fpu.rs

@@ -0,0 +1,147 @@
+use core::{
+    arch::{
+        asm,
+        x86_64::{_fxrstor64, _fxsave64},
+    },
+    ffi::c_void,
+    ptr::null_mut,
+};
+
+use alloc::boxed::Box;
+
+use crate::include::bindings::bindings::process_control_block;
+
+use super::asm::irqflags::{local_irq_restore, local_irq_save};
+/// https://www.felixcloutier.com/x86/fxsave#tbl-3-47
+#[repr(C, align(16))]
+#[derive(Debug, Copy, Clone)]
+pub struct FpState {
+    //0
+    fcw: u16,
+    fsw: u16,
+    ftw: u16,
+    fop: u16,
+    word2: u64,
+    //16
+    word3: u64,
+    mxcsr: u32,
+    mxcsr_mask: u32,
+    //32
+    mm: [u64; 16],
+    //160
+    xmm: [u64; 32],
+    //416
+    rest: [u64; 12],
+}
+
+impl Default for FpState {
+    fn default() -> Self {
+        Self {
+            fcw: 0x037f,
+            fsw: Default::default(),
+            ftw: Default::default(),
+            fop: Default::default(),
+            word2: Default::default(),
+            word3: Default::default(),
+            mxcsr: 0x1f80,
+            mxcsr_mask: Default::default(),
+            mm: Default::default(),
+            xmm: Default::default(),
+            rest: Default::default(),
+        }
+    }
+}
+impl FpState {
+    #[allow(dead_code)]
+    pub fn new() -> Self {
+        assert!(core::mem::size_of::<Self>() == 512);
+        return Self::default();
+    }
+    #[allow(dead_code)]
+    pub fn save(&mut self) {
+        unsafe {
+            _fxsave64(self as *mut FpState as *mut u8);
+        }
+    }
+    #[allow(dead_code)]
+    pub fn restore(&self) {
+        unsafe {
+            _fxrstor64(self as *const FpState as *const u8);
+        }
+    }
+
+    /// @brief 清空fp_state
+    pub fn clear(&mut self) {
+        *self = Self::default();
+    }
+}
+
+/// @brief 从用户态进入内核时，保存浮点寄存器，并关闭浮点功能
+pub fn fp_state_save(pcb: &mut process_control_block) {
+    // 该过程中不允许中断
+    let mut rflags: u64 = 0;
+    local_irq_save(&mut rflags);
+
+    let fp: &mut FpState = if pcb.fp_state == null_mut() {
+        let f = Box::leak(Box::new(FpState::default()));
+        pcb.fp_state = f as *mut FpState as usize as *mut c_void;
+        f
+    } else {
+        unsafe { (pcb.fp_state as usize as *mut FpState).as_mut().unwrap() }
+    };
+
+    // 保存浮点寄存器
+    fp.save();
+
+    // 关闭浮点功能
+    unsafe {
+        asm!(
+            "mov rax, cr4",
+            "and ax,~(3<<9)", //[9][10]->0
+            "mov cr4,rax",
+            "mov rax, cr0",
+            "and ax,~(02h)",    //[1]->0
+            "or ax, ~(0FFFBh)", //[2]->1
+            "mov cr0, rax"      /*
+                                "mov rax, cr0",
+                                "and ax, 0xFFFB",
+                                "or ax,0x2",
+                                "mov cr0,rax",
+                                "mov rax, cr4",
+                                "or ax,3<<9",
+                                "mov cr4, rax" */
+        )
+    }
+    local_irq_restore(&rflags);
+}
+
+/// @brief 从内核态返回用户态时，恢复浮点寄存器，并开启浮点功能
+pub fn fp_state_restore(pcb: &mut process_control_block) {
+    // 该过程中不允许中断
+    let mut rflags: u64 = 0;
+    local_irq_save(&mut rflags);
+
+    if pcb.fp_state == null_mut() {
+        panic!("fp_state_restore: fp_state is null. pid={}", pcb.pid);
+    }
+
+    unsafe {
+        asm! {
+            "mov rax, cr0",
+            "and ax, 0FFFBh",//[2]->0
+            "or ax,02h",//[1]->1
+            "mov cr0,rax",
+            "mov rax, cr4",
+            "or ax,3<<9",
+            "mov cr4, rax",
+            "clts",
+            "fninit"
+        }
+    }
+
+    let fp = unsafe { (pcb.fp_state as usize as *mut FpState).as_mut().unwrap() };
+    fp.restore();
+    fp.clear();
+
+    local_irq_restore(&rflags);
+}

kernel/src/arch/x86_64/mod.rs

@@ -5,3 +5,4 @@ pub mod cpu;
 pub mod interrupt;
 pub mod mm;
 pub mod sched;
+pub mod fpu;