在riscv上实现异常处理，能够进入异常处理程序 (#564)

kernel/src/arch/riscv64/cpu.rs

@@ -7,10 +7,13 @@ use crate::{
     smp::cpu::{ProcessorId, SmpCpuManager},
 };
 
+/// 栈对齐
+pub(super) const STACK_ALIGN: usize = 16;
+
 /// 获取当前cpu的id
 #[inline]
 pub fn current_cpu_id() -> ProcessorId {
-    let ptr: *const LocalContext = riscv::register::sscratch::read() as *const LocalContext;
+    let ptr: *const LocalContext = riscv::register::tp::read() as *const LocalContext;
 
     if core::intrinsics::unlikely(ptr.is_null()) {
         return boot_params().read_irqsave().arch.boot_hartid;
@@ -34,16 +37,29 @@ pub(super) fn local_context() -> &'static PerCpuVar<LocalContext> {
 
 /// Per cpu的上下文数据
 ///
-/// 每个CPU的sscratch寄存器指向这个结构体
+/// 每个CPU的tp寄存器指向这个结构体
+///
+/// 注意：
+///
+/// - 从用户态进入内核态时，会从sscratch寄存器加载这个结构体的地址到tp寄存器，并把sscratch寄存器清零
+/// - 从内核态进入用户态时，会将tp寄存器的值保存到sscratch寄存器
 #[derive(Debug)]
 pub(super) struct LocalContext {
     /// 当前cpu的id
-    current_cpu: ProcessorId,
+    pub current_cpu: ProcessorId,
+    // 当前进程的内核栈指针（暂存，当进入中断处理程序的时候需要保存到pcb，进程切换的时候需要重新设置这个值）
+    pub kernel_sp: usize,
+    // 当前进程的用户栈指针（暂存，当进入中断处理程序的时候需要保存到pcb，进程切换的时候需要重新设置这个值）
+    pub user_sp: usize,
 }
 
 impl LocalContext {
     fn new(cpu: ProcessorId) -> Self {
-        Self { current_cpu: cpu }
+        Self {
+            current_cpu: cpu,
+            kernel_sp: 0,
+            user_sp: 0,
+        }
     }
     pub fn current_cpu(&self) -> ProcessorId {
         self.current_cpu
@@ -53,16 +69,34 @@ impl LocalContext {
         self.current_cpu = cpu;
     }
 
+    pub fn kernel_sp(&self) -> usize {
+        self.kernel_sp
+    }
+
+    pub fn set_kernel_sp(&mut self, sp: usize) {
+        self.kernel_sp = sp;
+    }
+
+    pub fn user_sp(&self) -> usize {
+        self.user_sp
+    }
+
+    pub fn set_user_sp(&mut self, sp: usize) {
+        self.user_sp = sp;
+    }
+
     fn sync_to_cpu(&self) {
         let ptr = self as *const Self as usize;
-        riscv::register::sscratch::write(ptr);
+        riscv::register::sscratch::write(0);
+
+        // 写入tp寄存器
+        riscv::register::tp::write(ptr);
     }
 }
 
 /// 初始化本地上下文
 #[inline(never)]
 pub(super) fn init_local_context() {
-    kdebug!("init_local_context");
     let mut data = Vec::new();
 
     for i in 0..PerCpu::MAX_CPU_NUM {