Implement sys_read && allocate pid and kernel stack dynamically.

os/src/mm/memory_set.rs

@@ -47,6 +47,9 @@ impl MemorySet {
             areas: Vec::new(),
         }
     }
+    pub fn dealloc_all_frames(&mut self) {
+        *self = Self::new_bare();
+    }
     pub fn token(&self) -> usize {
         self.page_table.token()
     }
@@ -59,6 +62,14 @@ impl MemorySet {
             permission,
         ), None);
     }
+    pub fn remove_area_with_start_vpn(&mut self, start_vpn: VirtPageNum) {
+        if let Some((idx, area)) = self.areas.iter_mut().enumerate()
+            .find(|(_, area)| area.vpn_range.get_start() == start_vpn) {
+            area.unmap(&mut self.page_table);
+            self.areas.remove(idx);
+        }
+        panic!("Area not found!");
+    }
     fn push(&mut self, mut map_area: MapArea, data: Option<&[u8]>) {
         map_area.map(&mut self.page_table);
         if let Some(data) = data {
@@ -228,7 +239,6 @@ impl MapArea {
         let pte_flags = PTEFlags::from_bits(self.map_perm.bits).unwrap();
         page_table.map(vpn, ppn, pte_flags);
     }
-    #[allow(unused)]
     pub fn unmap_one(&mut self, page_table: &mut PageTable, vpn: VirtPageNum) {
         match self.map_type {
             MapType::Framed => {
@@ -243,7 +253,6 @@ impl MapArea {
             self.map_one(page_table, vpn);
         }
     }
-    #[allow(unused)]
     pub fn unmap(&mut self, page_table: &mut PageTable) {
         for vpn in self.vpn_range {
             self.unmap_one(page_table, vpn);

os/src/mm/page_table.rs

@@ -131,7 +131,7 @@ impl PageTable {
     }
 }
 
-pub fn translated_byte_buffer(token: usize, ptr: *const u8, len: usize) -> Vec<&'static [u8]> {
+pub fn translated_byte_buffer(token: usize, ptr: *const u8, len: usize) -> Vec<&'static mut [u8]> {
     let page_table = PageTable::from_token(token);
     let mut start = ptr as usize;
     let end = start + len;
@@ -146,7 +146,7 @@ pub fn translated_byte_buffer(token: usize, ptr: *const u8, len: usize) -> Vec<&
         vpn.step();
         let mut end_va: VirtAddr = vpn.into();
         end_va = end_va.min(VirtAddr::from(end));
-        v.push(&ppn.get_bytes_array()[start_va.page_offset()..end_va.page_offset()]);
+        v.push(&mut ppn.get_bytes_array()[start_va.page_offset()..end_va.page_offset()]);
         start = end_va.into();
     }
     v

os/src/syscall/fs.rs

@@ -1,6 +1,8 @@
 use crate::mm::translated_byte_buffer;
-use crate::task::current_user_token;
+use crate::task::{current_user_token, suspend_current_and_run_next};
+use crate::sbi::console_getchar;
 
+const FD_STDIN: usize = 0;
 const FD_STDOUT: usize = 1;
 
 pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
@@ -17,3 +19,28 @@ pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
         }
     }
 }
+
+pub fn sys_read(fd: usize, buf: *const u8, len: usize) -> isize {
+    match fd {
+        FD_STDIN => {
+            assert_eq!(len, 1, "Only support len = 1 in sys_read!");
+            let mut c: usize;
+            loop {
+                c = console_getchar();
+                if c == 0 {
+                    suspend_current_and_run_next();
+                    continue;
+                } else {
+                    break;
+                }
+            }
+            let ch = c as u8;
+            let mut buffers = translated_byte_buffer(current_user_token(), buf, len);
+            unsafe { buffers[0].as_mut_ptr().write_volatile(ch); }
+            1
+        }
+        _ => {
+            panic!("Unsupported fd in sys_read!");
+        }
+    }
+}

os/src/syscall/mod.rs

@@ -1,3 +1,4 @@
+const SYSCALL_READ: usize = 63;
 const SYSCALL_WRITE: usize = 64;
 const SYSCALL_EXIT: usize = 93;
 const SYSCALL_YIELD: usize = 124;
@@ -11,6 +12,7 @@ use process::*;
 
 pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
     match syscall_id {
+        SYSCALL_READ => sys_read(args[0], args[1] as *const u8, args[2]),
         SYSCALL_WRITE => sys_write(args[0], args[1] as *const u8, args[2]),
         SYSCALL_EXIT => sys_exit(args[0] as i32),
         SYSCALL_YIELD => sys_yield(),

os/src/task/mod.rs

@@ -3,6 +3,7 @@ mod switch;
 mod task;
 mod manager;
 mod processor;
+mod pid;
 
 use crate::loader::{get_num_app, get_app_data};
 use crate::trap::TrapContext;
@@ -14,6 +15,7 @@ use alloc::vec::Vec;
 use alloc::sync::Arc;
 use spin::Mutex;
 use manager::fetch_task;
+use pid::{PidHandle, pid_alloc, KernelStack};
 
 pub use context::TaskContext;
 pub use processor::{

os/src/task/pid.rs

@@ -0,0 +1,104 @@
+use alloc::vec::Vec;
+use lazy_static::*;
+use spin::Mutex;
+use crate::mm::{KERNEL_SPACE, MapPermission, VirtAddr};
+use crate::config::{
+    PAGE_SIZE,
+    TRAMPOLINE,
+    KERNEL_STACK_SIZE,
+};
+
+struct PidAllocator {
+    current: usize,
+    recycled: Vec<usize>,
+}
+
+impl PidAllocator {
+    pub fn new() -> Self {
+        PidAllocator {
+            current: 0,
+            recycled: Vec::new(),
+        }
+    }
+    pub fn alloc(&mut self) -> PidHandle {
+        if let Some(pid) = self.recycled.pop() {
+            PidHandle(pid)
+        } else {
+            self.current += 1;
+            PidHandle(self.current - 1)
+        }
+    }
+    pub fn dealloc(&mut self, pid: usize) {
+        assert!(pid < self.current);
+        assert!(
+            self.recycled.iter().find(|ppid| **ppid == pid).is_none(),
+            "pid {} has been deallocated!", pid
+        );
+        self.recycled.push(pid);
+    }
+}
+
+lazy_static! {
+    static ref PID_ALLOCATOR : Mutex<PidAllocator> = Mutex::new(PidAllocator::new());
+}
+
+pub struct PidHandle(pub usize);
+
+impl Drop for PidHandle {
+    fn drop(&mut self) {
+        PID_ALLOCATOR.lock().dealloc(self.0);
+    }
+}
+
+pub fn pid_alloc() -> PidHandle {
+    PID_ALLOCATOR.lock().alloc()
+}
+
+/// Return (bottom, top) of a kernel stack in kernel space.
+pub fn kernel_stack_position(app_id: usize) -> (usize, usize) {
+    let top = TRAMPOLINE - app_id * (KERNEL_STACK_SIZE + PAGE_SIZE);
+    let bottom = top - KERNEL_STACK_SIZE;
+    (bottom, top)
+}
+
+pub struct KernelStack {
+    pid: usize,
+}
+
+impl KernelStack {
+    pub fn new(pid_handle: &PidHandle) -> Self {
+        let pid = pid_handle.0;
+        let (kernel_stack_bottom, kernel_stack_top) = kernel_stack_position(pid);
+        KERNEL_SPACE
+            .lock()
+            .insert_framed_area(
+                kernel_stack_bottom.into(),
+                kernel_stack_top.into(),
+                MapPermission::R | MapPermission::W,
+            );
+        KernelStack {
+            pid: pid_handle.0,
+        }
+    }
+    pub fn push_on_top<T>(&self, value: T) -> *mut T where
+        T: Sized, {
+        let (_, kernel_stack_top) = kernel_stack_position(self.pid);
+        let ptr_mut = (kernel_stack_top - core::mem::size_of::<T>()) as *mut T;
+        unsafe { *ptr_mut = value; }
+        ptr_mut
+    }
+    pub fn get_top(&self) -> usize {
+        let (_, kernel_stack_top) = kernel_stack_position(self.pid);
+        kernel_stack_top
+    }
+}
+
+impl Drop for KernelStack {
+    fn drop(&mut self) {
+        let (kernel_stack_bottom, _) = kernel_stack_position(self.pid);
+        let kernel_stack_bottom_va: VirtAddr = kernel_stack_bottom.into();
+        KERNEL_SPACE
+            .lock()
+            .remove_area_with_start_vpn(kernel_stack_bottom_va.into());
+    }
+}

os/src/task/task.rs

@@ -2,12 +2,14 @@ use crate::mm::{MemorySet, MapPermission, PhysPageNum, KERNEL_SPACE, VirtAddr};
 use crate::trap::{TrapContext, trap_handler};
 use crate::config::{TRAP_CONTEXT, kernel_stack_position};
 use super::TaskContext;
+use super::{PidHandle, pid_alloc, KernelStack};
 
 pub struct TaskControlBlock {
     // immutable
     pub trap_cx_ppn: PhysPageNum,
     pub base_size: usize,
-    //pub pid: usize,
+    pub pid: PidHandle,
+    pub kernel_stack: KernelStack,
     // mutable
     pub task_cx_ptr: usize,
     pub task_status: TaskStatus,
@@ -32,23 +34,20 @@ impl TaskControlBlock {
             .unwrap()
             .ppn();
         let task_status = TaskStatus::Ready;
-        // map a kernel-stack in kernel space
-        let (kernel_stack_bottom, kernel_stack_top) = kernel_stack_position(app_id);
-        KERNEL_SPACE
-            .lock()
-            .insert_framed_area(
-                kernel_stack_bottom.into(),
-                kernel_stack_top.into(),
-                MapPermission::R | MapPermission::W,
-            );
-        let task_cx_ptr = (kernel_stack_top - core::mem::size_of::<TaskContext>()) as *mut TaskContext;
-        unsafe { *task_cx_ptr = TaskContext::goto_trap_return(); }
+        // alloc a pid and a kernel stack in kernel space
+        let pid_handle = pid_alloc();
+        let kernel_stack = KernelStack::new(&pid_handle);
+        let kernel_stack_top = kernel_stack.get_top();
+        // push a task context which goes to trap_return to the top of kernel stack
+        let task_cx_ptr = kernel_stack.push_on_top(TaskContext::goto_trap_return());
         let task_control_block = Self {
+            trap_cx_ppn,
+            base_size: user_sp,
+            pid: pid_handle,
+            kernel_stack,
             task_cx_ptr: task_cx_ptr as usize,
             task_status,
             memory_set,
-            trap_cx_ppn,
-            base_size: user_sp,
         };
         // prepare TrapContext in user space
         let trap_cx = task_control_block.get_trap_cx();