task2 finished

kernel/proc.c

@@ -123,14 +123,20 @@ allocproc(void)
 
 found:
   p->pid = allocpid();
-  p->state = USED;
 
   // Allocate a trapframe page.
   if((p->trapframe = (struct trapframe *)kalloc()) == 0){
+    release(&p->lock);
+    return 0;
+  }
+
+  // Allocate a usyscall page.
+  if((p->usyscall = (struct usyscall *)kalloc()) == 0){
     freeproc(p);
     release(&p->lock);
     return 0;
   }
+  p->usyscall->pid =  p->pid ;
 
   // An empty user page table.
   p->pagetable = proc_pagetable(p);
@@ -155,6 +161,9 @@ found:
 static void
 freeproc(struct proc *p)
 {
+  if (p->usyscall) {
+    kfree((void*)p->usyscall);
+  }
   if(p->trapframe)
     kfree((void*)p->trapframe);
   p->trapframe = 0;
@@ -202,6 +211,16 @@ proc_pagetable(struct proc *p)
     return 0;
   }
 
+  // map the usyscall just below TRAMPOFRAME, for trampoline.S.
+  // 这个页需要设置PTE_U为，使得用户态可以访问
+  if(mappages(pagetable, USYSCALL, PGSIZE,
+              (uint64)(p->usyscall), PTE_R | PTE_U) < 0){
+    uvmunmap(pagetable, TRAPFRAME, 1, 0);
+    uvmunmap(pagetable, TRAMPOLINE, 1, 0);
+    uvmfree(pagetable, 0);
+    return 0;
+  }
+
   return pagetable;
 }
 
@@ -210,6 +229,7 @@ proc_pagetable(struct proc *p)
 void
 proc_freepagetable(pagetable_t pagetable, uint64 sz)
 {
+  uvmunmap(pagetable, USYSCALL, 1, 0);
   uvmunmap(pagetable, TRAMPOLINE, 1, 0);
   uvmunmap(pagetable, TRAPFRAME, 1, 0);
   uvmfree(pagetable, sz);