finish task2

kernel/defs.h

@@ -162,6 +162,7 @@ void            kvminit(void);
 void            kvminithart(void);
 uint64          kvmpa(uint64);
 void            kvmmap(uint64, uint64, uint64, int);
+void            ukvmmap(pagetable_t, uint64, uint64, uint64, int);
 int             mappages(pagetable_t, uint64, uint64, uint64, int);
 pagetable_t     uvmcreate(void);
 void            uvminit(pagetable_t, uchar *, uint);
@@ -178,6 +179,7 @@ uint64          walkaddr(pagetable_t, uint64);
 int             copyout(pagetable_t, uint64, char *, uint64);
 int             copyin(pagetable_t, char *, uint64, uint64);
 int             copyinstr(pagetable_t, char *, uint64, uint64);
+void            vmprint(pagetable_t, int);
 
 // plic.c
 void            plicinit(void);

kernel/exec.c

@@ -116,6 +116,7 @@ exec(char *path, char **argv)
   p->trapframe->sp = sp; // initial stack pointer
   proc_freepagetable(oldpagetable, oldsz);
 
+  if(p->pid==1) vmprint(p->pagetable, 0);
   return argc; // this ends up in a0, the first argument to main(argc, argv)
 
  bad:

kernel/proc.c

@@ -20,6 +20,7 @@ static void wakeup1(struct proc *chan);
 static void freeproc(struct proc *p);
 
 extern char trampoline[]; // trampoline.S
+extern pagetable_t kernel_pagetable; // global kernel pagetable
 
 // initialize the proc table at boot time.
 void
@@ -120,6 +121,23 @@ allocproc(void)
     release(&p->lock);
     return 0;
   }
+  // 让每个进程的内核页表直接复用全局内核页表；
+  p->kpagetable = uvmcreate();
+  if(p->kpagetable == 0){
+    freeproc(p);
+    release(&p->lock);
+    return 0;
+  }
+  // 全局内核页表的第一个一级 PTE 占用 0x4000_0000
+  // 内核在这个地址以下的部分要重新映射；
+  // 最终 PLIC 以下的地址空间给进程用；
+  // CLINT 是 M 模式处理时钟的，不用映射；
+  for(int i = 1; i < 512; ++i){
+    p->kpagetable[i] = kernel_pagetable[i];
+  }
+  ukvmmap(p->kpagetable, UART0, UART0, PGSIZE, PTE_R | PTE_W);
+  ukvmmap(p->kpagetable, PLIC, PLIC, 0x400000, PTE_R | PTE_W);
+  ukvmmap(p->kpagetable, VIRTIO0, VIRTIO0, PGSIZE, PTE_R | PTE_W);
 
   // Set up new context to start executing at forkret,
   // which returns to user space.
@@ -142,6 +160,21 @@ freeproc(struct proc *p)
   if(p->pagetable)
     proc_freepagetable(p->pagetable, p->sz);
   p->pagetable = 0;
+  if(p->kpagetable){
+    // 页表项：只需要释放第一个一级页表项；
+    // 物理内存：不需要释放任何物理内存；
+    pagetable_t lv2 = (pagetable_t)PTE2PA(p->kpagetable[0]);
+    for(int i = 0; i < 512; ++i){
+      pte_t pte = lv2[i];
+      if(pte & PTE_V){
+        uint64 lv3 = PTE2PA(pte);
+        kfree((void*)lv3);
+      }
+    }
+    kfree((void*)lv2);
+    kfree((void*)p->kpagetable);
+  }
+  p->kpagetable = 0;
   p->sz = 0;
   p->pid = 0;
   p->parent = 0;
@@ -473,8 +506,12 @@ scheduler(void)
         // before jumping back to us.
         p->state = RUNNING;
         c->proc = p;
+        // 切换到目标进程的内核页表
+        w_satp(MAKE_SATP(p->kpagetable));
+        sfence_vma();
         swtch(&c->context, &p->context);
-
+        w_satp(MAKE_SATP(kernel_pagetable));
+        sfence_vma();
         // Process is done running for now.
         // It should have changed its p->state before coming back.
         c->proc = 0;

kernel/proc.h

@@ -98,6 +98,7 @@ struct proc {
   uint64 kstack;               // Virtual address of kernel stack
   uint64 sz;                   // Size of process memory (bytes)
   pagetable_t pagetable;       // User page table
+  pagetable_t kpagetable;      // Kernel page table
   struct trapframe *trapframe; // data page for trampoline.S
   struct context context;      // swtch() here to run process
   struct file *ofile[NOFILE];  // Open files

kernel/vm.c

@@ -121,6 +121,13 @@ kvmmap(uint64 va, uint64 pa, uint64 sz, int perm)
     panic("kvmmap");
 }
 
+void
+ukvmmap(pagetable_t pagetable, uint64 va, uint64 pa, uint64 sz, int perm)
+{
+  if(mappages(pagetable, va, sz, pa, perm) != 0)
+    panic("ukvmmap");
+}
+
 // translate a kernel virtual address to
 // a physical address. only needed for
 // addresses on the stack.
@@ -440,3 +447,25 @@ copyinstr(pagetable_t pagetable, char *dst, uint64 srcva, uint64 max)
     return -1;
   }
 }
+
+// 打印页表项
+void vmprint(pagetable_t pagetable, int dep){
+  if(!dep){
+    printf("page table %p\n", pagetable);
+  }
+  // there are 2^9 = 512 PTEs in a page table.
+  for(int i = 0; i < 512; i++){
+    pte_t pte = pagetable[i];
+    if((pte & PTE_V)){
+      printf("..");
+      for(int j = 0; j < dep; ++j){
+        printf(" ..");
+      }
+      printf("%d: pte %p pa %p\n", i, pte, PTE2PA(pte));
+      if(dep != 2){
+        uint64 child = PTE2PA(pte);
+        vmprint((pagetable_t)child, dep + 1);
+      }
+    }
+  }
+}