Merge branch 'cow' into net

Conflicts:
	.gitignore
	Makefile
	conf/lab.mk
	kernel/defs.h
	kernel/syscall.c
	kernel/vm.c
	user/pingpong.c
	user/user.h
	user/usys.pl

1 files changed, 44 insertions, 15 deletions

diff --git a/kernel/vm.c b/kernel/vm.c
index 7119242..be7d042 100644
--- a/kernel/vm.c
+++ b/kernel/vm.c
@@ -320,20 +320,26 @@ uvmcopy(pagetable_t old, pagetable_t new, uint64 sz)
   pte_t *pte;
   uint64 pa, i;
   uint flags;
-  char *mem;
+  // char *mem;
 
   for(i = 0; i < sz; i += PGSIZE){
     if((pte = walk(old, i, 0)) == 0)
       panic("uvmcopy: pte should exist");
     if((*pte & PTE_V) == 0)
       panic("uvmcopy: page not present");
-    pa = PTE2PA(*pte);
-    flags = PTE_FLAGS(*pte);
+    // do not do the actual copy, just increase the refcnt and mark pages readonly COW
+    /*
     if((mem = kalloc()) == 0)
       goto err;
     memmove(mem, (char*)pa, PGSIZE);
-    if(mappages(new, i, PGSIZE, (uint64)mem, flags) != 0){
-      kfree(mem);
+    */
+    *pte &= ~PTE_W;
+    *pte |= PTE_C;
+    pa = PTE2PA(*pte);
+    refcnt_inc(pa);
+    flags = PTE_FLAGS(*pte);
+    if(mappages(new, i, PGSIZE, (uint64)pa, flags) != 0){
+      // kfree(mem);
       goto err;
     }
   }
@@ -364,22 +370,21 @@ int
 copyout(pagetable_t pagetable, uint64 dstva, char *src, uint64 len)
 {
   uint64 n, va0, pa0;
-  pte_t *pte;
+  // pte_t *pte;
 
   while(len > 0){
     va0 = PGROUNDDOWN(dstva);
-    if (va0 >= MAXVA)
-      return -1;
-    if((pte = walk(pagetable, va0, 0)) == 0) {
-      // printf("copyout: pte should exist 0x%x %d\n", dstva, len);
-      return -1;
-    }
-
 
-    // forbid copyout over read-only user text pages.
-    if((*pte & PTE_W) == 0)
+    if(cow_handler(pagetable, va0) < 0)
       return -1;
     
+    /*
+    pte = walk(pagetable, va0, 0);
+    if(pte == 0 || (*pte & PTE_V) == 0 || (*pte & PTE_U) == 0 ||
+       (*pte & PTE_W) == 0)
+      return -1;
+    pa0 = PTE2PA(*pte);
+    */
     pa0 = walkaddr(pagetable, va0);
     if(pa0 == 0)
       return -1;
@@ -463,5 +468,29 @@ copyinstr(pagetable_t pagetable, char *dst, uint64 srcva, uint64 max)
   }
 }
 
+static void
+walkprint(pagetable_t pgtbl, int level)
+{
+  for(int i = 0; i < 512; i++){
+    pte_t pte = pgtbl[i];
+    if(pte & PTE_V){
+      for(int j = 0; j < level; j++){
+        printf(" ..");
+      }
+      printf("%d: pte %p pa %p\n", i, pte, PTE2PA(pte));
+      if((pte & (PTE_R|PTE_W|PTE_X)) == 0){
+        // this PTE points to a lower-level page table.
+        walkprint((pagetable_t)PTE2PA(pte), level+1);
+      }
+    }
+  }
+}
 
+// Print the contents of a page table
+void
+vmprint(pagetable_t pgtbl)
+{
+  printf("page table %p\n", pgtbl);
 
+  walkprint(pgtbl, 1);
+}