X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fuserprog%2Fpagedir.c;h=3ad8123557a37dace964bcc18be56a431605f87d;hb=7d4e3dda080a47db88616f1c0d975f2091be47f1;hp=6c819c790efb9afff04980dd2f162f0a6f3d5469;hpb=18f989e9fa405e5c3bd7b5f5458e22db0e28740b;p=pintos-anon

diff --git a/src/userprog/pagedir.c b/src/userprog/pagedir.c
index 6c819c7..3ad8123 100644
--- a/src/userprog/pagedir.c
+++ b/src/userprog/pagedir.c
@@ -6,6 +6,8 @@
 #include "threads/mmu.h"
 #include "threads/palloc.h"
 
+static uint32_t *active_pd (void);
+
 /* Creates a new page directory that has mappings for kernel
    virtual addresses, but none for user virtual addresses.
    Returns the new page directory, or a null pointer if memory
@@ -13,7 +15,7 @@
 uint32_t *
 pagedir_create (void) 
 {
-  uint32_t *pd = palloc_get (0);
+  uint32_t *pd = palloc_get_page (0);
   memcpy (pd, base_page_dir, PGSIZE);
   return pd;
 }
@@ -28,6 +30,7 @@ pagedir_destroy (uint32_t *pd)
   if (pd == NULL)
     return;
 
+  ASSERT (pd != base_page_dir);
   for (pde = pd; pde < pd + pd_no (PHYS_BASE); pde++)
     if (*pde & PG_P) 
       {
@@ -36,25 +39,30 @@ pagedir_destroy (uint32_t *pd)
         
         for (pte = pt; pte < pt + PGSIZE / sizeof *pte; pte++)
           if (*pte & PG_P) 
-            palloc_free (pte_get_page (*pte));
-        palloc_free (pt);
+            palloc_free_page (pte_get_page (*pte));
+        palloc_free_page (pt);
       }
-  palloc_free (pd);
+  palloc_free_page (pd);
 }
 
-/* Returns the mapping of user virtual address UADDR in page
-   directory PD into a kernel virtual address.
-   If UADDR is unmapped, behavior varies based on CREATE:
-   if CREATE is true, then a new, zeroed page is created and a
+/* Returns the address of the page table entry for user virtual
+   address UADDR in page directory PD.
+   If PD does not have a page table for UADDR, behavior varies
+   based on CREATE:
+   if CREATE is true, then a new page table is created and a
    pointer into it is returned,
-   otherwise a null pointer is returned. */
+   otherwise a null pointer is returned.
+   Also returns a null pointer if UADDR is a kernel address. */
 static uint32_t *
 lookup_page (uint32_t *pd, void *uaddr, bool create)
 {
   uint32_t *pt, *pde;
 
   ASSERT (pd != NULL);
-  ASSERT (uaddr < PHYS_BASE);
+
+  /* Make sure it's a user address. */
+  if (uaddr >= PHYS_BASE)
+    return NULL;
 
   /* Check for a page table for UADDR.
      If one is missing, create one if requested. */
@@ -63,7 +71,7 @@ lookup_page (uint32_t *pd, void *uaddr, bool create)
     {
       if (create)
         {
-          pt = palloc_get (PAL_ZERO);
+          pt = palloc_get_page (PAL_ZERO);
           if (pt == NULL) 
             return NULL; 
       
@@ -93,7 +101,8 @@ pagedir_set_page (uint32_t *pd, void *upage, void *kpage,
 
   ASSERT (pg_ofs (upage) == 0);
   ASSERT (pg_ofs (kpage) == 0);
-  ASSERT (lookup_page (pd, upage, false) == NULL);
+  ASSERT (upage < PHYS_BASE);
+  ASSERT (pagedir_get_page (pd, upage) == NULL);
 
   pte = lookup_page (pd, upage, true);
   if (pte != NULL) 
@@ -112,7 +121,63 @@ void *
 pagedir_get_page (uint32_t *pd, const void *uaddr) 
 {
   uint32_t *pte = lookup_page (pd, (void *) uaddr, false);
-  return pte != NULL && *pte != 0 ? pte_get_page (*pte) : NULL;
+  return (pte != NULL && *pte != 0
+          ? (uint8_t *) pte_get_page (*pte) + pg_ofs (uaddr)
+          : NULL);
+}
+
+/* Clears any mapping for user virtual address UPAGE in page
+   directory PD.
+   UPAGE need not already be mapped. */
+void
+pagedir_clear_page (uint32_t *pd, void *upage) 
+{
+  uint32_t *pte = lookup_page (pd, upage, false);
+  if (pte != NULL && *pte != 0)
+    {
+      *pte = 0;
+
+      if (active_pd () == pd) 
+        {
+          /* We cleared a page-table entry in the active page
+             table, so we have to invalidate the TLB.  See
+             [IA32-v3], section 3.11. */
+          pagedir_activate (pd);
+        }
+    }
+
+}
+
+/* Returns true if the PTE for user virtual page UPAGE in PD is
+   dirty, that is, if the page has been modified since the PTE
+   was installed.
+   Returns false if PD contains no PDE for UPAGE. */
+bool
+pagedir_test_dirty (uint32_t *pd, const void *upage) 
+{
+  uint32_t *pte = lookup_page (pd, (void *) upage, false);
+  return pte != NULL && (*pte & PG_D) != 0;
+}
+
+/* Returns true if the PTE for user virtual page UPAGE in PD has
+   been accessed recently, that is, between the time the PTE was
+   installed and the last time it was cleared.
+   Returns false if PD contains no PDE for UPAGE. */
+bool
+pagedir_test_accessed (uint32_t *pd, const void *upage) 
+{
+  uint32_t *pte = lookup_page (pd, (void *) upage, false);
+  return pte != NULL && (*pte & PG_A) != 0;
+}
+
+/* Resets the accessed bit in the PTE for user virtual page UPAGE
+   in PD. */
+void
+pagedir_clear_accessed (uint32_t *pd, const void *upage) 
+{
+  uint32_t *pte = lookup_page (pd, (void *) upage, false);
+  if (pte != NULL) 
+    *pte &= ~(uint32_t) PG_A;
 }
 
 /* Loads page directory PD into the CPU's page directory base
@@ -122,5 +187,23 @@ pagedir_activate (uint32_t *pd)
 {
   if (pd == NULL)
     pd = base_page_dir;
-  asm volatile ("movl %0,%%cr3" :: "r" (vtop (pd)));
+
+  /* Store the physical address of the page directory into CR3
+     aka PDBR (page directory base register).  This activates our
+     new page tables immediately.  See [IA32-v2a] "MOV--Move
+     to/from Control Registers" and [IA32-v3] 3.7.5. */
+  asm volatile ("mov %%cr3, %0" :: "r" (vtop (pd)));
+}
+
+/* Returns the currently active page directory. */
+static uint32_t *
+active_pd (void) 
+{
+  /* Copy CR3, the page directory base register (PDBR), into
+     `pd'.
+     See [IA32-v2a] "MOV--Move to/from Control Registers" and
+     [IA32-v3] 3.7.5. */
+  uint32_t *pd;
+  asm ("mov %0, %%cr3" : "=r" (pd));
+  return pd;
 }