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Comment.
[pintos-anon]
/
src
/
userprog
/
pagedir.c
diff --git
a/src/userprog/pagedir.c
b/src/userprog/pagedir.c
index fa8f244d88220a954e43ebc880e1140d242643f4..c0a015ae831ab20e88311538fb3eb541c0894b25 100644
(file)
--- a/
src/userprog/pagedir.c
+++ b/
src/userprog/pagedir.c
@@
-121,7
+121,9
@@
void *
pagedir_get_page (uint32_t *pd, const void *uaddr)
{
uint32_t *pte = lookup_page (pd, (void *) uaddr, false);
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
}
/* Clears any mapping for user virtual address UPAGE in page
@@
-185,6
+187,11
@@
pagedir_activate (uint32_t *pd)
{
if (pd == NULL)
pd = base_page_dir;
{
if (pd == NULL)
pd = base_page_dir;
+
+ /* 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 ("movl %0,%%cr3" :: "r" (vtop (pd)));
}
asm volatile ("movl %0,%%cr3" :: "r" (vtop (pd)));
}
@@
-192,8
+199,11
@@
pagedir_activate (uint32_t *pd)
static uint32_t *
active_pd (void)
{
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;
uint32_t *pd;
-
asm ("movl %%cr3,%0" : "=r" (pd));
return pd;
}
asm ("movl %%cr3,%0" : "=r" (pd));
return pd;
}