#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
+ allocation fails. */
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;
}
+/* Destroys page directory PD, freeing all the pages it
+ references. */
void
pagedir_destroy (uint32_t *pd)
{
uint32_t *pde;
+ if (pd == NULL)
+ return;
+
+ ASSERT (pd != base_page_dir);
for (pde = pd; pde < pd + pd_no (PHYS_BASE); pde++)
if (*pde & PG_P)
{
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 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.
+ Also returns a null pointer if UADDR is a kernel address. */
static uint32_t *
-lookup_page (uint32_t *pd, void *upage, bool create)
+lookup_page (uint32_t *pd, void *uaddr, bool create)
{
- uint32_t *pt;
- uint32_t *pde;
+ uint32_t *pt, *pde;
ASSERT (pd != NULL);
- ASSERT (pg_ofs (upage) == 0);
- ASSERT (upage < PHYS_BASE);
- /* Check for a page table for UPAGE.
+ /* 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. */
- pde = pd + pd_no (upage);
+ pde = pd + pd_no (uaddr);
if (*pde == 0)
{
if (create)
{
- pt = palloc_get (PAL_ZERO);
+ pt = palloc_get_page (PAL_ZERO);
if (pt == NULL)
return NULL;
/* Return the page table entry. */
pt = pde_get_pt (*pde);
- return &pt[pt_no (upage)];
+ return &pt[pt_no (uaddr)];
}
+/* Adds a mapping from user virtual address UPAGE to kernel
+ virtual address KPAGE in page directory PD.
+ UPAGE must not already be mapped.
+ If WRITABLE is true, the new page is read/write;
+ otherwise it is read-only.
+ Returns true if successful, false if memory allocation
+ failed. */
bool
pagedir_set_page (uint32_t *pd, void *upage, void *kpage,
bool writable)
{
uint32_t *pte;
+ ASSERT (pg_ofs (upage) == 0);
ASSERT (pg_ofs (kpage) == 0);
+ ASSERT (upage < PHYS_BASE);
+ ASSERT (pagedir_get_page (pd, upage) == NULL);
pte = lookup_page (pd, upage, true);
if (pte != NULL)
return false;
}
+/* Returns the kernel virtual address that user virtual address
+ UADDR is mapped to in PD, or a null pointer if there is no
+ mapping. */
void *
-pagedir_get_page (uint32_t *pd, void *upage)
+pagedir_get_page (uint32_t *pd, const void *uaddr)
{
- uint32_t *pte = lookup_page (pd, upage, false);
- return pte != NULL && *pte != 0 ? pte_get_page (*pte) : NULL;
+ uint32_t *pte = lookup_page (pd, (void *) uaddr, false);
+ 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)
+pagedir_clear_page (uint32_t *pd, void *upage)
{
uint32_t *pte = lookup_page (pd, upage, false);
- if (pte != NULL)
- *pte = 0;
+ 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
+ register. */
void
pagedir_activate (uint32_t *pd)
{
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)));
}
+
+/* Returns the currently active page directory. */
+static uint32_t *
+active_pd (void)
+{
+ uint32_t *pd;
+
+ /* Copy CR3, the page directory base register (PDBR), into `pd'
+ for us to exmaine. See [IA32-v2a] "MOV--Move to/from
+ Control Registers" and [IA32-v3] 3.7.5. */
+ asm ("movl %%cr3,%0" : "=r" (pd));
+ return pd;
+}
projects / pintos-anon / blobdiff