#include <stddef.h>
#include <string.h>
#include "threads/init.h"
-#include "threads/mmu.h"
+#include "threads/pte.h"
#include "threads/palloc.h"
+static uint32_t *active_pd (void);
+static void invalidate_pagedir (uint32_t *);
+
/* 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
pagedir_create (void)
{
uint32_t *pd = palloc_get_page (0);
- memcpy (pd, base_page_dir, PGSIZE);
+ if (pd != NULL)
+ memcpy (pd, base_page_dir, PGSIZE);
return pd;
}
ASSERT (pd != base_page_dir);
for (pde = pd; pde < pd + pd_no (PHYS_BASE); pde++)
- if (*pde & PG_P)
+ if (*pde & PTE_P)
{
uint32_t *pt = pde_get_pt (*pde);
uint32_t *pte;
for (pte = pt; pte < pt + PGSIZE / sizeof *pte; pte++)
- if (*pte & PG_P)
+ if (*pte & PTE_P)
palloc_free_page (pte_get_page (*pte));
palloc_free_page (pt);
}
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
- pointer into it is returned,
- otherwise a null pointer is returned.
- Also returns a null pointer if UADDR is a kernel address. */
+/* Returns the address of the page table entry for virtual
+ address VADDR in page directory PD.
+ If PD does not have a page table for VADDR, behavior depends
+ 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. */
static uint32_t *
-lookup_page (uint32_t *pd, void *uaddr, bool create)
+lookup_page (uint32_t *pd, const void *vaddr, bool create)
{
uint32_t *pt, *pde;
ASSERT (pd != NULL);
- /* Make sure it's a user address. */
- if (uaddr >= PHYS_BASE)
- return NULL;
+ /* Shouldn't create new kernel virtual mappings. */
+ ASSERT (!create || is_user_vaddr (vaddr));
- /* Check for a page table for UADDR.
+ /* Check for a page table for VADDR.
If one is missing, create one if requested. */
- pde = pd + pd_no (uaddr);
+ pde = pd + pd_no (vaddr);
if (*pde == 0)
{
if (create)
/* Return the page table entry. */
pt = pde_get_pt (*pde);
- return &pt[pt_no (uaddr)];
+ return &pt[pt_no (vaddr)];
}
-/* Adds a mapping from user virtual address UPAGE to kernel
- virtual address KPAGE in page directory PD.
+/* Adds a mapping in page directory PD from user virtual page
+ UPAGE to the physical frame identified by kernel virtual
+ address KPAGE.
UPAGE must not already be mapped.
+ KPAGE should probably be a page obtained from the user pool
+ with palloc_get_page().
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)
+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);
+ ASSERT (is_user_vaddr (upage));
+ ASSERT (vtop (kpage) >> PTSHIFT < ram_pages);
+ ASSERT (pd != base_page_dir);
pte = lookup_page (pd, upage, true);
+
if (pte != NULL)
{
+ ASSERT ((*pte & PTE_P) == 0);
*pte = pte_create_user (kpage, writable);
return true;
}
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. */
+/* Looks up the physical address that corresponds to user virtual
+ address UADDR in PD. Returns the kernel virtual address
+ corresponding to that physical address, or a null pointer if
+ UADDR is unmapped. */
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;
+ uint32_t *pte;
+
+ ASSERT (is_user_vaddr (uaddr));
+
+ pte = lookup_page (pd, uaddr, false);
+ if (pte != NULL && (*pte & PTE_P) != 0)
+ return pte_get_page (*pte) + pg_ofs (uaddr);
+ else
+ return NULL;
+}
+
+/* Marks user virtual page UPAGE "not present" in page
+ directory PD. Later accesses to the page will fault. Other
+ bits in the page table entry are preserved.
+ UPAGE need not be mapped. */
+void
+pagedir_clear_page (uint32_t *pd, void *upage)
+{
+ uint32_t *pte;
+
+ ASSERT (pg_ofs (upage) == 0);
+ ASSERT (is_user_vaddr (upage));
+
+ pte = lookup_page (pd, upage, false);
+ if (pte != NULL && (*pte & PTE_P) != 0)
+ {
+ *pte &= ~PTE_P;
+ invalidate_pagedir (pd);
+ }
+}
+
+/* Returns true if the PTE for virtual page VPAGE in PD is dirty,
+ that is, if the page has been modified since the PTE was
+ installed.
+ Returns false if PD contains no PTE for VPAGE. */
+bool
+pagedir_is_dirty (uint32_t *pd, const void *vpage)
+{
+ uint32_t *pte = lookup_page (pd, vpage, false);
+ return pte != NULL && (*pte & PTE_D) != 0;
+}
+
+/* Set the dirty bit to DIRTY in the PTE for virtual page VPAGE
+ in PD. */
+void
+pagedir_set_dirty (uint32_t *pd, const void *vpage, bool dirty)
+{
+ uint32_t *pte = lookup_page (pd, vpage, false);
+ if (pte != NULL)
+ {
+ if (dirty)
+ *pte |= PTE_D;
+ else
+ {
+ *pte &= ~(uint32_t) PTE_D;
+ invalidate_pagedir (pd);
+ }
+ }
+}
+
+/* Returns true if the PTE for virtual page VPAGE 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 PTE for VPAGE. */
+bool
+pagedir_is_accessed (uint32_t *pd, const void *vpage)
+{
+ uint32_t *pte = lookup_page (pd, vpage, false);
+ return pte != NULL && (*pte & PTE_A) != 0;
+}
+
+/* Sets the accessed bit to ACCESSED in the PTE for virtual page
+ VPAGE in PD. */
+void
+pagedir_set_accessed (uint32_t *pd, const void *vpage, bool accessed)
+{
+ uint32_t *pte = lookup_page (pd, vpage, false);
+ if (pte != NULL)
+ {
+ if (accessed)
+ *pte |= PTE_A;
+ else
+ {
+ *pte &= ~(uint32_t) PTE_A;
+ invalidate_pagedir (pd);
+ }
+ }
}
/* Loads page directory PD into the CPU's page directory base
{
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-v3a] 3.7.5 "Base
+ Address of the Page Directory". */
+ asm volatile ("movl %0, %%cr3" : : "r" (vtop (pd)) : "memory");
+}
+
+/* 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-v3a] 3.7.5 "Base Address of the Page Directory". */
+ uintptr_t pd;
+ asm volatile ("movl %%cr3, %0" : "=r" (pd));
+ return ptov (pd);
+}
+
+/* Seom page table changes can cause the CPU's translation
+ lookaside buffer (TLB) to become out-of-sync with the page
+ table. When this happens, we have to "invalidate" the TLB by
+ re-activating it.
+
+ This function invalidates the TLB if PD is the active page
+ directory. (If PD is not active then its entries are not in
+ the TLB, so there is no need to invalidate anything.) */
+static void
+invalidate_pagedir (uint32_t *pd)
+{
+ if (active_pd () == pd)
+ {
+ /* Re-activating PD clears the TLB. See [IA32-v3a] 3.12
+ "Translation Lookaside Buffers (TLBs)". */
+ pagedir_activate (pd);
+ }
}
projects / pintos-anon / blobdiff