From: Ben Pfaff Date: Tue, 21 Sep 2004 02:48:58 +0000 (+0000) Subject: Comments. X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=18f989e9fa405e5c3bd7b5f5458e22db0e28740b;p=pintos-anon Comments. Remove pagedir_clear_page(). Add assertions to pagedir_set_page(). --- diff --git a/src/userprog/pagedir.c b/src/userprog/pagedir.c index 1edd0ff..6c819c7 100644 --- a/src/userprog/pagedir.c +++ b/src/userprog/pagedir.c @@ -6,6 +6,10 @@ #include "threads/mmu.h" #include "threads/palloc.h" +/* 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) { @@ -14,6 +18,8 @@ pagedir_create (void) return pd; } +/* Destroys page directory PD, freeing all the pages it + references. */ void pagedir_destroy (uint32_t *pd) { @@ -36,18 +42,23 @@ pagedir_destroy (uint32_t *pd) palloc_free (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. */ 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 (upage < PHYS_BASE); + ASSERT (uaddr < PHYS_BASE); - /* Check for a page table for UPAGE. + /* 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) @@ -64,16 +75,25 @@ lookup_page (uint32_t *pd, void *upage, bool create) /* 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 (lookup_page (pd, upage, false) == NULL); pte = lookup_page (pd, upage, true); if (pte != NULL) @@ -85,21 +105,18 @@ pagedir_set_page (uint32_t *pd, void *upage, void *kpage, 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, const void *upage) +pagedir_get_page (uint32_t *pd, const void *uaddr) { - uint32_t *pte = lookup_page (pd, (void *) upage, false); + uint32_t *pte = lookup_page (pd, (void *) uaddr, false); return pte != NULL && *pte != 0 ? pte_get_page (*pte) : NULL; } -void -pagedir_clear_page (uint32_t *pd, void *upage) -{ - uint32_t *pte = lookup_page (pd, upage, false); - if (pte != NULL) - *pte = 0; -} - +/* Loads page directory PD into the CPU's page directory base + register. */ void pagedir_activate (uint32_t *pd) { diff --git a/src/userprog/pagedir.h b/src/userprog/pagedir.h index d3e2ce8..6915a30 100644 --- a/src/userprog/pagedir.h +++ b/src/userprog/pagedir.h @@ -5,12 +5,9 @@ #include uint32_t *pagedir_create (void); -void pagedir_destroy (uint32_t *); -bool pagedir_set_page (uint32_t *pagedir, void *upage, void *kpage, - bool writable); -void *pagedir_get_page (uint32_t *pagedir, const void *upage); -void pagedir_clear_page (uint32_t *pagedir, void *upage); - -void pagedir_activate (uint32_t *pagedir); +void pagedir_destroy (uint32_t *pd); +bool pagedir_set_page (uint32_t *pd, void *upage, void *kpage, bool rw); +void *pagedir_get_page (uint32_t *pd, const void *upage); +void pagedir_activate (uint32_t *pd); #endif /* userprog/pagedir.h */