X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fuserprog%2Fpagedir.c;h=c0a015ae831ab20e88311538fb3eb541c0894b25;hb=6dca07ec0e8cde38f64f0c9f543b8e52ba169e94;hp=7c392e61d5fee657b773b879ca4377bce1d62e32;hpb=0ce986c23de0e197709dbd77e461e26f1532e518;p=pintos-anon diff --git a/src/userprog/pagedir.c b/src/userprog/pagedir.c index 7c392e6..c0a015a 100644 --- 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); - 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 @@ -168,23 +170,14 @@ pagedir_test_accessed (uint32_t *pd, const void *upage) return pte != NULL && (*pte & PG_A) != 0; } -/* Returns true if the PTE for user virtual page UPAGE in PD has - been accessed recently, and then resets the accessed bit for - that page. - Returns false and has no effect if PD contains no PDE for - UPAGE. */ -bool -pagedir_test_accessed_and_clear (uint32_t *pd, const void *upage) +/* 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) - { - bool accessed = (*pte & PG_A) != 0; - *pte &= ~(uint32_t) PG_A; - return accessed; - } - else - return false; + *pte &= ~(uint32_t) PG_A; } /* Loads page directory PD into the CPU's page directory base @@ -194,6 +187,11 @@ 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))); } @@ -201,8 +199,11 @@ pagedir_activate (uint32_t *pd) 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 ("movl %%cr3,%0" : "=r" (pd)); return pd; }