From: Ben Pfaff Date: Thu, 20 Apr 2006 05:03:50 +0000 (+0000) Subject: Improve comments. X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d51aeb9e448d8a05d4263a7459c857ff2fb9d3b2;hp=12c2ab650ed14efb587c47f7533f657628943d8e;p=pintos-anon Improve comments. --- diff --git a/src/threads/mmu.h b/src/threads/mmu.h index e635b1e..9f71d4a 100644 --- a/src/threads/mmu.h +++ b/src/threads/mmu.h @@ -9,24 +9,24 @@ /* Virtual to physical translation works like this on an x86: - - The top 10 bits of the virtual address (bits 22:32) are used + - The top 10 bits of the virtual address (bits 22:31) are used to index into the page directory. If the PDE is marked "present," the physical address of a page table is read from the PDE thus obtained. If the PDE is marked "not present" then a page fault occurs. - - The next 10 bits of the virtual address (bits 12:22) are + - The next 10 bits of the virtual address (bits 12:21) are used to index into the page table. If the PTE is marked "present," the physical address of a data page is read from the PTE thus obtained. If the PTE is marked "not present" then a page fault occurs. - - The bottom 12 bits of the virtual address (bits 0:12) are + - The bottom 12 bits of the virtual address (bits 0:11) are added to the data page's physical base address, producing the final physical address. - 32 22 12 0 + 31 22 21 12 11 0 +--------------------------------------------------------------------+ | Page Directory Index | Page Table Index | Page Offset | +--------------------------------------------------------------------+ @@ -147,7 +147,7 @@ vtop (const void *vaddr) PDEs and PTEs share a common format: - 32 12 0 + 31 12 11 0 +------------------------------------+------------------------+ | Physical Address | Flags | +------------------------------------+------------------------+