diff options
| -rw-r--r-- | README | 2 | ||||
| -rw-r--r-- | vm.c | 24 |
2 files changed, 13 insertions, 13 deletions
@@ -26,7 +26,7 @@ In addition, we are grateful for the patches contributed by Greg Price, Yandong Mao, and Hitoshi Mitake. The code in the files that constitute xv6 is -Copyright 2006-2007 Frans Kaashoek, Robert Morris, and Russ Cox. +Copyright 2006-2011 Frans Kaashoek, Robert Morris, and Russ Cox. ERROR REPORTS @@ -18,7 +18,7 @@ seginit(void) { struct cpu *c; - // Map virtual addresses to linear addresses using identity map. + // Map "logical" addresses to virtual addresses using identity map. // Cannot share a CODE descriptor for both kernel and user // because it would have to have DPL_USR, but the CPU forbids // an interrupt from CPL=0 to DPL=3. @@ -40,7 +40,7 @@ seginit(void) } // Return the address of the PTE in page table pgdir -// that corresponds to linear address va. If alloc!=0, +// that corresponds to virtual address va. If alloc!=0, // create any required page table pages. static pte_t * walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void)) @@ -64,17 +64,17 @@ walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void)) return &pgtab[PTX(va)]; } -// Create PTEs for linear addresses starting at la that refer to +// Create PTEs for virtual addresses starting at la that refer to // physical addresses starting at pa. la and size might not // be page-aligned. static int -mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm, char* (*alloc)(void)) +mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm, char* (*alloc)(void)) { char *a, *last; pte_t *pte; - a = PGROUNDDOWN(la); - last = PGROUNDDOWN(la + size - 1); + a = PGROUNDDOWN(va); + last = PGROUNDDOWN(va + size - 1); for(;;){ pte = walkpgdir(pgdir, a, alloc); if(pte == 0) @@ -90,7 +90,7 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm, char* (*alloc)(vo return 0; } -// The mappings from logical to linear are one to one (i.e., +// The mappings from logical to virtual are one to one (i.e., // segmentation doesn't do anything). // There is one page table per process, plus one that's used // when a CPU is not running any process (kpgdir). @@ -98,7 +98,6 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm, char* (*alloc)(vo // page protection bits prevent it from using anything other // than its memory. // -// // setupkvm() and exec() set up every page table like this: // 0..USERTOP : user memory (text, data, stack, heap), mapped to some unused phys mem // KERNBASE..KERNBASE+1M: mapped to 0..1M @@ -112,9 +111,9 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm, char* (*alloc)(vo // (which is inaccessible in user mode). The user program sits in // the bottom of the address space, and the kernel at the top at KERNBASE. static struct kmap { - void *l; - uint p; - uint e; + void *virt; + uint phys_start; + uint phys_end; int perm; } kmap[] = { { P2V(0), 0, 1024*1024, PTE_W}, // First 1Mbyte contains BIOS and some IO devices @@ -135,7 +134,8 @@ setupkvm(char* (*alloc)(void)) memset(pgdir, 0, PGSIZE); k = kmap; for(k = kmap; k < &kmap[NELEM(kmap)]; k++) - if(mappages(pgdir, k->l, k->e - k->p, (uint)k->p, k->perm, alloc) < 0) + if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, (uint)k->phys_start, + k->perm, alloc) < 0) return 0; return pgdir; |