diff options
Diffstat (limited to 'vm.c')
| -rw-r--r-- | vm.c | 66 |
1 files changed, 34 insertions, 32 deletions
@@ -43,7 +43,7 @@ seginit(void) // 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)) +walkpgdir(pde_t *pgdir, const void *va, int alloc) { pde_t *pde; pte_t *pgtab; @@ -52,7 +52,7 @@ walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void)) if(*pde & PTE_P){ pgtab = (pte_t*)p2v(PTE_ADDR(*pde)); } else { - if(!alloc || (pgtab = (pte_t*)alloc()) == 0) + if(!alloc || (pgtab = (pte_t*)kalloc()) == 0) return 0; // Make sure all those PTE_P bits are zero. memset(pgtab, 0, PGSIZE); @@ -68,8 +68,7 @@ walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void)) // physical addresses starting at pa. va and size might not // be page-aligned. static int -mappages(pde_t *pgdir, void *va, uint size, uint pa, - int perm, char* (*alloc)(void)) +mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm) { char *a, *last; pte_t *pte; @@ -77,7 +76,7 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa, a = (char*)PGROUNDDOWN((uint)va); last = (char*)PGROUNDDOWN(((uint)va) + size - 1); for(;;){ - if((pte = walkpgdir(pgdir, a, alloc)) == 0) + if((pte = walkpgdir(pgdir, a, 1)) == 0) return -1; if(*pte & PTE_P) panic("remap"); @@ -90,53 +89,56 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa, return 0; } -// 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). A user process uses the same page table as the kernel; the -// page protection bits prevent it from accessing kernel memory. +// There is one page table per process, plus one that's used when +// a CPU is not running any process (kpgdir). The kernel uses the +// current process's page table during system calls and interrupts; +// page protection bits prevent user code from using the kernel's +// mappings. // // setupkvm() and exec() set up every page table like this: -// 0..KERNBASE: user memory (text+data+stack+heap), mapped to some free -// phys memory +// +// 0..KERNBASE: user memory (text+data+stack+heap), mapped to +// phys memory allocated by the kernel // KERNBASE..KERNBASE+EXTMEM: mapped to 0..EXTMEM (for I/O space) -// KERNBASE+EXTMEM..KERNBASE+end: mapped to EXTMEM..end kernel, -// w. no write permission -// KERNBASE+end..KERBASE+PHYSTOP: mapped to end..PHYSTOP, -// rw data + free memory +// KERNBASE+EXTMEM..data: mapped to EXTMEM..V2P(data) +// for the kernel's instructions and r/o data +// data..KERNBASE+PHYSTOP: mapped to V2P(data)..PHYSTOP, +// rw data + free physical memory // 0xfe000000..0: mapped direct (devices such as ioapic) // -// The kernel allocates memory for its heap and for user memory -// between KERNBASE+end and the end of physical memory (PHYSTOP). -// The user program sits in the bottom of the address space, and the -// kernel at the top at KERNBASE. +// The kernel allocates physical memory for its heap and for user memory +// between V2P(end) and the end of physical memory (PHYSTOP) +// (directly addressable from end..P2V(PHYSTOP)). + +// This table defines the kernel's mappings, which are present in +// every process's page table. static struct kmap { void *virt; uint phys_start; uint phys_end; int perm; } kmap[] = { - { P2V(0), 0, 1024*1024, PTE_W}, // I/O space - { (void*)KERNLINK, V2P(KERNLINK), V2P(data), 0}, // kernel text+rodata - { data, V2P(data), PHYSTOP, PTE_W}, // kernel data, memory - { (void*)DEVSPACE, DEVSPACE, 0, PTE_W}, // more devices + { (void*) KERNBASE, 0, EXTMEM, PTE_W}, // I/O space + { (void*) KERNLINK, V2P(KERNLINK), V2P(data), 0}, // kernel text+rodata + { (void*) data, V2P(data), PHYSTOP, PTE_W}, // kernel data, memory + { (void*) DEVSPACE, DEVSPACE, 0, PTE_W}, // more devices }; // Set up kernel part of a page table. pde_t* -setupkvm(char* (*alloc)(void)) +setupkvm() { pde_t *pgdir; struct kmap *k; - if((pgdir = (pde_t*)alloc()) == 0) + if((pgdir = (pde_t*)kalloc()) == 0) return 0; memset(pgdir, 0, PGSIZE); if (p2v(PHYSTOP) > (void*)DEVSPACE) panic("PHYSTOP too high"); for(k = kmap; k < &kmap[NELEM(kmap)]; k++) if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, - (uint)k->phys_start, k->perm, alloc) < 0) + (uint)k->phys_start, k->perm) < 0) return 0; return pgdir; } @@ -146,7 +148,7 @@ setupkvm(char* (*alloc)(void)) void kvmalloc(void) { - kpgdir = setupkvm(enter_alloc); + kpgdir = setupkvm(); switchkvm(); } @@ -185,7 +187,7 @@ inituvm(pde_t *pgdir, char *init, uint sz) panic("inituvm: more than a page"); mem = kalloc(); memset(mem, 0, PGSIZE); - mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc); + mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U); memmove(mem, init, sz); } @@ -235,7 +237,7 @@ allocuvm(pde_t *pgdir, uint oldsz, uint newsz) return 0; } memset(mem, 0, PGSIZE); - mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc); + mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U); } return newsz; } @@ -312,7 +314,7 @@ copyuvm(pde_t *pgdir, uint sz) uint pa, i; char *mem; - if((d = setupkvm(kalloc)) == 0) + if((d = setupkvm()) == 0) return 0; for(i = 0; i < sz; i += PGSIZE){ if((pte = walkpgdir(pgdir, (void *) i, 0)) == 0) @@ -323,7 +325,7 @@ copyuvm(pde_t *pgdir, uint sz) if((mem = kalloc()) == 0) goto bad; memmove(mem, (char*)p2v(pa), PGSIZE); - if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc) < 0) + if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U) < 0) goto bad; } return d; |