diff options
Diffstat (limited to 'vm.c')
| -rw-r--r-- | vm.c | 26 |
1 files changed, 25 insertions, 1 deletions
@@ -198,7 +198,7 @@ uva2ka(pde_t *pgdir, char *uva) int allocuvm(pde_t *pgdir, char *addr, uint sz) { - if (addr + sz >= (char*)USERTOP) + if (addr + sz > (char*)USERTOP) return 0; char *first = PGROUNDDOWN(addr); char *last = PGROUNDDOWN(addr + sz - 1); @@ -218,6 +218,30 @@ allocuvm(pde_t *pgdir, char *addr, uint sz) return 1; } +// deallocate some of the user pages, in response to sbrk() +// with a negative argument. if addr is not page-aligned, +// then only deallocates starting at the next page boundary. +int +deallocuvm(pde_t *pgdir, char *addr, uint sz) +{ + if (addr + sz > (char*)USERTOP) + return 0; + char *first = (char*) PGROUNDUP((uint)addr); + char *last = PGROUNDDOWN(addr + sz - 1); + char *a; + for(a = first; a <= last; a += PGSIZE){ + pte_t *pte = walkpgdir(pgdir, a, 0); + if(pte && (*pte & PTE_P) != 0){ + uint pa = PTE_ADDR(*pte); + if(pa == 0) + panic("deallocuvm"); + kfree((void *) pa, PGSIZE); + *pte = 0; + } + } + return 1; +} + // free a page table and all the physical memory pages // in the user part. void |