1 /* 2 * Copyright (C) 2002 Jeff Dike (jdike@karaya.com) 3 * Licensed under the GPL 4 */ 5 6 #include "linux/config.h" 7 #include "linux/sched.h" 8 #include "linux/list.h" 9 #include "linux/spinlock.h" 10 #include "linux/slab.h" 11 #include "linux/errno.h" 12 #include "linux/mm.h" 13 #include "asm/current.h" 14 #include "asm/segment.h" 15 #include "asm/mmu.h" 16 #include "asm/pgalloc.h" 17 #include "asm/pgtable.h" 18 #include "os.h" 19 #include "skas.h" 20 21 extern int __syscall_stub_start; 22 23 static int init_stub_pte(struct mm_struct *mm, unsigned long proc, 24 unsigned long kernel) 25 { 26 pgd_t *pgd; 27 pud_t *pud; 28 pmd_t *pmd; 29 pte_t *pte; 30 31 spin_lock(&mm->page_table_lock); 32 pgd = pgd_offset(mm, proc); 33 pud = pud_alloc(mm, pgd, proc); 34 if (!pud) 35 goto out; 36 37 pmd = pmd_alloc(mm, pud, proc); 38 if (!pmd) 39 goto out_pmd; 40 41 pte = pte_alloc_map(mm, pmd, proc); 42 if (!pte) 43 goto out_pte; 44 45 /* There's an interaction between the skas0 stub pages, stack 46 * randomization, and the BUG at the end of exit_mmap. exit_mmap 47 * checks that the number of page tables freed is the same as had 48 * been allocated. If the stack is on the last page table page, 49 * then the stack pte page will be freed, and if not, it won't. To 50 * avoid having to know where the stack is, or if the process mapped 51 * something at the top of its address space for some other reason, 52 * we set TASK_SIZE to end at the start of the last page table. 53 * This keeps exit_mmap off the last page, but introduces a leak 54 * of that page. So, we hang onto it here and free it in 55 * destroy_context_skas. 56 */ 57 58 mm->context.skas.last_page_table = pmd_page_kernel(*pmd); 59 60 *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT)); 61 *pte = pte_mkexec(*pte); 62 *pte = pte_wrprotect(*pte); 63 spin_unlock(&mm->page_table_lock); 64 return(0); 65 66 out_pmd: 67 pud_free(pud); 68 out_pte: 69 pmd_free(pmd); 70 out: 71 spin_unlock(&mm->page_table_lock); 72 return(-ENOMEM); 73 } 74 75 int init_new_context_skas(struct task_struct *task, struct mm_struct *mm) 76 { 77 struct mm_struct *cur_mm = current->mm; 78 struct mm_id *mm_id = &mm->context.skas.id; 79 unsigned long stack; 80 int from, ret; 81 82 if(proc_mm){ 83 if((cur_mm != NULL) && (cur_mm != &init_mm)) 84 from = cur_mm->context.skas.id.u.mm_fd; 85 else from = -1; 86 87 ret = new_mm(from); 88 if(ret < 0){ 89 printk("init_new_context_skas - new_mm failed, " 90 "errno = %d\n", ret); 91 return ret; 92 } 93 mm_id->u.mm_fd = ret; 94 } 95 else { 96 /* This zeros the entry that pgd_alloc didn't, needed since 97 * we are about to reinitialize it, and want mm.nr_ptes to 98 * be accurate. 99 */ 100 mm->pgd[USER_PTRS_PER_PGD] = __pgd(0); 101 102 ret = init_stub_pte(mm, CONFIG_STUB_CODE, 103 (unsigned long) &__syscall_stub_start); 104 if(ret) 105 goto out; 106 107 ret = -ENOMEM; 108 stack = get_zeroed_page(GFP_KERNEL); 109 if(stack == 0) 110 goto out; 111 mm_id->stack = stack; 112 113 ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack); 114 if(ret) 115 goto out_free; 116 117 mm->nr_ptes--; 118 mm_id->u.pid = start_userspace(stack); 119 } 120 121 return 0; 122 123 out_free: 124 free_page(mm_id->stack); 125 out: 126 return ret; 127 } 128 129 void destroy_context_skas(struct mm_struct *mm) 130 { 131 struct mmu_context_skas *mmu = &mm->context.skas; 132 133 if(proc_mm) 134 os_close_file(mmu->id.u.mm_fd); 135 else { 136 os_kill_ptraced_process(mmu->id.u.pid, 1); 137 free_page(mmu->id.stack); 138 free_page(mmu->last_page_table); 139 } 140 } 141