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 "asm/ldt.h" 19 #include "os.h" 20 #include "skas.h" 21 22 extern int __syscall_stub_start; 23 24 static int init_stub_pte(struct mm_struct *mm, unsigned long proc, 25 unsigned long kernel) 26 { 27 pgd_t *pgd; 28 pud_t *pud; 29 pmd_t *pmd; 30 pte_t *pte; 31 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 #ifdef CONFIG_3_LEVEL_PGTABLES 60 mm->context.skas.last_pmd = (unsigned long) __va(pud_val(*pud)); 61 #endif 62 63 *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT)); 64 *pte = pte_mkexec(*pte); 65 *pte = pte_wrprotect(*pte); 66 return(0); 67 68 out_pmd: 69 pud_free(pud); 70 out_pte: 71 pmd_free(pmd); 72 out: 73 return(-ENOMEM); 74 } 75 76 int init_new_context_skas(struct task_struct *task, struct mm_struct *mm) 77 { 78 struct mmu_context_skas *from_mm = NULL; 79 struct mmu_context_skas *to_mm = &mm->context.skas; 80 unsigned long stack = 0; 81 int ret = -ENOMEM; 82 83 if(skas_needs_stub){ 84 stack = get_zeroed_page(GFP_KERNEL); 85 if(stack == 0) 86 goto out; 87 88 /* This zeros the entry that pgd_alloc didn't, needed since 89 * we are about to reinitialize it, and want mm.nr_ptes to 90 * be accurate. 91 */ 92 mm->pgd[USER_PTRS_PER_PGD] = __pgd(0); 93 94 ret = init_stub_pte(mm, CONFIG_STUB_CODE, 95 (unsigned long) &__syscall_stub_start); 96 if(ret) 97 goto out_free; 98 99 ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack); 100 if(ret) 101 goto out_free; 102 103 mm->nr_ptes--; 104 } 105 106 to_mm->id.stack = stack; 107 if(current->mm != NULL && current->mm != &init_mm) 108 from_mm = ¤t->mm->context.skas; 109 110 if(proc_mm){ 111 ret = new_mm(stack); 112 if(ret < 0){ 113 printk("init_new_context_skas - new_mm failed, " 114 "errno = %d\n", ret); 115 goto out_free; 116 } 117 to_mm->id.u.mm_fd = ret; 118 } 119 else { 120 if(from_mm) 121 to_mm->id.u.pid = copy_context_skas0(stack, 122 from_mm->id.u.pid); 123 else to_mm->id.u.pid = start_userspace(stack); 124 } 125 126 ret = init_new_ldt(to_mm, from_mm); 127 if(ret < 0){ 128 printk("init_new_context_skas - init_ldt" 129 " failed, errno = %d\n", ret); 130 goto out_free; 131 } 132 133 return 0; 134 135 out_free: 136 if(to_mm->id.stack != 0) 137 free_page(to_mm->id.stack); 138 out: 139 return ret; 140 } 141 142 void destroy_context_skas(struct mm_struct *mm) 143 { 144 struct mmu_context_skas *mmu = &mm->context.skas; 145 146 if(proc_mm) 147 os_close_file(mmu->id.u.mm_fd); 148 else 149 os_kill_ptraced_process(mmu->id.u.pid, 1); 150 151 if(!proc_mm || !ptrace_faultinfo){ 152 free_page(mmu->id.stack); 153 pte_lock_deinit(virt_to_page(mmu->last_page_table)); 154 pte_free_kernel((pte_t *) mmu->last_page_table); 155 dec_zone_page_state(virt_to_page(mmu->last_page_table), NR_PAGETABLE); 156 #ifdef CONFIG_3_LEVEL_PGTABLES 157 pmd_free((pmd_t *) mmu->last_pmd); 158 #endif 159 } 160 } 161