1 /* 2 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de) 3 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 4 * Licensed under the GPL 5 */ 6 7 #include <linux/mm.h> 8 #include <linux/sched.h> 9 #include <linux/slab.h> 10 #include <asm/pgalloc.h> 11 #include <asm/pgtable.h> 12 #include <asm/sections.h> 13 #include <as-layout.h> 14 #include <os.h> 15 #include <skas.h> 16 17 static int init_stub_pte(struct mm_struct *mm, unsigned long proc, 18 unsigned long kernel) 19 { 20 pgd_t *pgd; 21 pud_t *pud; 22 pmd_t *pmd; 23 pte_t *pte; 24 25 pgd = pgd_offset(mm, proc); 26 pud = pud_alloc(mm, pgd, proc); 27 if (!pud) 28 goto out; 29 30 pmd = pmd_alloc(mm, pud, proc); 31 if (!pmd) 32 goto out_pmd; 33 34 pte = pte_alloc_map(mm, pmd, proc); 35 if (!pte) 36 goto out_pte; 37 38 *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT)); 39 *pte = pte_mkread(*pte); 40 return 0; 41 42 out_pte: 43 pmd_free(mm, pmd); 44 out_pmd: 45 pud_free(mm, pud); 46 out: 47 return -ENOMEM; 48 } 49 50 int init_new_context(struct task_struct *task, struct mm_struct *mm) 51 { 52 struct mm_context *from_mm = NULL; 53 struct mm_context *to_mm = &mm->context; 54 unsigned long stack = 0; 55 int ret = -ENOMEM; 56 57 stack = get_zeroed_page(GFP_KERNEL); 58 if (stack == 0) 59 goto out; 60 61 to_mm->id.stack = stack; 62 if (current->mm != NULL && current->mm != &init_mm) 63 from_mm = ¤t->mm->context; 64 65 block_signals(); 66 if (from_mm) 67 to_mm->id.u.pid = copy_context_skas0(stack, 68 from_mm->id.u.pid); 69 else to_mm->id.u.pid = start_userspace(stack); 70 unblock_signals(); 71 72 if (to_mm->id.u.pid < 0) { 73 ret = to_mm->id.u.pid; 74 goto out_free; 75 } 76 77 ret = init_new_ldt(to_mm, from_mm); 78 if (ret < 0) { 79 printk(KERN_ERR "init_new_context_skas - init_ldt" 80 " failed, errno = %d\n", ret); 81 goto out_free; 82 } 83 84 return 0; 85 86 out_free: 87 if (to_mm->id.stack != 0) 88 free_page(to_mm->id.stack); 89 out: 90 return ret; 91 } 92 93 void uml_setup_stubs(struct mm_struct *mm) 94 { 95 int err, ret; 96 97 ret = init_stub_pte(mm, STUB_CODE, 98 (unsigned long) __syscall_stub_start); 99 if (ret) 100 goto out; 101 102 ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack); 103 if (ret) 104 goto out; 105 106 mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start); 107 mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack); 108 109 /* dup_mmap already holds mmap_sem */ 110 err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START, 111 VM_READ | VM_MAYREAD | VM_EXEC | 112 VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP, 113 mm->context.stub_pages); 114 if (err) { 115 printk(KERN_ERR "install_special_mapping returned %d\n", err); 116 goto out; 117 } 118 return; 119 120 out: 121 force_sigsegv(SIGSEGV, current); 122 } 123 124 void arch_exit_mmap(struct mm_struct *mm) 125 { 126 pte_t *pte; 127 128 pte = virt_to_pte(mm, STUB_CODE); 129 if (pte != NULL) 130 pte_clear(mm, STUB_CODE, pte); 131 132 pte = virt_to_pte(mm, STUB_DATA); 133 if (pte == NULL) 134 return; 135 136 pte_clear(mm, STUB_DATA, pte); 137 } 138 139 void destroy_context(struct mm_struct *mm) 140 { 141 struct mm_context *mmu = &mm->context; 142 143 /* 144 * If init_new_context wasn't called, this will be 145 * zero, resulting in a kill(0), which will result in the 146 * whole UML suddenly dying. Also, cover negative and 147 * 1 cases, since they shouldn't happen either. 148 */ 149 if (mmu->id.u.pid < 2) { 150 printk(KERN_ERR "corrupt mm_context - pid = %d\n", 151 mmu->id.u.pid); 152 return; 153 } 154 os_kill_ptraced_process(mmu->id.u.pid, 1); 155 156 free_page(mmu->id.stack); 157 free_ldt(mmu); 158 } 159