1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp. 4 * <benh@kernel.crashing.org> 5 * Copyright (C) 2012 ARM Limited 6 * Copyright (C) 2015 Regents of the University of California 7 */ 8 9 #include <linux/elf.h> 10 #include <linux/mm.h> 11 #include <linux/slab.h> 12 #include <linux/binfmts.h> 13 #include <linux/err.h> 14 #include <asm/page.h> 15 #include <asm/vdso.h> 16 #include <linux/time_namespace.h> 17 #include <vdso/datapage.h> 18 #include <vdso/vsyscall.h> 19 20 enum vvar_pages { 21 VVAR_DATA_PAGE_OFFSET, 22 VVAR_TIMENS_PAGE_OFFSET, 23 VVAR_NR_PAGES, 24 }; 25 26 #define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT) 27 28 static union vdso_data_store vdso_data_store __page_aligned_data; 29 struct vdso_data *vdso_data = vdso_data_store.data; 30 31 struct __vdso_info { 32 const char *name; 33 const char *vdso_code_start; 34 const char *vdso_code_end; 35 unsigned long vdso_pages; 36 /* Code Mapping */ 37 struct vm_special_mapping *cm; 38 }; 39 40 static struct __vdso_info vdso_info; 41 #ifdef CONFIG_COMPAT 42 static struct __vdso_info compat_vdso_info; 43 #endif 44 45 static int vdso_mremap(const struct vm_special_mapping *sm, 46 struct vm_area_struct *new_vma) 47 { 48 current->mm->context.vdso = (void *)new_vma->vm_start; 49 50 return 0; 51 } 52 53 static void __init __vdso_init(struct __vdso_info *vdso_info) 54 { 55 unsigned int i; 56 struct page **vdso_pagelist; 57 unsigned long pfn; 58 59 if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4)) 60 panic("vDSO is not a valid ELF object!\n"); 61 62 vdso_info->vdso_pages = ( 63 vdso_info->vdso_code_end - 64 vdso_info->vdso_code_start) >> 65 PAGE_SHIFT; 66 67 vdso_pagelist = kcalloc(vdso_info->vdso_pages, 68 sizeof(struct page *), 69 GFP_KERNEL); 70 if (vdso_pagelist == NULL) 71 panic("vDSO kcalloc failed!\n"); 72 73 /* Grab the vDSO code pages. */ 74 pfn = sym_to_pfn(vdso_info->vdso_code_start); 75 76 for (i = 0; i < vdso_info->vdso_pages; i++) 77 vdso_pagelist[i] = pfn_to_page(pfn + i); 78 79 vdso_info->cm->pages = vdso_pagelist; 80 } 81 82 #ifdef CONFIG_TIME_NS 83 struct vdso_data *arch_get_vdso_data(void *vvar_page) 84 { 85 return (struct vdso_data *)(vvar_page); 86 } 87 88 static const struct vm_special_mapping rv_vvar_map; 89 90 /* 91 * The vvar mapping contains data for a specific time namespace, so when a task 92 * changes namespace we must unmap its vvar data for the old namespace. 93 * Subsequent faults will map in data for the new namespace. 94 * 95 * For more details see timens_setup_vdso_data(). 96 */ 97 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 98 { 99 struct mm_struct *mm = task->mm; 100 struct vm_area_struct *vma; 101 VMA_ITERATOR(vmi, mm, 0); 102 103 mmap_read_lock(mm); 104 105 for_each_vma(vmi, vma) { 106 if (vma_is_special_mapping(vma, &rv_vvar_map)) 107 zap_vma_pages(vma); 108 } 109 110 mmap_read_unlock(mm); 111 return 0; 112 } 113 #endif 114 115 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 116 struct vm_area_struct *vma, struct vm_fault *vmf) 117 { 118 struct page *timens_page = find_timens_vvar_page(vma); 119 unsigned long pfn; 120 121 switch (vmf->pgoff) { 122 case VVAR_DATA_PAGE_OFFSET: 123 if (timens_page) 124 pfn = page_to_pfn(timens_page); 125 else 126 pfn = sym_to_pfn(vdso_data); 127 break; 128 #ifdef CONFIG_TIME_NS 129 case VVAR_TIMENS_PAGE_OFFSET: 130 /* 131 * If a task belongs to a time namespace then a namespace 132 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 133 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 134 * offset. 135 * See also the comment near timens_setup_vdso_data(). 136 */ 137 if (!timens_page) 138 return VM_FAULT_SIGBUS; 139 pfn = sym_to_pfn(vdso_data); 140 break; 141 #endif /* CONFIG_TIME_NS */ 142 default: 143 return VM_FAULT_SIGBUS; 144 } 145 146 return vmf_insert_pfn(vma, vmf->address, pfn); 147 } 148 149 static const struct vm_special_mapping rv_vvar_map = { 150 .name = "[vvar]", 151 .fault = vvar_fault, 152 }; 153 154 static struct vm_special_mapping rv_vdso_map __ro_after_init = { 155 .name = "[vdso]", 156 .mremap = vdso_mremap, 157 }; 158 159 static struct __vdso_info vdso_info __ro_after_init = { 160 .name = "vdso", 161 .vdso_code_start = vdso_start, 162 .vdso_code_end = vdso_end, 163 .cm = &rv_vdso_map, 164 }; 165 166 #ifdef CONFIG_COMPAT 167 static struct vm_special_mapping rv_compat_vdso_map __ro_after_init = { 168 .name = "[vdso]", 169 .mremap = vdso_mremap, 170 }; 171 172 static struct __vdso_info compat_vdso_info __ro_after_init = { 173 .name = "compat_vdso", 174 .vdso_code_start = compat_vdso_start, 175 .vdso_code_end = compat_vdso_end, 176 .cm = &rv_compat_vdso_map, 177 }; 178 #endif 179 180 static int __init vdso_init(void) 181 { 182 __vdso_init(&vdso_info); 183 #ifdef CONFIG_COMPAT 184 __vdso_init(&compat_vdso_info); 185 #endif 186 187 return 0; 188 } 189 arch_initcall(vdso_init); 190 191 static int __setup_additional_pages(struct mm_struct *mm, 192 struct linux_binprm *bprm, 193 int uses_interp, 194 struct __vdso_info *vdso_info) 195 { 196 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 197 void *ret; 198 199 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 200 201 vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT; 202 /* Be sure to map the data page */ 203 vdso_mapping_len = vdso_text_len + VVAR_SIZE; 204 205 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 206 if (IS_ERR_VALUE(vdso_base)) { 207 ret = ERR_PTR(vdso_base); 208 goto up_fail; 209 } 210 211 ret = _install_special_mapping(mm, vdso_base, VVAR_SIZE, 212 (VM_READ | VM_MAYREAD | VM_PFNMAP), &rv_vvar_map); 213 if (IS_ERR(ret)) 214 goto up_fail; 215 216 vdso_base += VVAR_SIZE; 217 mm->context.vdso = (void *)vdso_base; 218 219 ret = 220 _install_special_mapping(mm, vdso_base, vdso_text_len, 221 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC), 222 vdso_info->cm); 223 224 if (IS_ERR(ret)) 225 goto up_fail; 226 227 return 0; 228 229 up_fail: 230 mm->context.vdso = NULL; 231 return PTR_ERR(ret); 232 } 233 234 #ifdef CONFIG_COMPAT 235 int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 236 int uses_interp) 237 { 238 struct mm_struct *mm = current->mm; 239 int ret; 240 241 if (mmap_write_lock_killable(mm)) 242 return -EINTR; 243 244 ret = __setup_additional_pages(mm, bprm, uses_interp, 245 &compat_vdso_info); 246 mmap_write_unlock(mm); 247 248 return ret; 249 } 250 #endif 251 252 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 253 { 254 struct mm_struct *mm = current->mm; 255 int ret; 256 257 if (mmap_write_lock_killable(mm)) 258 return -EINTR; 259 260 ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info); 261 mmap_write_unlock(mm); 262 263 return ret; 264 } 265