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 19 enum vvar_pages { 20 VVAR_DATA_PAGE_OFFSET, 21 VVAR_TIMENS_PAGE_OFFSET, 22 VVAR_NR_PAGES, 23 }; 24 25 enum rv_vdso_map { 26 RV_VDSO_MAP_VVAR, 27 RV_VDSO_MAP_VDSO, 28 }; 29 30 #define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT) 31 32 /* 33 * The vDSO data page. 34 */ 35 static union { 36 struct vdso_data data; 37 u8 page[PAGE_SIZE]; 38 } vdso_data_store __page_aligned_data; 39 struct vdso_data *vdso_data = &vdso_data_store.data; 40 41 struct __vdso_info { 42 const char *name; 43 const char *vdso_code_start; 44 const char *vdso_code_end; 45 unsigned long vdso_pages; 46 /* Data Mapping */ 47 struct vm_special_mapping *dm; 48 /* Code Mapping */ 49 struct vm_special_mapping *cm; 50 }; 51 52 static struct __vdso_info vdso_info; 53 #ifdef CONFIG_COMPAT 54 static struct __vdso_info compat_vdso_info; 55 #endif 56 57 static int vdso_mremap(const struct vm_special_mapping *sm, 58 struct vm_area_struct *new_vma) 59 { 60 current->mm->context.vdso = (void *)new_vma->vm_start; 61 62 return 0; 63 } 64 65 static void __init __vdso_init(struct __vdso_info *vdso_info) 66 { 67 unsigned int i; 68 struct page **vdso_pagelist; 69 unsigned long pfn; 70 71 if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4)) 72 panic("vDSO is not a valid ELF object!\n"); 73 74 vdso_info->vdso_pages = ( 75 vdso_info->vdso_code_end - 76 vdso_info->vdso_code_start) >> 77 PAGE_SHIFT; 78 79 vdso_pagelist = kcalloc(vdso_info->vdso_pages, 80 sizeof(struct page *), 81 GFP_KERNEL); 82 if (vdso_pagelist == NULL) 83 panic("vDSO kcalloc failed!\n"); 84 85 /* Grab the vDSO code pages. */ 86 pfn = sym_to_pfn(vdso_info->vdso_code_start); 87 88 for (i = 0; i < vdso_info->vdso_pages; i++) 89 vdso_pagelist[i] = pfn_to_page(pfn + i); 90 91 vdso_info->cm->pages = vdso_pagelist; 92 } 93 94 #ifdef CONFIG_TIME_NS 95 struct vdso_data *arch_get_vdso_data(void *vvar_page) 96 { 97 return (struct vdso_data *)(vvar_page); 98 } 99 100 /* 101 * The vvar mapping contains data for a specific time namespace, so when a task 102 * changes namespace we must unmap its vvar data for the old namespace. 103 * Subsequent faults will map in data for the new namespace. 104 * 105 * For more details see timens_setup_vdso_data(). 106 */ 107 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 108 { 109 struct mm_struct *mm = task->mm; 110 struct vm_area_struct *vma; 111 VMA_ITERATOR(vmi, mm, 0); 112 113 mmap_read_lock(mm); 114 115 for_each_vma(vmi, vma) { 116 if (vma_is_special_mapping(vma, vdso_info.dm)) 117 zap_vma_pages(vma); 118 #ifdef CONFIG_COMPAT 119 if (vma_is_special_mapping(vma, compat_vdso_info.dm)) 120 zap_vma_pages(vma); 121 #endif 122 } 123 124 mmap_read_unlock(mm); 125 return 0; 126 } 127 #endif 128 129 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 130 struct vm_area_struct *vma, struct vm_fault *vmf) 131 { 132 struct page *timens_page = find_timens_vvar_page(vma); 133 unsigned long pfn; 134 135 switch (vmf->pgoff) { 136 case VVAR_DATA_PAGE_OFFSET: 137 if (timens_page) 138 pfn = page_to_pfn(timens_page); 139 else 140 pfn = sym_to_pfn(vdso_data); 141 break; 142 #ifdef CONFIG_TIME_NS 143 case VVAR_TIMENS_PAGE_OFFSET: 144 /* 145 * If a task belongs to a time namespace then a namespace 146 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 147 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 148 * offset. 149 * See also the comment near timens_setup_vdso_data(). 150 */ 151 if (!timens_page) 152 return VM_FAULT_SIGBUS; 153 pfn = sym_to_pfn(vdso_data); 154 break; 155 #endif /* CONFIG_TIME_NS */ 156 default: 157 return VM_FAULT_SIGBUS; 158 } 159 160 return vmf_insert_pfn(vma, vmf->address, pfn); 161 } 162 163 static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = { 164 [RV_VDSO_MAP_VVAR] = { 165 .name = "[vvar]", 166 .fault = vvar_fault, 167 }, 168 [RV_VDSO_MAP_VDSO] = { 169 .name = "[vdso]", 170 .mremap = vdso_mremap, 171 }, 172 }; 173 174 static struct __vdso_info vdso_info __ro_after_init = { 175 .name = "vdso", 176 .vdso_code_start = vdso_start, 177 .vdso_code_end = vdso_end, 178 .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR], 179 .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO], 180 }; 181 182 #ifdef CONFIG_COMPAT 183 static struct vm_special_mapping rv_compat_vdso_maps[] __ro_after_init = { 184 [RV_VDSO_MAP_VVAR] = { 185 .name = "[vvar]", 186 .fault = vvar_fault, 187 }, 188 [RV_VDSO_MAP_VDSO] = { 189 .name = "[vdso]", 190 .mremap = vdso_mremap, 191 }, 192 }; 193 194 static struct __vdso_info compat_vdso_info __ro_after_init = { 195 .name = "compat_vdso", 196 .vdso_code_start = compat_vdso_start, 197 .vdso_code_end = compat_vdso_end, 198 .dm = &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR], 199 .cm = &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO], 200 }; 201 #endif 202 203 static int __init vdso_init(void) 204 { 205 __vdso_init(&vdso_info); 206 #ifdef CONFIG_COMPAT 207 __vdso_init(&compat_vdso_info); 208 #endif 209 210 return 0; 211 } 212 arch_initcall(vdso_init); 213 214 static int __setup_additional_pages(struct mm_struct *mm, 215 struct linux_binprm *bprm, 216 int uses_interp, 217 struct __vdso_info *vdso_info) 218 { 219 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 220 void *ret; 221 222 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 223 224 vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT; 225 /* Be sure to map the data page */ 226 vdso_mapping_len = vdso_text_len + VVAR_SIZE; 227 228 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 229 if (IS_ERR_VALUE(vdso_base)) { 230 ret = ERR_PTR(vdso_base); 231 goto up_fail; 232 } 233 234 ret = _install_special_mapping(mm, vdso_base, VVAR_SIZE, 235 (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info->dm); 236 if (IS_ERR(ret)) 237 goto up_fail; 238 239 vdso_base += VVAR_SIZE; 240 mm->context.vdso = (void *)vdso_base; 241 242 ret = 243 _install_special_mapping(mm, vdso_base, vdso_text_len, 244 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC), 245 vdso_info->cm); 246 247 if (IS_ERR(ret)) 248 goto up_fail; 249 250 return 0; 251 252 up_fail: 253 mm->context.vdso = NULL; 254 return PTR_ERR(ret); 255 } 256 257 #ifdef CONFIG_COMPAT 258 int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 259 int uses_interp) 260 { 261 struct mm_struct *mm = current->mm; 262 int ret; 263 264 if (mmap_write_lock_killable(mm)) 265 return -EINTR; 266 267 ret = __setup_additional_pages(mm, bprm, uses_interp, 268 &compat_vdso_info); 269 mmap_write_unlock(mm); 270 271 return ret; 272 } 273 #endif 274 275 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 276 { 277 struct mm_struct *mm = current->mm; 278 int ret; 279 280 if (mmap_write_lock_killable(mm)) 281 return -EINTR; 282 283 ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info); 284 mmap_write_unlock(mm); 285 286 return ret; 287 } 288