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 18 #ifdef CONFIG_GENERIC_TIME_VSYSCALL 19 #include <vdso/datapage.h> 20 #else 21 struct vdso_data { 22 }; 23 #endif 24 25 extern char vdso_start[], vdso_end[]; 26 #ifdef CONFIG_COMPAT 27 extern char compat_vdso_start[], compat_vdso_end[]; 28 #endif 29 30 enum vvar_pages { 31 VVAR_DATA_PAGE_OFFSET, 32 VVAR_TIMENS_PAGE_OFFSET, 33 VVAR_NR_PAGES, 34 }; 35 36 enum rv_vdso_map { 37 RV_VDSO_MAP_VVAR, 38 RV_VDSO_MAP_VDSO, 39 }; 40 41 #define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT) 42 43 /* 44 * The vDSO data page. 45 */ 46 static union { 47 struct vdso_data data; 48 u8 page[PAGE_SIZE]; 49 } vdso_data_store __page_aligned_data; 50 struct vdso_data *vdso_data = &vdso_data_store.data; 51 52 struct __vdso_info { 53 const char *name; 54 const char *vdso_code_start; 55 const char *vdso_code_end; 56 unsigned long vdso_pages; 57 /* Data Mapping */ 58 struct vm_special_mapping *dm; 59 /* Code Mapping */ 60 struct vm_special_mapping *cm; 61 }; 62 63 static struct __vdso_info vdso_info; 64 #ifdef CONFIG_COMPAT 65 static struct __vdso_info compat_vdso_info; 66 #endif 67 68 static int vdso_mremap(const struct vm_special_mapping *sm, 69 struct vm_area_struct *new_vma) 70 { 71 current->mm->context.vdso = (void *)new_vma->vm_start; 72 73 return 0; 74 } 75 76 static void __init __vdso_init(struct __vdso_info *vdso_info) 77 { 78 unsigned int i; 79 struct page **vdso_pagelist; 80 unsigned long pfn; 81 82 if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4)) 83 panic("vDSO is not a valid ELF object!\n"); 84 85 vdso_info->vdso_pages = ( 86 vdso_info->vdso_code_end - 87 vdso_info->vdso_code_start) >> 88 PAGE_SHIFT; 89 90 vdso_pagelist = kcalloc(vdso_info->vdso_pages, 91 sizeof(struct page *), 92 GFP_KERNEL); 93 if (vdso_pagelist == NULL) 94 panic("vDSO kcalloc failed!\n"); 95 96 /* Grab the vDSO code pages. */ 97 pfn = sym_to_pfn(vdso_info->vdso_code_start); 98 99 for (i = 0; i < vdso_info->vdso_pages; i++) 100 vdso_pagelist[i] = pfn_to_page(pfn + i); 101 102 vdso_info->cm->pages = vdso_pagelist; 103 } 104 105 #ifdef CONFIG_TIME_NS 106 struct vdso_data *arch_get_vdso_data(void *vvar_page) 107 { 108 return (struct vdso_data *)(vvar_page); 109 } 110 111 /* 112 * The vvar mapping contains data for a specific time namespace, so when a task 113 * changes namespace we must unmap its vvar data for the old namespace. 114 * Subsequent faults will map in data for the new namespace. 115 * 116 * For more details see timens_setup_vdso_data(). 117 */ 118 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 119 { 120 struct mm_struct *mm = task->mm; 121 struct vm_area_struct *vma; 122 VMA_ITERATOR(vmi, mm, 0); 123 124 mmap_read_lock(mm); 125 126 for_each_vma(vmi, vma) { 127 unsigned long size = vma->vm_end - vma->vm_start; 128 129 if (vma_is_special_mapping(vma, vdso_info.dm)) 130 zap_page_range(vma, vma->vm_start, size); 131 #ifdef CONFIG_COMPAT 132 if (vma_is_special_mapping(vma, compat_vdso_info.dm)) 133 zap_page_range(vma, vma->vm_start, size); 134 #endif 135 } 136 137 mmap_read_unlock(mm); 138 return 0; 139 } 140 141 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 142 { 143 if (likely(vma->vm_mm == current->mm)) 144 return current->nsproxy->time_ns->vvar_page; 145 146 /* 147 * VM_PFNMAP | VM_IO protect .fault() handler from being called 148 * through interfaces like /proc/$pid/mem or 149 * process_vm_{readv,writev}() as long as there's no .access() 150 * in special_mapping_vmops. 151 * For more details check_vma_flags() and __access_remote_vm() 152 */ 153 WARN(1, "vvar_page accessed remotely"); 154 155 return NULL; 156 } 157 #else 158 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 159 { 160 return NULL; 161 } 162 #endif 163 164 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 165 struct vm_area_struct *vma, struct vm_fault *vmf) 166 { 167 struct page *timens_page = find_timens_vvar_page(vma); 168 unsigned long pfn; 169 170 switch (vmf->pgoff) { 171 case VVAR_DATA_PAGE_OFFSET: 172 if (timens_page) 173 pfn = page_to_pfn(timens_page); 174 else 175 pfn = sym_to_pfn(vdso_data); 176 break; 177 #ifdef CONFIG_TIME_NS 178 case VVAR_TIMENS_PAGE_OFFSET: 179 /* 180 * If a task belongs to a time namespace then a namespace 181 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 182 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 183 * offset. 184 * See also the comment near timens_setup_vdso_data(). 185 */ 186 if (!timens_page) 187 return VM_FAULT_SIGBUS; 188 pfn = sym_to_pfn(vdso_data); 189 break; 190 #endif /* CONFIG_TIME_NS */ 191 default: 192 return VM_FAULT_SIGBUS; 193 } 194 195 return vmf_insert_pfn(vma, vmf->address, pfn); 196 } 197 198 static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = { 199 [RV_VDSO_MAP_VVAR] = { 200 .name = "[vvar]", 201 .fault = vvar_fault, 202 }, 203 [RV_VDSO_MAP_VDSO] = { 204 .name = "[vdso]", 205 .mremap = vdso_mremap, 206 }, 207 }; 208 209 static struct __vdso_info vdso_info __ro_after_init = { 210 .name = "vdso", 211 .vdso_code_start = vdso_start, 212 .vdso_code_end = vdso_end, 213 .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR], 214 .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO], 215 }; 216 217 #ifdef CONFIG_COMPAT 218 static struct vm_special_mapping rv_compat_vdso_maps[] __ro_after_init = { 219 [RV_VDSO_MAP_VVAR] = { 220 .name = "[vvar]", 221 .fault = vvar_fault, 222 }, 223 [RV_VDSO_MAP_VDSO] = { 224 .name = "[vdso]", 225 .mremap = vdso_mremap, 226 }, 227 }; 228 229 static struct __vdso_info compat_vdso_info __ro_after_init = { 230 .name = "compat_vdso", 231 .vdso_code_start = compat_vdso_start, 232 .vdso_code_end = compat_vdso_end, 233 .dm = &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR], 234 .cm = &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO], 235 }; 236 #endif 237 238 static int __init vdso_init(void) 239 { 240 __vdso_init(&vdso_info); 241 #ifdef CONFIG_COMPAT 242 __vdso_init(&compat_vdso_info); 243 #endif 244 245 return 0; 246 } 247 arch_initcall(vdso_init); 248 249 static int __setup_additional_pages(struct mm_struct *mm, 250 struct linux_binprm *bprm, 251 int uses_interp, 252 struct __vdso_info *vdso_info) 253 { 254 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 255 void *ret; 256 257 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 258 259 vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT; 260 /* Be sure to map the data page */ 261 vdso_mapping_len = vdso_text_len + VVAR_SIZE; 262 263 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 264 if (IS_ERR_VALUE(vdso_base)) { 265 ret = ERR_PTR(vdso_base); 266 goto up_fail; 267 } 268 269 ret = _install_special_mapping(mm, vdso_base, VVAR_SIZE, 270 (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info->dm); 271 if (IS_ERR(ret)) 272 goto up_fail; 273 274 vdso_base += VVAR_SIZE; 275 mm->context.vdso = (void *)vdso_base; 276 277 ret = 278 _install_special_mapping(mm, vdso_base, vdso_text_len, 279 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC), 280 vdso_info->cm); 281 282 if (IS_ERR(ret)) 283 goto up_fail; 284 285 return 0; 286 287 up_fail: 288 mm->context.vdso = NULL; 289 return PTR_ERR(ret); 290 } 291 292 #ifdef CONFIG_COMPAT 293 int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 294 int uses_interp) 295 { 296 struct mm_struct *mm = current->mm; 297 int ret; 298 299 if (mmap_write_lock_killable(mm)) 300 return -EINTR; 301 302 ret = __setup_additional_pages(mm, bprm, uses_interp, 303 &compat_vdso_info); 304 mmap_write_unlock(mm); 305 306 return ret; 307 } 308 #endif 309 310 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 311 { 312 struct mm_struct *mm = current->mm; 313 int ret; 314 315 if (mmap_write_lock_killable(mm)) 316 return -EINTR; 317 318 ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info); 319 mmap_write_unlock(mm); 320 321 return ret; 322 } 323