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