1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * VDSO implementations. 4 * 5 * Copyright (C) 2012 ARM Limited 6 * 7 * Author: Will Deacon <will.deacon@arm.com> 8 */ 9 10 #include <linux/cache.h> 11 #include <linux/clocksource.h> 12 #include <linux/elf.h> 13 #include <linux/err.h> 14 #include <linux/errno.h> 15 #include <linux/gfp.h> 16 #include <linux/kernel.h> 17 #include <linux/mm.h> 18 #include <linux/sched.h> 19 #include <linux/signal.h> 20 #include <linux/slab.h> 21 #include <linux/time_namespace.h> 22 #include <linux/timekeeper_internal.h> 23 #include <linux/vmalloc.h> 24 #include <vdso/datapage.h> 25 #include <vdso/helpers.h> 26 #include <vdso/vsyscall.h> 27 28 #include <asm/cacheflush.h> 29 #include <asm/signal32.h> 30 #include <asm/vdso.h> 31 32 enum vdso_abi { 33 VDSO_ABI_AA64, 34 VDSO_ABI_AA32, 35 }; 36 37 enum vvar_pages { 38 VVAR_DATA_PAGE_OFFSET, 39 VVAR_TIMENS_PAGE_OFFSET, 40 VVAR_NR_PAGES, 41 }; 42 43 struct vdso_abi_info { 44 const char *name; 45 const char *vdso_code_start; 46 const char *vdso_code_end; 47 unsigned long vdso_pages; 48 /* Data Mapping */ 49 struct vm_special_mapping *dm; 50 /* Code Mapping */ 51 struct vm_special_mapping *cm; 52 }; 53 54 static struct vdso_abi_info vdso_info[] __ro_after_init = { 55 [VDSO_ABI_AA64] = { 56 .name = "vdso", 57 .vdso_code_start = vdso_start, 58 .vdso_code_end = vdso_end, 59 }, 60 #ifdef CONFIG_COMPAT_VDSO 61 [VDSO_ABI_AA32] = { 62 .name = "vdso32", 63 .vdso_code_start = vdso32_start, 64 .vdso_code_end = vdso32_end, 65 }, 66 #endif /* CONFIG_COMPAT_VDSO */ 67 }; 68 69 /* 70 * The vDSO data page. 71 */ 72 static union { 73 struct vdso_data data[CS_BASES]; 74 u8 page[PAGE_SIZE]; 75 } vdso_data_store __page_aligned_data; 76 struct vdso_data *vdso_data = vdso_data_store.data; 77 78 static int vdso_mremap(const struct vm_special_mapping *sm, 79 struct vm_area_struct *new_vma) 80 { 81 current->mm->context.vdso = (void *)new_vma->vm_start; 82 83 return 0; 84 } 85 86 static int __init __vdso_init(enum vdso_abi abi) 87 { 88 int i; 89 struct page **vdso_pagelist; 90 unsigned long pfn; 91 92 if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) { 93 pr_err("vDSO is not a valid ELF object!\n"); 94 return -EINVAL; 95 } 96 97 vdso_info[abi].vdso_pages = ( 98 vdso_info[abi].vdso_code_end - 99 vdso_info[abi].vdso_code_start) >> 100 PAGE_SHIFT; 101 102 vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, 103 sizeof(struct page *), 104 GFP_KERNEL); 105 if (vdso_pagelist == NULL) 106 return -ENOMEM; 107 108 /* Grab the vDSO code pages. */ 109 pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); 110 111 for (i = 0; i < vdso_info[abi].vdso_pages; i++) 112 vdso_pagelist[i] = pfn_to_page(pfn + i); 113 114 vdso_info[abi].cm->pages = vdso_pagelist; 115 116 return 0; 117 } 118 119 #ifdef CONFIG_TIME_NS 120 struct vdso_data *arch_get_vdso_data(void *vvar_page) 121 { 122 return (struct vdso_data *)(vvar_page); 123 } 124 125 /* 126 * The vvar mapping contains data for a specific time namespace, so when a task 127 * changes namespace we must unmap its vvar data for the old namespace. 128 * Subsequent faults will map in data for the new namespace. 129 * 130 * For more details see timens_setup_vdso_data(). 131 */ 132 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 133 { 134 struct mm_struct *mm = task->mm; 135 struct vm_area_struct *vma; 136 VMA_ITERATOR(vmi, mm, 0); 137 138 mmap_read_lock(mm); 139 140 for_each_vma(vmi, vma) { 141 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm)) 142 zap_vma_pages(vma); 143 #ifdef CONFIG_COMPAT_VDSO 144 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm)) 145 zap_vma_pages(vma); 146 #endif 147 } 148 149 mmap_read_unlock(mm); 150 return 0; 151 } 152 #endif 153 154 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 155 struct vm_area_struct *vma, struct vm_fault *vmf) 156 { 157 struct page *timens_page = find_timens_vvar_page(vma); 158 unsigned long pfn; 159 160 switch (vmf->pgoff) { 161 case VVAR_DATA_PAGE_OFFSET: 162 if (timens_page) 163 pfn = page_to_pfn(timens_page); 164 else 165 pfn = sym_to_pfn(vdso_data); 166 break; 167 #ifdef CONFIG_TIME_NS 168 case VVAR_TIMENS_PAGE_OFFSET: 169 /* 170 * If a task belongs to a time namespace then a namespace 171 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 172 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 173 * offset. 174 * See also the comment near timens_setup_vdso_data(). 175 */ 176 if (!timens_page) 177 return VM_FAULT_SIGBUS; 178 pfn = sym_to_pfn(vdso_data); 179 break; 180 #endif /* CONFIG_TIME_NS */ 181 default: 182 return VM_FAULT_SIGBUS; 183 } 184 185 return vmf_insert_pfn(vma, vmf->address, pfn); 186 } 187 188 static int __setup_additional_pages(enum vdso_abi abi, 189 struct mm_struct *mm, 190 struct linux_binprm *bprm, 191 int uses_interp) 192 { 193 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 194 unsigned long gp_flags = 0; 195 void *ret; 196 197 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 198 199 vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; 200 /* Be sure to map the data page */ 201 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; 202 203 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 204 if (IS_ERR_VALUE(vdso_base)) { 205 ret = ERR_PTR(vdso_base); 206 goto up_fail; 207 } 208 209 ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, 210 VM_READ|VM_MAYREAD|VM_PFNMAP, 211 vdso_info[abi].dm); 212 if (IS_ERR(ret)) 213 goto up_fail; 214 215 if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti()) 216 gp_flags = VM_ARM64_BTI; 217 218 vdso_base += VVAR_NR_PAGES * PAGE_SIZE; 219 mm->context.vdso = (void *)vdso_base; 220 ret = _install_special_mapping(mm, vdso_base, vdso_text_len, 221 VM_READ|VM_EXEC|gp_flags| 222 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 223 vdso_info[abi].cm); 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 /* 236 * Create and map the vectors page for AArch32 tasks. 237 */ 238 enum aarch32_map { 239 AA32_MAP_VECTORS, /* kuser helpers */ 240 AA32_MAP_SIGPAGE, 241 AA32_MAP_VVAR, 242 AA32_MAP_VDSO, 243 }; 244 245 static struct page *aarch32_vectors_page __ro_after_init; 246 static struct page *aarch32_sig_page __ro_after_init; 247 248 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm, 249 struct vm_area_struct *new_vma) 250 { 251 current->mm->context.sigpage = (void *)new_vma->vm_start; 252 253 return 0; 254 } 255 256 static struct vm_special_mapping aarch32_vdso_maps[] = { 257 [AA32_MAP_VECTORS] = { 258 .name = "[vectors]", /* ABI */ 259 .pages = &aarch32_vectors_page, 260 }, 261 [AA32_MAP_SIGPAGE] = { 262 .name = "[sigpage]", /* ABI */ 263 .pages = &aarch32_sig_page, 264 .mremap = aarch32_sigpage_mremap, 265 }, 266 [AA32_MAP_VVAR] = { 267 .name = "[vvar]", 268 .fault = vvar_fault, 269 }, 270 [AA32_MAP_VDSO] = { 271 .name = "[vdso]", 272 .mremap = vdso_mremap, 273 }, 274 }; 275 276 static int aarch32_alloc_kuser_vdso_page(void) 277 { 278 extern char __kuser_helper_start[], __kuser_helper_end[]; 279 int kuser_sz = __kuser_helper_end - __kuser_helper_start; 280 unsigned long vdso_page; 281 282 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 283 return 0; 284 285 vdso_page = get_zeroed_page(GFP_KERNEL); 286 if (!vdso_page) 287 return -ENOMEM; 288 289 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start, 290 kuser_sz); 291 aarch32_vectors_page = virt_to_page(vdso_page); 292 return 0; 293 } 294 295 #define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1 296 static int aarch32_alloc_sigpage(void) 297 { 298 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; 299 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; 300 __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD); 301 void *sigpage; 302 303 sigpage = (void *)__get_free_page(GFP_KERNEL); 304 if (!sigpage) 305 return -ENOMEM; 306 307 memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison)); 308 memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz); 309 aarch32_sig_page = virt_to_page(sigpage); 310 return 0; 311 } 312 313 static int __init __aarch32_alloc_vdso_pages(void) 314 { 315 316 if (!IS_ENABLED(CONFIG_COMPAT_VDSO)) 317 return 0; 318 319 vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR]; 320 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO]; 321 322 return __vdso_init(VDSO_ABI_AA32); 323 } 324 325 static int __init aarch32_alloc_vdso_pages(void) 326 { 327 int ret; 328 329 ret = __aarch32_alloc_vdso_pages(); 330 if (ret) 331 return ret; 332 333 ret = aarch32_alloc_sigpage(); 334 if (ret) 335 return ret; 336 337 return aarch32_alloc_kuser_vdso_page(); 338 } 339 arch_initcall(aarch32_alloc_vdso_pages); 340 341 static int aarch32_kuser_helpers_setup(struct mm_struct *mm) 342 { 343 void *ret; 344 345 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 346 return 0; 347 348 /* 349 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's 350 * not safe to CoW the page containing the CPU exception vectors. 351 */ 352 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE, 353 VM_READ | VM_EXEC | 354 VM_MAYREAD | VM_MAYEXEC, 355 &aarch32_vdso_maps[AA32_MAP_VECTORS]); 356 357 return PTR_ERR_OR_ZERO(ret); 358 } 359 360 static int aarch32_sigreturn_setup(struct mm_struct *mm) 361 { 362 unsigned long addr; 363 void *ret; 364 365 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); 366 if (IS_ERR_VALUE(addr)) { 367 ret = ERR_PTR(addr); 368 goto out; 369 } 370 371 /* 372 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and 373 * set breakpoints. 374 */ 375 ret = _install_special_mapping(mm, addr, PAGE_SIZE, 376 VM_READ | VM_EXEC | VM_MAYREAD | 377 VM_MAYWRITE | VM_MAYEXEC, 378 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]); 379 if (IS_ERR(ret)) 380 goto out; 381 382 mm->context.sigpage = (void *)addr; 383 384 out: 385 return PTR_ERR_OR_ZERO(ret); 386 } 387 388 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 389 { 390 struct mm_struct *mm = current->mm; 391 int ret; 392 393 if (mmap_write_lock_killable(mm)) 394 return -EINTR; 395 396 ret = aarch32_kuser_helpers_setup(mm); 397 if (ret) 398 goto out; 399 400 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) { 401 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm, 402 uses_interp); 403 if (ret) 404 goto out; 405 } 406 407 ret = aarch32_sigreturn_setup(mm); 408 out: 409 mmap_write_unlock(mm); 410 return ret; 411 } 412 #endif /* CONFIG_COMPAT */ 413 414 enum aarch64_map { 415 AA64_MAP_VVAR, 416 AA64_MAP_VDSO, 417 }; 418 419 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { 420 [AA64_MAP_VVAR] = { 421 .name = "[vvar]", 422 .fault = vvar_fault, 423 }, 424 [AA64_MAP_VDSO] = { 425 .name = "[vdso]", 426 .mremap = vdso_mremap, 427 }, 428 }; 429 430 static int __init vdso_init(void) 431 { 432 vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR]; 433 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO]; 434 435 return __vdso_init(VDSO_ABI_AA64); 436 } 437 arch_initcall(vdso_init); 438 439 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 440 { 441 struct mm_struct *mm = current->mm; 442 int ret; 443 444 if (mmap_write_lock_killable(mm)) 445 return -EINTR; 446 447 ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp); 448 mmap_write_unlock(mm); 449 450 return ret; 451 } 452