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 extern char vdso_start[], vdso_end[]; 33 extern char vdso32_start[], vdso32_end[]; 34 35 enum vdso_abi { 36 VDSO_ABI_AA64, 37 VDSO_ABI_AA32, 38 }; 39 40 enum vvar_pages { 41 VVAR_DATA_PAGE_OFFSET, 42 VVAR_TIMENS_PAGE_OFFSET, 43 VVAR_NR_PAGES, 44 }; 45 46 struct vdso_abi_info { 47 const char *name; 48 const char *vdso_code_start; 49 const char *vdso_code_end; 50 unsigned long vdso_pages; 51 /* Data Mapping */ 52 struct vm_special_mapping *dm; 53 /* Code Mapping */ 54 struct vm_special_mapping *cm; 55 }; 56 57 static struct vdso_abi_info vdso_info[] __ro_after_init = { 58 [VDSO_ABI_AA64] = { 59 .name = "vdso", 60 .vdso_code_start = vdso_start, 61 .vdso_code_end = vdso_end, 62 }, 63 #ifdef CONFIG_COMPAT_VDSO 64 [VDSO_ABI_AA32] = { 65 .name = "vdso32", 66 .vdso_code_start = vdso32_start, 67 .vdso_code_end = vdso32_end, 68 }, 69 #endif /* CONFIG_COMPAT_VDSO */ 70 }; 71 72 /* 73 * The vDSO data page. 74 */ 75 static union { 76 struct vdso_data data[CS_BASES]; 77 u8 page[PAGE_SIZE]; 78 } vdso_data_store __page_aligned_data; 79 struct vdso_data *vdso_data = vdso_data_store.data; 80 81 static int __vdso_remap(enum vdso_abi abi, 82 const struct vm_special_mapping *sm, 83 struct vm_area_struct *new_vma) 84 { 85 unsigned long new_size = new_vma->vm_end - new_vma->vm_start; 86 unsigned long vdso_size = vdso_info[abi].vdso_code_end - 87 vdso_info[abi].vdso_code_start; 88 89 if (vdso_size != new_size) 90 return -EINVAL; 91 92 current->mm->context.vdso = (void *)new_vma->vm_start; 93 94 return 0; 95 } 96 97 static int __vdso_init(enum vdso_abi abi) 98 { 99 int i; 100 struct page **vdso_pagelist; 101 unsigned long pfn; 102 103 if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) { 104 pr_err("vDSO is not a valid ELF object!\n"); 105 return -EINVAL; 106 } 107 108 vdso_info[abi].vdso_pages = ( 109 vdso_info[abi].vdso_code_end - 110 vdso_info[abi].vdso_code_start) >> 111 PAGE_SHIFT; 112 113 vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, 114 sizeof(struct page *), 115 GFP_KERNEL); 116 if (vdso_pagelist == NULL) 117 return -ENOMEM; 118 119 /* Grab the vDSO code pages. */ 120 pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); 121 122 for (i = 0; i < vdso_info[abi].vdso_pages; i++) 123 vdso_pagelist[i] = pfn_to_page(pfn + i); 124 125 vdso_info[abi].cm->pages = vdso_pagelist; 126 127 return 0; 128 } 129 130 #ifdef CONFIG_TIME_NS 131 struct vdso_data *arch_get_vdso_data(void *vvar_page) 132 { 133 return (struct vdso_data *)(vvar_page); 134 } 135 136 /* 137 * The vvar mapping contains data for a specific time namespace, so when a task 138 * changes namespace we must unmap its vvar data for the old namespace. 139 * Subsequent faults will map in data for the new namespace. 140 * 141 * For more details see timens_setup_vdso_data(). 142 */ 143 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 144 { 145 struct mm_struct *mm = task->mm; 146 struct vm_area_struct *vma; 147 148 mmap_read_lock(mm); 149 150 for (vma = mm->mmap; vma; vma = vma->vm_next) { 151 unsigned long size = vma->vm_end - vma->vm_start; 152 153 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm)) 154 zap_page_range(vma, vma->vm_start, size); 155 #ifdef CONFIG_COMPAT_VDSO 156 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm)) 157 zap_page_range(vma, vma->vm_start, size); 158 #endif 159 } 160 161 mmap_read_unlock(mm); 162 return 0; 163 } 164 165 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 166 { 167 if (likely(vma->vm_mm == current->mm)) 168 return current->nsproxy->time_ns->vvar_page; 169 170 /* 171 * VM_PFNMAP | VM_IO protect .fault() handler from being called 172 * through interfaces like /proc/$pid/mem or 173 * process_vm_{readv,writev}() as long as there's no .access() 174 * in special_mapping_vmops. 175 * For more details check_vma_flags() and __access_remote_vm() 176 */ 177 WARN(1, "vvar_page accessed remotely"); 178 179 return NULL; 180 } 181 #else 182 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 183 { 184 return NULL; 185 } 186 #endif 187 188 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 189 struct vm_area_struct *vma, struct vm_fault *vmf) 190 { 191 struct page *timens_page = find_timens_vvar_page(vma); 192 unsigned long pfn; 193 194 switch (vmf->pgoff) { 195 case VVAR_DATA_PAGE_OFFSET: 196 if (timens_page) 197 pfn = page_to_pfn(timens_page); 198 else 199 pfn = sym_to_pfn(vdso_data); 200 break; 201 #ifdef CONFIG_TIME_NS 202 case VVAR_TIMENS_PAGE_OFFSET: 203 /* 204 * If a task belongs to a time namespace then a namespace 205 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 206 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 207 * offset. 208 * See also the comment near timens_setup_vdso_data(). 209 */ 210 if (!timens_page) 211 return VM_FAULT_SIGBUS; 212 pfn = sym_to_pfn(vdso_data); 213 break; 214 #endif /* CONFIG_TIME_NS */ 215 default: 216 return VM_FAULT_SIGBUS; 217 } 218 219 return vmf_insert_pfn(vma, vmf->address, pfn); 220 } 221 222 static int vvar_mremap(const struct vm_special_mapping *sm, 223 struct vm_area_struct *new_vma) 224 { 225 unsigned long new_size = new_vma->vm_end - new_vma->vm_start; 226 227 if (new_size != VVAR_NR_PAGES * PAGE_SIZE) 228 return -EINVAL; 229 230 return 0; 231 } 232 233 static int __setup_additional_pages(enum vdso_abi abi, 234 struct mm_struct *mm, 235 struct linux_binprm *bprm, 236 int uses_interp) 237 { 238 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 239 unsigned long gp_flags = 0; 240 void *ret; 241 242 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 243 244 vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; 245 /* Be sure to map the data page */ 246 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; 247 248 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 249 if (IS_ERR_VALUE(vdso_base)) { 250 ret = ERR_PTR(vdso_base); 251 goto up_fail; 252 } 253 254 ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, 255 VM_READ|VM_MAYREAD|VM_PFNMAP, 256 vdso_info[abi].dm); 257 if (IS_ERR(ret)) 258 goto up_fail; 259 260 if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti()) 261 gp_flags = VM_ARM64_BTI; 262 263 vdso_base += VVAR_NR_PAGES * PAGE_SIZE; 264 mm->context.vdso = (void *)vdso_base; 265 ret = _install_special_mapping(mm, vdso_base, vdso_text_len, 266 VM_READ|VM_EXEC|gp_flags| 267 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 268 vdso_info[abi].cm); 269 if (IS_ERR(ret)) 270 goto up_fail; 271 272 return 0; 273 274 up_fail: 275 mm->context.vdso = NULL; 276 return PTR_ERR(ret); 277 } 278 279 #ifdef CONFIG_COMPAT 280 /* 281 * Create and map the vectors page for AArch32 tasks. 282 */ 283 static int aarch32_vdso_mremap(const struct vm_special_mapping *sm, 284 struct vm_area_struct *new_vma) 285 { 286 return __vdso_remap(VDSO_ABI_AA32, sm, new_vma); 287 } 288 289 enum aarch32_map { 290 AA32_MAP_VECTORS, /* kuser helpers */ 291 AA32_MAP_SIGPAGE, 292 AA32_MAP_VVAR, 293 AA32_MAP_VDSO, 294 }; 295 296 static struct page *aarch32_vectors_page __ro_after_init; 297 static struct page *aarch32_sig_page __ro_after_init; 298 299 static struct vm_special_mapping aarch32_vdso_maps[] = { 300 [AA32_MAP_VECTORS] = { 301 .name = "[vectors]", /* ABI */ 302 .pages = &aarch32_vectors_page, 303 }, 304 [AA32_MAP_SIGPAGE] = { 305 .name = "[sigpage]", /* ABI */ 306 .pages = &aarch32_sig_page, 307 }, 308 [AA32_MAP_VVAR] = { 309 .name = "[vvar]", 310 .fault = vvar_fault, 311 .mremap = vvar_mremap, 312 }, 313 [AA32_MAP_VDSO] = { 314 .name = "[vdso]", 315 .mremap = aarch32_vdso_mremap, 316 }, 317 }; 318 319 static int aarch32_alloc_kuser_vdso_page(void) 320 { 321 extern char __kuser_helper_start[], __kuser_helper_end[]; 322 int kuser_sz = __kuser_helper_end - __kuser_helper_start; 323 unsigned long vdso_page; 324 325 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 326 return 0; 327 328 vdso_page = get_zeroed_page(GFP_ATOMIC); 329 if (!vdso_page) 330 return -ENOMEM; 331 332 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start, 333 kuser_sz); 334 aarch32_vectors_page = virt_to_page(vdso_page); 335 flush_dcache_page(aarch32_vectors_page); 336 return 0; 337 } 338 339 static int aarch32_alloc_sigpage(void) 340 { 341 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; 342 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; 343 unsigned long sigpage; 344 345 sigpage = get_zeroed_page(GFP_ATOMIC); 346 if (!sigpage) 347 return -ENOMEM; 348 349 memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz); 350 aarch32_sig_page = virt_to_page(sigpage); 351 flush_dcache_page(aarch32_sig_page); 352 return 0; 353 } 354 355 static int __aarch32_alloc_vdso_pages(void) 356 { 357 358 if (!IS_ENABLED(CONFIG_COMPAT_VDSO)) 359 return 0; 360 361 vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR]; 362 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO]; 363 364 return __vdso_init(VDSO_ABI_AA32); 365 } 366 367 static int __init aarch32_alloc_vdso_pages(void) 368 { 369 int ret; 370 371 ret = __aarch32_alloc_vdso_pages(); 372 if (ret) 373 return ret; 374 375 ret = aarch32_alloc_sigpage(); 376 if (ret) 377 return ret; 378 379 return aarch32_alloc_kuser_vdso_page(); 380 } 381 arch_initcall(aarch32_alloc_vdso_pages); 382 383 static int aarch32_kuser_helpers_setup(struct mm_struct *mm) 384 { 385 void *ret; 386 387 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 388 return 0; 389 390 /* 391 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's 392 * not safe to CoW the page containing the CPU exception vectors. 393 */ 394 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE, 395 VM_READ | VM_EXEC | 396 VM_MAYREAD | VM_MAYEXEC, 397 &aarch32_vdso_maps[AA32_MAP_VECTORS]); 398 399 return PTR_ERR_OR_ZERO(ret); 400 } 401 402 static int aarch32_sigreturn_setup(struct mm_struct *mm) 403 { 404 unsigned long addr; 405 void *ret; 406 407 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); 408 if (IS_ERR_VALUE(addr)) { 409 ret = ERR_PTR(addr); 410 goto out; 411 } 412 413 /* 414 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and 415 * set breakpoints. 416 */ 417 ret = _install_special_mapping(mm, addr, PAGE_SIZE, 418 VM_READ | VM_EXEC | VM_MAYREAD | 419 VM_MAYWRITE | VM_MAYEXEC, 420 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]); 421 if (IS_ERR(ret)) 422 goto out; 423 424 mm->context.sigpage = (void *)addr; 425 426 out: 427 return PTR_ERR_OR_ZERO(ret); 428 } 429 430 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 431 { 432 struct mm_struct *mm = current->mm; 433 int ret; 434 435 if (mmap_write_lock_killable(mm)) 436 return -EINTR; 437 438 ret = aarch32_kuser_helpers_setup(mm); 439 if (ret) 440 goto out; 441 442 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) { 443 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm, 444 uses_interp); 445 if (ret) 446 goto out; 447 } 448 449 ret = aarch32_sigreturn_setup(mm); 450 out: 451 mmap_write_unlock(mm); 452 return ret; 453 } 454 #endif /* CONFIG_COMPAT */ 455 456 static int vdso_mremap(const struct vm_special_mapping *sm, 457 struct vm_area_struct *new_vma) 458 { 459 return __vdso_remap(VDSO_ABI_AA64, sm, new_vma); 460 } 461 462 enum aarch64_map { 463 AA64_MAP_VVAR, 464 AA64_MAP_VDSO, 465 }; 466 467 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { 468 [AA64_MAP_VVAR] = { 469 .name = "[vvar]", 470 .fault = vvar_fault, 471 .mremap = vvar_mremap, 472 }, 473 [AA64_MAP_VDSO] = { 474 .name = "[vdso]", 475 .mremap = vdso_mremap, 476 }, 477 }; 478 479 static int __init vdso_init(void) 480 { 481 vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR]; 482 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO]; 483 484 return __vdso_init(VDSO_ABI_AA64); 485 } 486 arch_initcall(vdso_init); 487 488 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 489 { 490 struct mm_struct *mm = current->mm; 491 int ret; 492 493 if (mmap_write_lock_killable(mm)) 494 return -EINTR; 495 496 ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp); 497 mmap_write_unlock(mm); 498 499 return ret; 500 } 501