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 unsigned long size = vma->vm_end - vma->vm_start; 142 143 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm)) 144 zap_page_range(vma, vma->vm_start, size); 145 #ifdef CONFIG_COMPAT_VDSO 146 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm)) 147 zap_page_range(vma, vma->vm_start, size); 148 #endif 149 } 150 151 mmap_read_unlock(mm); 152 return 0; 153 } 154 155 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 156 { 157 if (likely(vma->vm_mm == current->mm)) 158 return current->nsproxy->time_ns->vvar_page; 159 160 /* 161 * VM_PFNMAP | VM_IO protect .fault() handler from being called 162 * through interfaces like /proc/$pid/mem or 163 * process_vm_{readv,writev}() as long as there's no .access() 164 * in special_mapping_vmops. 165 * For more details check_vma_flags() and __access_remote_vm() 166 */ 167 WARN(1, "vvar_page accessed remotely"); 168 169 return NULL; 170 } 171 #else 172 static struct page *find_timens_vvar_page(struct vm_area_struct *vma) 173 { 174 return NULL; 175 } 176 #endif 177 178 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 179 struct vm_area_struct *vma, struct vm_fault *vmf) 180 { 181 struct page *timens_page = find_timens_vvar_page(vma); 182 unsigned long pfn; 183 184 switch (vmf->pgoff) { 185 case VVAR_DATA_PAGE_OFFSET: 186 if (timens_page) 187 pfn = page_to_pfn(timens_page); 188 else 189 pfn = sym_to_pfn(vdso_data); 190 break; 191 #ifdef CONFIG_TIME_NS 192 case VVAR_TIMENS_PAGE_OFFSET: 193 /* 194 * If a task belongs to a time namespace then a namespace 195 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 196 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 197 * offset. 198 * See also the comment near timens_setup_vdso_data(). 199 */ 200 if (!timens_page) 201 return VM_FAULT_SIGBUS; 202 pfn = sym_to_pfn(vdso_data); 203 break; 204 #endif /* CONFIG_TIME_NS */ 205 default: 206 return VM_FAULT_SIGBUS; 207 } 208 209 return vmf_insert_pfn(vma, vmf->address, pfn); 210 } 211 212 static int __setup_additional_pages(enum vdso_abi abi, 213 struct mm_struct *mm, 214 struct linux_binprm *bprm, 215 int uses_interp) 216 { 217 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 218 unsigned long gp_flags = 0; 219 void *ret; 220 221 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 222 223 vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; 224 /* Be sure to map the data page */ 225 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; 226 227 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 228 if (IS_ERR_VALUE(vdso_base)) { 229 ret = ERR_PTR(vdso_base); 230 goto up_fail; 231 } 232 233 ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, 234 VM_READ|VM_MAYREAD|VM_PFNMAP, 235 vdso_info[abi].dm); 236 if (IS_ERR(ret)) 237 goto up_fail; 238 239 if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti()) 240 gp_flags = VM_ARM64_BTI; 241 242 vdso_base += VVAR_NR_PAGES * PAGE_SIZE; 243 mm->context.vdso = (void *)vdso_base; 244 ret = _install_special_mapping(mm, vdso_base, vdso_text_len, 245 VM_READ|VM_EXEC|gp_flags| 246 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 247 vdso_info[abi].cm); 248 if (IS_ERR(ret)) 249 goto up_fail; 250 251 return 0; 252 253 up_fail: 254 mm->context.vdso = NULL; 255 return PTR_ERR(ret); 256 } 257 258 #ifdef CONFIG_COMPAT 259 /* 260 * Create and map the vectors page for AArch32 tasks. 261 */ 262 enum aarch32_map { 263 AA32_MAP_VECTORS, /* kuser helpers */ 264 AA32_MAP_SIGPAGE, 265 AA32_MAP_VVAR, 266 AA32_MAP_VDSO, 267 }; 268 269 static struct page *aarch32_vectors_page __ro_after_init; 270 static struct page *aarch32_sig_page __ro_after_init; 271 272 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm, 273 struct vm_area_struct *new_vma) 274 { 275 current->mm->context.sigpage = (void *)new_vma->vm_start; 276 277 return 0; 278 } 279 280 static struct vm_special_mapping aarch32_vdso_maps[] = { 281 [AA32_MAP_VECTORS] = { 282 .name = "[vectors]", /* ABI */ 283 .pages = &aarch32_vectors_page, 284 }, 285 [AA32_MAP_SIGPAGE] = { 286 .name = "[sigpage]", /* ABI */ 287 .pages = &aarch32_sig_page, 288 .mremap = aarch32_sigpage_mremap, 289 }, 290 [AA32_MAP_VVAR] = { 291 .name = "[vvar]", 292 .fault = vvar_fault, 293 }, 294 [AA32_MAP_VDSO] = { 295 .name = "[vdso]", 296 .mremap = vdso_mremap, 297 }, 298 }; 299 300 static int aarch32_alloc_kuser_vdso_page(void) 301 { 302 extern char __kuser_helper_start[], __kuser_helper_end[]; 303 int kuser_sz = __kuser_helper_end - __kuser_helper_start; 304 unsigned long vdso_page; 305 306 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 307 return 0; 308 309 vdso_page = get_zeroed_page(GFP_KERNEL); 310 if (!vdso_page) 311 return -ENOMEM; 312 313 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start, 314 kuser_sz); 315 aarch32_vectors_page = virt_to_page(vdso_page); 316 return 0; 317 } 318 319 #define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1 320 static int aarch32_alloc_sigpage(void) 321 { 322 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; 323 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; 324 __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD); 325 void *sigpage; 326 327 sigpage = (void *)__get_free_page(GFP_KERNEL); 328 if (!sigpage) 329 return -ENOMEM; 330 331 memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison)); 332 memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz); 333 aarch32_sig_page = virt_to_page(sigpage); 334 return 0; 335 } 336 337 static int __init __aarch32_alloc_vdso_pages(void) 338 { 339 340 if (!IS_ENABLED(CONFIG_COMPAT_VDSO)) 341 return 0; 342 343 vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR]; 344 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO]; 345 346 return __vdso_init(VDSO_ABI_AA32); 347 } 348 349 static int __init aarch32_alloc_vdso_pages(void) 350 { 351 int ret; 352 353 ret = __aarch32_alloc_vdso_pages(); 354 if (ret) 355 return ret; 356 357 ret = aarch32_alloc_sigpage(); 358 if (ret) 359 return ret; 360 361 return aarch32_alloc_kuser_vdso_page(); 362 } 363 arch_initcall(aarch32_alloc_vdso_pages); 364 365 static int aarch32_kuser_helpers_setup(struct mm_struct *mm) 366 { 367 void *ret; 368 369 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 370 return 0; 371 372 /* 373 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's 374 * not safe to CoW the page containing the CPU exception vectors. 375 */ 376 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE, 377 VM_READ | VM_EXEC | 378 VM_MAYREAD | VM_MAYEXEC, 379 &aarch32_vdso_maps[AA32_MAP_VECTORS]); 380 381 return PTR_ERR_OR_ZERO(ret); 382 } 383 384 static int aarch32_sigreturn_setup(struct mm_struct *mm) 385 { 386 unsigned long addr; 387 void *ret; 388 389 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); 390 if (IS_ERR_VALUE(addr)) { 391 ret = ERR_PTR(addr); 392 goto out; 393 } 394 395 /* 396 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and 397 * set breakpoints. 398 */ 399 ret = _install_special_mapping(mm, addr, PAGE_SIZE, 400 VM_READ | VM_EXEC | VM_MAYREAD | 401 VM_MAYWRITE | VM_MAYEXEC, 402 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]); 403 if (IS_ERR(ret)) 404 goto out; 405 406 mm->context.sigpage = (void *)addr; 407 408 out: 409 return PTR_ERR_OR_ZERO(ret); 410 } 411 412 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 413 { 414 struct mm_struct *mm = current->mm; 415 int ret; 416 417 if (mmap_write_lock_killable(mm)) 418 return -EINTR; 419 420 ret = aarch32_kuser_helpers_setup(mm); 421 if (ret) 422 goto out; 423 424 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) { 425 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm, 426 uses_interp); 427 if (ret) 428 goto out; 429 } 430 431 ret = aarch32_sigreturn_setup(mm); 432 out: 433 mmap_write_unlock(mm); 434 return ret; 435 } 436 #endif /* CONFIG_COMPAT */ 437 438 enum aarch64_map { 439 AA64_MAP_VVAR, 440 AA64_MAP_VDSO, 441 }; 442 443 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { 444 [AA64_MAP_VVAR] = { 445 .name = "[vvar]", 446 .fault = vvar_fault, 447 }, 448 [AA64_MAP_VDSO] = { 449 .name = "[vdso]", 450 .mremap = vdso_mremap, 451 }, 452 }; 453 454 static int __init vdso_init(void) 455 { 456 vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR]; 457 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO]; 458 459 return __vdso_init(VDSO_ABI_AA64); 460 } 461 arch_initcall(vdso_init); 462 463 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 464 { 465 struct mm_struct *mm = current->mm; 466 int ret; 467 468 if (mmap_write_lock_killable(mm)) 469 return -EINTR; 470 471 ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp); 472 mmap_write_unlock(mm); 473 474 return ret; 475 } 476