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 struct vdso_abi_info { 38 const char *name; 39 const char *vdso_code_start; 40 const char *vdso_code_end; 41 unsigned long vdso_pages; 42 /* Data Mapping */ 43 struct vm_special_mapping *dm; 44 /* Code Mapping */ 45 struct vm_special_mapping *cm; 46 }; 47 48 static struct vdso_abi_info vdso_info[] __ro_after_init = { 49 [VDSO_ABI_AA64] = { 50 .name = "vdso", 51 .vdso_code_start = vdso_start, 52 .vdso_code_end = vdso_end, 53 }, 54 #ifdef CONFIG_COMPAT_VDSO 55 [VDSO_ABI_AA32] = { 56 .name = "vdso32", 57 .vdso_code_start = vdso32_start, 58 .vdso_code_end = vdso32_end, 59 }, 60 #endif /* CONFIG_COMPAT_VDSO */ 61 }; 62 63 /* 64 * The vDSO data page. 65 */ 66 static union vdso_data_store vdso_data_store __page_aligned_data; 67 struct vdso_data *vdso_data = vdso_data_store.data; 68 69 static int vdso_mremap(const struct vm_special_mapping *sm, 70 struct vm_area_struct *new_vma) 71 { 72 current->mm->context.vdso = (void *)new_vma->vm_start; 73 74 return 0; 75 } 76 77 static int __init __vdso_init(enum vdso_abi abi) 78 { 79 int i; 80 struct page **vdso_pagelist; 81 unsigned long pfn; 82 83 if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) { 84 pr_err("vDSO is not a valid ELF object!\n"); 85 return -EINVAL; 86 } 87 88 vdso_info[abi].vdso_pages = ( 89 vdso_info[abi].vdso_code_end - 90 vdso_info[abi].vdso_code_start) >> 91 PAGE_SHIFT; 92 93 vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, 94 sizeof(struct page *), 95 GFP_KERNEL); 96 if (vdso_pagelist == NULL) 97 return -ENOMEM; 98 99 /* Grab the vDSO code pages. */ 100 pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); 101 102 for (i = 0; i < vdso_info[abi].vdso_pages; i++) 103 vdso_pagelist[i] = pfn_to_page(pfn + i); 104 105 vdso_info[abi].cm->pages = vdso_pagelist; 106 107 return 0; 108 } 109 110 #ifdef CONFIG_TIME_NS 111 struct vdso_data *arch_get_vdso_data(void *vvar_page) 112 { 113 return (struct vdso_data *)(vvar_page); 114 } 115 116 /* 117 * The vvar mapping contains data for a specific time namespace, so when a task 118 * changes namespace we must unmap its vvar data for the old namespace. 119 * Subsequent faults will map in data for the new namespace. 120 * 121 * For more details see timens_setup_vdso_data(). 122 */ 123 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 124 { 125 struct mm_struct *mm = task->mm; 126 struct vm_area_struct *vma; 127 VMA_ITERATOR(vmi, mm, 0); 128 129 mmap_read_lock(mm); 130 131 for_each_vma(vmi, vma) { 132 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm)) 133 zap_vma_pages(vma); 134 #ifdef CONFIG_COMPAT_VDSO 135 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm)) 136 zap_vma_pages(vma); 137 #endif 138 } 139 140 mmap_read_unlock(mm); 141 return 0; 142 } 143 #endif 144 145 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 146 struct vm_area_struct *vma, struct vm_fault *vmf) 147 { 148 struct page *timens_page = find_timens_vvar_page(vma); 149 unsigned long pfn; 150 151 switch (vmf->pgoff) { 152 case VVAR_DATA_PAGE_OFFSET: 153 if (timens_page) 154 pfn = page_to_pfn(timens_page); 155 else 156 pfn = sym_to_pfn(vdso_data); 157 break; 158 #ifdef CONFIG_TIME_NS 159 case VVAR_TIMENS_PAGE_OFFSET: 160 /* 161 * If a task belongs to a time namespace then a namespace 162 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 163 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 164 * offset. 165 * See also the comment near timens_setup_vdso_data(). 166 */ 167 if (!timens_page) 168 return VM_FAULT_SIGBUS; 169 pfn = sym_to_pfn(vdso_data); 170 break; 171 #endif /* CONFIG_TIME_NS */ 172 default: 173 return VM_FAULT_SIGBUS; 174 } 175 176 return vmf_insert_pfn(vma, vmf->address, pfn); 177 } 178 179 static int __setup_additional_pages(enum vdso_abi abi, 180 struct mm_struct *mm, 181 struct linux_binprm *bprm, 182 int uses_interp) 183 { 184 unsigned long vdso_base, vdso_text_len, vdso_mapping_len; 185 unsigned long gp_flags = 0; 186 void *ret; 187 188 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); 189 190 vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; 191 /* Be sure to map the data page */ 192 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; 193 194 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); 195 if (IS_ERR_VALUE(vdso_base)) { 196 ret = ERR_PTR(vdso_base); 197 goto up_fail; 198 } 199 200 ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, 201 VM_READ|VM_MAYREAD|VM_PFNMAP, 202 vdso_info[abi].dm); 203 if (IS_ERR(ret)) 204 goto up_fail; 205 206 if (system_supports_bti_kernel()) 207 gp_flags = VM_ARM64_BTI; 208 209 vdso_base += VVAR_NR_PAGES * PAGE_SIZE; 210 mm->context.vdso = (void *)vdso_base; 211 ret = _install_special_mapping(mm, vdso_base, vdso_text_len, 212 VM_READ|VM_EXEC|gp_flags| 213 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 214 vdso_info[abi].cm); 215 if (IS_ERR(ret)) 216 goto up_fail; 217 218 return 0; 219 220 up_fail: 221 mm->context.vdso = NULL; 222 return PTR_ERR(ret); 223 } 224 225 #ifdef CONFIG_COMPAT 226 /* 227 * Create and map the vectors page for AArch32 tasks. 228 */ 229 enum aarch32_map { 230 AA32_MAP_VECTORS, /* kuser helpers */ 231 AA32_MAP_SIGPAGE, 232 AA32_MAP_VVAR, 233 AA32_MAP_VDSO, 234 }; 235 236 static struct page *aarch32_vectors_page __ro_after_init; 237 static struct page *aarch32_sig_page __ro_after_init; 238 239 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm, 240 struct vm_area_struct *new_vma) 241 { 242 current->mm->context.sigpage = (void *)new_vma->vm_start; 243 244 return 0; 245 } 246 247 static struct vm_special_mapping aarch32_vdso_maps[] = { 248 [AA32_MAP_VECTORS] = { 249 .name = "[vectors]", /* ABI */ 250 .pages = &aarch32_vectors_page, 251 }, 252 [AA32_MAP_SIGPAGE] = { 253 .name = "[sigpage]", /* ABI */ 254 .pages = &aarch32_sig_page, 255 .mremap = aarch32_sigpage_mremap, 256 }, 257 [AA32_MAP_VVAR] = { 258 .name = "[vvar]", 259 .fault = vvar_fault, 260 }, 261 [AA32_MAP_VDSO] = { 262 .name = "[vdso]", 263 .mremap = vdso_mremap, 264 }, 265 }; 266 267 static int aarch32_alloc_kuser_vdso_page(void) 268 { 269 extern char __kuser_helper_start[], __kuser_helper_end[]; 270 int kuser_sz = __kuser_helper_end - __kuser_helper_start; 271 unsigned long vdso_page; 272 273 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 274 return 0; 275 276 vdso_page = get_zeroed_page(GFP_KERNEL); 277 if (!vdso_page) 278 return -ENOMEM; 279 280 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start, 281 kuser_sz); 282 aarch32_vectors_page = virt_to_page((void *)vdso_page); 283 return 0; 284 } 285 286 #define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1 287 static int aarch32_alloc_sigpage(void) 288 { 289 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; 290 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; 291 __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD); 292 void *sigpage; 293 294 sigpage = (void *)__get_free_page(GFP_KERNEL); 295 if (!sigpage) 296 return -ENOMEM; 297 298 memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison)); 299 memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz); 300 aarch32_sig_page = virt_to_page(sigpage); 301 return 0; 302 } 303 304 static int __init __aarch32_alloc_vdso_pages(void) 305 { 306 307 if (!IS_ENABLED(CONFIG_COMPAT_VDSO)) 308 return 0; 309 310 vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR]; 311 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO]; 312 313 return __vdso_init(VDSO_ABI_AA32); 314 } 315 316 static int __init aarch32_alloc_vdso_pages(void) 317 { 318 int ret; 319 320 ret = __aarch32_alloc_vdso_pages(); 321 if (ret) 322 return ret; 323 324 ret = aarch32_alloc_sigpage(); 325 if (ret) 326 return ret; 327 328 return aarch32_alloc_kuser_vdso_page(); 329 } 330 arch_initcall(aarch32_alloc_vdso_pages); 331 332 static int aarch32_kuser_helpers_setup(struct mm_struct *mm) 333 { 334 void *ret; 335 336 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 337 return 0; 338 339 /* 340 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's 341 * not safe to CoW the page containing the CPU exception vectors. 342 */ 343 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE, 344 VM_READ | VM_EXEC | 345 VM_MAYREAD | VM_MAYEXEC, 346 &aarch32_vdso_maps[AA32_MAP_VECTORS]); 347 348 return PTR_ERR_OR_ZERO(ret); 349 } 350 351 static int aarch32_sigreturn_setup(struct mm_struct *mm) 352 { 353 unsigned long addr; 354 void *ret; 355 356 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); 357 if (IS_ERR_VALUE(addr)) { 358 ret = ERR_PTR(addr); 359 goto out; 360 } 361 362 /* 363 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and 364 * set breakpoints. 365 */ 366 ret = _install_special_mapping(mm, addr, PAGE_SIZE, 367 VM_READ | VM_EXEC | VM_MAYREAD | 368 VM_MAYWRITE | VM_MAYEXEC, 369 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]); 370 if (IS_ERR(ret)) 371 goto out; 372 373 mm->context.sigpage = (void *)addr; 374 375 out: 376 return PTR_ERR_OR_ZERO(ret); 377 } 378 379 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 380 { 381 struct mm_struct *mm = current->mm; 382 int ret; 383 384 if (mmap_write_lock_killable(mm)) 385 return -EINTR; 386 387 ret = aarch32_kuser_helpers_setup(mm); 388 if (ret) 389 goto out; 390 391 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) { 392 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm, 393 uses_interp); 394 if (ret) 395 goto out; 396 } 397 398 ret = aarch32_sigreturn_setup(mm); 399 out: 400 mmap_write_unlock(mm); 401 return ret; 402 } 403 #endif /* CONFIG_COMPAT */ 404 405 enum aarch64_map { 406 AA64_MAP_VVAR, 407 AA64_MAP_VDSO, 408 }; 409 410 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { 411 [AA64_MAP_VVAR] = { 412 .name = "[vvar]", 413 .fault = vvar_fault, 414 }, 415 [AA64_MAP_VDSO] = { 416 .name = "[vdso]", 417 .mremap = vdso_mremap, 418 }, 419 }; 420 421 static int __init vdso_init(void) 422 { 423 vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR]; 424 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO]; 425 426 return __vdso_init(VDSO_ABI_AA64); 427 } 428 arch_initcall(vdso_init); 429 430 int arch_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 = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp); 439 mmap_write_unlock(mm); 440 441 return ret; 442 } 443