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/vmalloc.h> 23 #include <vdso/datapage.h> 24 #include <vdso/helpers.h> 25 #include <vdso/vsyscall.h> 26 27 #include <asm/cacheflush.h> 28 #include <asm/signal32.h> 29 #include <asm/vdso.h> 30 31 enum vdso_abi { 32 VDSO_ABI_AA64, 33 VDSO_ABI_AA32, 34 }; 35 36 struct vdso_abi_info { 37 const char *name; 38 const char *vdso_code_start; 39 const char *vdso_code_end; 40 unsigned long vdso_pages; 41 /* Code Mapping */ 42 struct vm_special_mapping *cm; 43 }; 44 45 static struct vdso_abi_info vdso_info[] __ro_after_init = { 46 [VDSO_ABI_AA64] = { 47 .name = "vdso", 48 .vdso_code_start = vdso_start, 49 .vdso_code_end = vdso_end, 50 }, 51 #ifdef CONFIG_COMPAT_VDSO 52 [VDSO_ABI_AA32] = { 53 .name = "vdso32", 54 .vdso_code_start = vdso32_start, 55 .vdso_code_end = vdso32_end, 56 }, 57 #endif /* CONFIG_COMPAT_VDSO */ 58 }; 59 60 /* 61 * The vDSO data page. 62 */ 63 static union vdso_data_store vdso_data_store __page_aligned_data; 64 struct vdso_data *vdso_data = vdso_data_store.data; 65 66 static int vdso_mremap(const struct vm_special_mapping *sm, 67 struct vm_area_struct *new_vma) 68 { 69 current->mm->context.vdso = (void *)new_vma->vm_start; 70 71 return 0; 72 } 73 74 static int __init __vdso_init(enum vdso_abi abi) 75 { 76 int i; 77 struct page **vdso_pagelist; 78 unsigned long pfn; 79 80 if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) { 81 pr_err("vDSO is not a valid ELF object!\n"); 82 return -EINVAL; 83 } 84 85 vdso_info[abi].vdso_pages = ( 86 vdso_info[abi].vdso_code_end - 87 vdso_info[abi].vdso_code_start) >> 88 PAGE_SHIFT; 89 90 vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, 91 sizeof(struct page *), 92 GFP_KERNEL); 93 if (vdso_pagelist == NULL) 94 return -ENOMEM; 95 96 /* Grab the vDSO code pages. */ 97 pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); 98 99 for (i = 0; i < vdso_info[abi].vdso_pages; i++) 100 vdso_pagelist[i] = pfn_to_page(pfn + i); 101 102 vdso_info[abi].cm->pages = vdso_pagelist; 103 104 return 0; 105 } 106 107 #ifdef CONFIG_TIME_NS 108 struct vdso_data *arch_get_vdso_data(void *vvar_page) 109 { 110 return (struct vdso_data *)(vvar_page); 111 } 112 113 static const struct vm_special_mapping vvar_map; 114 115 /* 116 * The vvar mapping contains data for a specific time namespace, so when a task 117 * changes namespace we must unmap its vvar data for the old namespace. 118 * Subsequent faults will map in data for the new namespace. 119 * 120 * For more details see timens_setup_vdso_data(). 121 */ 122 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 123 { 124 struct mm_struct *mm = task->mm; 125 struct vm_area_struct *vma; 126 VMA_ITERATOR(vmi, mm, 0); 127 128 mmap_read_lock(mm); 129 130 for_each_vma(vmi, vma) { 131 if (vma_is_special_mapping(vma, &vvar_map)) 132 zap_vma_pages(vma); 133 } 134 135 mmap_read_unlock(mm); 136 return 0; 137 } 138 #endif 139 140 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 141 struct vm_area_struct *vma, struct vm_fault *vmf) 142 { 143 struct page *timens_page = find_timens_vvar_page(vma); 144 unsigned long pfn; 145 146 switch (vmf->pgoff) { 147 case VVAR_DATA_PAGE_OFFSET: 148 if (timens_page) 149 pfn = page_to_pfn(timens_page); 150 else 151 pfn = sym_to_pfn(vdso_data); 152 break; 153 #ifdef CONFIG_TIME_NS 154 case VVAR_TIMENS_PAGE_OFFSET: 155 /* 156 * If a task belongs to a time namespace then a namespace 157 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 158 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 159 * offset. 160 * See also the comment near timens_setup_vdso_data(). 161 */ 162 if (!timens_page) 163 return VM_FAULT_SIGBUS; 164 pfn = sym_to_pfn(vdso_data); 165 break; 166 #endif /* CONFIG_TIME_NS */ 167 default: 168 return VM_FAULT_SIGBUS; 169 } 170 171 return vmf_insert_pfn(vma, vmf->address, pfn); 172 } 173 174 static const struct vm_special_mapping vvar_map = { 175 .name = "[vvar]", 176 .fault = vvar_fault, 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 &vvar_map); 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_VDSO, 233 }; 234 235 static struct page *aarch32_vectors_page __ro_after_init; 236 static struct page *aarch32_sig_page __ro_after_init; 237 238 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm, 239 struct vm_area_struct *new_vma) 240 { 241 current->mm->context.sigpage = (void *)new_vma->vm_start; 242 243 return 0; 244 } 245 246 static struct vm_special_mapping aarch32_vdso_maps[] = { 247 [AA32_MAP_VECTORS] = { 248 .name = "[vectors]", /* ABI */ 249 .pages = &aarch32_vectors_page, 250 }, 251 [AA32_MAP_SIGPAGE] = { 252 .name = "[sigpage]", /* ABI */ 253 .pages = &aarch32_sig_page, 254 .mremap = aarch32_sigpage_mremap, 255 }, 256 [AA32_MAP_VDSO] = { 257 .name = "[vdso]", 258 .mremap = vdso_mremap, 259 }, 260 }; 261 262 static int aarch32_alloc_kuser_vdso_page(void) 263 { 264 extern char __kuser_helper_start[], __kuser_helper_end[]; 265 int kuser_sz = __kuser_helper_end - __kuser_helper_start; 266 unsigned long vdso_page; 267 268 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 269 return 0; 270 271 vdso_page = get_zeroed_page(GFP_KERNEL); 272 if (!vdso_page) 273 return -ENOMEM; 274 275 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start, 276 kuser_sz); 277 aarch32_vectors_page = virt_to_page((void *)vdso_page); 278 return 0; 279 } 280 281 #define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1 282 static int aarch32_alloc_sigpage(void) 283 { 284 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; 285 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; 286 __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD); 287 void *sigpage; 288 289 sigpage = (void *)__get_free_page(GFP_KERNEL); 290 if (!sigpage) 291 return -ENOMEM; 292 293 memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison)); 294 memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz); 295 aarch32_sig_page = virt_to_page(sigpage); 296 return 0; 297 } 298 299 static int __init __aarch32_alloc_vdso_pages(void) 300 { 301 302 if (!IS_ENABLED(CONFIG_COMPAT_VDSO)) 303 return 0; 304 305 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO]; 306 307 return __vdso_init(VDSO_ABI_AA32); 308 } 309 310 static int __init aarch32_alloc_vdso_pages(void) 311 { 312 int ret; 313 314 ret = __aarch32_alloc_vdso_pages(); 315 if (ret) 316 return ret; 317 318 ret = aarch32_alloc_sigpage(); 319 if (ret) 320 return ret; 321 322 return aarch32_alloc_kuser_vdso_page(); 323 } 324 arch_initcall(aarch32_alloc_vdso_pages); 325 326 static int aarch32_kuser_helpers_setup(struct mm_struct *mm) 327 { 328 void *ret; 329 330 if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) 331 return 0; 332 333 /* 334 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's 335 * not safe to CoW the page containing the CPU exception vectors. 336 */ 337 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE, 338 VM_READ | VM_EXEC | 339 VM_MAYREAD | VM_MAYEXEC, 340 &aarch32_vdso_maps[AA32_MAP_VECTORS]); 341 342 return PTR_ERR_OR_ZERO(ret); 343 } 344 345 static int aarch32_sigreturn_setup(struct mm_struct *mm) 346 { 347 unsigned long addr; 348 void *ret; 349 350 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); 351 if (IS_ERR_VALUE(addr)) { 352 ret = ERR_PTR(addr); 353 goto out; 354 } 355 356 /* 357 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and 358 * set breakpoints. 359 */ 360 ret = _install_special_mapping(mm, addr, PAGE_SIZE, 361 VM_READ | VM_EXEC | VM_MAYREAD | 362 VM_MAYWRITE | VM_MAYEXEC, 363 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]); 364 if (IS_ERR(ret)) 365 goto out; 366 367 mm->context.sigpage = (void *)addr; 368 369 out: 370 return PTR_ERR_OR_ZERO(ret); 371 } 372 373 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 374 { 375 struct mm_struct *mm = current->mm; 376 int ret; 377 378 if (mmap_write_lock_killable(mm)) 379 return -EINTR; 380 381 ret = aarch32_kuser_helpers_setup(mm); 382 if (ret) 383 goto out; 384 385 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) { 386 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm, 387 uses_interp); 388 if (ret) 389 goto out; 390 } 391 392 ret = aarch32_sigreturn_setup(mm); 393 out: 394 mmap_write_unlock(mm); 395 return ret; 396 } 397 #endif /* CONFIG_COMPAT */ 398 399 static struct vm_special_mapping aarch64_vdso_map __ro_after_init = { 400 .name = "[vdso]", 401 .mremap = vdso_mremap, 402 }; 403 404 static int __init vdso_init(void) 405 { 406 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_map; 407 408 return __vdso_init(VDSO_ABI_AA64); 409 } 410 arch_initcall(vdso_init); 411 412 int arch_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 = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp); 421 mmap_write_unlock(mm); 422 423 return ret; 424 } 425