arch/arm64/kernel/vdso.c

   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_mremap(const struct vm_special_mapping *sm,
  82                 struct vm_area_struct *new_vma)
  83 {
  84         current->mm->context.vdso = (void *)new_vma->vm_start;
  85
  86         return 0;
  87 }
  88
  89 static int __vdso_init(enum vdso_abi abi)
  90 {
  91         int i;
  92         struct page **vdso_pagelist;
  93         unsigned long pfn;
  94
  95         if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
  96                 pr_err("vDSO is not a valid ELF object!\n");
  97                 return -EINVAL;
  98         }
  99
 100         vdso_info[abi].vdso_pages = (
 101                         vdso_info[abi].vdso_code_end -
 102                         vdso_info[abi].vdso_code_start) >>
 103                         PAGE_SHIFT;
 104
 105         vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
 106                                 sizeof(struct page *),
 107                                 GFP_KERNEL);
 108         if (vdso_pagelist == NULL)
 109                 return -ENOMEM;
 110
 111         /* Grab the vDSO code pages. */
 112         pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
 113
 114         for (i = 0; i < vdso_info[abi].vdso_pages; i++)
 115                 vdso_pagelist[i] = pfn_to_page(pfn + i);
 116
 117         vdso_info[abi].cm->pages = vdso_pagelist;
 118
 119         return 0;
 120 }
 121
 122 #ifdef CONFIG_TIME_NS
 123 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 124 {
 125         return (struct vdso_data *)(vvar_page);
 126 }
 127
 128 /*
 129  * The vvar mapping contains data for a specific time namespace, so when a task
 130  * changes namespace we must unmap its vvar data for the old namespace.
 131  * Subsequent faults will map in data for the new namespace.
 132  *
 133  * For more details see timens_setup_vdso_data().
 134  */
 135 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 136 {
 137         struct mm_struct *mm = task->mm;
 138         struct vm_area_struct *vma;
 139
 140         mmap_read_lock(mm);
 141
 142         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 143                 unsigned long size = vma->vm_end - vma->vm_start;
 144
 145                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
 146                         zap_page_range(vma, vma->vm_start, size);
 147 #ifdef CONFIG_COMPAT_VDSO
 148                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
 149                         zap_page_range(vma, vma->vm_start, size);
 150 #endif
 151         }
 152
 153         mmap_read_unlock(mm);
 154         return 0;
 155 }
 156
 157 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 158 {
 159         if (likely(vma->vm_mm == current->mm))
 160                 return current->nsproxy->time_ns->vvar_page;
 161
 162         /*
 163          * VM_PFNMAP | VM_IO protect .fault() handler from being called
 164          * through interfaces like /proc/$pid/mem or
 165          * process_vm_{readv,writev}() as long as there's no .access()
 166          * in special_mapping_vmops.
 167          * For more details check_vma_flags() and __access_remote_vm()
 168          */
 169         WARN(1, "vvar_page accessed remotely");
 170
 171         return NULL;
 172 }
 173 #else
 174 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 175 {
 176         return NULL;
 177 }
 178 #endif
 179
 180 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 181                              struct vm_area_struct *vma, struct vm_fault *vmf)
 182 {
 183         struct page *timens_page = find_timens_vvar_page(vma);
 184         unsigned long pfn;
 185
 186         switch (vmf->pgoff) {
 187         case VVAR_DATA_PAGE_OFFSET:
 188                 if (timens_page)
 189                         pfn = page_to_pfn(timens_page);
 190                 else
 191                         pfn = sym_to_pfn(vdso_data);
 192                 break;
 193 #ifdef CONFIG_TIME_NS
 194         case VVAR_TIMENS_PAGE_OFFSET:
 195                 /*
 196                  * If a task belongs to a time namespace then a namespace
 197                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 198                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 199                  * offset.
 200                  * See also the comment near timens_setup_vdso_data().
 201                  */
 202                 if (!timens_page)
 203                         return VM_FAULT_SIGBUS;
 204                 pfn = sym_to_pfn(vdso_data);
 205                 break;
 206 #endif /* CONFIG_TIME_NS */
 207         default:
 208                 return VM_FAULT_SIGBUS;
 209         }
 210
 211         return vmf_insert_pfn(vma, vmf->address, pfn);
 212 }
 213
 214 static int __setup_additional_pages(enum vdso_abi abi,
 215                                     struct mm_struct *mm,
 216                                     struct linux_binprm *bprm,
 217                                     int uses_interp)
 218 {
 219         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 220         unsigned long gp_flags = 0;
 221         void *ret;
 222
 223         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 224
 225         vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 226         /* Be sure to map the data page */
 227         vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 228
 229         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 230         if (IS_ERR_VALUE(vdso_base)) {
 231                 ret = ERR_PTR(vdso_base);
 232                 goto up_fail;
 233         }
 234
 235         ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 236                                        VM_READ|VM_MAYREAD|VM_PFNMAP,
 237                                        vdso_info[abi].dm);
 238         if (IS_ERR(ret))
 239                 goto up_fail;
 240
 241         if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
 242                 gp_flags = VM_ARM64_BTI;
 243
 244         vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 245         mm->context.vdso = (void *)vdso_base;
 246         ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 247                                        VM_READ|VM_EXEC|gp_flags|
 248                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 249                                        vdso_info[abi].cm);
 250         if (IS_ERR(ret))
 251                 goto up_fail;
 252
 253         return 0;
 254
 255 up_fail:
 256         mm->context.vdso = NULL;
 257         return PTR_ERR(ret);
 258 }
 259
 260 #ifdef CONFIG_COMPAT
 261 /*
 262  * Create and map the vectors page for AArch32 tasks.
 263  */
 264 enum aarch32_map {
 265         AA32_MAP_VECTORS, /* kuser helpers */
 266         AA32_MAP_SIGPAGE,
 267         AA32_MAP_VVAR,
 268         AA32_MAP_VDSO,
 269 };
 270
 271 static struct page *aarch32_vectors_page __ro_after_init;
 272 static struct page *aarch32_sig_page __ro_after_init;
 273
 274 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
 275                                   struct vm_area_struct *new_vma)
 276 {
 277         current->mm->context.sigpage = (void *)new_vma->vm_start;
 278
 279         return 0;
 280 }
 281
 282 static struct vm_special_mapping aarch32_vdso_maps[] = {
 283         [AA32_MAP_VECTORS] = {
 284                 .name   = "[vectors]", /* ABI */
 285                 .pages  = &aarch32_vectors_page,
 286         },
 287         [AA32_MAP_SIGPAGE] = {
 288                 .name   = "[sigpage]", /* ABI */
 289                 .pages  = &aarch32_sig_page,
 290                 .mremap = aarch32_sigpage_mremap,
 291         },
 292         [AA32_MAP_VVAR] = {
 293                 .name = "[vvar]",
 294                 .fault = vvar_fault,
 295         },
 296         [AA32_MAP_VDSO] = {
 297                 .name = "[vdso]",
 298                 .mremap = vdso_mremap,
 299         },
 300 };
 301
 302 static int aarch32_alloc_kuser_vdso_page(void)
 303 {
 304         extern char __kuser_helper_start[], __kuser_helper_end[];
 305         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 306         unsigned long vdso_page;
 307
 308         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 309                 return 0;
 310
 311         vdso_page = get_zeroed_page(GFP_KERNEL);
 312         if (!vdso_page)
 313                 return -ENOMEM;
 314
 315         memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 316                kuser_sz);
 317         aarch32_vectors_page = virt_to_page(vdso_page);
 318         return 0;
 319 }
 320
 321 #define COMPAT_SIGPAGE_POISON_WORD      0xe7fddef1
 322 static int aarch32_alloc_sigpage(void)
 323 {
 324         extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 325         int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 326         __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
 327         void *sigpage;
 328
 329         sigpage = (void *)__get_free_page(GFP_KERNEL);
 330         if (!sigpage)
 331                 return -ENOMEM;
 332
 333         memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
 334         memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
 335         aarch32_sig_page = virt_to_page(sigpage);
 336         return 0;
 337 }
 338
 339 static int __aarch32_alloc_vdso_pages(void)
 340 {
 341
 342         if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 343                 return 0;
 344
 345         vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 346         vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 347
 348         return __vdso_init(VDSO_ABI_AA32);
 349 }
 350
 351 static int __init aarch32_alloc_vdso_pages(void)
 352 {
 353         int ret;
 354
 355         ret = __aarch32_alloc_vdso_pages();
 356         if (ret)
 357                 return ret;
 358
 359         ret = aarch32_alloc_sigpage();
 360         if (ret)
 361                 return ret;
 362
 363         return aarch32_alloc_kuser_vdso_page();
 364 }
 365 arch_initcall(aarch32_alloc_vdso_pages);
 366
 367 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 368 {
 369         void *ret;
 370
 371         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 372                 return 0;
 373
 374         /*
 375          * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 376          * not safe to CoW the page containing the CPU exception vectors.
 377          */
 378         ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 379                                        VM_READ | VM_EXEC |
 380                                        VM_MAYREAD | VM_MAYEXEC,
 381                                        &aarch32_vdso_maps[AA32_MAP_VECTORS]);
 382
 383         return PTR_ERR_OR_ZERO(ret);
 384 }
 385
 386 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 387 {
 388         unsigned long addr;
 389         void *ret;
 390
 391         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 392         if (IS_ERR_VALUE(addr)) {
 393                 ret = ERR_PTR(addr);
 394                 goto out;
 395         }
 396
 397         /*
 398          * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 399          * set breakpoints.
 400          */
 401         ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 402                                        VM_READ | VM_EXEC | VM_MAYREAD |
 403                                        VM_MAYWRITE | VM_MAYEXEC,
 404                                        &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 405         if (IS_ERR(ret))
 406                 goto out;
 407
 408         mm->context.sigpage = (void *)addr;
 409
 410 out:
 411         return PTR_ERR_OR_ZERO(ret);
 412 }
 413
 414 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 415 {
 416         struct mm_struct *mm = current->mm;
 417         int ret;
 418
 419         if (mmap_write_lock_killable(mm))
 420                 return -EINTR;
 421
 422         ret = aarch32_kuser_helpers_setup(mm);
 423         if (ret)
 424                 goto out;
 425
 426         if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
 427                 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
 428                                                uses_interp);
 429                 if (ret)
 430                         goto out;
 431         }
 432
 433         ret = aarch32_sigreturn_setup(mm);
 434 out:
 435         mmap_write_unlock(mm);
 436         return ret;
 437 }
 438 #endif /* CONFIG_COMPAT */
 439
 440 enum aarch64_map {
 441         AA64_MAP_VVAR,
 442         AA64_MAP_VDSO,
 443 };
 444
 445 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 446         [AA64_MAP_VVAR] = {
 447                 .name   = "[vvar]",
 448                 .fault = vvar_fault,
 449         },
 450         [AA64_MAP_VDSO] = {
 451                 .name   = "[vdso]",
 452                 .mremap = vdso_mremap,
 453         },
 454 };
 455
 456 static int __init vdso_init(void)
 457 {
 458         vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 459         vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
 460
 461         return __vdso_init(VDSO_ABI_AA64);
 462 }
 463 arch_initcall(vdso_init);
 464
 465 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 466 {
 467         struct mm_struct *mm = current->mm;
 468         int ret;
 469
 470         if (mmap_write_lock_killable(mm))
 471                 return -EINTR;
 472
 473         ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
 474         mmap_write_unlock(mm);
 475
 476         return ret;
 477 }