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 __init __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         VMA_ITERATOR(vmi, mm, 0);
 140
 141         mmap_read_lock(mm);
 142
 143         for_each_vma(vmi, vma) {
 144                 unsigned long size = vma->vm_end - vma->vm_start;
 145
 146                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
 147                         zap_page_range(vma, vma->vm_start, size);
 148 #ifdef CONFIG_COMPAT_VDSO
 149                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
 150                         zap_page_range(vma, vma->vm_start, size);
 151 #endif
 152         }
 153
 154         mmap_read_unlock(mm);
 155         return 0;
 156 }
 157
 158 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 159 {
 160         if (likely(vma->vm_mm == current->mm))
 161                 return current->nsproxy->time_ns->vvar_page;
 162
 163         /*
 164          * VM_PFNMAP | VM_IO protect .fault() handler from being called
 165          * through interfaces like /proc/$pid/mem or
 166          * process_vm_{readv,writev}() as long as there's no .access()
 167          * in special_mapping_vmops.
 168          * For more details check_vma_flags() and __access_remote_vm()
 169          */
 170         WARN(1, "vvar_page accessed remotely");
 171
 172         return NULL;
 173 }
 174 #else
 175 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 176 {
 177         return NULL;
 178 }
 179 #endif
 180
 181 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 182                              struct vm_area_struct *vma, struct vm_fault *vmf)
 183 {
 184         struct page *timens_page = find_timens_vvar_page(vma);
 185         unsigned long pfn;
 186
 187         switch (vmf->pgoff) {
 188         case VVAR_DATA_PAGE_OFFSET:
 189                 if (timens_page)
 190                         pfn = page_to_pfn(timens_page);
 191                 else
 192                         pfn = sym_to_pfn(vdso_data);
 193                 break;
 194 #ifdef CONFIG_TIME_NS
 195         case VVAR_TIMENS_PAGE_OFFSET:
 196                 /*
 197                  * If a task belongs to a time namespace then a namespace
 198                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 199                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 200                  * offset.
 201                  * See also the comment near timens_setup_vdso_data().
 202                  */
 203                 if (!timens_page)
 204                         return VM_FAULT_SIGBUS;
 205                 pfn = sym_to_pfn(vdso_data);
 206                 break;
 207 #endif /* CONFIG_TIME_NS */
 208         default:
 209                 return VM_FAULT_SIGBUS;
 210         }
 211
 212         return vmf_insert_pfn(vma, vmf->address, pfn);
 213 }
 214
 215 static int __setup_additional_pages(enum vdso_abi abi,
 216                                     struct mm_struct *mm,
 217                                     struct linux_binprm *bprm,
 218                                     int uses_interp)
 219 {
 220         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 221         unsigned long gp_flags = 0;
 222         void *ret;
 223
 224         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 225
 226         vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 227         /* Be sure to map the data page */
 228         vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 229
 230         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 231         if (IS_ERR_VALUE(vdso_base)) {
 232                 ret = ERR_PTR(vdso_base);
 233                 goto up_fail;
 234         }
 235
 236         ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 237                                        VM_READ|VM_MAYREAD|VM_PFNMAP,
 238                                        vdso_info[abi].dm);
 239         if (IS_ERR(ret))
 240                 goto up_fail;
 241
 242         if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
 243                 gp_flags = VM_ARM64_BTI;
 244
 245         vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 246         mm->context.vdso = (void *)vdso_base;
 247         ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 248                                        VM_READ|VM_EXEC|gp_flags|
 249                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 250                                        vdso_info[abi].cm);
 251         if (IS_ERR(ret))
 252                 goto up_fail;
 253
 254         return 0;
 255
 256 up_fail:
 257         mm->context.vdso = NULL;
 258         return PTR_ERR(ret);
 259 }
 260
 261 #ifdef CONFIG_COMPAT
 262 /*
 263  * Create and map the vectors page for AArch32 tasks.
 264  */
 265 enum aarch32_map {
 266         AA32_MAP_VECTORS, /* kuser helpers */
 267         AA32_MAP_SIGPAGE,
 268         AA32_MAP_VVAR,
 269         AA32_MAP_VDSO,
 270 };
 271
 272 static struct page *aarch32_vectors_page __ro_after_init;
 273 static struct page *aarch32_sig_page __ro_after_init;
 274
 275 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
 276                                   struct vm_area_struct *new_vma)
 277 {
 278         current->mm->context.sigpage = (void *)new_vma->vm_start;
 279
 280         return 0;
 281 }
 282
 283 static struct vm_special_mapping aarch32_vdso_maps[] = {
 284         [AA32_MAP_VECTORS] = {
 285                 .name   = "[vectors]", /* ABI */
 286                 .pages  = &aarch32_vectors_page,
 287         },
 288         [AA32_MAP_SIGPAGE] = {
 289                 .name   = "[sigpage]", /* ABI */
 290                 .pages  = &aarch32_sig_page,
 291                 .mremap = aarch32_sigpage_mremap,
 292         },
 293         [AA32_MAP_VVAR] = {
 294                 .name = "[vvar]",
 295                 .fault = vvar_fault,
 296         },
 297         [AA32_MAP_VDSO] = {
 298                 .name = "[vdso]",
 299                 .mremap = vdso_mremap,
 300         },
 301 };
 302
 303 static int aarch32_alloc_kuser_vdso_page(void)
 304 {
 305         extern char __kuser_helper_start[], __kuser_helper_end[];
 306         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 307         unsigned long vdso_page;
 308
 309         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 310                 return 0;
 311
 312         vdso_page = get_zeroed_page(GFP_KERNEL);
 313         if (!vdso_page)
 314                 return -ENOMEM;
 315
 316         memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 317                kuser_sz);
 318         aarch32_vectors_page = virt_to_page(vdso_page);
 319         return 0;
 320 }
 321
 322 #define COMPAT_SIGPAGE_POISON_WORD      0xe7fddef1
 323 static int aarch32_alloc_sigpage(void)
 324 {
 325         extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 326         int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 327         __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
 328         void *sigpage;
 329
 330         sigpage = (void *)__get_free_page(GFP_KERNEL);
 331         if (!sigpage)
 332                 return -ENOMEM;
 333
 334         memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
 335         memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
 336         aarch32_sig_page = virt_to_page(sigpage);
 337         return 0;
 338 }
 339
 340 static int __init __aarch32_alloc_vdso_pages(void)
 341 {
 342
 343         if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 344                 return 0;
 345
 346         vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 347         vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 348
 349         return __vdso_init(VDSO_ABI_AA32);
 350 }
 351
 352 static int __init aarch32_alloc_vdso_pages(void)
 353 {
 354         int ret;
 355
 356         ret = __aarch32_alloc_vdso_pages();
 357         if (ret)
 358                 return ret;
 359
 360         ret = aarch32_alloc_sigpage();
 361         if (ret)
 362                 return ret;
 363
 364         return aarch32_alloc_kuser_vdso_page();
 365 }
 366 arch_initcall(aarch32_alloc_vdso_pages);
 367
 368 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 369 {
 370         void *ret;
 371
 372         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 373                 return 0;
 374
 375         /*
 376          * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 377          * not safe to CoW the page containing the CPU exception vectors.
 378          */
 379         ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 380                                        VM_READ | VM_EXEC |
 381                                        VM_MAYREAD | VM_MAYEXEC,
 382                                        &aarch32_vdso_maps[AA32_MAP_VECTORS]);
 383
 384         return PTR_ERR_OR_ZERO(ret);
 385 }
 386
 387 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 388 {
 389         unsigned long addr;
 390         void *ret;
 391
 392         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 393         if (IS_ERR_VALUE(addr)) {
 394                 ret = ERR_PTR(addr);
 395                 goto out;
 396         }
 397
 398         /*
 399          * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 400          * set breakpoints.
 401          */
 402         ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 403                                        VM_READ | VM_EXEC | VM_MAYREAD |
 404                                        VM_MAYWRITE | VM_MAYEXEC,
 405                                        &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 406         if (IS_ERR(ret))
 407                 goto out;
 408
 409         mm->context.sigpage = (void *)addr;
 410
 411 out:
 412         return PTR_ERR_OR_ZERO(ret);
 413 }
 414
 415 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 416 {
 417         struct mm_struct *mm = current->mm;
 418         int ret;
 419
 420         if (mmap_write_lock_killable(mm))
 421                 return -EINTR;
 422
 423         ret = aarch32_kuser_helpers_setup(mm);
 424         if (ret)
 425                 goto out;
 426
 427         if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
 428                 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
 429                                                uses_interp);
 430                 if (ret)
 431                         goto out;
 432         }
 433
 434         ret = aarch32_sigreturn_setup(mm);
 435 out:
 436         mmap_write_unlock(mm);
 437         return ret;
 438 }
 439 #endif /* CONFIG_COMPAT */
 440
 441 enum aarch64_map {
 442         AA64_MAP_VVAR,
 443         AA64_MAP_VDSO,
 444 };
 445
 446 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 447         [AA64_MAP_VVAR] = {
 448                 .name   = "[vvar]",
 449                 .fault = vvar_fault,
 450         },
 451         [AA64_MAP_VDSO] = {
 452                 .name   = "[vdso]",
 453                 .mremap = vdso_mremap,
 454         },
 455 };
 456
 457 static int __init vdso_init(void)
 458 {
 459         vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 460         vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
 461
 462         return __vdso_init(VDSO_ABI_AA64);
 463 }
 464 arch_initcall(vdso_init);
 465
 466 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 467 {
 468         struct mm_struct *mm = current->mm;
 469         int ret;
 470
 471         if (mmap_write_lock_killable(mm))
 472                 return -EINTR;
 473
 474         ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
 475         mmap_write_unlock(mm);
 476
 477         return ret;
 478 }