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 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 vdso_data_store vdso_data_store __page_aligned_data;
  73 struct vdso_data *vdso_data = vdso_data_store.data;
  74
  75 static int vdso_mremap(const struct vm_special_mapping *sm,
  76                 struct vm_area_struct *new_vma)
  77 {
  78         current->mm->context.vdso = (void *)new_vma->vm_start;
  79
  80         return 0;
  81 }
  82
  83 static int __init __vdso_init(enum vdso_abi abi)
  84 {
  85         int i;
  86         struct page **vdso_pagelist;
  87         unsigned long pfn;
  88
  89         if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
  90                 pr_err("vDSO is not a valid ELF object!\n");
  91                 return -EINVAL;
  92         }
  93
  94         vdso_info[abi].vdso_pages = (
  95                         vdso_info[abi].vdso_code_end -
  96                         vdso_info[abi].vdso_code_start) >>
  97                         PAGE_SHIFT;
  98
  99         vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
 100                                 sizeof(struct page *),
 101                                 GFP_KERNEL);
 102         if (vdso_pagelist == NULL)
 103                 return -ENOMEM;
 104
 105         /* Grab the vDSO code pages. */
 106         pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
 107
 108         for (i = 0; i < vdso_info[abi].vdso_pages; i++)
 109                 vdso_pagelist[i] = pfn_to_page(pfn + i);
 110
 111         vdso_info[abi].cm->pages = vdso_pagelist;
 112
 113         return 0;
 114 }
 115
 116 #ifdef CONFIG_TIME_NS
 117 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 118 {
 119         return (struct vdso_data *)(vvar_page);
 120 }
 121
 122 /*
 123  * The vvar mapping contains data for a specific time namespace, so when a task
 124  * changes namespace we must unmap its vvar data for the old namespace.
 125  * Subsequent faults will map in data for the new namespace.
 126  *
 127  * For more details see timens_setup_vdso_data().
 128  */
 129 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 130 {
 131         struct mm_struct *mm = task->mm;
 132         struct vm_area_struct *vma;
 133         VMA_ITERATOR(vmi, mm, 0);
 134
 135         mmap_read_lock(mm);
 136
 137         for_each_vma(vmi, vma) {
 138                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
 139                         zap_vma_pages(vma);
 140 #ifdef CONFIG_COMPAT_VDSO
 141                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
 142                         zap_vma_pages(vma);
 143 #endif
 144         }
 145
 146         mmap_read_unlock(mm);
 147         return 0;
 148 }
 149 #endif
 150
 151 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 152                              struct vm_area_struct *vma, struct vm_fault *vmf)
 153 {
 154         struct page *timens_page = find_timens_vvar_page(vma);
 155         unsigned long pfn;
 156
 157         switch (vmf->pgoff) {
 158         case VVAR_DATA_PAGE_OFFSET:
 159                 if (timens_page)
 160                         pfn = page_to_pfn(timens_page);
 161                 else
 162                         pfn = sym_to_pfn(vdso_data);
 163                 break;
 164 #ifdef CONFIG_TIME_NS
 165         case VVAR_TIMENS_PAGE_OFFSET:
 166                 /*
 167                  * If a task belongs to a time namespace then a namespace
 168                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 169                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 170                  * offset.
 171                  * See also the comment near timens_setup_vdso_data().
 172                  */
 173                 if (!timens_page)
 174                         return VM_FAULT_SIGBUS;
 175                 pfn = sym_to_pfn(vdso_data);
 176                 break;
 177 #endif /* CONFIG_TIME_NS */
 178         default:
 179                 return VM_FAULT_SIGBUS;
 180         }
 181
 182         return vmf_insert_pfn(vma, vmf->address, pfn);
 183 }
 184
 185 static int __setup_additional_pages(enum vdso_abi abi,
 186                                     struct mm_struct *mm,
 187                                     struct linux_binprm *bprm,
 188                                     int uses_interp)
 189 {
 190         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 191         unsigned long gp_flags = 0;
 192         void *ret;
 193
 194         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 195
 196         vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 197         /* Be sure to map the data page */
 198         vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 199
 200         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 201         if (IS_ERR_VALUE(vdso_base)) {
 202                 ret = ERR_PTR(vdso_base);
 203                 goto up_fail;
 204         }
 205
 206         ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 207                                        VM_READ|VM_MAYREAD|VM_PFNMAP,
 208                                        vdso_info[abi].dm);
 209         if (IS_ERR(ret))
 210                 goto up_fail;
 211
 212         if (system_supports_bti_kernel())
 213                 gp_flags = VM_ARM64_BTI;
 214
 215         vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 216         mm->context.vdso = (void *)vdso_base;
 217         ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 218                                        VM_READ|VM_EXEC|gp_flags|
 219                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 220                                        vdso_info[abi].cm);
 221         if (IS_ERR(ret))
 222                 goto up_fail;
 223
 224         return 0;
 225
 226 up_fail:
 227         mm->context.vdso = NULL;
 228         return PTR_ERR(ret);
 229 }
 230
 231 #ifdef CONFIG_COMPAT
 232 /*
 233  * Create and map the vectors page for AArch32 tasks.
 234  */
 235 enum aarch32_map {
 236         AA32_MAP_VECTORS, /* kuser helpers */
 237         AA32_MAP_SIGPAGE,
 238         AA32_MAP_VVAR,
 239         AA32_MAP_VDSO,
 240 };
 241
 242 static struct page *aarch32_vectors_page __ro_after_init;
 243 static struct page *aarch32_sig_page __ro_after_init;
 244
 245 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
 246                                   struct vm_area_struct *new_vma)
 247 {
 248         current->mm->context.sigpage = (void *)new_vma->vm_start;
 249
 250         return 0;
 251 }
 252
 253 static struct vm_special_mapping aarch32_vdso_maps[] = {
 254         [AA32_MAP_VECTORS] = {
 255                 .name   = "[vectors]", /* ABI */
 256                 .pages  = &aarch32_vectors_page,
 257         },
 258         [AA32_MAP_SIGPAGE] = {
 259                 .name   = "[sigpage]", /* ABI */
 260                 .pages  = &aarch32_sig_page,
 261                 .mremap = aarch32_sigpage_mremap,
 262         },
 263         [AA32_MAP_VVAR] = {
 264                 .name = "[vvar]",
 265                 .fault = vvar_fault,
 266         },
 267         [AA32_MAP_VDSO] = {
 268                 .name = "[vdso]",
 269                 .mremap = vdso_mremap,
 270         },
 271 };
 272
 273 static int aarch32_alloc_kuser_vdso_page(void)
 274 {
 275         extern char __kuser_helper_start[], __kuser_helper_end[];
 276         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 277         unsigned long vdso_page;
 278
 279         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 280                 return 0;
 281
 282         vdso_page = get_zeroed_page(GFP_KERNEL);
 283         if (!vdso_page)
 284                 return -ENOMEM;
 285
 286         memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 287                kuser_sz);
 288         aarch32_vectors_page = virt_to_page((void *)vdso_page);
 289         return 0;
 290 }
 291
 292 #define COMPAT_SIGPAGE_POISON_WORD      0xe7fddef1
 293 static int aarch32_alloc_sigpage(void)
 294 {
 295         extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 296         int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 297         __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
 298         void *sigpage;
 299
 300         sigpage = (void *)__get_free_page(GFP_KERNEL);
 301         if (!sigpage)
 302                 return -ENOMEM;
 303
 304         memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
 305         memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
 306         aarch32_sig_page = virt_to_page(sigpage);
 307         return 0;
 308 }
 309
 310 static int __init __aarch32_alloc_vdso_pages(void)
 311 {
 312
 313         if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 314                 return 0;
 315
 316         vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 317         vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 318
 319         return __vdso_init(VDSO_ABI_AA32);
 320 }
 321
 322 static int __init aarch32_alloc_vdso_pages(void)
 323 {
 324         int ret;
 325
 326         ret = __aarch32_alloc_vdso_pages();
 327         if (ret)
 328                 return ret;
 329
 330         ret = aarch32_alloc_sigpage();
 331         if (ret)
 332                 return ret;
 333
 334         return aarch32_alloc_kuser_vdso_page();
 335 }
 336 arch_initcall(aarch32_alloc_vdso_pages);
 337
 338 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 339 {
 340         void *ret;
 341
 342         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 343                 return 0;
 344
 345         /*
 346          * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 347          * not safe to CoW the page containing the CPU exception vectors.
 348          */
 349         ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 350                                        VM_READ | VM_EXEC |
 351                                        VM_MAYREAD | VM_MAYEXEC,
 352                                        &aarch32_vdso_maps[AA32_MAP_VECTORS]);
 353
 354         return PTR_ERR_OR_ZERO(ret);
 355 }
 356
 357 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 358 {
 359         unsigned long addr;
 360         void *ret;
 361
 362         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 363         if (IS_ERR_VALUE(addr)) {
 364                 ret = ERR_PTR(addr);
 365                 goto out;
 366         }
 367
 368         /*
 369          * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 370          * set breakpoints.
 371          */
 372         ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 373                                        VM_READ | VM_EXEC | VM_MAYREAD |
 374                                        VM_MAYWRITE | VM_MAYEXEC,
 375                                        &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 376         if (IS_ERR(ret))
 377                 goto out;
 378
 379         mm->context.sigpage = (void *)addr;
 380
 381 out:
 382         return PTR_ERR_OR_ZERO(ret);
 383 }
 384
 385 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 386 {
 387         struct mm_struct *mm = current->mm;
 388         int ret;
 389
 390         if (mmap_write_lock_killable(mm))
 391                 return -EINTR;
 392
 393         ret = aarch32_kuser_helpers_setup(mm);
 394         if (ret)
 395                 goto out;
 396
 397         if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
 398                 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
 399                                                uses_interp);
 400                 if (ret)
 401                         goto out;
 402         }
 403
 404         ret = aarch32_sigreturn_setup(mm);
 405 out:
 406         mmap_write_unlock(mm);
 407         return ret;
 408 }
 409 #endif /* CONFIG_COMPAT */
 410
 411 enum aarch64_map {
 412         AA64_MAP_VVAR,
 413         AA64_MAP_VDSO,
 414 };
 415
 416 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 417         [AA64_MAP_VVAR] = {
 418                 .name   = "[vvar]",
 419                 .fault = vvar_fault,
 420         },
 421         [AA64_MAP_VDSO] = {
 422                 .name   = "[vdso]",
 423                 .mremap = vdso_mremap,
 424         },
 425 };
 426
 427 static int __init vdso_init(void)
 428 {
 429         vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 430         vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
 431
 432         return __vdso_init(VDSO_ABI_AA64);
 433 }
 434 arch_initcall(vdso_init);
 435
 436 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 437 {
 438         struct mm_struct *mm = current->mm;
 439         int ret;
 440
 441         if (mmap_write_lock_killable(mm))
 442                 return -EINTR;
 443
 444         ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
 445         mmap_write_unlock(mm);
 446
 447         return ret;
 448 }