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 <[email protected]>
   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 {
  73         struct vdso_data        data[CS_BASES];
  74         u8                      page[PAGE_SIZE];
  75 } vdso_data_store __page_aligned_data;
  76 struct vdso_data *vdso_data = vdso_data_store.data;
  77
  78 static int vdso_mremap(const struct vm_special_mapping *sm,
  79                 struct vm_area_struct *new_vma)
  80 {
  81         current->mm->context.vdso = (void *)new_vma->vm_start;
  82
  83         return 0;
  84 }
  85
  86 static int __init __vdso_init(enum vdso_abi abi)
  87 {
  88         int i;
  89         struct page **vdso_pagelist;
  90         unsigned long pfn;
  91
  92         if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
  93                 pr_err("vDSO is not a valid ELF object!\n");
  94                 return -EINVAL;
  95         }
  96
  97         vdso_info[abi].vdso_pages = (
  98                         vdso_info[abi].vdso_code_end -
  99                         vdso_info[abi].vdso_code_start) >>
 100                         PAGE_SHIFT;
 101
 102         vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
 103                                 sizeof(struct page *),
 104                                 GFP_KERNEL);
 105         if (vdso_pagelist == NULL)
 106                 return -ENOMEM;
 107
 108         /* Grab the vDSO code pages. */
 109         pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
 110
 111         for (i = 0; i < vdso_info[abi].vdso_pages; i++)
 112                 vdso_pagelist[i] = pfn_to_page(pfn + i);
 113
 114         vdso_info[abi].cm->pages = vdso_pagelist;
 115
 116         return 0;
 117 }
 118
 119 #ifdef CONFIG_TIME_NS
 120 struct vdso_data *arch_get_vdso_data(void *vvar_page)
 121 {
 122         return (struct vdso_data *)(vvar_page);
 123 }
 124
 125 /*
 126  * The vvar mapping contains data for a specific time namespace, so when a task
 127  * changes namespace we must unmap its vvar data for the old namespace.
 128  * Subsequent faults will map in data for the new namespace.
 129  *
 130  * For more details see timens_setup_vdso_data().
 131  */
 132 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 133 {
 134         struct mm_struct *mm = task->mm;
 135         struct vm_area_struct *vma;
 136         VMA_ITERATOR(vmi, mm, 0);
 137
 138         mmap_read_lock(mm);
 139
 140         for_each_vma(vmi, vma) {
 141                 unsigned long size = vma->vm_end - vma->vm_start;
 142
 143                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
 144                         zap_page_range(vma, vma->vm_start, size);
 145 #ifdef CONFIG_COMPAT_VDSO
 146                 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
 147                         zap_page_range(vma, vma->vm_start, size);
 148 #endif
 149         }
 150
 151         mmap_read_unlock(mm);
 152         return 0;
 153 }
 154 #endif
 155
 156 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 157                              struct vm_area_struct *vma, struct vm_fault *vmf)
 158 {
 159         struct page *timens_page = find_timens_vvar_page(vma);
 160         unsigned long pfn;
 161
 162         switch (vmf->pgoff) {
 163         case VVAR_DATA_PAGE_OFFSET:
 164                 if (timens_page)
 165                         pfn = page_to_pfn(timens_page);
 166                 else
 167                         pfn = sym_to_pfn(vdso_data);
 168                 break;
 169 #ifdef CONFIG_TIME_NS
 170         case VVAR_TIMENS_PAGE_OFFSET:
 171                 /*
 172                  * If a task belongs to a time namespace then a namespace
 173                  * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 174                  * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 175                  * offset.
 176                  * See also the comment near timens_setup_vdso_data().
 177                  */
 178                 if (!timens_page)
 179                         return VM_FAULT_SIGBUS;
 180                 pfn = sym_to_pfn(vdso_data);
 181                 break;
 182 #endif /* CONFIG_TIME_NS */
 183         default:
 184                 return VM_FAULT_SIGBUS;
 185         }
 186
 187         return vmf_insert_pfn(vma, vmf->address, pfn);
 188 }
 189
 190 static int __setup_additional_pages(enum vdso_abi abi,
 191                                     struct mm_struct *mm,
 192                                     struct linux_binprm *bprm,
 193                                     int uses_interp)
 194 {
 195         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 196         unsigned long gp_flags = 0;
 197         void *ret;
 198
 199         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 200
 201         vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 202         /* Be sure to map the data page */
 203         vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 204
 205         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 206         if (IS_ERR_VALUE(vdso_base)) {
 207                 ret = ERR_PTR(vdso_base);
 208                 goto up_fail;
 209         }
 210
 211         ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 212                                        VM_READ|VM_MAYREAD|VM_PFNMAP,
 213                                        vdso_info[abi].dm);
 214         if (IS_ERR(ret))
 215                 goto up_fail;
 216
 217         if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
 218                 gp_flags = VM_ARM64_BTI;
 219
 220         vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 221         mm->context.vdso = (void *)vdso_base;
 222         ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 223                                        VM_READ|VM_EXEC|gp_flags|
 224                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 225                                        vdso_info[abi].cm);
 226         if (IS_ERR(ret))
 227                 goto up_fail;
 228
 229         return 0;
 230
 231 up_fail:
 232         mm->context.vdso = NULL;
 233         return PTR_ERR(ret);
 234 }
 235
 236 #ifdef CONFIG_COMPAT
 237 /*
 238  * Create and map the vectors page for AArch32 tasks.
 239  */
 240 enum aarch32_map {
 241         AA32_MAP_VECTORS, /* kuser helpers */
 242         AA32_MAP_SIGPAGE,
 243         AA32_MAP_VVAR,
 244         AA32_MAP_VDSO,
 245 };
 246
 247 static struct page *aarch32_vectors_page __ro_after_init;
 248 static struct page *aarch32_sig_page __ro_after_init;
 249
 250 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
 251                                   struct vm_area_struct *new_vma)
 252 {
 253         current->mm->context.sigpage = (void *)new_vma->vm_start;
 254
 255         return 0;
 256 }
 257
 258 static struct vm_special_mapping aarch32_vdso_maps[] = {
 259         [AA32_MAP_VECTORS] = {
 260                 .name   = "[vectors]", /* ABI */
 261                 .pages  = &aarch32_vectors_page,
 262         },
 263         [AA32_MAP_SIGPAGE] = {
 264                 .name   = "[sigpage]", /* ABI */
 265                 .pages  = &aarch32_sig_page,
 266                 .mremap = aarch32_sigpage_mremap,
 267         },
 268         [AA32_MAP_VVAR] = {
 269                 .name = "[vvar]",
 270                 .fault = vvar_fault,
 271         },
 272         [AA32_MAP_VDSO] = {
 273                 .name = "[vdso]",
 274                 .mremap = vdso_mremap,
 275         },
 276 };
 277
 278 static int aarch32_alloc_kuser_vdso_page(void)
 279 {
 280         extern char __kuser_helper_start[], __kuser_helper_end[];
 281         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 282         unsigned long vdso_page;
 283
 284         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 285                 return 0;
 286
 287         vdso_page = get_zeroed_page(GFP_KERNEL);
 288         if (!vdso_page)
 289                 return -ENOMEM;
 290
 291         memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 292                kuser_sz);
 293         aarch32_vectors_page = virt_to_page(vdso_page);
 294         return 0;
 295 }
 296
 297 #define COMPAT_SIGPAGE_POISON_WORD      0xe7fddef1
 298 static int aarch32_alloc_sigpage(void)
 299 {
 300         extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 301         int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 302         __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
 303         void *sigpage;
 304
 305         sigpage = (void *)__get_free_page(GFP_KERNEL);
 306         if (!sigpage)
 307                 return -ENOMEM;
 308
 309         memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
 310         memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
 311         aarch32_sig_page = virt_to_page(sigpage);
 312         return 0;
 313 }
 314
 315 static int __init __aarch32_alloc_vdso_pages(void)
 316 {
 317
 318         if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 319                 return 0;
 320
 321         vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 322         vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 323
 324         return __vdso_init(VDSO_ABI_AA32);
 325 }
 326
 327 static int __init aarch32_alloc_vdso_pages(void)
 328 {
 329         int ret;
 330
 331         ret = __aarch32_alloc_vdso_pages();
 332         if (ret)
 333                 return ret;
 334
 335         ret = aarch32_alloc_sigpage();
 336         if (ret)
 337                 return ret;
 338
 339         return aarch32_alloc_kuser_vdso_page();
 340 }
 341 arch_initcall(aarch32_alloc_vdso_pages);
 342
 343 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 344 {
 345         void *ret;
 346
 347         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 348                 return 0;
 349
 350         /*
 351          * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 352          * not safe to CoW the page containing the CPU exception vectors.
 353          */
 354         ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 355                                        VM_READ | VM_EXEC |
 356                                        VM_MAYREAD | VM_MAYEXEC,
 357                                        &aarch32_vdso_maps[AA32_MAP_VECTORS]);
 358
 359         return PTR_ERR_OR_ZERO(ret);
 360 }
 361
 362 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 363 {
 364         unsigned long addr;
 365         void *ret;
 366
 367         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 368         if (IS_ERR_VALUE(addr)) {
 369                 ret = ERR_PTR(addr);
 370                 goto out;
 371         }
 372
 373         /*
 374          * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 375          * set breakpoints.
 376          */
 377         ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 378                                        VM_READ | VM_EXEC | VM_MAYREAD |
 379                                        VM_MAYWRITE | VM_MAYEXEC,
 380                                        &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 381         if (IS_ERR(ret))
 382                 goto out;
 383
 384         mm->context.sigpage = (void *)addr;
 385
 386 out:
 387         return PTR_ERR_OR_ZERO(ret);
 388 }
 389
 390 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 391 {
 392         struct mm_struct *mm = current->mm;
 393         int ret;
 394
 395         if (mmap_write_lock_killable(mm))
 396                 return -EINTR;
 397
 398         ret = aarch32_kuser_helpers_setup(mm);
 399         if (ret)
 400                 goto out;
 401
 402         if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
 403                 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
 404                                                uses_interp);
 405                 if (ret)
 406                         goto out;
 407         }
 408
 409         ret = aarch32_sigreturn_setup(mm);
 410 out:
 411         mmap_write_unlock(mm);
 412         return ret;
 413 }
 414 #endif /* CONFIG_COMPAT */
 415
 416 enum aarch64_map {
 417         AA64_MAP_VVAR,
 418         AA64_MAP_VDSO,
 419 };
 420
 421 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 422         [AA64_MAP_VVAR] = {
 423                 .name   = "[vvar]",
 424                 .fault = vvar_fault,
 425         },
 426         [AA64_MAP_VDSO] = {
 427                 .name   = "[vdso]",
 428                 .mremap = vdso_mremap,
 429         },
 430 };
 431
 432 static int __init vdso_init(void)
 433 {
 434         vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 435         vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
 436
 437         return __vdso_init(VDSO_ABI_AA64);
 438 }
 439 arch_initcall(vdso_init);
 440
 441 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 442 {
 443         struct mm_struct *mm = current->mm;
 444         int ret;
 445
 446         if (mmap_write_lock_killable(mm))
 447                 return -EINTR;
 448
 449         ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
 450         mmap_write_unlock(mm);
 451
 452         return ret;
 453 }