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