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/timekeeper_internal.h>
  22 #include <linux/vmalloc.h>
  23 #include <vdso/datapage.h>
  24 #include <vdso/helpers.h>
  25 #include <vdso/vsyscall.h>
  26
  27 #include <asm/cacheflush.h>
  28 #include <asm/signal32.h>
  29 #include <asm/vdso.h>
  30
  31 extern char vdso_start[], vdso_end[];
  32 #ifdef CONFIG_COMPAT_VDSO
  33 extern char vdso32_start[], vdso32_end[];
  34 #endif /* CONFIG_COMPAT_VDSO */
  35
  36 enum vdso_abi {
  37         VDSO_ABI_AA64,
  38 #ifdef CONFIG_COMPAT_VDSO
  39         VDSO_ABI_AA32,
  40 #endif /* CONFIG_COMPAT_VDSO */
  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_remap(enum vdso_abi abi,
  79                         const struct vm_special_mapping *sm,
  80                         struct vm_area_struct *new_vma)
  81 {
  82         unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
  83         unsigned long vdso_size = vdso_info[abi].vdso_code_end -
  84                                   vdso_info[abi].vdso_code_start;
  85
  86         if (vdso_size != new_size)
  87                 return -EINVAL;
  88
  89         current->mm->context.vdso = (void *)new_vma->vm_start;
  90
  91         return 0;
  92 }
  93
  94 static int __vdso_init(enum vdso_abi abi)
  95 {
  96         int i;
  97         struct page **vdso_pagelist;
  98         unsigned long pfn;
  99
 100         if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
 101                 pr_err("vDSO is not a valid ELF object!\n");
 102                 return -EINVAL;
 103         }
 104
 105         vdso_info[abi].vdso_pages = (
 106                         vdso_info[abi].vdso_code_end -
 107                         vdso_info[abi].vdso_code_start) >>
 108                         PAGE_SHIFT;
 109
 110         /* Allocate the vDSO pagelist, plus a page for the data. */
 111         vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages + 1,
 112                                 sizeof(struct page *),
 113                                 GFP_KERNEL);
 114         if (vdso_pagelist == NULL)
 115                 return -ENOMEM;
 116
 117         /* Grab the vDSO data page. */
 118         vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));
 119
 120
 121         /* Grab the vDSO code pages. */
 122         pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
 123
 124         for (i = 0; i < vdso_info[abi].vdso_pages; i++)
 125                 vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
 126
 127         vdso_info[abi].dm->pages = &vdso_pagelist[0];
 128         vdso_info[abi].cm->pages = &vdso_pagelist[1];
 129
 130         return 0;
 131 }
 132
 133 static int __setup_additional_pages(enum vdso_abi abi,
 134                                     struct mm_struct *mm,
 135                                     struct linux_binprm *bprm,
 136                                     int uses_interp)
 137 {
 138         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 139         unsigned long gp_flags = 0;
 140         void *ret;
 141
 142         vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 143         /* Be sure to map the data page */
 144         vdso_mapping_len = vdso_text_len + PAGE_SIZE;
 145
 146         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 147         if (IS_ERR_VALUE(vdso_base)) {
 148                 ret = ERR_PTR(vdso_base);
 149                 goto up_fail;
 150         }
 151
 152         ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
 153                                        VM_READ|VM_MAYREAD,
 154                                        vdso_info[abi].dm);
 155         if (IS_ERR(ret))
 156                 goto up_fail;
 157
 158         if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
 159                 gp_flags = VM_ARM64_BTI;
 160
 161         vdso_base += PAGE_SIZE;
 162         mm->context.vdso = (void *)vdso_base;
 163         ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 164                                        VM_READ|VM_EXEC|gp_flags|
 165                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 166                                        vdso_info[abi].cm);
 167         if (IS_ERR(ret))
 168                 goto up_fail;
 169
 170         return 0;
 171
 172 up_fail:
 173         mm->context.vdso = NULL;
 174         return PTR_ERR(ret);
 175 }
 176
 177 #ifdef CONFIG_COMPAT
 178 /*
 179  * Create and map the vectors page for AArch32 tasks.
 180  */
 181 #ifdef CONFIG_COMPAT_VDSO
 182 static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
 183                 struct vm_area_struct *new_vma)
 184 {
 185         return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
 186 }
 187 #endif /* CONFIG_COMPAT_VDSO */
 188
 189 enum aarch32_map {
 190         AA32_MAP_VECTORS, /* kuser helpers */
 191 #ifdef CONFIG_COMPAT_VDSO
 192         AA32_MAP_VVAR,
 193         AA32_MAP_VDSO,
 194 #else
 195         AA32_MAP_SIGPAGE
 196 #endif
 197 };
 198
 199 static struct page *aarch32_vectors_page __ro_after_init;
 200 #ifndef CONFIG_COMPAT_VDSO
 201 static struct page *aarch32_sig_page __ro_after_init;
 202 #endif
 203
 204 static struct vm_special_mapping aarch32_vdso_maps[] = {
 205         [AA32_MAP_VECTORS] = {
 206                 .name   = "[vectors]", /* ABI */
 207                 .pages  = &aarch32_vectors_page,
 208         },
 209 #ifdef CONFIG_COMPAT_VDSO
 210         [AA32_MAP_VVAR] = {
 211                 .name = "[vvar]",
 212         },
 213         [AA32_MAP_VDSO] = {
 214                 .name = "[vdso]",
 215                 .mremap = aarch32_vdso_mremap,
 216         },
 217 #else
 218         [AA32_MAP_SIGPAGE] = {
 219                 .name   = "[sigpage]", /* ABI */
 220                 .pages  = &aarch32_sig_page,
 221         },
 222 #endif /* CONFIG_COMPAT_VDSO */
 223 };
 224
 225 static int aarch32_alloc_kuser_vdso_page(void)
 226 {
 227         extern char __kuser_helper_start[], __kuser_helper_end[];
 228         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 229         unsigned long vdso_page;
 230
 231         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 232                 return 0;
 233
 234         vdso_page = get_zeroed_page(GFP_ATOMIC);
 235         if (!vdso_page)
 236                 return -ENOMEM;
 237
 238         memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 239                kuser_sz);
 240         aarch32_vectors_page = virt_to_page(vdso_page);
 241         flush_dcache_page(aarch32_vectors_page);
 242         return 0;
 243 }
 244
 245 #ifdef CONFIG_COMPAT_VDSO
 246 static int __aarch32_alloc_vdso_pages(void)
 247 {
 248         int ret;
 249
 250         vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 251         vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 252
 253         ret = __vdso_init(VDSO_ABI_AA32);
 254         if (ret)
 255                 return ret;
 256
 257         return aarch32_alloc_kuser_vdso_page();
 258 }
 259 #else
 260 static int __aarch32_alloc_vdso_pages(void)
 261 {
 262         extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 263         int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 264         unsigned long sigpage;
 265         int ret;
 266
 267         sigpage = get_zeroed_page(GFP_ATOMIC);
 268         if (!sigpage)
 269                 return -ENOMEM;
 270
 271         memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
 272         aarch32_sig_page = virt_to_page(sigpage);
 273         flush_dcache_page(aarch32_sig_page);
 274
 275         ret = aarch32_alloc_kuser_vdso_page();
 276         if (ret)
 277                 free_page(sigpage);
 278
 279         return ret;
 280 }
 281 #endif /* CONFIG_COMPAT_VDSO */
 282
 283 static int __init aarch32_alloc_vdso_pages(void)
 284 {
 285         return __aarch32_alloc_vdso_pages();
 286 }
 287 arch_initcall(aarch32_alloc_vdso_pages);
 288
 289 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 290 {
 291         void *ret;
 292
 293         if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 294                 return 0;
 295
 296         /*
 297          * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 298          * not safe to CoW the page containing the CPU exception vectors.
 299          */
 300         ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 301                                        VM_READ | VM_EXEC |
 302                                        VM_MAYREAD | VM_MAYEXEC,
 303                                        &aarch32_vdso_maps[AA32_MAP_VECTORS]);
 304
 305         return PTR_ERR_OR_ZERO(ret);
 306 }
 307
 308 #ifndef CONFIG_COMPAT_VDSO
 309 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 310 {
 311         unsigned long addr;
 312         void *ret;
 313
 314         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 315         if (IS_ERR_VALUE(addr)) {
 316                 ret = ERR_PTR(addr);
 317                 goto out;
 318         }
 319
 320         /*
 321          * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 322          * set breakpoints.
 323          */
 324         ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 325                                        VM_READ | VM_EXEC | VM_MAYREAD |
 326                                        VM_MAYWRITE | VM_MAYEXEC,
 327                                        &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 328         if (IS_ERR(ret))
 329                 goto out;
 330
 331         mm->context.vdso = (void *)addr;
 332
 333 out:
 334         return PTR_ERR_OR_ZERO(ret);
 335 }
 336 #endif /* !CONFIG_COMPAT_VDSO */
 337
 338 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 339 {
 340         struct mm_struct *mm = current->mm;
 341         int ret;
 342
 343         if (mmap_write_lock_killable(mm))
 344                 return -EINTR;
 345
 346         ret = aarch32_kuser_helpers_setup(mm);
 347         if (ret)
 348                 goto out;
 349
 350 #ifdef CONFIG_COMPAT_VDSO
 351         ret = __setup_additional_pages(VDSO_ABI_AA32,
 352                                        mm,
 353                                        bprm,
 354                                        uses_interp);
 355 #else
 356         ret = aarch32_sigreturn_setup(mm);
 357 #endif /* CONFIG_COMPAT_VDSO */
 358
 359 out:
 360         mmap_write_unlock(mm);
 361         return ret;
 362 }
 363 #endif /* CONFIG_COMPAT */
 364
 365 static int vdso_mremap(const struct vm_special_mapping *sm,
 366                 struct vm_area_struct *new_vma)
 367 {
 368         return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
 369 }
 370
 371 enum aarch64_map {
 372         AA64_MAP_VVAR,
 373         AA64_MAP_VDSO,
 374 };
 375
 376 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 377         [AA64_MAP_VVAR] = {
 378                 .name   = "[vvar]",
 379         },
 380         [AA64_MAP_VDSO] = {
 381                 .name   = "[vdso]",
 382                 .mremap = vdso_mremap,
 383         },
 384 };
 385
 386 static int __init vdso_init(void)
 387 {
 388         vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 389         vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
 390
 391         return __vdso_init(VDSO_ABI_AA64);
 392 }
 393 arch_initcall(vdso_init);
 394
 395 int arch_setup_additional_pages(struct linux_binprm *bprm,
 396                                 int uses_interp)
 397 {
 398         struct mm_struct *mm = current->mm;
 399         int ret;
 400
 401         if (mmap_write_lock_killable(mm))
 402                 return -EINTR;
 403
 404         ret = __setup_additional_pages(VDSO_ABI_AA64,
 405                                        mm,
 406                                        bprm,
 407                                        uses_interp);
 408
 409         mmap_write_unlock(mm);
 410
 411         return ret;
 412 }