LXR linux/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
  32extern char vdso_start[], vdso_end[];
  33extern char vdso32_start[], vdso32_end[];
  34
  35enum vdso_abi {
  36        VDSO_ABI_AA64,
  37        VDSO_ABI_AA32,
  38};
  39
  40enum vvar_pages {
  41        VVAR_DATA_PAGE_OFFSET,
  42        VVAR_TIMENS_PAGE_OFFSET,
  43        VVAR_NR_PAGES,
  44};
  45
  46struct 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
  57static 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 */
  75static union {
  76        struct vdso_data        data[CS_BASES];
  77        u8                      page[PAGE_SIZE];
  78} vdso_data_store __page_aligned_data;
  79struct vdso_data *vdso_data = vdso_data_store.data;
  80
  81static 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
  89static 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
 123struct 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 */
 135int 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
 140        mmap_read_lock(mm);
 141
 142        for (vma = mm->mmap; vma; vma = vma->vm_next) {
 143                unsigned long size = vma->vm_end - vma->vm_start;
 144
 145                if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
 146                        zap_page_range(vma, vma->vm_start, size);
 147#ifdef CONFIG_COMPAT_VDSO
 148                if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
 149                        zap_page_range(vma, vma->vm_start, size);
 150#endif
 151        }
 152
 153        mmap_read_unlock(mm);
 154        return 0;
 155}
 156
 157static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 158{
 159        if (likely(vma->vm_mm == current->mm))
 160                return current->nsproxy->time_ns->vvar_page;
 161
 162        /*
 163         * VM_PFNMAP | VM_IO protect .fault() handler from being called
 164         * through interfaces like /proc/$pid/mem or
 165         * process_vm_{readv,writev}() as long as there's no .access()
 166         * in special_mapping_vmops.
 167         * For more details check_vma_flags() and __access_remote_vm()
 168         */
 169        WARN(1, "vvar_page accessed remotely");
 170
 171        return NULL;
 172}
 173#else
 174static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 175{
 176        return NULL;
 177}
 178#endif
 179
 180static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 181                             struct vm_area_struct *vma, struct vm_fault *vmf)
 182{
 183        struct page *timens_page = find_timens_vvar_page(vma);
 184        unsigned long pfn;
 185
 186        switch (vmf->pgoff) {
 187        case VVAR_DATA_PAGE_OFFSET:
 188                if (timens_page)
 189                        pfn = page_to_pfn(timens_page);
 190                else
 191                        pfn = sym_to_pfn(vdso_data);
 192                break;
 193#ifdef CONFIG_TIME_NS
 194        case VVAR_TIMENS_PAGE_OFFSET:
 195                /*
 196                 * If a task belongs to a time namespace then a namespace
 197                 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 198                 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 199                 * offset.
 200                 * See also the comment near timens_setup_vdso_data().
 201                 */
 202                if (!timens_page)
 203                        return VM_FAULT_SIGBUS;
 204                pfn = sym_to_pfn(vdso_data);
 205                break;
 206#endif /* CONFIG_TIME_NS */
 207        default:
 208                return VM_FAULT_SIGBUS;
 209        }
 210
 211        return vmf_insert_pfn(vma, vmf->address, pfn);
 212}
 213
 214static int __setup_additional_pages(enum vdso_abi abi,
 215                                    struct mm_struct *mm,
 216                                    struct linux_binprm *bprm,
 217                                    int uses_interp)
 218{
 219        unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 220        unsigned long gp_flags = 0;
 221        void *ret;
 222
 223        BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
 224
 225        vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
 226        /* Be sure to map the data page */
 227        vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 228
 229        vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 230        if (IS_ERR_VALUE(vdso_base)) {
 231                ret = ERR_PTR(vdso_base);
 232                goto up_fail;
 233        }
 234
 235        ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 236                                       VM_READ|VM_MAYREAD|VM_PFNMAP,
 237                                       vdso_info[abi].dm);
 238        if (IS_ERR(ret))
 239                goto up_fail;
 240
 241        if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
 242                gp_flags = VM_ARM64_BTI;
 243
 244        vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 245        mm->context.vdso = (void *)vdso_base;
 246        ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 247                                       VM_READ|VM_EXEC|gp_flags|
 248                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 249                                       vdso_info[abi].cm);
 250        if (IS_ERR(ret))
 251                goto up_fail;
 252
 253        return 0;
 254
 255up_fail:
 256        mm->context.vdso = NULL;
 257        return PTR_ERR(ret);
 258}
 259
 260#ifdef CONFIG_COMPAT
 261/*
 262 * Create and map the vectors page for AArch32 tasks.
 263 */
 264enum aarch32_map {
 265        AA32_MAP_VECTORS, /* kuser helpers */
 266        AA32_MAP_SIGPAGE,
 267        AA32_MAP_VVAR,
 268        AA32_MAP_VDSO,
 269};
 270
 271static struct page *aarch32_vectors_page __ro_after_init;
 272static struct page *aarch32_sig_page __ro_after_init;
 273
 274static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
 275                                  struct vm_area_struct *new_vma)
 276{
 277        current->mm->context.sigpage = (void *)new_vma->vm_start;
 278
 279        return 0;
 280}
 281
 282static struct vm_special_mapping aarch32_vdso_maps[] = {
 283        [AA32_MAP_VECTORS] = {
 284                .name   = "[vectors]", /* ABI */
 285                .pages  = &aarch32_vectors_page,
 286        },
 287        [AA32_MAP_SIGPAGE] = {
 288                .name   = "[sigpage]", /* ABI */
 289                .pages  = &aarch32_sig_page,
 290                .mremap = aarch32_sigpage_mremap,
 291        },
 292        [AA32_MAP_VVAR] = {
 293                .name = "[vvar]",
 294                .fault = vvar_fault,
 295        },
 296        [AA32_MAP_VDSO] = {
 297                .name = "[vdso]",
 298                .mremap = vdso_mremap,
 299        },
 300};
 301
 302static int aarch32_alloc_kuser_vdso_page(void)
 303{
 304        extern char __kuser_helper_start[], __kuser_helper_end[];
 305        int kuser_sz = __kuser_helper_end - __kuser_helper_start;
 306        unsigned long vdso_page;
 307
 308        if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 309                return 0;
 310
 311        vdso_page = get_zeroed_page(GFP_KERNEL);
 312        if (!vdso_page)
 313                return -ENOMEM;
 314
 315        memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
 316               kuser_sz);
 317        aarch32_vectors_page = virt_to_page(vdso_page);
 318        return 0;
 319}
 320
 321#define COMPAT_SIGPAGE_POISON_WORD      0xe7fddef1
 322static int aarch32_alloc_sigpage(void)
 323{
 324        extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 325        int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
 326        __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
 327        void *sigpage;
 328
 329        sigpage = (void *)__get_free_page(GFP_KERNEL);
 330        if (!sigpage)
 331                return -ENOMEM;
 332
 333        memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
 334        memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
 335        aarch32_sig_page = virt_to_page(sigpage);
 336        return 0;
 337}
 338
 339static int __init __aarch32_alloc_vdso_pages(void)
 340{
 341
 342        if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 343                return 0;
 344
 345        vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 346        vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 347
 348        return __vdso_init(VDSO_ABI_AA32);
 349}
 350
 351static int __init aarch32_alloc_vdso_pages(void)
 352{
 353        int ret;
 354
 355        ret = __aarch32_alloc_vdso_pages();
 356        if (ret)
 357                return ret;
 358
 359        ret = aarch32_alloc_sigpage();
 360        if (ret)
 361                return ret;
 362
 363        return aarch32_alloc_kuser_vdso_page();
 364}
 365arch_initcall(aarch32_alloc_vdso_pages);
 366
 367static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 368{
 369        void *ret;
 370
 371        if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
 372                return 0;
 373
 374        /*
 375         * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
 376         * not safe to CoW the page containing the CPU exception vectors.
 377         */
 378        ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
 379                                       VM_READ | VM_EXEC |
 380                                       VM_MAYREAD | VM_MAYEXEC,
 381                                       &aarch32_vdso_maps[AA32_MAP_VECTORS]);
 382
 383        return PTR_ERR_OR_ZERO(ret);
 384}
 385
 386static int aarch32_sigreturn_setup(struct mm_struct *mm)
 387{
 388        unsigned long addr;
 389        void *ret;
 390
 391        addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
 392        if (IS_ERR_VALUE(addr)) {
 393                ret = ERR_PTR(addr);
 394                goto out;
 395        }
 396
 397        /*
 398         * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
 399         * set breakpoints.
 400         */
 401        ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 402                                       VM_READ | VM_EXEC | VM_MAYREAD |
 403                                       VM_MAYWRITE | VM_MAYEXEC,
 404                                       &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
 405        if (IS_ERR(ret))
 406                goto out;
 407
 408        mm->context.sigpage = (void *)addr;
 409
 410out:
 411        return PTR_ERR_OR_ZERO(ret);
 412}
 413
 414int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 415{
 416        struct mm_struct *mm = current->mm;
 417        int ret;
 418
 419        if (mmap_write_lock_killable(mm))
 420                return -EINTR;
 421
 422        ret = aarch32_kuser_helpers_setup(mm);
 423        if (ret)
 424                goto out;
 425
 426        if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
 427                ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
 428                                               uses_interp);
 429                if (ret)
 430                        goto out;
 431        }
 432
 433        ret = aarch32_sigreturn_setup(mm);
 434out:
 435        mmap_write_unlock(mm);
 436        return ret;
 437}
 438#endif /* CONFIG_COMPAT */
 439
 440enum aarch64_map {
 441        AA64_MAP_VVAR,
 442        AA64_MAP_VDSO,
 443};
 444
 445static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 446        [AA64_MAP_VVAR] = {
 447                .name   = "[vvar]",
 448                .fault = vvar_fault,
 449        },
 450        [AA64_MAP_VDSO] = {
 451                .name   = "[vdso]",
 452                .mremap = vdso_mremap,
 453        },
 454};
 455
 456static int __init vdso_init(void)
 457{
 458        vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
 459        vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
 460
 461        return __vdso_init(VDSO_ABI_AA64);
 462}
 463arch_initcall(vdso_init);
 464
 465int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 466{
 467        struct mm_struct *mm = current->mm;
 468        int ret;
 469
 470        if (mmap_write_lock_killable(mm))
 471                return -EINTR;
 472
 473        ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
 474        mmap_write_unlock(mm);
 475
 476        return ret;
 477}
 478