arch/x86/entry/vdso/vma.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2007 Andi Kleen, SUSE Labs.
   4  *
   5  * This contains most of the x86 vDSO kernel-side code.
   6  */
   7 #include <linux/mm.h>
   8 #include <linux/err.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/task_stack.h>
  11 #include <linux/slab.h>
  12 #include <linux/init.h>
  13 #include <linux/random.h>
  14 #include <linux/elf.h>
  15 #include <linux/cpu.h>
  16 #include <linux/ptrace.h>
  17 #include <linux/time_namespace.h>
  18
  19 #include <asm/pvclock.h>
  20 #include <asm/vgtod.h>
  21 #include <asm/proto.h>
  22 #include <asm/vdso.h>
  23 #include <asm/vvar.h>
  24 #include <asm/tlb.h>
  25 #include <asm/page.h>
  26 #include <asm/desc.h>
  27 #include <asm/cpufeature.h>
  28 #include <clocksource/hyperv_timer.h>
  29
  30 #undef _ASM_X86_VVAR_H
  31 #define EMIT_VVAR(name, offset) \
  32         const size_t name ## _offset = offset;
  33 #include <asm/vvar.h>
  34
  35 struct vdso_data *arch_get_vdso_data(void *vvar_page)
  36 {
  37         return (struct vdso_data *)(vvar_page + _vdso_data_offset);
  38 }
  39 #undef EMIT_VVAR
  40
  41 #if defined(CONFIG_X86_64)
  42 unsigned int __read_mostly vdso64_enabled = 1;
  43 #endif
  44
  45 void __init init_vdso_image(const struct vdso_image *image)
  46 {
  47         BUG_ON(image->size % PAGE_SIZE != 0);
  48
  49         apply_alternatives((struct alt_instr *)(image->data + image->alt),
  50                            (struct alt_instr *)(image->data + image->alt +
  51                                                 image->alt_len));
  52 }
  53
  54 struct linux_binprm;
  55
  56 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
  57                       struct vm_area_struct *vma, struct vm_fault *vmf)
  58 {
  59         const struct vdso_image *image = vma->vm_mm->context.vdso_image;
  60
  61         if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
  62                 return VM_FAULT_SIGBUS;
  63
  64         vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
  65         get_page(vmf->page);
  66         return 0;
  67 }
  68
  69 static void vdso_fix_landing(const struct vdso_image *image,
  70                 struct vm_area_struct *new_vma)
  71 {
  72 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
  73         if (in_ia32_syscall() && image == &vdso_image_32) {
  74                 struct pt_regs *regs = current_pt_regs();
  75                 unsigned long vdso_land = image->sym_int80_landing_pad;
  76                 unsigned long old_land_addr = vdso_land +
  77                         (unsigned long)current->mm->context.vdso;
  78
  79                 /* Fixing userspace landing - look at do_fast_syscall_32 */
  80                 if (regs->ip == old_land_addr)
  81                         regs->ip = new_vma->vm_start + vdso_land;
  82         }
  83 #endif
  84 }
  85
  86 static int vdso_mremap(const struct vm_special_mapping *sm,
  87                 struct vm_area_struct *new_vma)
  88 {
  89         unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
  90         const struct vdso_image *image = current->mm->context.vdso_image;
  91
  92         if (image->size != new_size)
  93                 return -EINVAL;
  94
  95         vdso_fix_landing(image, new_vma);
  96         current->mm->context.vdso = (void __user *)new_vma->vm_start;
  97
  98         return 0;
  99 }
 100
 101 static int vvar_mremap(const struct vm_special_mapping *sm,
 102                 struct vm_area_struct *new_vma)
 103 {
 104         const struct vdso_image *image = new_vma->vm_mm->context.vdso_image;
 105         unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
 106
 107         if (new_size != -image->sym_vvar_start)
 108                 return -EINVAL;
 109
 110         return 0;
 111 }
 112
 113 #ifdef CONFIG_TIME_NS
 114 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 115 {
 116         if (likely(vma->vm_mm == current->mm))
 117                 return current->nsproxy->time_ns->vvar_page;
 118
 119         /*
 120          * VM_PFNMAP | VM_IO protect .fault() handler from being called
 121          * through interfaces like /proc/$pid/mem or
 122          * process_vm_{readv,writev}() as long as there's no .access()
 123          * in special_mapping_vmops().
 124          * For more details check_vma_flags() and __access_remote_vm()
 125          */
 126
 127         WARN(1, "vvar_page accessed remotely");
 128
 129         return NULL;
 130 }
 131 #else
 132 static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 133 {
 134         return NULL;
 135 }
 136 #endif
 137
 138 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 139                       struct vm_area_struct *vma, struct vm_fault *vmf)
 140 {
 141         const struct vdso_image *image = vma->vm_mm->context.vdso_image;
 142         unsigned long pfn;
 143         long sym_offset;
 144
 145         if (!image)
 146                 return VM_FAULT_SIGBUS;
 147
 148         sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
 149                 image->sym_vvar_start;
 150
 151         /*
 152          * Sanity check: a symbol offset of zero means that the page
 153          * does not exist for this vdso image, not that the page is at
 154          * offset zero relative to the text mapping.  This should be
 155          * impossible here, because sym_offset should only be zero for
 156          * the page past the end of the vvar mapping.
 157          */
 158         if (sym_offset == 0)
 159                 return VM_FAULT_SIGBUS;
 160
 161         if (sym_offset == image->sym_vvar_page) {
 162                 struct page *timens_page = find_timens_vvar_page(vma);
 163
 164                 pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
 165
 166                 /*
 167                  * If a task belongs to a time namespace then a namespace
 168                  * specific VVAR is mapped with the sym_vvar_page offset and
 169                  * the real VVAR page is mapped with the sym_timens_page
 170                  * offset.
 171                  * See also the comment near timens_setup_vdso_data().
 172                  */
 173                 if (timens_page) {
 174                         unsigned long addr;
 175                         vm_fault_t err;
 176
 177                         /*
 178                          * Optimization: inside time namespace pre-fault
 179                          * VVAR page too. As on timens page there are only
 180                          * offsets for clocks on VVAR, it'll be faulted
 181                          * shortly by VDSO code.
 182                          */
 183                         addr = vmf->address + (image->sym_timens_page - sym_offset);
 184                         err = vmf_insert_pfn(vma, addr, pfn);
 185                         if (unlikely(err & VM_FAULT_ERROR))
 186                                 return err;
 187
 188                         pfn = page_to_pfn(timens_page);
 189                 }
 190
 191                 return vmf_insert_pfn(vma, vmf->address, pfn);
 192         } else if (sym_offset == image->sym_pvclock_page) {
 193                 struct pvclock_vsyscall_time_info *pvti =
 194                         pvclock_get_pvti_cpu0_va();
 195                 if (pvti && vclock_was_used(VCLOCK_PVCLOCK)) {
 196                         return vmf_insert_pfn_prot(vma, vmf->address,
 197                                         __pa(pvti) >> PAGE_SHIFT,
 198                                         pgprot_decrypted(vma->vm_page_prot));
 199                 }
 200         } else if (sym_offset == image->sym_hvclock_page) {
 201                 struct ms_hyperv_tsc_page *tsc_pg = hv_get_tsc_page();
 202
 203                 if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
 204                         return vmf_insert_pfn(vma, vmf->address,
 205                                         virt_to_phys(tsc_pg) >> PAGE_SHIFT);
 206         } else if (sym_offset == image->sym_timens_page) {
 207                 struct page *timens_page = find_timens_vvar_page(vma);
 208
 209                 if (!timens_page)
 210                         return VM_FAULT_SIGBUS;
 211
 212                 pfn = __pa_symbol(&__vvar_page) >> PAGE_SHIFT;
 213                 return vmf_insert_pfn(vma, vmf->address, pfn);
 214         }
 215
 216         return VM_FAULT_SIGBUS;
 217 }
 218
 219 static const struct vm_special_mapping vdso_mapping = {
 220         .name = "[vdso]",
 221         .fault = vdso_fault,
 222         .mremap = vdso_mremap,
 223 };
 224 static const struct vm_special_mapping vvar_mapping = {
 225         .name = "[vvar]",
 226         .fault = vvar_fault,
 227         .mremap = vvar_mremap,
 228 };
 229
 230 /*
 231  * Add vdso and vvar mappings to current process.
 232  * @image          - blob to map
 233  * @addr           - request a specific address (zero to map at free addr)
 234  */
 235 static int map_vdso(const struct vdso_image *image, unsigned long addr)
 236 {
 237         struct mm_struct *mm = current->mm;
 238         struct vm_area_struct *vma;
 239         unsigned long text_start;
 240         int ret = 0;
 241
 242         if (down_write_killable(&mm->mmap_sem))
 243                 return -EINTR;
 244
 245         addr = get_unmapped_area(NULL, addr,
 246                                  image->size - image->sym_vvar_start, 0, 0);
 247         if (IS_ERR_VALUE(addr)) {
 248                 ret = addr;
 249                 goto up_fail;
 250         }
 251
 252         text_start = addr - image->sym_vvar_start;
 253
 254         /*
 255          * MAYWRITE to allow gdb to COW and set breakpoints
 256          */
 257         vma = _install_special_mapping(mm,
 258                                        text_start,
 259                                        image->size,
 260                                        VM_READ|VM_EXEC|
 261                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 262                                        &vdso_mapping);
 263
 264         if (IS_ERR(vma)) {
 265                 ret = PTR_ERR(vma);
 266                 goto up_fail;
 267         }
 268
 269         vma = _install_special_mapping(mm,
 270                                        addr,
 271                                        -image->sym_vvar_start,
 272                                        VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
 273                                        VM_PFNMAP,
 274                                        &vvar_mapping);
 275
 276         if (IS_ERR(vma)) {
 277                 ret = PTR_ERR(vma);
 278                 do_munmap(mm, text_start, image->size, NULL);
 279         } else {
 280                 current->mm->context.vdso = (void __user *)text_start;
 281                 current->mm->context.vdso_image = image;
 282         }
 283
 284 up_fail:
 285         up_write(&mm->mmap_sem);
 286         return ret;
 287 }
 288
 289 #ifdef CONFIG_X86_64
 290 /*
 291  * Put the vdso above the (randomized) stack with another randomized
 292  * offset.  This way there is no hole in the middle of address space.
 293  * To save memory make sure it is still in the same PTE as the stack
 294  * top.  This doesn't give that many random bits.
 295  *
 296  * Note that this algorithm is imperfect: the distribution of the vdso
 297  * start address within a PMD is biased toward the end.
 298  *
 299  * Only used for the 64-bit and x32 vdsos.
 300  */
 301 static unsigned long vdso_addr(unsigned long start, unsigned len)
 302 {
 303         unsigned long addr, end;
 304         unsigned offset;
 305
 306         /*
 307          * Round up the start address.  It can start out unaligned as a result
 308          * of stack start randomization.
 309          */
 310         start = PAGE_ALIGN(start);
 311
 312         /* Round the lowest possible end address up to a PMD boundary. */
 313         end = (start + len + PMD_SIZE - 1) & PMD_MASK;
 314         if (end >= TASK_SIZE_MAX)
 315                 end = TASK_SIZE_MAX;
 316         end -= len;
 317
 318         if (end > start) {
 319                 offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
 320                 addr = start + (offset << PAGE_SHIFT);
 321         } else {
 322                 addr = start;
 323         }
 324
 325         /*
 326          * Forcibly align the final address in case we have a hardware
 327          * issue that requires alignment for performance reasons.
 328          */
 329         addr = align_vdso_addr(addr);
 330
 331         return addr;
 332 }
 333
 334 static int map_vdso_randomized(const struct vdso_image *image)
 335 {
 336         unsigned long addr = vdso_addr(current->mm->start_stack, image->size-image->sym_vvar_start);
 337
 338         return map_vdso(image, addr);
 339 }
 340 #endif
 341
 342 int map_vdso_once(const struct vdso_image *image, unsigned long addr)
 343 {
 344         struct mm_struct *mm = current->mm;
 345         struct vm_area_struct *vma;
 346
 347         down_write(&mm->mmap_sem);
 348         /*
 349          * Check if we have already mapped vdso blob - fail to prevent
 350          * abusing from userspace install_speciall_mapping, which may
 351          * not do accounting and rlimit right.
 352          * We could search vma near context.vdso, but it's a slowpath,
 353          * so let's explicitly check all VMAs to be completely sure.
 354          */
 355         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 356                 if (vma_is_special_mapping(vma, &vdso_mapping) ||
 357                                 vma_is_special_mapping(vma, &vvar_mapping)) {
 358                         up_write(&mm->mmap_sem);
 359                         return -EEXIST;
 360                 }
 361         }
 362         up_write(&mm->mmap_sem);
 363
 364         return map_vdso(image, addr);
 365 }
 366
 367 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 368 static int load_vdso32(void)
 369 {
 370         if (vdso32_enabled != 1)  /* Other values all mean "disabled" */
 371                 return 0;
 372
 373         return map_vdso(&vdso_image_32, 0);
 374 }
 375 #endif
 376
 377 #ifdef CONFIG_X86_64
 378 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 379 {
 380         if (!vdso64_enabled)
 381                 return 0;
 382
 383         return map_vdso_randomized(&vdso_image_64);
 384 }
 385
 386 #ifdef CONFIG_COMPAT
 387 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 388                                        int uses_interp)
 389 {
 390 #ifdef CONFIG_X86_X32_ABI
 391         if (test_thread_flag(TIF_X32)) {
 392                 if (!vdso64_enabled)
 393                         return 0;
 394                 return map_vdso_randomized(&vdso_image_x32);
 395         }
 396 #endif
 397 #ifdef CONFIG_IA32_EMULATION
 398         return load_vdso32();
 399 #else
 400         return 0;
 401 #endif
 402 }
 403 #endif
 404 #else
 405 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 406 {
 407         return load_vdso32();
 408 }
 409 #endif
 410
 411 #ifdef CONFIG_X86_64
 412 static __init int vdso_setup(char *s)
 413 {
 414         vdso64_enabled = simple_strtoul(s, NULL, 0);
 415         return 0;
 416 }
 417 __setup("vdso=", vdso_setup);
 418
 419 static int __init init_vdso(void)
 420 {
 421         init_vdso_image(&vdso_image_64);
 422
 423 #ifdef CONFIG_X86_X32_ABI
 424         init_vdso_image(&vdso_image_x32);
 425 #endif
 426
 427         return 0;
 428 }
 429 subsys_initcall(init_vdso);
 430 #endif /* CONFIG_X86_64 */