kprobe/dbi_kprobes_deps.c

   1 /*
   2  *  Dynamic Binary Instrumentation Module based on KProbes
   3  *  modules/kprobe/dbi_kprobes_deps.h
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18  *
  19  * Copyright (C) Samsung Electronics, 2006-2010
  20  *
  21  * 2008-2009    Alexey Gerenkov <a.gerenkov@samsung.com> User-Space
  22  *              Probes initial implementation; Support x86/ARM/MIPS for both user and kernel spaces.
  23  * 2010         Ekaterina Gorelkina <e.gorelkina@samsung.com>: redesign module for separating core and arch parts
  24  *
  25
  26  */
  27
  28 #include <linux/module.h>
  29 #include <linux/sched.h>
  30
  31 #include <asm/pgtable.h>
  32
  33 #include "dbi_kprobes_deps.h"
  34 #include "dbi_kdebug.h"
  35
  36
  37 #include <linux/slab.h>
  38
  39 unsigned int *sched_addr;
  40 unsigned int *fork_addr;
  41
  42
  43 #define GUP_FLAGS_WRITE                  0x1
  44 #define GUP_FLAGS_WRITE                  0x1
  45 #define GUP_FLAGS_FORCE                  0x2
  46 #define GUP_FLAGS_IGNORE_VMA_PERMISSIONS 0x4
  47 #define GUP_FLAGS_IGNORE_SIGKILL         0x8
  48
  49 #if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 29)
  50 struct mm_struct* init_mm_ptr;
  51 struct mm_struct init_mm;
  52 #endif
  53
  54
  55 DECLARE_MOD_CB_DEP(kallsyms_search, unsigned long, const char *name);
  56
  57 DECLARE_MOD_FUNC_DEP(access_process_vm, int, struct task_struct * tsk, unsigned long addr, void *buf, int len, int write);
  58
  59 DECLARE_MOD_FUNC_DEP(find_extend_vma, struct vm_area_struct *, struct mm_struct * mm, unsigned long addr);
  60
  61 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2, 6, 30)
  62 #if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 18)
  63 DECLARE_MOD_FUNC_DEP(handle_mm_fault, int, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access);
  64 #endif
  65 #else
  66 DECLARE_MOD_FUNC_DEP(handle_mm_fault, int, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, unsigned int flags);
  67 #endif /* LINUX_VERSION_CODE <= KERNEL_VERSION(2, 6, 30) */
  68
  69 DECLARE_MOD_FUNC_DEP(get_gate_vma, struct vm_area_struct *, struct task_struct *tsk);
  70
  71 #ifdef CONFIG_HUGETLB_PAGE
  72 DECLARE_MOD_FUNC_DEP(follow_hugetlb_page, int, struct mm_struct *mm, struct vm_area_struct *vma, struct page **pages, struct vm_area_struct **vmas, unsigned long *position, int *length, int i, int write);
  73 #endif
  74
  75 #ifdef  __HAVE_ARCH_GATE_AREA
  76 DECLARE_MOD_FUNC_DEP(in_gate_area, int, struct task_struct *tsk,unsigned long addr);
  77 #else
  78 DECLARE_MOD_FUNC_DEP(in_gate_area_no_task, int, unsigned long addr);
  79 #endif
  80 DECLARE_MOD_FUNC_DEP(follow_page, \
  81                 struct page *, struct vm_area_struct * vma, \
  82                 unsigned long address, unsigned int foll_flags);
  83 DECLARE_MOD_FUNC_DEP(__flush_anon_page, \
  84                 void, struct vm_area_struct *vma, struct page *page, \
  85                 unsigned long vmaddr);
  86 DECLARE_MOD_FUNC_DEP(vm_normal_page, \
  87                 struct page *, struct vm_area_struct *vma, \
  88                 unsigned long addr, pte_t pte);
  89
  90 DECLARE_MOD_FUNC_DEP(flush_ptrace_access, \
  91                 void, struct vm_area_struct *vma, struct page *page, \
  92                 unsigned long uaddr, void *kaddr, unsigned long len, int write);
  93
  94
  95 #if (LINUX_VERSION_CODE != KERNEL_VERSION(2, 6, 16))
  96 DECLARE_MOD_FUNC_DEP(put_task_struct, \
  97                 void, struct task_struct *tsk);
  98 #else
  99 DECLARE_MOD_FUNC_DEP(put_task_struct, \
 100                 void, struct rcu_head * rhp);
 101 #endif
 102
 103         DECLARE_MOD_DEP_WRAPPER(access_process_vm, int, struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 104 IMP_MOD_DEP_WRAPPER (access_process_vm, tsk, addr, buf, len, write)
 105
 106         DECLARE_MOD_DEP_WRAPPER (find_extend_vma, struct vm_area_struct *, struct mm_struct * mm, unsigned long addr)
 107 IMP_MOD_DEP_WRAPPER (find_extend_vma, mm, addr)
 108
 109 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2, 6, 30)
 110 #if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 18)
 111         DECLARE_MOD_DEP_WRAPPER (handle_mm_fault, \
 112                         int, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access)
 113 IMP_MOD_DEP_WRAPPER (handle_mm_fault, mm, vma, address, write_access)
 114 #endif
 115 #else
 116         DECLARE_MOD_DEP_WRAPPER (handle_mm_fault, \
 117                         int, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, unsigned int flags)
 118 IMP_MOD_DEP_WRAPPER (handle_mm_fault, mm, vma, address, flags)
 119 #endif
 120
 121         DECLARE_MOD_DEP_WRAPPER (get_gate_vma, \
 122                         struct vm_area_struct *, struct task_struct *tsk)
 123 IMP_MOD_DEP_WRAPPER (get_gate_vma, tsk)
 124
 125 #ifdef CONFIG_HUGETLB_PAGE
 126         DECLARE_MOD_DEP_WRAPPER (follow_hugetlb_page, int, struct mm_struct *mm, struct vm_area_struct *vma, struct page **pages, struct vm_area_struct **vmas, unsigned long *position, int *length, int i, int write)
 127         IMP_MOD_DEP_WRAPPER (follow_hugetlb_page, mm, vma, pages, vmas, position, length, i, write)
 128 #endif
 129
 130 #ifdef  __HAVE_ARCH_GATE_AREA
 131         DECLARE_MOD_DEP_WRAPPER (in_gate_area, int, struct task_struct *tsk, unsigned long addr)
 132         IMP_MOD_DEP_WRAPPER (in_gate_area, tsk, addr)
 133 #else
 134         DECLARE_MOD_DEP_WRAPPER (in_gate_area_no_task, int, unsigned long addr)
 135 IMP_MOD_DEP_WRAPPER (in_gate_area_no_task, addr)
 136 #endif
 137
 138 #if (LINUX_VERSION_CODE != KERNEL_VERSION(2, 6, 11))
 139         DECLARE_MOD_DEP_WRAPPER (follow_page, \
 140                         struct page *, struct vm_area_struct * vma, \
 141                         unsigned long address, unsigned int foll_flags)
 142 IMP_MOD_DEP_WRAPPER (follow_page, vma, address, foll_flags)
 143 #endif
 144         DECLARE_MOD_DEP_WRAPPER (__flush_anon_page, \
 145                         void, struct vm_area_struct *vma, \
 146                         struct page *page, unsigned long vmaddr)
 147 IMP_MOD_DEP_WRAPPER (__flush_anon_page, vma, page, vmaddr)
 148
 149         DECLARE_MOD_DEP_WRAPPER(vm_normal_page, \
 150                         struct page *, struct vm_area_struct *vma, \
 151                         unsigned long addr, pte_t pte)
 152 IMP_MOD_DEP_WRAPPER (vm_normal_page, vma, addr, pte)
 153
 154         DECLARE_MOD_DEP_WRAPPER (flush_ptrace_access, \
 155                         void, struct vm_area_struct *vma, struct page *page, \
 156                         unsigned long uaddr, void *kaddr, unsigned long len, int write)
 157 IMP_MOD_DEP_WRAPPER (flush_ptrace_access, vma, page, uaddr, kaddr, len, write)
 158
 159 int init_module_dependencies()
 160 {
 161
 162 #if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 29)
 163         init_mm_ptr = (struct mm_struct*) kallsyms_search ("init_mm");
 164         memcmp(init_mm_ptr, &init_mm, sizeof(struct mm_struct));
 165 #endif
 166
 167 #if LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 18)
 168         INIT_MOD_DEP_VAR(handle_mm_fault, handle_mm_fault);
 169 #endif
 170
 171         INIT_MOD_DEP_VAR(flush_ptrace_access, flush_ptrace_access);
 172         INIT_MOD_DEP_VAR(find_extend_vma, find_extend_vma);
 173         INIT_MOD_DEP_VAR(get_gate_vma, get_gate_vma);
 174
 175 #ifdef CONFIG_HUGETLB_PAGE
 176         INIT_MOD_DEP_VAR(follow_hugetlb_page, follow_hugetlb_page);
 177 #endif
 178
 179 #ifdef  __HAVE_ARCH_GATE_AREA
 180         INIT_MOD_DEP_VAR(in_gate_area, in_gate_area);
 181 #else
 182         INIT_MOD_DEP_VAR(in_gate_area_no_task, in_gate_area_no_task);
 183 #endif
 184         INIT_MOD_DEP_VAR(follow_page, follow_page);
 185
 186         INIT_MOD_DEP_VAR(__flush_anon_page, __flush_anon_page);
 187         INIT_MOD_DEP_VAR(vm_normal_page, vm_normal_page);
 188         INIT_MOD_DEP_VAR(access_process_vm, access_process_vm);
 189
 190 #if (LINUX_VERSION_CODE != KERNEL_VERSION(2, 6, 16))
 191 # if (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 11))
 192         INIT_MOD_DEP_VAR(put_task_struct, put_task_struct);
 193 # else
 194         INIT_MOD_DEP_VAR(put_task_struct, __put_task_struct);
 195 # endif
 196 #else /*2.6.16 */
 197         INIT_MOD_DEP_VAR(put_task_struct, __put_task_struct_cb);
 198 #endif
 199
 200         return 0;
 201 }
 202
 203 #define GUP_FLAGS_WRITE                  0x1
 204 #define GUP_FLAGS_FORCE                  0x2
 205 #define GUP_FLAGS_IGNORE_VMA_PERMISSIONS 0x4
 206 #define GUP_FLAGS_IGNORE_SIGKILL         0x8
 207
 208 #if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,18)
 209 static inline int use_zero_page(struct vm_area_struct *vma)
 210 {
 211         /*
 212          * We don't want to optimize FOLL_ANON for make_pages_present()
 213          * when it tries to page in a VM_LOCKED region. As to VM_SHARED,
 214          * we want to get the page from the page tables to make sure
 215          * that we serialize and update with any other user of that
 216          * mapping.
 217          */
 218         if (vma->vm_flags & (VM_LOCKED | VM_SHARED))
 219                 return 0;
 220         /*
 221          * And if we have a fault routine, it's not an anonymous region.
 222          */
 223         return !vma->vm_ops || !vma->vm_ops->fault;
 224 }
 225
 226 int __get_user_pages_uprobe(struct task_struct *tsk, struct mm_struct *mm,
 227                      unsigned long start, int len, int flags,
 228                 struct page **pages, struct vm_area_struct **vmas)
 229 {
 230         int i;
 231         unsigned int vm_flags = 0;
 232         int write = !!(flags & GUP_FLAGS_WRITE);
 233         int force = !!(flags & GUP_FLAGS_FORCE);
 234         int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
 235         int ignore_sigkill = !!(flags & GUP_FLAGS_IGNORE_SIGKILL);
 236
 237         if (len <= 0)
 238                 return 0;
 239         /*
 240          * Require read or write permissions.
 241          * If 'force' is set, we only require the "MAY" flags.
 242          */
 243         vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
 244         vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
 245         i = 0;
 246
 247         do {
 248                 struct vm_area_struct *vma;
 249                 unsigned int foll_flags;
 250
 251                 //vma = find_extend_vma(mm, start);
 252                 vma = find_vma(mm, start);
 253                 if (!vma && in_gate_area(tsk, start)) {
 254                         unsigned long pg = start & PAGE_MASK;
 255                         struct vm_area_struct *gate_vma = get_gate_vma(tsk);
 256                         pgd_t *pgd;
 257                         pud_t *pud;
 258                         pmd_t *pmd;
 259                         pte_t *pte;
 260
 261                         /* user gate pages are read-only */
 262                         if (!ignore && write)
 263                                 return i ? : -EFAULT;
 264                         if (pg > TASK_SIZE)
 265                                 pgd = pgd_offset_k(pg);
 266                         else
 267                                 pgd = pgd_offset_gate(mm, pg);
 268                         BUG_ON(pgd_none(*pgd));
 269                         pud = pud_offset(pgd, pg);
 270                         BUG_ON(pud_none(*pud));
 271                         pmd = pmd_offset(pud, pg);
 272                         if (pmd_none(*pmd))
 273                                 return i ? : -EFAULT;
 274                         pte = pte_offset_map(pmd, pg);
 275                         if (pte_none(*pte)) {
 276                                 pte_unmap(pte);
 277                                 return i ? : -EFAULT;
 278                         }
 279                         if (pages) {
 280                                 struct page *page = vm_normal_page(gate_vma, start, *pte);
 281                                 pages[i] = page;
 282                                 if (page)
 283                                         get_page(page);
 284                         }
 285                         pte_unmap(pte);
 286                         if (vmas)
 287                                 vmas[i] = gate_vma;
 288                         i++;
 289                         start += PAGE_SIZE;
 290                         len--;
 291                         continue;
 292                 }
 293
 294                 if (!vma ||
 295                     (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
 296                     (!ignore && !(vm_flags & vma->vm_flags)))
 297                         return i ? : -EFAULT;
 298
 299                 if (is_vm_hugetlb_page(vma)) {
 300 #if  LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
 301                         i = follow_hugetlb_page(mm, vma, pages, vmas,
 302                                                 &start, &len, i);
 303 #else
 304                         i = follow_hugetlb_page(mm, vma, pages, vmas,
 305                                                 &start, &len, i, write);
 306 #endif
 307                         continue;
 308                 }
 309
 310                 foll_flags = FOLL_TOUCH;
 311                 if (pages)
 312                         foll_flags |= FOLL_GET;
 313
 314 #if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,18)
 315 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,30)
 316                 if (!write && use_zero_page(vma))
 317                   foll_flags |= FOLL_ANON;
 318 #endif
 319 #endif
 320
 321                 do {
 322                         struct page *page;
 323
 324 #if 0
 325                         /*
 326                          * If we have a pending SIGKILL, don't keep faulting
 327                          * pages and potentially allocating memory, unless
 328                          * current is handling munlock--e.g., on exit. In
 329                          * that case, we are not allocating memory.  Rather,
 330                          * we're only unlocking already resident/mapped pages.
 331                          */
 332                         if (unlikely(!ignore_sigkill &&
 333                                         fatal_signal_pending(current)))
 334                                 return i ? i : -ERESTARTSYS;
 335 #endif
 336
 337                         if (write)
 338                                 foll_flags |= FOLL_WRITE;
 339
 340
 341                         //cond_resched();
 342
 343                         DBPRINTF ("pages = %p vma = %p\n", pages, vma);
 344                         while (!(page = follow_page(vma, start, foll_flags))) {
 345                                 int ret;
 346                                 ret = handle_mm_fault(mm, vma, start,
 347                                                 foll_flags & FOLL_WRITE);
 348
 349 #if  LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
 350                                 if (ret & VM_FAULT_WRITE)
 351                                   foll_flags &= ~FOLL_WRITE;
 352
 353                                 switch (ret & ~VM_FAULT_WRITE) {
 354                                 case VM_FAULT_MINOR:
 355                                   tsk->min_flt++;
 356                                   break;
 357                                 case VM_FAULT_MAJOR:
 358                                   tsk->maj_flt++;
 359                                   break;
 360                                 case VM_FAULT_SIGBUS:
 361                                   return i ? i : -EFAULT;
 362                                 case VM_FAULT_OOM:
 363                                   return i ? i : -ENOMEM;
 364                                 default:
 365                                   BUG();
 366                                 }
 367
 368 #else
 369                                 if (ret & VM_FAULT_ERROR) {
 370                                   if (ret & VM_FAULT_OOM)
 371                                     return i ? i : -ENOMEM;
 372                                   else if (ret & VM_FAULT_SIGBUS)
 373                                     return i ? i : -EFAULT;
 374                                   BUG();
 375                                 }
 376                                 if (ret & VM_FAULT_MAJOR)
 377                                   tsk->maj_flt++;
 378                                 else
 379                                   tsk->min_flt++;
 380
 381                                 /*
 382                                  * The VM_FAULT_WRITE bit tells us that
 383                                  * do_wp_page has broken COW when necessary,
 384                                  * even if maybe_mkwrite decided not to set
 385                                  * pte_write. We can thus safely do subsequent
 386                                  * page lookups as if they were reads. But only
 387                                  * do so when looping for pte_write is futile:
 388                                  * in some cases userspace may also be wanting
 389                                  * to write to the gotten user page, which a
 390                                  * read fault here might prevent (a readonly
 391                                  * page might get reCOWed by userspace write).
 392                                  */
 393                                 if ((ret & VM_FAULT_WRITE) &&
 394                                     !(vma->vm_flags & VM_WRITE))
 395                                   foll_flags &= ~FOLL_WRITE;
 396
 397                                 //cond_resched();
 398 #endif
 399
 400                         }
 401
 402                         if (IS_ERR(page))
 403                                 return i ? i : PTR_ERR(page);
 404                         if (pages) {
 405                                 pages[i] = page;
 406
 407 #if  LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
 408                                 flush_anon_page(page, start);
 409 #else
 410                                 flush_anon_page(vma, page, start);
 411 #endif
 412                                 flush_dcache_page(page);
 413                         }
 414                         if (vmas)
 415                                 vmas[i] = vma;
 416                         i++;
 417                         start += PAGE_SIZE;
 418                         len--;
 419                 } while (len && start < vma->vm_end);
 420         } while (len);
 421         return i;
 422 }
 423 #endif
 424
 425
 426 int get_user_pages_uprobe(struct task_struct *tsk, struct mm_struct *mm,
 427                 unsigned long start, int len, int write, int force,
 428                 struct page **pages, struct vm_area_struct **vmas)
 429 {
 430 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 29)
 431         int flags = 0;
 432
 433         if (write)
 434                 flags |= GUP_FLAGS_WRITE;
 435         if (force)
 436                 flags |= GUP_FLAGS_FORCE;
 437
 438         return __get_user_pages_uprobe(tsk, mm,
 439                                 start, len, flags,
 440                                 pages, vmas);
 441 #else
 442         return get_user_pages(tsk, mm, start, len, write, force, pages, vmas);
 443 #endif
 444 }
 445
 446
 447 int access_process_vm_atomic(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 448 {
 449         struct mm_struct *mm;
 450         struct vm_area_struct *vma;
 451         void *old_buf = buf;
 452         unsigned long addr1 = addr;
 453         unsigned int* inst_buf = (unsigned int*)buf;
 454
 455
 456         mm = get_task_mm(tsk);
 457         if (!mm)
 458                 return 0;
 459
 460         down_read(&mm->mmap_sem);
 461         /* ignore errors, just check how much was successfully transferred */
 462         while (len) {
 463                 int bytes, ret, offset;
 464                 void *maddr;
 465                 struct page *page = NULL;
 466
 467                 ret = get_user_pages_uprobe(tsk, mm, addr, 1,
 468                                 write, 1, &page, &vma);
 469
 470                 if (ret <= 0) {
 471                         /*
 472                          * Check if this is a VM_IO | VM_PFNMAP VMA, which
 473                          * we can access using slightly different code.
 474                          */
 475 #ifdef CONFIG_HAVE_IOREMAP_PROT
 476                         vma = find_vma(mm, addr);
 477                         if (!vma)
 478                                 break;
 479                         if (vma->vm_ops && vma->vm_ops->access)
 480                                 ret = vma->vm_ops->access(vma, addr, buf,
 481                                                           len, write);
 482                         if (ret <= 0)
 483 #endif
 484                                 break;
 485                         bytes = ret;
 486                 } else {
 487                         bytes = len;
 488                         offset = addr & (PAGE_SIZE-1);
 489                         if (bytes > PAGE_SIZE-offset)
 490                                 bytes = PAGE_SIZE-offset;
 491
 492                         maddr = kmap(page);
 493                         if (write) {
 494                                 copy_to_user_page(vma, page, addr,
 495                                                   maddr + offset, buf, bytes);
 496                                 set_page_dirty_lock(page);
 497                         } else {
 498                                 copy_from_user_page(vma, page, addr,
 499                                                     buf, maddr + offset, bytes);
 500                         }
 501                         kunmap(page);
 502                         page_cache_release(page);
 503                 }
 504                 len -= bytes;
 505                 buf += bytes;
 506                 addr += bytes;
 507         }
 508         up_read(&mm->mmap_sem);
 509         mmput(mm);
 510
 511
 512         if(addr1 == 0xad327238)
 513         {
 514                         printk(">>>>> %s\n", tsk->comm);
 515                         printk(">>>>> %x\n", inst_buf[0]);
 516         }
 517
 518
 519         return buf - old_buf;
 520 }
 521
 522 int page_present (struct mm_struct *mm, unsigned long address)
 523 {
 524         pgd_t *pgd;
 525         pud_t *pud;
 526         pmd_t *pmd;
 527         pte_t *ptep, pte;
 528         unsigned long pfn;
 529
 530         pgd = pgd_offset(mm, address);
 531         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 532                 goto out;
 533
 534         pud = pud_offset(pgd, address);
 535         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
 536                 goto out;
 537
 538         pmd = pmd_offset(pud, address);
 539         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 540                 goto out;
 541
 542         ptep = pte_offset_map(pmd, address);
 543         if (!ptep)
 544                 goto out;
 545
 546         pte = *ptep;
 547         pte_unmap(ptep);
 548         if (pte_present(pte)) {
 549                 pfn = pte_pfn(pte);
 550                 if (pfn_valid(pfn)) {
 551                         return 1;
 552                 }
 553         }
 554
 555 out:
 556         return 0;
 557 }
 558
 559
 560 EXPORT_SYMBOL_GPL (page_present);
 561 EXPORT_SYMBOL_GPL (get_user_pages_uprobe);
 562 EXPORT_SYMBOL_GPL (access_process_vm_atomic);
 563