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