mmap.c 4.7 KB

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  1. /*
  2. * flexible mmap layout support
  3. *
  4. * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
  5. * All Rights Reserved.
  6. *
  7. * This program is free software; you can redistribute it and/or modify
  8. * it under the terms of the GNU General Public License as published by
  9. * the Free Software Foundation; either version 2 of the License, or
  10. * (at your option) any later version.
  11. *
  12. * This program is distributed in the hope that it will be useful,
  13. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15. * GNU General Public License for more details.
  16. *
  17. * You should have received a copy of the GNU General Public License
  18. * along with this program; if not, write to the Free Software
  19. * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  20. *
  21. *
  22. * Started by Ingo Molnar <mingo@elte.hu>
  23. */
  24. #include <linux/personality.h>
  25. #include <linux/mm.h>
  26. #include <linux/mman.h>
  27. #include <linux/module.h>
  28. #include <linux/random.h>
  29. #include <linux/compat.h>
  30. #include <asm/pgalloc.h>
  31. static unsigned long stack_maxrandom_size(void)
  32. {
  33. if (!(current->flags & PF_RANDOMIZE))
  34. return 0;
  35. if (current->personality & ADDR_NO_RANDOMIZE)
  36. return 0;
  37. return STACK_RND_MASK << PAGE_SHIFT;
  38. }
  39. /*
  40. * Top of mmap area (just below the process stack).
  41. *
  42. * Leave at least a ~32 MB hole.
  43. */
  44. #define MIN_GAP (32*1024*1024)
  45. #define MAX_GAP (STACK_TOP/6*5)
  46. static inline int mmap_is_legacy(void)
  47. {
  48. if (current->personality & ADDR_COMPAT_LAYOUT)
  49. return 1;
  50. if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  51. return 1;
  52. return sysctl_legacy_va_layout;
  53. }
  54. static unsigned long mmap_rnd(void)
  55. {
  56. if (!(current->flags & PF_RANDOMIZE))
  57. return 0;
  58. /* 8MB randomization for mmap_base */
  59. return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
  60. }
  61. static unsigned long mmap_base_legacy(void)
  62. {
  63. return TASK_UNMAPPED_BASE + mmap_rnd();
  64. }
  65. static inline unsigned long mmap_base(void)
  66. {
  67. unsigned long gap = rlimit(RLIMIT_STACK);
  68. if (gap < MIN_GAP)
  69. gap = MIN_GAP;
  70. else if (gap > MAX_GAP)
  71. gap = MAX_GAP;
  72. gap &= PAGE_MASK;
  73. return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
  74. }
  75. #ifndef CONFIG_64BIT
  76. /*
  77. * This function, called very early during the creation of a new
  78. * process VM image, sets up which VM layout function to use:
  79. */
  80. void arch_pick_mmap_layout(struct mm_struct *mm)
  81. {
  82. /*
  83. * Fall back to the standard layout if the personality
  84. * bit is set, or if the expected stack growth is unlimited:
  85. */
  86. if (mmap_is_legacy()) {
  87. mm->mmap_base = mmap_base_legacy();
  88. mm->get_unmapped_area = arch_get_unmapped_area;
  89. } else {
  90. mm->mmap_base = mmap_base();
  91. mm->get_unmapped_area = arch_get_unmapped_area_topdown;
  92. }
  93. }
  94. #else
  95. int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
  96. {
  97. if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
  98. return 0;
  99. if (!(flags & MAP_FIXED))
  100. addr = 0;
  101. if ((addr + len) >= TASK_SIZE)
  102. return crst_table_upgrade(current->mm, 1UL << 53);
  103. return 0;
  104. }
  105. static unsigned long
  106. s390_get_unmapped_area(struct file *filp, unsigned long addr,
  107. unsigned long len, unsigned long pgoff, unsigned long flags)
  108. {
  109. struct mm_struct *mm = current->mm;
  110. unsigned long area;
  111. int rc;
  112. area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
  113. if (!(area & ~PAGE_MASK))
  114. return area;
  115. if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
  116. /* Upgrade the page table to 4 levels and retry. */
  117. rc = crst_table_upgrade(mm, 1UL << 53);
  118. if (rc)
  119. return (unsigned long) rc;
  120. area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
  121. }
  122. return area;
  123. }
  124. static unsigned long
  125. s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
  126. const unsigned long len, const unsigned long pgoff,
  127. const unsigned long flags)
  128. {
  129. struct mm_struct *mm = current->mm;
  130. unsigned long area;
  131. int rc;
  132. area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
  133. if (!(area & ~PAGE_MASK))
  134. return area;
  135. if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
  136. /* Upgrade the page table to 4 levels and retry. */
  137. rc = crst_table_upgrade(mm, 1UL << 53);
  138. if (rc)
  139. return (unsigned long) rc;
  140. area = arch_get_unmapped_area_topdown(filp, addr, len,
  141. pgoff, flags);
  142. }
  143. return area;
  144. }
  145. /*
  146. * This function, called very early during the creation of a new
  147. * process VM image, sets up which VM layout function to use:
  148. */
  149. void arch_pick_mmap_layout(struct mm_struct *mm)
  150. {
  151. /*
  152. * Fall back to the standard layout if the personality
  153. * bit is set, or if the expected stack growth is unlimited:
  154. */
  155. if (mmap_is_legacy()) {
  156. mm->mmap_base = mmap_base_legacy();
  157. mm->get_unmapped_area = s390_get_unmapped_area;
  158. } else {
  159. mm->mmap_base = mmap_base();
  160. mm->get_unmapped_area = s390_get_unmapped_area_topdown;
  161. }
  162. }
  163. #endif