mmu.c 3.5 KB

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  1. /*
  2. * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3. * Licensed under the GPL
  4. */
  5. #include "linux/mm.h"
  6. #include "linux/sched.h"
  7. #include "linux/slab.h"
  8. #include "asm/pgalloc.h"
  9. #include "asm/pgtable.h"
  10. #include "as-layout.h"
  11. #include "os.h"
  12. #include "skas.h"
  13. extern int __syscall_stub_start;
  14. static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  15. unsigned long kernel)
  16. {
  17. pgd_t *pgd;
  18. pud_t *pud;
  19. pmd_t *pmd;
  20. pte_t *pte;
  21. pgd = pgd_offset(mm, proc);
  22. pud = pud_alloc(mm, pgd, proc);
  23. if (!pud)
  24. goto out;
  25. pmd = pmd_alloc(mm, pud, proc);
  26. if (!pmd)
  27. goto out_pmd;
  28. pte = pte_alloc_map(mm, NULL, pmd, proc);
  29. if (!pte)
  30. goto out_pte;
  31. *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
  32. *pte = pte_mkread(*pte);
  33. return 0;
  34. out_pte:
  35. pmd_free(mm, pmd);
  36. out_pmd:
  37. pud_free(mm, pud);
  38. out:
  39. return -ENOMEM;
  40. }
  41. int init_new_context(struct task_struct *task, struct mm_struct *mm)
  42. {
  43. struct mm_context *from_mm = NULL;
  44. struct mm_context *to_mm = &mm->context;
  45. unsigned long stack = 0;
  46. int ret = -ENOMEM;
  47. if (skas_needs_stub) {
  48. stack = get_zeroed_page(GFP_KERNEL);
  49. if (stack == 0)
  50. goto out;
  51. }
  52. to_mm->id.stack = stack;
  53. if (current->mm != NULL && current->mm != &init_mm)
  54. from_mm = &current->mm->context;
  55. if (proc_mm) {
  56. ret = new_mm(stack);
  57. if (ret < 0) {
  58. printk(KERN_ERR "init_new_context_skas - "
  59. "new_mm failed, errno = %d\n", ret);
  60. goto out_free;
  61. }
  62. to_mm->id.u.mm_fd = ret;
  63. }
  64. else {
  65. if (from_mm)
  66. to_mm->id.u.pid = copy_context_skas0(stack,
  67. from_mm->id.u.pid);
  68. else to_mm->id.u.pid = start_userspace(stack);
  69. if (to_mm->id.u.pid < 0) {
  70. ret = to_mm->id.u.pid;
  71. goto out_free;
  72. }
  73. }
  74. ret = init_new_ldt(to_mm, from_mm);
  75. if (ret < 0) {
  76. printk(KERN_ERR "init_new_context_skas - init_ldt"
  77. " failed, errno = %d\n", ret);
  78. goto out_free;
  79. }
  80. return 0;
  81. out_free:
  82. if (to_mm->id.stack != 0)
  83. free_page(to_mm->id.stack);
  84. out:
  85. return ret;
  86. }
  87. void uml_setup_stubs(struct mm_struct *mm)
  88. {
  89. int err, ret;
  90. if (!skas_needs_stub)
  91. return;
  92. ret = init_stub_pte(mm, STUB_CODE,
  93. (unsigned long) &__syscall_stub_start);
  94. if (ret)
  95. goto out;
  96. ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
  97. if (ret)
  98. goto out;
  99. mm->context.stub_pages[0] = virt_to_page(&__syscall_stub_start);
  100. mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
  101. /* dup_mmap already holds mmap_sem */
  102. err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
  103. VM_READ | VM_MAYREAD | VM_EXEC |
  104. VM_MAYEXEC | VM_DONTCOPY,
  105. mm->context.stub_pages);
  106. if (err) {
  107. printk(KERN_ERR "install_special_mapping returned %d\n", err);
  108. goto out;
  109. }
  110. return;
  111. out:
  112. force_sigsegv(SIGSEGV, current);
  113. }
  114. void arch_exit_mmap(struct mm_struct *mm)
  115. {
  116. pte_t *pte;
  117. pte = virt_to_pte(mm, STUB_CODE);
  118. if (pte != NULL)
  119. pte_clear(mm, STUB_CODE, pte);
  120. pte = virt_to_pte(mm, STUB_DATA);
  121. if (pte == NULL)
  122. return;
  123. pte_clear(mm, STUB_DATA, pte);
  124. }
  125. void destroy_context(struct mm_struct *mm)
  126. {
  127. struct mm_context *mmu = &mm->context;
  128. if (proc_mm)
  129. os_close_file(mmu->id.u.mm_fd);
  130. else {
  131. /*
  132. * If init_new_context wasn't called, this will be
  133. * zero, resulting in a kill(0), which will result in the
  134. * whole UML suddenly dying. Also, cover negative and
  135. * 1 cases, since they shouldn't happen either.
  136. */
  137. if (mmu->id.u.pid < 2) {
  138. printk(KERN_ERR "corrupt mm_context - pid = %d\n",
  139. mmu->id.u.pid);
  140. return;
  141. }
  142. os_kill_ptraced_process(mmu->id.u.pid, 1);
  143. }
  144. if (skas_needs_stub)
  145. free_page(mmu->id.stack);
  146. free_ldt(mmu);
  147. }