ldt.h 1.2 KB

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  1. /*
  2. * ldt.h
  3. *
  4. * Definitions of structures used with the modify_ldt system call.
  5. */
  6. #ifndef _ASM_X86_LDT_H
  7. #define _ASM_X86_LDT_H
  8. /* Maximum number of LDT entries supported. */
  9. #define LDT_ENTRIES 8192
  10. /* The size of each LDT entry. */
  11. #define LDT_ENTRY_SIZE 8
  12. #ifndef __ASSEMBLY__
  13. /*
  14. * Note on 64bit base and limit is ignored and you cannot set DS/ES/CS
  15. * not to the default values if you still want to do syscalls. This
  16. * call is more for 32bit mode therefore.
  17. */
  18. struct user_desc {
  19. unsigned int entry_number;
  20. unsigned int base_addr;
  21. unsigned int limit;
  22. unsigned int seg_32bit:1;
  23. unsigned int contents:2;
  24. unsigned int read_exec_only:1;
  25. unsigned int limit_in_pages:1;
  26. unsigned int seg_not_present:1;
  27. unsigned int useable:1;
  28. #ifdef __x86_64__
  29. /*
  30. * Because this bit is not present in 32-bit user code, user
  31. * programs can pass uninitialized values here. Therefore, in
  32. * any context in which a user_desc comes from a 32-bit program,
  33. * the kernel must act as though lm == 0, regardless of the
  34. * actual value.
  35. */
  36. unsigned int lm:1;
  37. #endif
  38. };
  39. #define MODIFY_LDT_CONTENTS_DATA 0
  40. #define MODIFY_LDT_CONTENTS_STACK 1
  41. #define MODIFY_LDT_CONTENTS_CODE 2
  42. #endif /* !__ASSEMBLY__ */
  43. #endif /* _ASM_X86_LDT_H */