arch/x86/include/uapi/asm/ldt.h

   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
   9 /* Maximum number of LDT entries supported. */
  10 #define LDT_ENTRIES     8192
  11 /* The size of each LDT entry. */
  12 #define LDT_ENTRY_SIZE  8
  13
  14 #ifndef __ASSEMBLY__
  15 /*
  16  * Note on 64bit base and limit is ignored and you cannot set DS/ES/CS
  17  * not to the default values if you still want to do syscalls. This
  18  * call is more for 32bit mode therefore.
  19  */
  20 struct user_desc {
  21         unsigned int  entry_number;
  22         unsigned int  base_addr;
  23         unsigned int  limit;
  24         unsigned int  seg_32bit:1;
  25         unsigned int  contents:2;
  26         unsigned int  read_exec_only:1;
  27         unsigned int  limit_in_pages:1;
  28         unsigned int  seg_not_present:1;
  29         unsigned int  useable:1;
  30 #ifdef __x86_64__
  31         /*
  32          * Because this bit is not present in 32-bit user code, user
  33          * programs can pass uninitialized values here.  Therefore, in
  34          * any context in which a user_desc comes from a 32-bit program,
  35          * the kernel must act as though lm == 0, regardless of the
  36          * actual value.
  37          */
  38         unsigned int  lm:1;
  39 #endif
  40 };
  41
  42 #define MODIFY_LDT_CONTENTS_DATA        0
  43 #define MODIFY_LDT_CONTENTS_STACK       1
  44 #define MODIFY_LDT_CONTENTS_CODE        2
  45
  46 #endif /* !__ASSEMBLY__ */
  47 #endif /* _ASM_X86_LDT_H */