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

   1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2 /*
   3  * ldt.h
   4  *
   5  * Definitions of structures used with the modify_ldt system call.
   6  */
   7 #ifndef _ASM_X86_LDT_H
   8 #define _ASM_X86_LDT_H
   9
  10 /* Maximum number of LDT entries supported. */
  11 #define LDT_ENTRIES     8192
  12 /* The size of each LDT entry. */
  13 #define LDT_ENTRY_SIZE  8
  14
  15 #ifndef __ASSEMBLY__
  16 /*
  17  * Note on 64bit base and limit is ignored and you cannot set DS/ES/CS
  18  * not to the default values if you still want to do syscalls. This
  19  * call is more for 32bit mode therefore.
  20  */
  21 struct user_desc {
  22         unsigned int  entry_number;
  23         unsigned int  base_addr;
  24         unsigned int  limit;
  25         unsigned int  seg_32bit:1;
  26         unsigned int  contents:2;
  27         unsigned int  read_exec_only:1;
  28         unsigned int  limit_in_pages:1;
  29         unsigned int  seg_not_present:1;
  30         unsigned int  useable:1;
  31 #ifdef __x86_64__
  32         /*
  33          * Because this bit is not present in 32-bit user code, user
  34          * programs can pass uninitialized values here.  Therefore, in
  35          * any context in which a user_desc comes from a 32-bit program,
  36          * the kernel must act as though lm == 0, regardless of the
  37          * actual value.
  38          */
  39         unsigned int  lm:1;
  40 #endif
  41 };
  42
  43 #define MODIFY_LDT_CONTENTS_DATA        0
  44 #define MODIFY_LDT_CONTENTS_STACK       1
  45 #define MODIFY_LDT_CONTENTS_CODE        2
  46
  47 #endif /* !__ASSEMBLY__ */
  48 #endif /* _ASM_X86_LDT_H */