Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/x86/include/uapi/asm/ldt.h
26495 views
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 __ASSEMBLER__

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 /* !__ASSEMBLER__ */

48
#endif /* _ASM_X86_LDT_H */

49


50