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 */
21struct 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 */
49