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 */
49