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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 */
48