uapi/asm/ldt.h

0001 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
0002 /*
0003  * ldt.h
0004  *
0005  * Definitions of structures used with the modify_ldt system call.
0006  */
0007 #ifndef _ASM_X86_LDT_H
0008 #define _ASM_X86_LDT_H
0009
0010 /* Maximum number of LDT entries supported. */
0011 #define LDT_ENTRIES 8192
0012 /* The size of each LDT entry. */
0013 #define LDT_ENTRY_SIZE  8
0014
0015 #ifndef __ASSEMBLY__
0016 /*
0017  * Note on 64bit base and limit is ignored and you cannot set DS/ES/CS
0018  * not to the default values if you still want to do syscalls. This
0019  * call is more for 32bit mode therefore.
0020  */
0021 struct user_desc {
0022     unsigned int  entry_number;
0023     unsigned int  base_addr;
0024     unsigned int  limit;
0025     unsigned int  seg_32bit:1;
0026     unsigned int  contents:2;
0027     unsigned int  read_exec_only:1;
0028     unsigned int  limit_in_pages:1;
0029     unsigned int  seg_not_present:1;
0030     unsigned int  useable:1;
0031 #ifdef __x86_64__
0032     /*
0033      * Because this bit is not present in 32-bit user code, user
0034      * programs can pass uninitialized values here.  Therefore, in
0035      * any context in which a user_desc comes from a 32-bit program,
0036      * the kernel must act as though lm == 0, regardless of the
0037      * actual value.
0038      */
0039     unsigned int  lm:1;
0040 #endif
0041 };
0042
0043 #define MODIFY_LDT_CONTENTS_DATA    0
0044 #define MODIFY_LDT_CONTENTS_STACK   1
0045 #define MODIFY_LDT_CONTENTS_CODE    2
0046
0047 #endif /* !__ASSEMBLY__ */
0048 #endif /* _ASM_X86_LDT_H */