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