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       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 */