linux/include/uapi/asm-generic/sembuf.h
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   1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2#ifndef __ASM_GENERIC_SEMBUF_H
   3#define __ASM_GENERIC_SEMBUF_H
   4
   5#include <asm/bitsperlong.h>
   6
   7/*
   8 * The semid64_ds structure for x86 architecture.
   9 * Note extra padding because this structure is passed back and forth
  10 * between kernel and user space.
  11 *
  12 * semid64_ds was originally meant to be architecture specific, but
  13 * everyone just ended up making identical copies without specific
  14 * optimizations, so we may just as well all use the same one.
  15 *
  16 * 64 bit architectures use a 64-bit __kernel_time_t here, while
  17 * 32 bit architectures have a pair of unsigned long values.
  18 * so they do not need the first two padding words.
  19 *
  20 * On big-endian systems, the padding is in the wrong place for
  21 * historic reasons, so user space has to reconstruct a time_t
  22 * value using
  23 *
  24 * user_semid_ds.sem_otime = kernel_semid64_ds.sem_otime +
  25 *              ((long long)kernel_semid64_ds.sem_otime_high << 32)
  26 *
  27 * Pad space is left for 2 miscellaneous 32-bit values
  28 */
  29struct semid64_ds {
  30        struct ipc64_perm sem_perm;     /* permissions .. see ipc.h */
  31#if __BITS_PER_LONG == 64
  32        __kernel_time_t sem_otime;      /* last semop time */
  33        __kernel_time_t sem_ctime;      /* last change time */
  34#else
  35        unsigned long   sem_otime;      /* last semop time */
  36        unsigned long   sem_otime_high;
  37        unsigned long   sem_ctime;      /* last change time */
  38        unsigned long   sem_ctime_high;
  39#endif
  40        unsigned long   sem_nsems;      /* no. of semaphores in array */
  41        unsigned long   __unused3;
  42        unsigned long   __unused4;
  43};
  44
  45#endif /* __ASM_GENERIC_SEMBUF_H */
  46