Arnd Bergmann <arnd@xxxxxxxx> writes: > Most architectures now use the asm-generic copy of the sysvipc data > structures (msqid64_ds, semid64_ds, shmid64_ds), which use 32-bit > __kernel_time_t on 32-bit architectures but have padding behind them to > allow extending the type to 64-bit. > > Unfortunately, that fails on all big-endian architectures, which have the > padding on the wrong side. As so many of them get it wrong, we decided to > not bother even trying to fix it up when we introduced the asm-generic > copy. Instead we always use the padding word now to provide the upper > 32 bits of the seconds value, regardless of the endianess. > > A libc implementation on a typical big-endian system can deal with > this by providing its own copy of the structure definition to user > space, and swapping the two 32-bit words before returning from the > semctl/shmctl/msgctl system calls. > > ARM64 and s/390 are architectures that use these generic headers and > also provide support for compat mode on 64-bit kernels, so we adapt > their copies here as well. > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > include/uapi/asm-generic/msgbuf.h | 17 ++++++++--------- > include/uapi/asm-generic/sembuf.h | 26 ++++++++++++++++---------- > include/uapi/asm-generic/shmbuf.h | 17 ++++++++--------- > 3 files changed, 32 insertions(+), 28 deletions(-) > > diff --git a/include/uapi/asm-generic/msgbuf.h b/include/uapi/asm-generic/msgbuf.h > index fb306ebdb36f..d2169cae93b8 100644 > --- a/include/uapi/asm-generic/msgbuf.h > +++ b/include/uapi/asm-generic/msgbuf.h > @@ -18,23 +18,22 @@ > * On big-endian systems, the padding is in the wrong place. > * > * Pad space is left for: > - * - 64-bit time_t to solve y2038 problem > * - 2 miscellaneous 32-bit values > */ > > struct msqid64_ds { > struct ipc64_perm msg_perm; > +#if __BITS_PER_LONG == 64 > __kernel_time_t msg_stime; /* last msgsnd time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused1; > -#endif > __kernel_time_t msg_rtime; /* last msgrcv time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused2; > -#endif > __kernel_time_t msg_ctime; /* last change time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused3; > +#else > + unsigned long msg_stime; /* last msgsnd time */ > + unsigned long msg_stime_high; > + unsigned long msg_rtime; /* last msgrcv time */ > + unsigned long msg_rtime_high; > + unsigned long msg_ctime; /* last change time */ > + unsigned long msg_ctime_high; > #endif I suspect you want to use __kernel_ulong_t here instead of a raw unsigned long. If nothing else it seems inconsistent to use typedefs in one half of the structure and no typedefs in the other half. > __kernel_ulong_t msg_cbytes; /* current number of bytes on queue */ > __kernel_ulong_t msg_qnum; /* number of messages in queue */ > diff --git a/include/uapi/asm-generic/sembuf.h b/include/uapi/asm-generic/sembuf.h > index cbf9cfe977d6..0bae010f1b64 100644 > --- a/include/uapi/asm-generic/sembuf.h > +++ b/include/uapi/asm-generic/sembuf.h > @@ -13,23 +13,29 @@ > * everyone just ended up making identical copies without specific > * optimizations, so we may just as well all use the same one. > * > - * 64 bit architectures typically define a 64 bit __kernel_time_t, > + * 64 bit architectures use a 64-bit __kernel_time_t here, while > + * 32 bit architectures have a pair of unsigned long values. > * so they do not need the first two padding words. > - * On big-endian systems, the padding is in the wrong place. > * > - * Pad space is left for: > - * - 64-bit time_t to solve y2038 problem > - * - 2 miscellaneous 32-bit values > + * On big-endian systems, the padding is in the wrong place for > + * historic reasons, so user space has to reconstruct a time_t > + * value using > + * > + * user_semid_ds.sem_otime = kernel_semid64_ds.sem_otime + > + * ((long long)kernel_semid64_ds.sem_otime_high << 32) > + * > + * Pad space is left for 2 miscellaneous 32-bit values > */ > struct semid64_ds { > struct ipc64_perm sem_perm; /* permissions .. see ipc.h */ > +#if __BITS_PER_LONG == 64 > __kernel_time_t sem_otime; /* last semop time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused1; > -#endif > __kernel_time_t sem_ctime; /* last change time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused2; > +#else > + unsigned long sem_otime; /* last semop time */ > + unsigned long sem_otime_high; > + unsigned long sem_ctime; /* last change time */ > + unsigned long sem_ctime_high; > #endif > unsigned long sem_nsems; /* no. of semaphores in array */ > unsigned long __unused3; > diff --git a/include/uapi/asm-generic/shmbuf.h b/include/uapi/asm-generic/shmbuf.h > index 2b6c3bb97f97..602f1b5b462b 100644 > --- a/include/uapi/asm-generic/shmbuf.h > +++ b/include/uapi/asm-generic/shmbuf.h > @@ -19,24 +19,23 @@ > * > * > * Pad space is left for: > - * - 64-bit time_t to solve y2038 problem > * - 2 miscellaneous 32-bit values > */ > > struct shmid64_ds { > struct ipc64_perm shm_perm; /* operation perms */ > size_t shm_segsz; /* size of segment (bytes) */ > +#if __BITS_PER_LONG == 64 > __kernel_time_t shm_atime; /* last attach time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused1; > -#endif > __kernel_time_t shm_dtime; /* last detach time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused2; > -#endif > __kernel_time_t shm_ctime; /* last change time */ > -#if __BITS_PER_LONG != 64 > - unsigned long __unused3; > +#else > + unsigned long shm_atime; /* last attach time */ > + unsigned long shm_atime_high; > + unsigned long shm_dtime; /* last detach time */ > + unsigned long shm_dtime_high; > + unsigned long shm_ctime; /* last change time */ > + unsigned long shm_ctime_high; > #endif > __kernel_pid_t shm_cpid; /* pid of creator */ > __kernel_pid_t shm_lpid; /* pid of last operator */ -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html