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authorArnd Bergmann <arnd@arndb.de>2015-05-05 23:13:15 +0200
committerArnd Bergmann <arnd@arndb.de>2018-04-20 15:57:50 +0200
commitf991f01571281b82e5e6ca74445f5d3f42d72212 (patch)
tree8fac76e5a5d6fdc776fb8b6c4eb8a74b49118a26 /include/uapi/asm-generic/sembuf.h
parenttime: Change nanosleep to safe __kernel_* types (diff)
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y2038: asm-generic: Extend sysvipc data structures
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. Note that msqid64_ds and shmid64_ds were broken on x32 since commit f4b4aae18288 ("x86/headers/uapi: Fix __BITS_PER_LONG value for x32 builds"). I have sent a separate fix for that, but as we no longer have to worry about x32 here, I no longer worry about x32 here and use 'unsigned long' instead of __kernel_ulong_t. Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/uapi/asm-generic/sembuf.h')
-rw-r--r--include/uapi/asm-generic/sembuf.h26
1 files changed, 16 insertions, 10 deletions
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;