Merge tag 'y2038-ipc' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground into timers/2038

Pull 'y2038: IPC system call conversion' from Arnd Bergmann:

"This is a follow-up to Deepa's work on the timekeeping system calls,
 providing a y2038-safe syscall API for SYSVIPC. It uses a combination
 of two strategies:

 For sys_msgctl, sys_semctl and sys_shmctl, I do not introduce a completely
 new set of replacement system calls, but instead extend the existing
 ones to return data in the reserved fields of the normal data structure.

 This should be completely transparent to any existing user space, and
 only after the 32-bit time_t wraps, it will make a difference in the
 returned data.

 libc implementations will consequently have to provide their own data
 structures when they move to 64-bit time_t, and convert the structures
 in user space from the ones returned by the kernel.

 In contrast, mq_timedsend, mq_timedreceive and and semtimedop all do
 need to change because having a libc redefine the timespec type
 breaks the ABI, so with this series there will be two separate entry
 points for 32-bit architectures.

 There are three cases here:

 - little-endian architectures (except powerpc and mips) can use
   the normal layout and just cast the data structure to the user space
   type that contains 64-bit numbers.

 - parisc and sparc can do the same thing with big-endian user space

 - little-endian powerpc and most big-endian architectures have
   to flip the upper and lower 32-bit halves of the time_t value in memory,
   but can otherwise keep using the normal layout

 - mips and big-endian xtensa need to be more careful because
   they are not consistent in their definitions, and they have to provide
   custom libc implementations for the system calls to use 64-bit time_t."

1 files changed, 21 insertions, 2 deletions

diff --git a/arch/mips/include/uapi/asm/shmbuf.h b/arch/mips/include/uapi/asm/shmbuf.h
index 379e6bca518b..9b9bba3401f2 100644
--- a/arch/mips/include/uapi/asm/shmbuf.h
+++ b/arch/mips/include/uapi/asm/shmbuf.h
@@ -7,10 +7,13 @@
  * Note extra padding because this structure is passed back and forth
  * between kernel and user space.
  *
- * Pad space is left for:
- * - 2 miscellaneous 32-bit rsp. 64-bit values
+ * As MIPS was lacking proper padding after shm_?time, we use 48 bits
+ * of the padding at the end to store a few additional bits of the time.
+ * libc implementations need to take care to convert this into a proper
+ * data structure when moving to 64-bit time_t.
  */
 
+#ifdef __mips64
 struct shmid64_ds {
 	struct ipc64_perm	shm_perm;	/* operation perms */
 	size_t			shm_segsz;	/* size of segment (bytes) */
@@ -23,6 +26,22 @@ struct shmid64_ds {
 	unsigned long		__unused1;
 	unsigned long		__unused2;
 };
+#else
+struct shmid64_ds {
+	struct ipc64_perm	shm_perm;	/* operation perms */
+	size_t			shm_segsz;	/* size of segment (bytes) */
+	unsigned long		shm_atime;	/* last attach time */
+	unsigned long		shm_dtime;	/* last detach time */
+	unsigned long		shm_ctime;	/* last change time */
+	__kernel_pid_t		shm_cpid;	/* pid of creator */
+	__kernel_pid_t		shm_lpid;	/* pid of last operator */
+	unsigned long		shm_nattch;	/* no. of current attaches */
+	unsigned short		shm_atime_high;
+	unsigned short		shm_dtime_high;
+	unsigned short		shm_ctime_high;
+	unsigned short		__unused1;
+};
+#endif
 
 struct shminfo64 {
 	unsigned long	shmmax;