sysv: linux: Add 64-bit time_t variant for semctl

Different than others 64-bit time_t syscalls, the SysIPC interface
does not provide a new set of syscall for y2038 safeness.  Instead it
uses unused fields in semid_ds structure to return the high bits for
the timestamps.

To provide a y2038 safe interface a new symbol __semctl64 is added
and __semctl is change to call it instead (it adds some extra buffer
copying for the 32 bit time_t implementation).

Two new structures are added:

  1. kernel_semid64_ds: used internally only on 32-bit architectures
     to issue the syscall.  A handful of architectures (hppa, i386,
     mips, powerpc32, sparc32) require specific implementations due
     their kernel ABI.

  2. semid_ds64: this is only for __TIMESIZE != 64 to use along with
     the 64-bit semctl.  It is different than the kernel struct because
     the exported 64-bit time_t might require different alignment
     depending on the architecture ABI.

So the resulting implementation does:

  1. For 64-bit architectures it assumes semid_ds already contains
     64-bit time_t fields and will result in just the __semctl symbol
     using the __semctl64 code.  The semid_ds argument is passed as-is
     to the syscall.

  2. For 32-bit architectures with default 64-bit time_t (newer ABIs
     such riscv32 or arc), it will also result in only one exported
     symbol but with the required high/low handling.

     It might be possible to optimize it further to avoid the
     kernel_semid64_ds to semun transformation if the exported ABI
     for the architectures matches the expected kernel ABI, but the
     implementation is already complex enough and don't think this
     should be a hotspot in any case.

  3. Finally for 32-bit architecture with both 32-bit and 64-bit time_t
     support we follow the already set way to provide one symbol with
     64-bit time_t support and implement the 32-bit time_t support
     using the 64-bit one.

     The default 32-bit symbol will allocate and copy the semid_ds
     over multiple buffers, but this should be deprecated in favor
     of the __semctl64 anyway.

Checked on i686-linux-gnu and x86_64-linux-gnu.  I also did some sniff
tests on powerpc, powerpc64, mips, mips64, armhf, sparcv9, and
sparc64.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Tested-by: Alistair Francis <alistair.francis@wdc.com>
Tested-by: Vineet Gupta <vgupta@synopsys.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

2 files changed, 40 insertions, 14 deletions

diff --git a/sysdeps/unix/sysv/linux/bits/types/struct_semid64_ds.h b/sysdeps/unix/sysv/linux/bits/types/struct_semid64_ds.h
new file mode 100644
index 0000000000..bda9eb4469
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/types/struct_semid64_ds.h
@@ -0,0 +1,33 @@
+/* Generic implementation of the semaphore struct semid64_ds.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SYS_SEM_H
+# error "Never include <bits/types/struct_semid_ds.h> directly; use <sys/sem.h> instead."
+#endif
+
+#if __TIMESIZE == 64
+# define __semid64_ds semid_ds
+#else
+struct __semid64_ds
+{
+  struct ipc_perm sem_perm;		/* operation permission struct */
+  __time64_t sem_otime;			/* last semop() time */
+  __time64_t sem_ctime;			/* last time changed by semctl() */
+  __syscall_ulong_t sem_nsems;		/* number of semaphores in set */
+};
+#endif
diff --git a/sysdeps/unix/sysv/linux/bits/types/struct_semid_ds.h b/sysdeps/unix/sysv/linux/bits/types/struct_semid_ds.h
index 4222e6a59f..bc26d8be08 100644
--- a/sysdeps/unix/sysv/linux/bits/types/struct_semid_ds.h
+++ b/sysdeps/unix/sysv/linux/bits/types/struct_semid_ds.h
@@ -21,26 +21,19 @@
 #endif
 
 /* Data structure describing a set of semaphores.  */
-#if __TIMESIZE == 32
 struct semid_ds
 {
   struct ipc_perm sem_perm;        /* operation permission struct */
+#if __TIMESIZE == 32
   __time_t sem_otime;              /* last semop() time */
-  __syscall_ulong_t __glibc_reserved1;
+  __syscall_ulong_t __sem_otime_high;
   __time_t sem_ctime;             /* last time changed by semctl() */
-  __syscall_ulong_t __glibc_reserved2;
-  __syscall_ulong_t sem_nsems;    /* number of semaphores in set */
-  __syscall_ulong_t __glibc_reserved3;
-  __syscall_ulong_t __glibc_reserved4;
-};
+  __syscall_ulong_t __sem_ctime_high;
 #else
-struct semid_ds
-{
-  struct ipc_perm sem_perm;		/* operation permission struct */
-  __time_t sem_otime;			/* last semop() time */
-  __time_t sem_ctime;			/* last time changed by semctl() */
-  __syscall_ulong_t sem_nsems;		/* number of semaphores in set */
+  __time_t sem_otime;
+  __time_t sem_ctime;
+#endif
+  __syscall_ulong_t sem_nsems;    /* number of semaphores in set */
   __syscall_ulong_t __glibc_reserved3;
   __syscall_ulong_t __glibc_reserved4;
 };
-#endif