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

To provide a y2038 safe interface a new symbol __shmctl64 is added
and __shmctl 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_shmid64_ds: used internally only on 32-bit architectures
     to issue the syscall.  A handful of architectures (hppa, i386,
     mips, powerpc32, and sparc32) require specific implementations
     due to their kernel ABI.

  2. shmid_ds64: this is only for __TIMESIZE != 64 to use along with
     the 64-bit shmctl.  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 shmid_ds already contains
     64-bit time_t fields and will result in just the __shmctl symbol
     using the __shmctl64 code.  The shmid_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 time handling.

  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 of the 64-bit one.

     The default 32-bit symbol will allocate and copy the shmid_ds
     over multiple buffers, but this should be deprecated in favor
     of the __shmctl64 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: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

2 files changed, 40 insertions, 3 deletions

diff --git a/sysdeps/unix/sysv/linux/bits/types/struct_shmid64_ds.h b/sysdeps/unix/sysv/linux/bits/types/struct_shmid64_ds.h
new file mode 100644
index 0000000000..f71e0d28ff
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/types/struct_shmid64_ds.h
@@ -0,0 +1,37 @@
+/* Generic implementation of the shared memory struct shmid_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_SHM_H
+# error "Never include <bits/types/struct_shmid_ds.h> directly; use <sys/shm.h> instead."
+#endif
+
+#if __TIMESIZE == 64
+# define __shmid64_ds shmid_ds
+#else
+struct __shmid64_ds
+{
+  struct ipc_perm shm_perm;	/* operation permission struct */
+  size_t shm_segsz;		/* size of segment in bytes */
+  __time64_t shm_atime;		/* time of last shmat() */
+  __time64_t shm_dtime;		/* time of last shmdt() */
+  __time64_t shm_ctime;		/* time of last change by shmctl() */
+  __pid_t shm_cpid;		/* pid of creator */
+  __pid_t shm_lpid;		/* pid of last shmop */
+  shmatt_t shm_nattch;		/* number of current attaches */
+};
+#endif
diff --git a/sysdeps/unix/sysv/linux/bits/types/struct_shmid_ds.h b/sysdeps/unix/sysv/linux/bits/types/struct_shmid_ds.h
index 61ed4a08c3..836a7d50e9 100644
--- a/sysdeps/unix/sysv/linux/bits/types/struct_shmid_ds.h
+++ b/sysdeps/unix/sysv/linux/bits/types/struct_shmid_ds.h
@@ -27,11 +27,11 @@ struct shmid_ds
     size_t shm_segsz;			/* size of segment in bytes */
 #if __TIMESIZE == 32
     __time_t shm_atime;			/* time of last shmat() */
-    unsigned long int __glibc_reserved1;
+    unsigned long int __shm_atime_high;
     __time_t shm_dtime;			/* time of last shmdt() */
-    unsigned long int __glibc_reserved2;
+    unsigned long int __shm_dtime_high;
     __time_t shm_ctime;			/* time of last change by shmctl() */
-    unsigned long int __glibc_reserved3;
+    unsigned long int __shm_ctime_high;
 #else
     __time_t shm_atime;			/* time of last shmat() */
     __time_t shm_dtime;			/* time of last shmdt() */