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>

1 files changed, 17 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/i386/struct_kernel_shmid64_ds.h b/sysdeps/unix/sysv/linux/i386/struct_kernel_shmid64_ds.h
new file mode 100644
index 0000000000..6a0a0d9c71
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/i386/struct_kernel_shmid64_ds.h
@@ -0,0 +1,17 @@
+/* Analogous to kernel struct compat_shmid64_ds used on shmctl.  */
+struct kernel_shmid64_ds
+{
+  struct ipc_perm shm_perm;
+  size_t shm_segsz;
+  unsigned long int shm_atime;
+  unsigned long int shm_atime_high;
+  unsigned long int shm_dtime;
+  unsigned long int shm_dtime_high;
+  unsigned long int shm_ctime;
+  unsigned long int shm_ctime_high;
+  __pid_t shm_cpid;
+  __pid_t shm_lpid;
+  unsigned long int shm_nattch;
+  unsigned long int __unused4;
+  unsigned long int __unused5;
+};