glibc/sysdeps/unix/sysv/linux/struct_kernel_semid64_ds.h

/* Analogous to kernel struct semid64_ds used on semctl.  */
struct kernel_semid64_ds
{
  struct ipc_perm sem_perm;
  unsigned long sem_otime;
  unsigned long sem_otime_high;
  unsigned long sem_ctime;
  unsigned long sem_ctime_high;
  unsigned long sem_nsems;
  unsigned long __unused1;
  unsigned long __unused2;
};
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> 2020-06-29 16:35:50 +00:00			`/* Analogous to kernel struct semid64_ds used on semctl. */`
			`struct kernel_semid64_ds`
			`{`
			`struct ipc_perm sem_perm;`
			`unsigned long sem_otime;`
			`unsigned long sem_otime_high;`
			`unsigned long sem_ctime;`
			`unsigned long sem_ctime_high;`
			`unsigned long sem_nsems;`
			`unsigned long __unused1;`
			`unsigned long __unused2;`
			`};`