shmctl64 was introduced as a private interface between libc & ipcs as part
of the fix for:
4481071 ipcs(1) confused by 16G shared memory segments and other large animals

It was undocumented and is thus treated as effectively Project Private.

It was extended by PSARC 2002/174 to include the zone id information needed
in this case.

For the purposes of this case/contract, the interface is defined as:

     int shmctl64(int shmid, int cmd, struct shmid_ds64 *buf);

     The shmctl64() function provides a variety  of  shared  memory
     control  operations  as  specified  by  cmd, similar to shmctl(2).
     Other than the command options accepted and the data structure
     returned, this interface should be expected to operate the same
     as shmctl(2).

     This contract covers use of the IPC_STAT64 operation, which like
     shmctl's IPC_STAT fills in the buffer pointed to by buf with the
     current values for the data  structure associated with shmid.

     This contract includes these structures, defined in <sys/ipc_impl.h>,
     which will be used for the data returned via the buf pointer:

     typedef struct ipc_perm64 {
        uid_t   ipcx_uid;       /* owner's user id */
        gid_t   ipcx_gid;       /* owner's group id */
        uid_t   ipcx_cuid;      /* creator's user id */
        gid_t   ipcx_cgid;      /* creator's group id */
        mode_t  ipcx_mode;      /* access modes */
        key_t   ipcx_key;       /* key */
        projid_t ipcx_projid;   /* allocating project id */
        zoneid_t ipcx_zoneid;   /* creator's zone id */
     } ipc_perm64_t;

     struct shmid_ds64 {
        ipc_perm64_t    shmx_perm;      /* operation permission struct */
        pid_t           shmx_lpid;      /* pid of last shmop */
        pid_t           shmx_cpid;      /* pid of creator */
        uint64_t        shmx_segsz;     /* size of segment in bytes */
        uint64_t        shmx_nattch;    /* # of attaches */
        uint64_t        shmx_cnattch;   /* # of ISM attaches */
        uint64_t        shmx_lkcnt;     /* lock count ??? */
        ipc_time_t      shmx_atime;     /* last shmat time */
        ipc_time_t      shmx_dtime;     /* last shmdt time */
        ipc_time_t      shmx_ctime;     /* last change time */
     };