NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO
#include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h>int semctl(int semid, int semnum, int cmd, ...);
The semctl() function provides a variety of semaphore control operations as specified by cmd. The fourth argument is optional, depending upon the operation requested. If required, it is of type union semun, which must be explicitly declared by the application program.
union semun { int val; struct semid_ds *buf; ushort_t *array; } arg ;
The permission required for a semaphore operation is given as {token}, where token is the type of permission needed. The types of permission are interpreted as follows:
00400 READ by user 00200 ALTER by user 00040 READ by group 00020 ALTER by group 00004 READ by others 00002 ALTER by others
The commands described hereafter as [READ] operations all require that the calling process have discretionary read access to the data structure referenced by semid, or that the effective privilege set of the process
include PRIV_IPC_DAC_READ
. Likewise, the commands described as [ALTER] operations all require that the calling process have discretionary write access to the data structure referenced by semid, or that the effective privilege set of the
process include PRIV_IPC_DAC_WRITE
.
If the sensitivity label of the object does not match the sensitivity label of the calling process, then the process must have these privileges asserted: PRIV_IPC_MAC_READ
for [READ] operations; PRIV_IPC_MAC_WRITE
for [ALTER] operations.
See the Semaphore Operation Permissions subsection of the DEFINITIONS section of intro(2) for more information. The following semaphore operations as specified by cmd are executed with respect to the semaphore specified by semid and semnum.
Return the value of semval (see intro(2)). {READ}
Set the value of semval to arg.val. {ALTER} When this command is successfully executed, the semadj value corresponding to the specified semaphore in all processes is cleared.
Return the value of (int) sempid. {READ}
Return the value of semncnt. {READ}
Return the value of semzcnt. {READ}
The following operations return and set, respectively, every semval in the set of semaphores.
Place semvals into array pointed to by arg.array. {READ}
Set semvals according to the array pointed to by arg.array. {ALTER}. When this cmd is successfully executed, the semadj values corresponding to each specified semaphore in all processes are cleared.
The following operations are also available.
Place the current value of each member of the data structure associated with semid into the structure pointed to by arg.buf. The contents of this structure are defined in intro(2). {READ}
Set the value of the following members of the data structure associated with semid to the corresponding value found in the structure pointed to by arg.buf:
sem_perm.uid sem_perm.gid sem_perm.mode /* access permission bits only */
This command can be executed only by a process that either has an effective user ID equal to sem_perm.cuid or sem_perm.uid in the data structure associated with semid, or has the PRIV_IPC_OWNER
privilege in its set of effective privileges. In addition, the process must either have mandatory write access to the Semaphore set or have asserted the PRIV_IPC_MAC_WRITE
privilege.
Remove from the system the semaphore identifier specified by semid and destroy the set of semaphores and data structure associated with that identifier. This command can be executed only by a
process that either has an effective user ID equal to sem_perm.cuid or sem_perm.uid in the data structure associated with semid, or has the PRIV_IPC_OWNER
privilege asserted. In addition, the process must
also have mandatory write access to the Semaphore set or have asserted the PRIV_IPC_MAC_WRITE
privilege.
Upon successful completion, the value returned depends on cmd as follows:
the value of semval
the value of (int) sempid
the value of semncnt
the value of semzcnt
All other successful completions return 0; otherwise, -1 is returned and errno is set to indicate the error.
The semctl() function will fail if:
Operation permission is denied to the calling process (see intro(2)), and the process lacks the appropriate privilege override(s) in its set of effective privileges.
The semid argument is not a valid semaphore identifier; the semnum argument is less than 0 or greater than sem_nsems -1; or the cmd argument is not a valid command or is IPC_SET and sem_perm.uid or sem_perm.gid is not valid.
cmd is equal to IPC_RMID or IPC_SET and the effective user of the calling process is not equal to the value of sem_perm.cuid or sem_perm.uid in the data structure associated with semid, and the appropriate privilege is not asserted.
The cmd argument is IPC_STAT and uid or gid is too large to be stored in the structure pointed to by arg.buf.
The cmd argument is SETVAL or SETALL and the value to which semval is to be set is greater than the system imposed maximum.
Appropriate privilege is required to override access checks.
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO