shmctl(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO

NAME

shmctl- Shared memory control operations

SYNOPSIS

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

int shmctl(int shmid, int cmd, struct shmid_ds *buf);

DESCRIPTION

The shmctl() function provides a variety of shared memory control operations as specified by cmd. The permission required for a shared memory control 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    WRITE by user
00040    READ by group
00020    WRITE by group
00004    READ by others
00002    WRITE by others

See the Shared Memory Operation Permissions section of intro(2) for more information.

The following operations require the specified tokens:

IPC_STAT

Place the current value of each member of the data structure associated with shmid into the structure pointed to by buf. The contents of this structure are defined in intro(2) {READ}

The calling process must either have mandatory read access to the shared-memory segment or have asserted the PRIV_IPC_MAC_READ privilege, and either have discretionary read access to the data structure or have PRIV_IPC_DAC_READ in its set of effective privileges.

IPC_SET

Set the value of the following members of the data structure associated with shmid to the corresponding value found in the structure pointed to by buf:

shm_perm.uid
shm_perm.gid
shm_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 PRIV_IPC_OWNER 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.

IPC_RMID

Remove from the system the shared-memory identifier specified by shmid and destroy the shared-memory segment and data structure associated with the identifier. This command can be executed only by a process that either has an effective user ID equal to shm_perm.cuid or shm_perm.uid in the data structure associated with shmid, or has PRIV_IPC_OWNER in its set of effective privileges. In addition, the process must either have mandatory write access to the shared memory segment or have asserted the PRIV_IPC_MAC_WRITE privilege.

SHM_LOCK

Lock the shared-memory segment specified by shmid in memory. This command can be executed only by a process that has discretionary and mandatory read access (or the appropriate privilege override) and also has PRIV_SYS_CONFIG in its effective privilege set.

SHM_UNLOCK

Unlock the shared-memory segment specified by shmid. This command can be executed only by a process that has discretionary and mandatory read access (or the appropriate privilege override) and also has PRIV_SYS_CONFIG in its effective privilege set.

Shared memory segments must be explicitly removed after the last reference to them has been removed.

RETURN VALUES

shmctl() returns:

0

On success.

-1

On failure, and sets errno to indicate the error.

ERRORS

The shmctl() function will fail if:

EACCES

cmd is equal to IPC_STAT. {READ} operation permission is denied to the calling process, and the calling process does not have the appropriate privilege(s) in its set of effective privileges.

EFAULT

The buf argument points to an illegal address.

EINVAL

The shmid argument is not a valid shared memory identifier; or the cmd argument is not a valid command or is IPC_SET and shm_perm.uid or shm_perm.gid is not valid.

ENOMEM

The cmd argument is equal to SHM_LOCK and there is not enough memory.

EOVERFLOW

The cmd argument is IPC_STAT and uid or gid is too large to be stored in the structure pointed to by buf.

EPERM

cmd is equal to IPC_RMID or IPC_SET. The effective user ID of the calling process does not match the value of shm_perm.cuid or shm_perm.uid in the data structure associated with shmid; or the mandatory access check failed; and the calling process does not have the appropriate privilege overrides(s) in its set of effective privileges.

cmd is equal to SHM_LOCK or SHM_UNLOCK and PRIV_SYS_CONFIG is not in the effective privilege set of the process.

SUMMARY OF TRUSTED SOLARIS CHANGES

Appropriate privilege is required to override access checks.

SEE ALSO

Trusted Solaris 8 Reference Manual

ipcs(1), intro(2), shmget(2), shmop(2)

Trusted Solaris 8  Last Revised 27 Nov 1996

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO