shmget(2)

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

NAME

shmget, shmgetl– Get shared memory segment identifier

SYNOPSIS

cc [flags…] file … -ltsol [library…]


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

int shmget(key_t key, size_t size, int shmflg);


#include <sys/tsol/ipcl.h>

int shmgetl(key_t key, size_t size, int shmflg, const bslabel_t *slabel);

DESCRIPTION

A shared-memory segment is identified by a unique combination of key and sensitivity label. This qualification of keys by sensitivity labels allows applications that use shared-memory segments to be run at multiple process sensitivity labels without inadvertently sharing data. shmget() returns the shared-memory identifier associated with the union of key and the sensitivity label of the calling process.

shmgetl() returns the shared-memory identifier associated with the union of key and slabel. If the value of slabel does not match the sensitivity label of the calling process, then the effective privilege set of the process must include the necessary privileges: PRIV_IPC_MAC_READ and PRIV_IPC_MAC_WRITE.

If discretionary read/write access is denied to the calling process as specified by the low-order 9 bits of shmflg, both shmget() and shmgetl() require one or both of these privileges: PRIV_IPC_DAC_READ and PRIV_IPC_DAC_WRITE.

The shmget() function returns the shared memory identifier associated with key.

A shared memory identifier and associated data structure and shared memory segment of at least size bytes (see intro(3)) are created for key if one of the following are true:

• The key argument is equal to IPC_PRIVATE.

• The key argument does not already have a shared memory identifier associated with it, and (shmflg&IPC_CREAT) is true.

Upon creation, the data structure associated with the new shared memory identifier is initialized as follows:

• The values of shm_perm.cuid, shm_perm.uid, shm_perm.cgid, and shm_perm.gid are set equal to the effective user ID and effective group ID, respectively, of the calling process.

• The access permission bits of shm_perm.mode are set equal to the access permission bits of shmflg. shm_segsz is set equal to the value of size.

• The values of shm_lpid, shm_nattch shm_atime, and shm_dtime are set equal to 0.

• The shm_ctime is set equal to the current time.

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

RETURN VALUES

Upon successful completion, a non-negative integer representing a shared memory identifier is returned. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

The shmget() function will fail if:

EACCES

A shared memory identifier exists for the union of key and sensitivity label, but operation permission (see intro(3)) as specified by the low-order 9 bits of shmflg would not be granted.

The calling process, which failed the check for discretionary or mandatory access, does not have the appropriate privilege override(s) in its set of effective privileges.

EEXIST

A shared memory identifier exists for key but both (shmflg&IPC_CREATE) and (shmflg&IPC_EXCL) are true.

EFAULT

slabel points to an illegal address.

EINVAL

The size argument is less than the system-imposed minimum or greater than the system-imposed maximum.

EINVAL

A shared memory identifier exists for key but the size of the segment associated with it is less than size and size is not equal to 0.

The label pointed to by slabel is not a valid sensitivity label.

ENOENT

A shared memory identifier does not exist for the union of key and sensitivity label, and (shmflg&IPC_CREATE) is false.

ENOMEM

A shared memory identifier and associated shared memory segment are to be created but the amount of available memory is not sufficient to fill the request.

ENOSPC

A shared memory identifier is to be created but the system-imposed limit on the maximum number of allowed shared memory identifiers system-wide would be exceeded.

SUMMARY OF TRUSTED SOLARIS CHANGES

Appropriate privilege is required to override access checks.

Sensitivity labels are used together with key to determine shared-memory identifiers.

SEE ALSO

Trusted Solaris 8 HW 12/02 Reference Manual

shmctl(2), shmop(2), intro(3)

SunOS 5.8 Reference Manual

ftok(3C)

SunOS 5.8  Last Revised 1 May 2000

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