/**************************************************************************** * mm/shm/shmctl.c * * Copyright (C) 2014 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include #include #include #include "shm/shm.h" #ifdef CONFIG_MM_SHM /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: shmctl * * Description: * The shmctl() function provides a variety of shared memory control * operations as specified by cmd. The following values for cmd are * available: * * - IPC_STAT * Place the current value of each member of the shmid_ds data * structure associated with shmid into the structure pointed to by * buf. * - IPC_SET * Set the value of the shm_perm.mode member of the shmid_ds data * structure associated with shmid to the corresponding value found * in the structure pointed to by buf. * - IPC_RMID * Remove the shared memory identifier specified by shmid from the * system and destroy the shared memory segment and shmid_ds data * structure associated with it. * * Input Parameters: * shmid - Shared memory identifier * cmd - shmctl() command * buf - Data associated with the shmctl() command * * Returned Value: * Upon successful completion, shmctl() will return 0; otherwise, it will * return -1 and set errno to indicate the error. * * - EACCES * The argument cmd is equal to IPC_STAT and the calling process does * not have read permission. * - EINVAL * The value of shmid is not a valid shared memory identifier, or the * value of cmd is not a valid command. * - EPERM * The argument cmd is equal to IPC_RMID or IPC_SET and the effective * user ID of the calling process is not equal to that of a process * with appropriate privileges and it is not equal to the value of * shm_perm.cuid or shm_perm.uid in the data structure associated with * shmid. * - EOVERFLOW * The cmd argument is IPC_STAT and the gid or uid value is too large * to be stored in the structure pointed to by the buf argument. * * POSIX Deviations: * - IPC_SET. Does not set the shm_perm.uid or shm_perm.gid * members of the shmid_ds data structure associated with shmid * because user and group IDs are not yet supported by NuttX * - IPC_SET. Does not restrict the operation to processes with * appropriate privileges or matching user IDs in shmid_ds data * structure associated with shmid. Again because user IDs and * user/group privileges are are not yet supported by NuttX * - IPC_RMID. Does not restrict the operation to processes with * appropriate privileges or matching user IDs in shmid_ds data * structure associated with shmid. Again because user IDs and * user/group privileges are are not yet supported by NuttX * ****************************************************************************/ int shmctl(int shmid, int cmd, struct shmid_ds *buf) { FAR struct shm_region_s *region; int ret; DEBUGASSERT(shmid >= 0 && shmid < CONFIG_ARCH_SHM_MAXREGIONS); region = &g_shminfo.si_region[shmid]; DEBUGASSERT((region->sr_flags & SRFLAG_INUSE) != 0); /* Get exclusive access to the region data structure */ ret = sem_wait(®ion->sr_sem); if (ret < 0) { shmerr("ERROR: sem_wait failed: %d\n", ret); return ret; } /* Handle the request according to the received cmd */ switch (cmd) { case IPC_STAT: { /* Place the current value of each member of the shmid_ds data * structure associated with shmid into the structure pointed to * by buf. */ DEBUGASSERT(buf); memcpy(buf, ®ion->sr_ds, sizeof(struct shmid_ds)); } break; case IPC_SET: { /* Set the value of the shm_perm.mode member of the shmid_ds * data structure associated with shmid to the corresponding * value found in the structure pointed to by buf. */ region->sr_ds.shm_perm.mode = buf->shm_perm.mode; } break; case IPC_RMID: { /* Are any processes attached to the region? */ if (region->sr_ds.shm_nattch > 0) { /* Yes.. just set the UNLINKED flag. The region will be removed when there are no longer any processes attached to it. */ region->sr_flags |= SRFLAG_UNLINKED; } else { /* No.. free the entry now */ shm_destroy(shmid); /* Don't try anything further on the deleted region */ return OK; } } break; default: shmerr("ERROR: Unrecognized command: %d\n", cmd); ret = -EINVAL; goto errout_with_semaphore; } /* Save the process ID of the last operation */ region = &g_shminfo.si_region[shmid]; region->sr_ds.shm_lpid = getpid(); /* Save the time of the last shmctl() */ region->sr_ds.shm_ctime = time(NULL); /* Release our lock on the entry */ sem_post(®ion->sr_sem); return ret; errout_with_semaphore: sem_post(®ion->sr_sem); set_errno(-ret); return ERROR; } /**************************************************************************** * Name: shm_destroy * * Description: * Destroy a memory region. This function is called: * * - On certain conditions when shmget() is not successful in instantiating * the full memory region and we need to clean up and free a table entry. * - When shmctl() is called with cmd == IPC_RMID and there are no * processes attached to the memory region. * - When shmdt() is called after the last process detaches from memory * region after it was previously marked for deletion by shmctl(). * * Input Parameters: * shmid - Shared memory identifier * * Returned Value: * None * * Assumption: * The caller holds either the region table semaphore or else the * semaphore on the particular entry being deleted. * ****************************************************************************/ void shm_destroy(int shmid) { FAR struct shm_region_s *region = &g_shminfo.si_region[shmid]; int i; /* Free all of the allocated physical pages */ for (i = 0; i < CONFIG_ARCH_SHM_NPAGES && region->sr_pages[i] != 0; i++) { mm_pgfree(region->sr_pages[i], 1); } /* Reset the region entry to its initial state */ sem_destroy(®ion->sr_sem); memset(region, 0, sizeof(struct shm_region_s)); } #endif /* CONFIG_MM_SHM */