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Flesh out shmctl() logic

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This commit is contained in:
Gregory Nutt 2014-09-23 11:41:05 -06:00
parent 5efd5738e9
commit 115634ff4d
4 changed files with 222 additions and 31 deletions
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29
Documentation/NuttxUserGuide.html
View File

@ -9259,21 +9259,13 @@ int shmctl(int shmid, int cmd, FAR struct shmid_ds *buf);
<li>
<p>
<code>IPC_SET</code>.
Set the value of the following members of the <code>shmid_ds</code> data structure associated with <code>shmid</code> to the corresponding value found in the structure pointed to by <code>buf</code>:
</p>
<ul>
<code>shm_perm.uid</code><br>
<code>shm_perm.gid</code><br>
<code>shm_perm.mode</code> (Low-order nine bits).
</ul>
<p>
<code>IPC_SET</code> can only be executed by a process that has an effective user ID equal to either that of a process with appropriate privileges or to the value of <code>shm_perm.cuid</code> or <code>shm_perm.uid</code> in the <code>shmid_ds</code> data structure associated with <code>shmid</code>.
Set the value of the <code>shm_perm.mode</code> member of the <code>shmid_ds</code> data structure associated with <code>shmid</code> to the corresponding value found in the structure pointed to by <code>buf</code>.
</p>
</li>
<li>
<p>
<code>IPC_RMID</code>.
Remove the shared memory identifier specified by <code>shmid</code> from the system and destroy the shared memory segment and <code>shmid_ds</code> data structure associated with it. <code>IPC_RMID</code> can only be executed by a process that has an effective user ID equal to either that of a process with appropriate privileges or to the value of <code>shm_perm.cuid</code> or <code>shm_perm.uid</code> in the <code>shmid_ds</code> data structure associated with <code>shmid</code>.
Remove the shared memory identifier specified by <code>shmid</code> from the system and destroy the shared memory segment and <code>shmid_ds</code> data structure associated with it.
</p>
</li>
</ul>
@ -9307,6 +9299,23 @@ int shmctl(int shmid, int cmd, FAR struct shmid_ds *buf);
The <code>cmd</code> argument is <code>IPC_STAT</code> and the <code>gid</code> or <code>uid</code> value is too large to be stored in the structure pointed to by the <code>buf</code> argument.
</li>
</ul>
<p>
<b>POSIX Deviations</b>
<p>
<ul>
<li>
<code>IPC_SET</code>.
Does not set the the <code>shm_perm.uid</code> or <code>shm_perm.gid</code>members of the <code>shmid_ds</code> data structure associated with <code>shmid</code> because user and group IDs are not yet supported by NuttX
</li>
<li>
<code>IPC_SET</code>.
Does not restrict the operation to processes with appropriate privileges or matching user IDs in <code>shmid_ds</code> data structure associated with <code>shmid</code>. Again because user IDs and user/group privileges are are not yet supported by NuttX
</li>
<li>
<code>IPC_RMID</code>.
Does not restrict the operation to processes with appropriate privileges or matching user IDs in <code>shmid_ds</code> data structure associated with <code>shmid</code>. Again because user IDs and user/group privileges are are not yet supported by NuttX
</li>
</ul>
<h3><a name="shmdt">2.12.4 <code>shmdt</code></a></h3>
<p>

27
mm/shm/shm.h
View File

@ -102,5 +102,32 @@ extern struct shm_info_s g_shminfo;
* Public Function Prototypes
****************************************************************************/
/****************************************************************************
* 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);
#endif /* CONFIG_MM_SHM */
#endif /* __MM_SHM_SHM_H */

177
mm/shm/shmctl.c
View File

@ -41,7 +41,17 @@
#include <sys/shm.h>
#include <sys/ipc.h>
#include <unistd.h>
#include <string.h>
#include <semaphore.h>
#include <time.h>
#include <errno.h>
#include <assert.h>
#include <nuttx/shm.h>
#include <nuttx/pgalloc.h>
#include "shm/shm.h"
#ifdef CONFIG_MM_SHM
@ -78,26 +88,13 @@
* structure associated with shmid into the structure pointed to by
* buf.
* - IPC_SET
* Set the value of the following members of the shmid_ds data
* 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:
*
* shm_perm.uid
* shm_perm.gid
* shm_perm.mode Low-order nine bits.
*
* IPC_SET can only be executed by a process that has an effective
* user ID equal to either that of a process with appropriate
* privileges or to the value of shm_perm.cuid or shm_perm.uid in the
* shmid_ds data structure associated with shmid.
* 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. IPC_RMID can only be executed by a
* process that has an effective user ID equal to either that of a
* process with appropriate privileges or to the value of
* shm_perm.cuid or shm_perm.uid in the shmid_ds data structure
* associated with shmid.
* structure associated with it.
*
* Input Parameters:
* shmid - Shared memory identifier
@ -124,13 +121,157 @@
* 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 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)
{
#warning Not implemented
set_errno(ENOSYS);
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(&region->sr_sem);
if (ret < 0)
{
shmdbg("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, &region->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:
shmdbg("Unrecognized command: %d\n", cmd);
ret = -EINVAL;
goto errout_with_semaphore;
}
/* Save the process ID of the 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(&region->sr_sem);
return ret;
errout_with_semaphore:
sem_post(&region->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(&region->sr_sem);
memset(region, 0, sizeof(struct shm_region_s));
}
#endif /* CONFIG_MM_SHM */

20
mm/shm/shmget.c
View File

@ -41,6 +41,7 @@
#include <sys/shm.h>
#include <sys/ipc.h>
#include <unistd.h>
#include <semaphore.h>
#include <string.h>
#include <errno.h>
@ -251,6 +252,7 @@ static int shm_extend(int shmid, size_t size)
static int shm_create(key_t key, size_t size, int shmflg)
{
FAR struct shm_region_s *region;
int shmid;
int ret;
@ -275,11 +277,16 @@ static int shm_create(key_t key, size_t size, int shmflg)
if (ret < 0)
{
/* Free any partial allocations and unreserve the region */
#warning "Missing logic"
shm_destroy(shmid);
return ret;
}
/* Save the process ID of the creator */
region = &g_shminfo.si_region[shmid];
region->sr_ds.shm_cpid = getpid();
/* Return the shared memory ID */
return shmid;
@ -431,7 +438,7 @@ int shmget(key_t key, size_t size, int shmflg)
/* Is the region big enough for the request? */
region = &g_shminfo.si_region[shmid];
region = &g_shminfo.si_region[shmid];
if (region->sr_ds.shm_segsz < size)
{
/* We we asked to create the region? If so we can just
@ -460,6 +467,14 @@ int shmget(key_t key, size_t size, int shmflg)
goto errout_with_semaphore;
}
}
/* The region is already big enough or else we successfully
* extended the size of the region. If the region was previously
* deleted, but waiting for processes to detach from the region,
* then it is no longer deleted.
*/
region->sr_flags = SRFLAG_INUSE;
}
/* Release our lock on the shared memory region list */
@ -477,4 +492,3 @@ errout:
}
#endif /* CONFIG_MM_SHM */