/**
* Open a shared memory object.
*
* This service establishes a connection between a shared memory object and a
* file descriptor. Further use of this descriptor will allow to dimension and
* map the shared memory into the calling context address space.
*
* One of the following access mode should be set in @a oflags:
* - O_RDONLY, meaning that the shared memory object may only be mapped with the
* PROT_READ flag;
* - O_WRONLY, meaning that the shared memory object may only be mapped with the
* PROT_WRITE flag;
* - O_RDWR, meaning that the shared memory object may be mapped with the
* PROT_READ | PROT_WRITE flag.
*
* If no shared memory object named @a name exists, and @a oflags has the @a
* O_CREAT bit set, the shared memory object is created by this function.
*
* If @a oflags has the two bits @a O_CREAT and @a O_EXCL set and the shared
* memory object alread exists, this service fails.
*
* If @a oflags has the bit @a O_TRUNC set, the shared memory exists and is not
* currently mapped, its size is truncated to 0.
*
* If @a oflags has the bit @a O_DIRECT set, the shared memory will be suitable
* for direct memory access (allocated in physically contiguous memory).
*
* @a name may be any arbitrary string, in which slashes have no particular
* meaning. However, for portability, using a name which starts with a slash and
* contains no other slash is recommended.
*
* @param name name of the shared memory object to open;
*
* @param oflags flags.
*
* @param mode ignored.
*
* @return a file descriptor on success;
* @return -1 with @a errno set if:
* - ENAMETOOLONG, the length of the @a name argument exceeds 64 characters;
* - EEXIST, the bits @a O_CREAT and @a O_EXCL were set in @a oflags and the
* shared memory object already exists;
* - ENOENT, the bit @a O_CREAT is not set in @a oflags and the shared memory
* object does not exist;
* - ENOSPC, insufficient memory exists in the system heap to create the shared
* memory object, increase CONFIG_XENO_OPT_SYS_HEAPSZ;
* - EPERM, the caller context is invalid;
* - EINVAL, the O_TRUNC flag was specified and the shared memory object is
* currently mapped;
* - EMFILE, too many descriptors are currently open.
*
* @par Valid contexts:
* - kernel module initialization or cleanup routine;
* - user-space thread (Xenomai threads switch to secondary mode).
*
* @see
* <a href="http://www.opengroup.org/onlinepubs/000095399/functions/shm_open.html">
* Specification.</a>
*
*/
int shm_open(const char *name, int oflags, mode_t mode)
{
pse51_node_t *node;
pse51_desc_t *desc;
pse51_shm_t *shm;
int err, fd;
spl_t s;
/* From root context only. */
if (xnpod_asynch_p() || !xnpod_root_p()) {
thread_set_errno(EPERM);
return -1;
}
xnlock_get_irqsave(&nklock, s);
err = pse51_node_get(&node, name, PSE51_SHM_MAGIC, oflags);
xnlock_put_irqrestore(&nklock, s);
if (err)
goto error;
if (node) {
shm = node2shm(node);
goto got_shm;
}
/* We must create the shared memory object, not yet allocated. */
shm = (pse51_shm_t *) xnmalloc(sizeof(*shm));
if (!shm) {
err = ENOSPC;
goto error;
}
xnlock_get_irqsave(&nklock, s);
err = pse51_node_add(&shm->nodebase, name, PSE51_SHM_MAGIC);
if (err && err != EEXIST)
goto err_unlock;
if (err == EEXIST) {
/* same shm was created in the mean time, rollback. */
err = pse51_node_get(&node, name, PSE51_SHM_MAGIC, oflags);
err_unlock:
xnlock_put_irqrestore(&nklock, s);
xnfree(shm);
if (err)
goto error;
shm = node2shm(node);
goto got_shm;
}
pse51_shm_init(shm);
xnlock_put_irqrestore(&nklock, s);
got_shm:
err = pse51_desc_create(&desc, &shm->nodebase,
oflags & (PSE51_PERMS_MASK | O_DIRECT));
if (err)
goto err_shm_put;
fd = pse51_desc_fd(desc);
if ((oflags & O_TRUNC) && ftruncate(fd, 0)) {
close(fd);
return -1;
}
return fd;
err_shm_put:
pse51_shm_put(shm, 1);
error:
thread_set_errno(err);
return -1;
}
/**
* Open a named semaphore.
*
* This service establishes a connection between the semaphore named @a name and
* the calling context (kernel-space as a whole, or user-space process).
*
* If no semaphore named @a name exists and @a oflags has the @a O_CREAT bit
* set, the semaphore is created by this function, using two more arguments:
* - a @a mode argument, of type @b mode_t, currently ignored;
* - a @a value argument, of type @b unsigned, specifying the initial value of
* the created semaphore.
*
* If @a oflags has the two bits @a O_CREAT and @a O_EXCL set and the semaphore
* already exists, this service fails.
*
* @a name may be any arbitrary string, in which slashes have no particular
* meaning. However, for portability, using a name which starts with a slash and
* contains no other slash is recommended.
*
* If sem_open() is called from the same context (kernel-space as a whole, or
* user-space process) several times with the same value of @a name, the same
* address is returned.
*
* @param name the name of the semaphore to be created;
*
* @param oflags flags.
*
* @return the address of the named semaphore on success;
* @return SEM_FAILED with @a errno set if:
* - ENAMETOOLONG, the length of the @a name argument exceeds 64 characters;
* - EEXIST, the bits @a O_CREAT and @a O_EXCL were set in @a oflags and the
* named semaphore already exists;
* - ENOENT, the bit @a O_CREAT is not set in @a oflags and the named semaphore
* does not exist;
* - ENOSPC, insufficient memory exists in the system heap to create the
* semaphore, increase CONFIG_XENO_OPT_SYS_HEAPSZ;
* - EINVAL, the @a value argument exceeds @a SEM_VALUE_MAX.
*
* @see
* <a href="http://www.opengroup.org/onlinepubs/000095399/functions/sem_open.html">
* Specification.</a>
*
*/
sem_t *sem_open(const char *name, int oflags, ...)
{
pse51_node_t *node;
nsem_t *named_sem;
unsigned value;
mode_t mode;
va_list ap;
spl_t s;
int err;
xnlock_get_irqsave(&nklock, s);
err = pse51_node_get(&node, name, PSE51_NAMED_SEM_MAGIC, oflags);
xnlock_put_irqrestore(&nklock, s);
if (err)
goto error;
if (node) {
named_sem = node2sem(node);
goto got_sem;
}
named_sem = (nsem_t *) xnmalloc(sizeof(*named_sem));
if (!named_sem) {
err = ENOSPC;
goto error;
}
named_sem->sembase.is_named = 1;
named_sem->descriptor.shadow_sem.sem = &named_sem->sembase;
va_start(ap, oflags);
mode = va_arg(ap, int); (void)mode; /* unused */
value = va_arg(ap, unsigned);
va_end(ap);
xnlock_get_irqsave(&nklock, s);
err = pse51_sem_init_inner(&named_sem->sembase, 1, value);
if (err) {
xnlock_put_irqrestore(&nklock, s);
xnfree(named_sem);
goto error;
}
err = pse51_node_add(&named_sem->nodebase, name, PSE51_NAMED_SEM_MAGIC);
if (err && err != EEXIST)
goto err_put_lock;
if (err == EEXIST) {
err = pse51_node_get(&node, name, PSE51_NAMED_SEM_MAGIC, oflags);
if (err)
goto err_put_lock;
xnlock_put_irqrestore(&nklock, s);
sem_destroy_inner(&named_sem->sembase,
pse51_kqueues(named_sem->sembase.pshared));
named_sem = node2sem(node);
goto got_sem;
}
xnlock_put_irqrestore(&nklock, s);
got_sem:
/* Set the magic, needed both at creation and when re-opening a semaphore
that was closed but not unlinked. */
named_sem->descriptor.shadow_sem.magic = PSE51_NAMED_SEM_MAGIC;
return &named_sem->descriptor.native_sem;
err_put_lock:
xnlock_put_irqrestore(&nklock, s);
sem_destroy_inner(&named_sem->sembase,
pse51_kqueues(named_sem->sembase.pshared));
error:
thread_set_errno(err);
return SEM_FAILED;
}
