posix: mutexattr: improvements for pthread_mutexattr_t

Previously, pthread_mutexattr_gettype() and
pthread_mutexattr_settype() were non-conformant and also
less safe, as they would not check whether a pthread_mutexattr_t
had been initialized prior to manipulating them. Furthermore,
they would potentially dereference NULL pointers.

Additionally, move the pthread_mutexattr_init() and
pthread_mutexattr_destroy() functions to the library, and add
some level of checking to them so that they are more than simply
static inline / no-op calls.

Lastly, reduce the size of struct pthread_mutexattr to only
what is necessary (one byte should suffice).

Signed-off-by: Christopher Friedt <cfriedt@meta.com>

include/zephyr/posix/posix_types.h

@@ -60,7 +60,8 @@ typedef struct k_sem sem_t;
 typedef uint32_t pthread_mutex_t;
 
 struct pthread_mutexattr {
-	int type;
+	unsigned char type: 2;
+	bool initialized: 1;
 };
 #if defined(CONFIG_MINIMAL_LIBC) || defined(CONFIG_PICOLIBC) || defined(CONFIG_ARMCLANG_STD_LIBC) \
 	|| defined(CONFIG_ARCMWDT_LIBC)

include/zephyr/posix/pthread.h

@@ -253,12 +253,7 @@ int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type);
  *
  * Note that pthread attribute structs are currently noops in Zephyr.
  */
-static inline int pthread_mutexattr_init(pthread_mutexattr_t *m)
+int pthread_mutexattr_init(pthread_mutexattr_t *attr);
-{
-	ARG_UNUSED(m);
-
-	return 0;
-}
 
 /**
  * @brief POSIX threading compatibility API
@@ -267,12 +262,7 @@ static inline int pthread_mutexattr_init(pthread_mutexattr_t *m)
  *
  * Note that pthread attribute structs are currently noops in Zephyr.
  */
-static inline int pthread_mutexattr_destroy(pthread_mutexattr_t *m)
+int pthread_mutexattr_destroy(pthread_mutexattr_t *attr);
-{
-	ARG_UNUSED(m);
-
-	return 0;
-}
 
 /**
  * @brief Declare a pthread barrier

lib/posix/options/mutex.c

@@ -311,16 +311,48 @@ int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *attr,
 	return 0;
 }
 
+int pthread_mutexattr_init(pthread_mutexattr_t *attr)
+{
+	struct pthread_mutexattr *const a = (struct pthread_mutexattr *)attr;
+
+	if (a == NULL) {
+		return EINVAL;
+	}
+
+	a->type = PTHREAD_MUTEX_DEFAULT;
+	a->initialized = true;
+
+	return 0;
+}
+
+int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
+{
+	struct pthread_mutexattr *const a = (struct pthread_mutexattr *)attr;
+
+	if (a == NULL || !a->initialized) {
+		return EINVAL;
+	}
+
+	*a = (struct pthread_mutexattr){0};
+
+	return 0;
+}
+
 /**
  * @brief Read type attribute for mutex.
  *
  * See IEEE 1003.1
  */
-int pthread_mutexattr_gettype(const pthread_mutexattr_t *_attr, int *type)
+int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type)
 {
-	const struct pthread_mutexattr *attr = (const struct pthread_mutexattr *)_attr;
+	const struct pthread_mutexattr *a = (const struct pthread_mutexattr *)attr;
+
+	if (a == NULL || type == NULL || !a->initialized) {
+		return EINVAL;
+	}
+
+	*type = a->type;
 
-	*type = attr->type;
 	return 0;
 }
 
@@ -329,19 +361,23 @@ int pthread_mutexattr_gettype(const pthread_mutexattr_t *_attr, int *type)
  *
  * See IEEE 1003.1
  */
-int pthread_mutexattr_settype(pthread_mutexattr_t *_attr, int type)
+int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
 {
-	struct pthread_mutexattr *attr = (struct pthread_mutexattr *)_attr;
+	struct pthread_mutexattr *const a = (struct pthread_mutexattr *)attr;
-	int retc = EINVAL;
 
-	if ((type == PTHREAD_MUTEX_NORMAL) ||
+	if (a == NULL || !a->initialized) {
-	    (type == PTHREAD_MUTEX_RECURSIVE) ||
+		return EINVAL;
-	    (type == PTHREAD_MUTEX_ERRORCHECK)) {
-		attr->type = type;
-		retc = 0;
 	}
 
-	return retc;
+	switch (type) {
+	case PTHREAD_MUTEX_NORMAL:
+	case PTHREAD_MUTEX_RECURSIVE:
+	case PTHREAD_MUTEX_ERRORCHECK:
+		a->type = type;
+		return 0;
+	default:
+		return EINVAL;
+	}
 }
 
 static int pthread_mutex_pool_init(void)