core: add mobj_reg_shm_put()

Adds mobj_reg_shm_put() for reference counting without cookie.

Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

2 files changed, 46 insertions, 0 deletions

diff --git a/core/arch/arm/include/mm/mobj.h b/core/arch/arm/include/mm/mobj.h
index fb5f257f..f72bb5f2 100644
--- a/core/arch/arm/include/mm/mobj.h
+++ b/core/arch/arm/include/mm/mobj.h
@@ -119,7 +119,26 @@ struct mobj *mobj_reg_shm_alloc(paddr_t *pages, size_t num_pages,
 
 void mobj_reg_shm_free_by_cookie(uint64_t cookie);
 
+/**
+ * mobj_reg_shm_get_by_cookie() - get a MOBJ based on cookie
+ * @cookie:	Cookie used by normal world when suppling the shared memory
+ *
+ * Searches for a registered shared memory MOBJ and if one with a matching
+ * @cookie is found its reference counter is increased before returning
+ * the MOBJ.
+ *
+ * Returns a valid pointer on success or NULL on failure.
+ */
 struct mobj *mobj_reg_shm_get_by_cookie(uint64_t cookie);
+
+/**
+ * mobj_reg_shm_put() - put a MOBJ
+ * @mobj:	Pointer to a registered shared memory MOBJ
+ *
+ * Decreases reference counter of the @mobj and frees it if the counter
+ * reaches 0.
+ */
+void mobj_reg_shm_put(struct mobj *mobj);
 void mobj_reg_shm_put_by_cookie(uint64_t cookie);
 
 TEE_Result mobj_reg_shm_release_by_cookie(uint64_t cookie);
diff --git a/core/arch/arm/mm/mobj.c b/core/arch/arm/mm/mobj.c
index ba4a483f..5be15dcd 100644
--- a/core/arch/arm/mm/mobj.c
+++ b/core/arch/arm/mm/mobj.c
@@ -531,6 +531,33 @@ struct mobj *mobj_reg_shm_get_by_cookie(uint64_t cookie)
 	return NULL;
 }
 
+void mobj_reg_shm_put(struct mobj *mobj)
+{
+	struct mobj_reg_shm *r = to_mobj_reg_shm(mobj);
+	uint32_t exceptions = cpu_spin_lock_xsave(&reg_shm_slist_lock);
+
+	/*
+	 * A put is supposed to match a get. The counter is supposed to be
+	 * larger than 1, if it isn't we're in trouble.
+	 */
+	if (refcount_dec(&r->refcount))
+		panic();
+
+	cpu_spin_unlock_xrestore(&reg_shm_slist_lock, exceptions);
+
+	/*
+	 * Note that we're reading this mutex protected variable without the
+	 * mutex acquired. This isn't a problem since an eventually missed
+	 * waiter who is waiting for this MOBJ will try again before hanging
+	 * in condvar_wait().
+	 */
+	if (shm_release_waiters) {
+		mutex_lock(&shm_mu);
+		condvar_broadcast(&shm_cv);
+		mutex_unlock(&shm_mu);
+	}
+}
+
 void mobj_reg_shm_put_by_cookie(uint64_t cookie)
 {
 	uint32_t exceptions = cpu_spin_lock_xsave(&reg_shm_slist_lock);