tee: new ioctl to a register tee_shm from a dmabuf file descriptor

Add a userspace API to create a tee_shm object that refers to a dmabuf
reference.

Userspace registers the dmabuf file descriptor as in a tee_shm object.
The registration is completed with a tee_shm returned file descriptor.

Userspace is free to close the dmabuf file descriptor after it has been
registered since all the resources are now held via the new tee_shm
object.

Closing the tee_shm file descriptor will eventually release all
resources used by the tee_shm object when all references are released.

The new IOCTL, TEE_IOC_SHM_REGISTER_FD, supports dmabuf references to
physically contiguous memory buffers. Dmabuf references acquired from
the TEE DMA-heap can be used as protected memory for Secure Video Path
and such use cases. It depends on the TEE and the TEE driver if dmabuf
references acquired by other means can be used.

A new tee_shm flag is added to identify tee_shm objects built from a
registered dmabuf, TEE_SHM_DMA_BUF.

Signed-off-by: Etienne Carriere <[e-mail]>
Signed-off-by: Olivier Masse <[e-mail]>
Reviewed-by: Sumit Garg <[e-mail]>
Signed-off-by: Jens Wiklander <[e-mail]>

drivers/tee/tee_core.c

···
 	return ret;
 }
 
+static int
+tee_ioctl_shm_register_fd(struct tee_context *ctx,
+			  struct tee_ioctl_shm_register_fd_data __user *udata)
+{
+	struct tee_ioctl_shm_register_fd_data data;
+	struct tee_shm *shm;
+	long ret;
+
+	if (copy_from_user(&data, udata, sizeof(data)))
+		return -EFAULT;
+
+	/* Currently no input flags are supported */
+	if (data.flags)
+		return -EINVAL;
+
+	shm = tee_shm_register_fd(ctx, data.fd);
+	if (IS_ERR(shm))
+		return -EINVAL;
+
+	data.id = shm->id;
+	data.flags = shm->flags;
+	data.size = shm->size;
+
+	if (copy_to_user(udata, &data, sizeof(data)))
+		ret = -EFAULT;
+	else
+		ret = tee_shm_get_fd(shm);
+
+	/*
+	 * When user space closes the file descriptor the shared memory
+	 * should be freed or if tee_shm_get_fd() failed then it will
+	 * be freed immediately.
+	 */
+	tee_shm_put(shm);
+	return ret;
+}
+
 static int param_from_user_memref(struct tee_context *ctx,
 				  struct tee_param_memref *memref,
 				  struct tee_ioctl_param *ip)
 {
 	struct tee_shm *shm;
+	size_t offs = 0;
 
 	/*
 	 * If a NULL pointer is passed to a TA in the TEE,
···
 			tee_shm_put(shm);
 			return -EINVAL;
 		}
+
+		if (shm->flags & TEE_SHM_DMA_BUF) {
+			struct tee_shm_dmabuf_ref *ref;
+
+			ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
+			if (ref->parent_shm) {
+				/*
+				 * The shm already has one reference to
+				 * ref->parent_shm so we are clear of 0.
+				 * We're getting another reference since
+				 * this shm will be used in the parameter
+				 * list instead of the shm we got with
+				 * tee_shm_get_from_id() above.
+				 */
+				refcount_inc(&ref->parent_shm->refcount);
+				tee_shm_put(shm);
+				shm = ref->parent_shm;
+				offs = ref->offset;
+			}
+		}
 	} else if (ctx->cap_memref_null) {
 		/* Pass NULL pointer to OP-TEE */
 		shm = NULL;
···
 		return -EINVAL;
 	}
 
-	memref->shm_offs = ip->a;
+	memref->shm_offs = ip->a + offs;
 	memref->size = ip->b;
 	memref->shm = shm;
 
···
 		return tee_ioctl_shm_alloc(ctx, uarg);
 	case TEE_IOC_SHM_REGISTER:
 		return tee_ioctl_shm_register(ctx, uarg);
+	case TEE_IOC_SHM_REGISTER_FD:
+		return tee_ioctl_shm_register_fd(ctx, uarg);
 	case TEE_IOC_OPEN_SESSION:
 		return tee_ioctl_open_session(ctx, uarg);
 	case TEE_IOC_INVOKE:

drivers/tee/tee_private.h

···
 #include <linux/mutex.h>
 #include <linux/types.h>
 
+/* extra references appended to shm object for registered shared memory */
+struct tee_shm_dmabuf_ref {
+	struct tee_shm shm;
+	size_t offset;
+	struct dma_buf *dmabuf;
+	struct tee_shm *parent_shm;
+};
+
 int tee_shm_get_fd(struct tee_shm *shm);
 
 bool tee_device_get(struct tee_device *teedev);

drivers/tee/tee_shm.c

···
  */
 #include <linux/anon_inodes.h>
 #include <linux/device.h>
+#include <linux/dma-buf.h>
 #include <linux/idr.h>
 #include <linux/io.h>
 #include <linux/mm.h>
···
 
 static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
 {
-	if (shm->flags & TEE_SHM_POOL) {
+	void *p = shm;
+
+	if (shm->flags & TEE_SHM_DMA_BUF) {
+		struct tee_shm_dmabuf_ref *ref;
+
+		ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
+		p = ref;
+		dma_buf_put(ref->dmabuf);
+	} else if (shm->flags & TEE_SHM_POOL) {
 		teedev->pool->ops->free(teedev->pool, shm);
 	} else if (shm->flags & TEE_SHM_DYNAMIC) {
 		int rc = teedev->desc->ops->shm_unregister(shm->ctx, shm);
···
 
 	teedev_ctx_put(shm->ctx);
 
-	kfree(shm);
+	kfree(p);
 
 	tee_device_put(teedev);
 }
···
  * tee_client_invoke_func(). The memory allocated is later freed with a
  * call to tee_shm_free().
  *
- * @returns a pointer to 'struct tee_shm'
+ * @returns a pointer to 'struct tee_shm' on success, and ERR_PTR on failure
  */
 struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size)
 {
···
 	return shm_alloc_helper(ctx, size, PAGE_SIZE, flags, -1);
 }
 EXPORT_SYMBOL_GPL(tee_shm_alloc_kernel_buf);
+
+struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd)
+{
+	struct tee_shm_dmabuf_ref *ref;
+	int rc;
+
+	if (!tee_device_get(ctx->teedev))
+		return ERR_PTR(-EINVAL);
+
+	teedev_ctx_get(ctx);
+
+	ref = kzalloc(sizeof(*ref), GFP_KERNEL);
+	if (!ref) {
+		rc = -ENOMEM;
+		goto err_put_tee;
+	}
+
+	refcount_set(&ref->shm.refcount, 1);
+	ref->shm.ctx = ctx;
+	ref->shm.id = -1;
+	ref->shm.flags = TEE_SHM_DMA_BUF;
+
+	ref->dmabuf = dma_buf_get(fd);
+	if (IS_ERR(ref->dmabuf)) {
+		rc = PTR_ERR(ref->dmabuf);
+		goto err_kfree_ref;
+	}
+
+	rc = tee_heap_update_from_dma_buf(ctx->teedev, ref->dmabuf,
+					  &ref->offset, &ref->shm,
+					  &ref->parent_shm);
+	if (rc)
+		goto err_put_dmabuf;
+
+	mutex_lock(&ref->shm.ctx->teedev->mutex);
+	ref->shm.id = idr_alloc(&ref->shm.ctx->teedev->idr, &ref->shm,
+				1, 0, GFP_KERNEL);
+	mutex_unlock(&ref->shm.ctx->teedev->mutex);
+	if (ref->shm.id < 0) {
+		rc = ref->shm.id;
+		goto err_put_dmabuf;
+	}
+
+	return &ref->shm;
+
+err_put_dmabuf:
+	dma_buf_put(ref->dmabuf);
+err_kfree_ref:
+	kfree(ref);
+err_put_tee:
+	teedev_ctx_put(ctx);
+	tee_device_put(ctx->teedev);
+
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(tee_shm_register_fd);
 
 /**
  * tee_shm_alloc_priv_buf() - Allocate shared memory for a privately shared
···
 
 	/* Refuse sharing shared memory provided by application */
 	if (shm->flags & TEE_SHM_USER_MAPPED)
+		return -EINVAL;
+	/* Refuse sharing registered DMA_bufs with the application */
+	if (shm->flags & TEE_SHM_DMA_BUF)
 		return -EINVAL;
 
 	/* check for overflowing the buffer's size */

include/linux/tee_core.h

···
 #define TEE_SHM_USER_MAPPED	BIT(1)  /* Memory mapped in user space */
 #define TEE_SHM_POOL		BIT(2)  /* Memory allocated from pool */
 #define TEE_SHM_PRIV		BIT(3)  /* Memory private to TEE driver */
+#define TEE_SHM_DMA_BUF		BIT(4)	/* Memory with dma-buf handle */
 
 #define TEE_DEVICE_FLAG_REGISTERED	0x1
 #define TEE_MAX_DEV_NAME_LEN		32

include/linux/tee_drv.h

···
 					    void *addr, size_t length);
 
 /**
+ * tee_shm_register_fd() - Register shared memory from file descriptor
+ *
+ * @ctx:	Context that allocates the shared memory
+ * @fd:		Shared memory file descriptor reference
+ *
+ * @returns a pointer to 'struct tee_shm' on success, and ERR_PTR on failure
+ */
+struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd);
+
+/**
  * tee_shm_free() - Free shared memory
  * @shm:	Handle to shared memory to free
  */

include/uapi/linux/tee.h

···
 };
 
 /**
+ * struct tee_ioctl_shm_register_fd_data - Shared memory registering argument
+ * @fd:		[in] File descriptor identifying dmabuf reference
+ * @size:	[out] Size of referenced memory
+ * @flags:	[in] Flags to/from allocation.
+ * @id:		[out] Identifier of the shared memory
+ *
+ * The flags field should currently be zero as input. Updated by the call
+ * with actual flags as defined by TEE_IOCTL_SHM_* above.
+ * This structure is used as argument for TEE_IOC_SHM_REGISTER_FD below.
+ */
+struct tee_ioctl_shm_register_fd_data {
+	__s64 fd;
+	__u64 size;
+	__u32 flags;
+	__s32 id;
+};
+
+/**
+ * TEE_IOC_SHM_REGISTER_FD - register a shared memory from a file descriptor
+ *
+ * Returns a file descriptor on success or < 0 on failure
+ *
+ * The returned file descriptor refers to the shared memory object in the
+ * kernel. The supplied file deccriptor can be closed if it's not needed
+ * for other purposes. The shared memory is freed when the descriptor is
+ * closed.
+ */
+#define TEE_IOC_SHM_REGISTER_FD	_IOWR(TEE_IOC_MAGIC, TEE_IOC_BASE + 8, \
+				     struct tee_ioctl_shm_register_fd_data)
+
+/**
  * TEE_IOC_SHM_REGISTER - Register shared memory argument
  *
  * Registers shared memory between the user space process and secure OS.