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

This change allows userland to create a tee_shm object that refers
to a dmabuf reference.

Userland provides a dmabuf file descriptor as buffer reference.
The created tee_shm object exported as a brand new dmabuf reference
used to provide a clean fd to userland. Userland shall closed this new
fd to release the tee_shm object resources. The initial dmabuf resources
are tracked independently through original dmabuf file descriptor.

Once the buffer is registered and until it is released, TEE driver
keeps a refcount on the registered dmabuf structure.

This change only support dmabuf references that relates to physically
contiguous memory buffers.

New tee_shm flag to identify tee_shm objects built from a registered
dmabuf: TEE_SHM_EXT_DMA_BUF. Such tee_shm structures are flagged both
TEE_SHM_DMA_BUF and TEE_SHM_EXT_DMA_BUF.

Signed-off-by: Etienne Carriere <[email protected]>
Reviewed-by: Jens Wiklander <[email protected]>

drivers/tee/tee_core.c

@@ -205,6 +205,42 @@ tee_ioctl_shm_register(struct tee_context *ctx,
 	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_OR_NULL(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 params_from_user(struct tee_context *ctx, struct tee_param *params,
 			    size_t num_params,
 			    struct tee_ioctl_param __user *uparams)
@@ -658,6 +694,8 @@ static long tee_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		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_shm.c

@@ -20,6 +20,14 @@
 #include <linux/tee_drv.h>
 #include "tee_private.h"
 
+/* extra references appended to shm object for registered shared memory */
+struct tee_shm_dmabuf_ref {
+     struct tee_shm shm;
+     struct dma_buf *dmabuf;
+     struct dma_buf_attachment *attach;
+     struct sg_table *sgt;
+};
+
 static void tee_shm_release(struct tee_shm *shm)
 {
 	struct tee_device *teedev = shm->teedev;
@@ -30,7 +38,15 @@ static void tee_shm_release(struct tee_shm *shm)
 		list_del(&shm->link);
 	mutex_unlock(&teedev->mutex);
 
-	if (shm->flags & TEE_SHM_POOL) {
+	if (shm->flags & TEE_SHM_EXT_DMA_BUF) {
+		struct tee_shm_dmabuf_ref *ref;
+
+		ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
+		dma_buf_unmap_attachment(ref->attach, ref->sgt,
+					 DMA_BIDIRECTIONAL);
+		dma_buf_detach(shm->dmabuf, ref->attach);
+		dma_buf_put(ref->dmabuf);
+	} else if (shm->flags & TEE_SHM_POOL) {
 		struct tee_shm_pool_mgr *poolm;
 
 		if (shm->flags & TEE_SHM_DMA_BUF)
@@ -57,7 +73,6 @@ static void tee_shm_release(struct tee_shm *shm)
 		teedev_ctx_put(shm->ctx);
 
 	kfree(shm);
-
 	tee_device_put(teedev);
 }
 
@@ -348,6 +363,100 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
 }
 EXPORT_SYMBOL_GPL(tee_shm_register);
 
+struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd)
+{
+	struct tee_shm_dmabuf_ref *ref;
+	void *rc;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	if (!tee_device_get(ctx->teedev))
+		return ERR_PTR(-EINVAL);
+
+	ref = kzalloc(sizeof(*ref), GFP_KERNEL);
+	if (!ref) {
+		rc = ERR_PTR(-ENOMEM);
+		goto err;
+	}
+
+	ref->shm.ctx = ctx;
+	ref->shm.teedev = ctx->teedev;
+	ref->shm.id = -1;
+
+	ref->dmabuf = dma_buf_get(fd);
+	if (!ref->dmabuf) {
+		rc = ERR_PTR(-EINVAL);
+		goto err;
+	}
+
+	ref->attach = dma_buf_attach(ref->dmabuf, &ref->shm.teedev->dev);
+	if (IS_ERR_OR_NULL(ref->attach)) {
+		rc = ERR_PTR(-EINVAL);
+		goto err;
+	}
+
+	ref->sgt = dma_buf_map_attachment(ref->attach, DMA_BIDIRECTIONAL);
+	if (IS_ERR_OR_NULL(ref->sgt)) {
+		rc = ERR_PTR(-EINVAL);
+		goto err;
+	}
+
+	if (sg_nents(ref->sgt->sgl) != 1) {
+		rc = ERR_PTR(-EINVAL);
+		goto err;
+	}
+
+	ref->shm.paddr = sg_dma_address(ref->sgt->sgl);
+	ref->shm.size = sg_dma_len(ref->sgt->sgl);
+	ref->shm.flags = TEE_SHM_DMA_BUF | TEE_SHM_EXT_DMA_BUF;
+
+	mutex_lock(&ref->shm.teedev->mutex);
+	ref->shm.id = idr_alloc(&ref->shm.teedev->idr, &ref->shm,
+				1, 0, GFP_KERNEL);
+	mutex_unlock(&ref->shm.teedev->mutex);
+	if (ref->shm.id < 0) {
+		rc = ERR_PTR(ref->shm.id);
+		goto err;
+	}
+
+	/* export a dmabuf to later get a userland ref */
+	exp_info.ops = &tee_shm_dma_buf_ops;
+	exp_info.size = ref->shm.size;
+	exp_info.flags = O_RDWR;
+	exp_info.priv = &ref->shm;
+
+	ref->shm.dmabuf = dma_buf_export(&exp_info);
+	if (IS_ERR(ref->shm.dmabuf)) {
+		rc = ERR_PTR(-EINVAL);
+		goto err;
+	}
+
+	mutex_lock(&ref->shm.teedev->mutex);
+	list_add_tail(&ref->shm.link, &ctx->list_shm);
+	mutex_unlock(&ref->shm.teedev->mutex);
+
+	return &ref->shm;
+
+err:
+	if (ref) {
+		if (ref->shm.id >= 0) {
+			mutex_lock(&ctx->teedev->mutex);
+			idr_remove(&ctx->teedev->idr, ref->shm.id);
+			mutex_unlock(&ctx->teedev->mutex);
+		}
+		if (ref->sgt)
+			dma_buf_unmap_attachment(ref->attach, ref->sgt,
+						 DMA_BIDIRECTIONAL);
+		if (ref->attach)
+			dma_buf_detach(ref->dmabuf, ref->attach);
+		if (ref->dmabuf)
+			dma_buf_put(ref->dmabuf);
+	}
+	kfree(ref);
+	tee_device_put(ctx->teedev);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(tee_shm_register_fd);
+
 /**
  * tee_shm_get_fd() - Increase reference count and return file descriptor
  * @shm:	Shared memory handle

include/linux/tee_drv.h

@@ -342,6 +342,16 @@ struct tee_shm *tee_shm_priv_alloc(struct tee_device *teedev, size_t size);
 struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
 				 size_t length, u32 flags);
 
+/**
+ * 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'
+ */
+struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd);
+
 /**
  * tee_shm_is_registered() - Check if shared memory object in registered in TEE
  * @shm:	Shared memory handle

include/uapi/linux/tee.h

@@ -117,6 +117,35 @@ struct tee_ioctl_shm_alloc_data {
 #define TEE_IOC_SHM_ALLOC	_IOWR(TEE_IOC_MAGIC, TEE_IOC_BASE + 1, \
 				     struct tee_ioctl_shm_alloc_data)
 
+/**
+ * struct tee_ioctl_shm_register_fd_data - Shared memory registering argument
+ * @fd:		[in] file descriptor identifying the shared memory
+ * @size:	[out] Size of shared memory to allocate
+ * @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_ALLOC below.
+ */
+struct tee_ioctl_shm_register_fd_data {
+	__s64 fd;
+	__u64 size;
+	__u32 flags;
+	__s32 id;
+} __aligned(8);
+
+/**
+ * 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 kernel
+ * land. 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)
+
 /**
  * struct tee_ioctl_buf_data - Variable sized buffer
  * @buf_ptr:	[in] A __user pointer to a buffer