optee: support protected memory allocation

Add support in the OP-TEE backend driver for protected memory
allocation. The support is limited to only the SMC ABI and for secure
video buffers.

OP-TEE is probed for the range of protected physical memory and a
memory pool allocator is initialized if OP-TEE have support for such
memory.

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

drivers/tee/optee/Kconfig

···
 
 	  Additional documentation on kernel security risks are at
 	  Documentation/tee/op-tee.rst.
+
+config OPTEE_STATIC_PROTMEM_POOL
+	bool
+	depends on HAS_IOMEM && TEE_DMABUF_HEAPS
+	default y

drivers/tee/optee/core.c

···
 	return 0;
 }
 
+int optee_set_dma_mask(struct optee *optee, u_int pa_width)
+{
+	u64 mask = DMA_BIT_MASK(min(64, pa_width));
+
+	return dma_coerce_mask_and_coherent(&optee->teedev->dev, mask);
+}
+
 static void optee_bus_scan(struct work_struct *work)
 {
 	WARN_ON(optee_enumerate_devices(PTA_CMD_GET_DEVICES_SUPP));

drivers/tee/optee/optee_private.h

···
 
 extern struct blocking_notifier_head optee_rpmb_intf_added;
 
+int optee_set_dma_mask(struct optee *optee, u_int pa_width);
+
 int optee_notif_init(struct optee *optee, u_int max_key);
 void optee_notif_uninit(struct optee *optee);
 int optee_notif_wait(struct optee *optee, u_int key, u32 timeout);

drivers/tee/optee/smc_abi.c

···
 }
 #endif
 
+static struct tee_protmem_pool *static_protmem_pool_init(struct optee *optee)
+{
+#if IS_ENABLED(CONFIG_OPTEE_STATIC_PROTMEM_POOL)
+	union {
+		struct arm_smccc_res smccc;
+		struct optee_smc_get_protmem_config_result result;
+	} res;
+	struct tee_protmem_pool *pool;
+	void *p;
+	int rc;
+
+	optee->smc.invoke_fn(OPTEE_SMC_GET_PROTMEM_CONFIG, 0, 0, 0, 0,
+			     0, 0, 0, &res.smccc);
+	if (res.result.status != OPTEE_SMC_RETURN_OK)
+		return ERR_PTR(-EINVAL);
+
+	rc = optee_set_dma_mask(optee, res.result.pa_width);
+	if (rc)
+		return ERR_PTR(rc);
+
+	/*
+	 * Map the memory as uncached to make sure the kernel can work with
+	 * __pfn_to_page() and friends since that's needed when passing the
+	 * protected DMA-buf to a device. The memory should otherwise not
+	 * be touched by the kernel since it's likely to cause an external
+	 * abort due to the protection status.
+	 */
+	p = devm_memremap(&optee->teedev->dev, res.result.start,
+			  res.result.size, MEMREMAP_WC);
+	if (IS_ERR(p))
+		return p;
+
+	pool = tee_protmem_static_pool_alloc(res.result.start, res.result.size);
+	if (IS_ERR(pool))
+		devm_memunmap(&optee->teedev->dev, p);
+
+	return pool;
+#else
+	return ERR_PTR(-EINVAL);
+#endif
+}
+
+static int optee_protmem_pool_init(struct optee *optee)
+{
+	enum tee_dma_heap_id heap_id = TEE_DMA_HEAP_SECURE_VIDEO_PLAY;
+	struct tee_protmem_pool *pool = ERR_PTR(-EINVAL);
+	int rc;
+
+	if (!(optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_PROTMEM))
+		return 0;
+
+	pool = static_protmem_pool_init(optee);
+	if (IS_ERR(pool))
+		return PTR_ERR(pool);
+
+	rc = tee_device_register_dma_heap(optee->teedev, heap_id, pool);
+	if (rc)
+		pool->ops->destroy_pool(pool);
+
+	return rc;
+}
+
 static int optee_probe(struct platform_device *pdev)
 {
 	optee_invoke_fn *invoke_fn;
···
 	optee = kzalloc(sizeof(*optee), GFP_KERNEL);
 	if (!optee) {
 		rc = -ENOMEM;
-		goto err_free_pool;
+		goto err_free_shm_pool;
 	}
 
 	optee->ops = &optee_ops;
···
 		pr_info("Asynchronous notifications enabled\n");
 	}
 
+	if (optee_protmem_pool_init(optee))
+		pr_info("Protected memory service not available\n");
+
 	/*
 	 * Ensure that there are no pre-existing shm objects before enabling
 	 * the shm cache so that there's no chance of receiving an invalid
···
 	tee_device_unregister(optee->teedev);
 err_free_optee:
 	kfree(optee);
-err_free_pool:
+err_free_shm_pool:
 	tee_shm_pool_free(pool);
 	if (memremaped_shm)
 		memunmap(memremaped_shm);