Re: [Tee-dev] [PATCH v2 4/4] hwrng: add OP-TEE based rng driver

On Thu, Jan 10, 2019 at 05:54:57PM +0530, Sumit Garg wrote:

On ARM SoC's with TrustZone enabled, peripherals like entropy sources might not be accessible to normal world (linux in this case) and rather accessible to secure world (OP-TEE in this case) only. So this driver aims to provides a generic interface to OP-TEE based random number generator service.

This driver registers on TEE bus to interact with OP-TEE based rng

device/service.

Signed-off-by: Sumit Garg sumit.garg@linaro.org

MAINTAINERS | 5 + drivers/char/hw_random/Kconfig | 15 ++ drivers/char/hw_random/Makefile | 1 + drivers/char/hw_random/optee-rng.c | 272 +++++++++++++++++++++++++++++++++++++ 4 files changed, 293 insertions(+) create mode 100644 drivers/char/hw_random/optee-rng.c

diff --git a/MAINTAINERS b/MAINTAINERS index 32d44447..502733c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -11260,6 +11260,11 @@ M: Jens Wiklander jens.wiklander@linaro.org S: Maintained F: drivers/tee/optee/ +OP-TEE RANDOM NUMBER GENERATOR (RNG) DRIVER +M: Sumit Garg sumit.garg@linaro.org +S: Maintained +F: drivers/char/hw_random/optee-rng.c

OPA-VNIC DRIVER M: Dennis Dalessandro dennis.dalessandro@intel.com M: Niranjana Vishwanathapura niranjana.vishwanathapura@intel.com diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig index dac895d..25a7d8f 100644 --- a/drivers/char/hw_random/Kconfig +++ b/drivers/char/hw_random/Kconfig @@ -424,6 +424,21 @@ config HW_RANDOM_EXYNOS will be called exynos-trng. If unsure, say Y.

+config HW_RANDOM_OPTEE

• tristate "OP-TEE based Random Number Generator support"
• depends on OPTEE
• default HW_RANDOM
• help

•  This  driver provides support for OP-TEE based Random Number
  

•  Generator on ARM SoCs where hardware entropy sources are not
  

•  accessible to normal world (Linux).
  

•  To compile this driver as a module, choose M here: the module
  

•  will be called optee-rng.
  

•  If unsure, say Y.
  

endif # HW_RANDOM config UML_RANDOM diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile index e35ec3c..7c9ef4a 100644 --- a/drivers/char/hw_random/Makefile +++ b/drivers/char/hw_random/Makefile @@ -38,3 +38,4 @@ obj-$(CONFIG_HW_RANDOM_CAVIUM) += cavium-rng.o cavium-rng-vf.o obj-$(CONFIG_HW_RANDOM_MTK) += mtk-rng.o obj-$(CONFIG_HW_RANDOM_S390) += s390-trng.o obj-$(CONFIG_HW_RANDOM_KEYSTONE) += ks-sa-rng.o +obj-$(CONFIG_HW_RANDOM_OPTEE) += optee-rng.o diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c new file mode 100644 index 0000000..ebfe1f2c --- /dev/null +++ b/drivers/char/hw_random/optee-rng.c @@ -0,0 +1,272 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Copyright (C) 2018-2019 Linaro Ltd.
• */

+#include <linux/delay.h> +#include <linux/of.h> +#include <linux/hw_random.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/tee_drv.h> +#include <linux/uuid.h>

+#define DRIVER_NAME "optee-rng"

+#define TEE_ERROR_HEALTH_TEST_FAIL 0x00000001

+/*

• • TA_CMD_GET_ENTROPY - Get Entropy from RNG
• • param[0] (inout memref) - Entropy buffer memory reference
• • param[1] unused
• • param[2] unused
• • param[3] unused
• • Result:
• • TEE_SUCCESS - Invoke command success
• • TEE_ERROR_BAD_PARAMETERS - Incorrect input param
• • TEE_ERROR_NOT_SUPPORTED - Requested entropy size greater than size of pool
• • TEE_ERROR_HEALTH_TEST_FAIL - Continuous health testing failed
• */

+#define TA_CMD_GET_ENTROPY 0x0

+/*

• • TA_CMD_GET_RNG_INFO - Get RNG information
• • param[0] (out value) - value.a: RNG data-rate in bytes per second

• •                    value.b: Quality/Entropy per 1024 bit of data
    

• • param[1] unused
• • param[2] unused
• • param[3] unused
• • Result:
• • TEE_SUCCESS - Invoke command success
• • TEE_ERROR_BAD_PARAMETERS - Incorrect input param
• */

+#define TA_CMD_GET_RNG_INFO 0x1

+#define MAX_ENTROPY_REQ_SZ (4 * 1024)

+static struct tee_context *ctx; +static struct tee_shm *entropy_shm_pool; +static u32 ta_rng_data_rate; +static u32 ta_rng_session_id;

+static size_t get_optee_rng_data(void *buf, size_t req_size) +{

• u32 ret = 0;
• u8 *rng_data = NULL;
• size_t rng_size = 0;
• struct tee_ioctl_invoke_arg inv_arg = {0};
• struct tee_param param[4] = {0};
• /* Invoke TA_CMD_GET_RNG function of Trusted App */

TA_CMD_GET_ENTROPY?

• inv_arg.func = TA_CMD_GET_ENTROPY;

• inv_arg.session = ta_rng_session_id;

• inv_arg.num_params = 4;

• /* Fill invoke cmd params */

• param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT;

• param[0].u.memref.shm = entropy_shm_pool;

• param[0].u.memref.size = req_size;

• param[0].u.memref.shm_offs = 0;

• ret = tee_client_invoke_func(ctx, &inv_arg, param);

• if ((ret < 0) || (inv_arg.ret != 0)) {

• pr_err("TA_CMD_GET_ENTROPY invoke function error: %x\n",
  

•        inv_arg.ret);
  

• return 0;
  

• }

• rng_data = tee_shm_get_va(entropy_shm_pool, 0);

• if (IS_ERR(rng_data)) {

• pr_err("tee_shm_get_va failed\n");
  

• return 0;
  

• }

• rng_size = param[0].u.memref.size;

• memcpy(buf, rng_data, rng_size);

• return rng_size;

+}

+static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait) +{

• u8 *data = buf;
• size_t read = 0, rng_size = 0;
• int timeout = 1;
• if (max > MAX_ENTROPY_REQ_SZ)

• max = MAX_ENTROPY_REQ_SZ;
  

• while (read == 0) {

• rng_size = get_optee_rng_data(data, (max - read));
  

• data += rng_size;
  

• read += rng_size;
  

• if (wait) {
  

• 	if (timeout-- == 0)
  

• 		return read;
  

• 	msleep((1000 * (max - read)) / ta_rng_data_rate);
  

• } else {
  

• 	return read;
  

• }
  

• }
• return read;

+}

+static int optee_rng_init(struct hwrng *rng) +{

• entropy_shm_pool = tee_shm_alloc(ctx, MAX_ENTROPY_REQ_SZ,

• 			 TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
  

• if (IS_ERR(entropy_shm_pool)) {

• pr_err("tee_shm_alloc failed\n");
  

• return PTR_ERR(entropy_shm_pool);
  

• }
• return 0;

+}

+static void optee_rng_cleanup(struct hwrng *rng) +{

• tee_shm_free(entropy_shm_pool);

+}

+static struct hwrng optee_rng = {

• .name = DRIVER_NAME,
• .init = optee_rng_init,
• .cleanup = optee_rng_cleanup,
• .read = optee_rng_read,

+};

+static int get_optee_rng_info(void) +{

• u32 ret = 0;
• struct tee_ioctl_invoke_arg inv_arg = {0};
• struct tee_param param[4] = {0};
• /* Invoke TA_CMD_GET_RNG function of Trusted App */

TA_CMD_GET_RNG_INFO?

• inv_arg.func = TA_CMD_GET_RNG_INFO;
• inv_arg.session = ta_rng_session_id;
• inv_arg.num_params = 4;
• /* Fill invoke cmd params */
• param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT;
• ret = tee_client_invoke_func(ctx, &inv_arg, param);
• if ((ret < 0) || (inv_arg.ret != 0)) {

• pr_err("TA_CMD_GET_RNG_INFO invoke function error: %x\n",
  

•        inv_arg.ret);
  

• return -EINVAL;
  

• }
• ta_rng_data_rate = param[0].u.value.a;
• optee_rng.quality = param[0].u.value.b;
• return 0;

+}

+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data) +{

• if (ver->impl_id == TEE_IMPL_ID_OPTEE)

• return 1;
  

• else

• return 0;
  

+}

+static int optee_rng_probe(struct device *dev) +{

• struct tee_client_device *rng_device = to_tee_client_device(dev);
• int ret = 0, err = -ENODEV;
• struct tee_ioctl_open_session_arg sess_arg = {0};
• /* Open context with TEE driver */
• ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, NULL);
• if (IS_ERR(ctx))

• return -ENODEV;
  

• /* Open session with hwrng Trusted App */
• memcpy(sess_arg.uuid, rng_device->id.uuid.b, TEE_IOCTL_UUID_LEN);
• sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
• sess_arg.num_params = 0;
• ret = tee_client_open_session(ctx, &sess_arg, NULL);
• if ((ret < 0) || (sess_arg.ret != 0)) {

• pr_err("tee_client_open_session failed, error: %x\n",
  

•        sess_arg.ret);
  

• err = -EINVAL;
  

• goto out_ctx;
  

• }
• ta_rng_session_id = sess_arg.session;
• err = get_optee_rng_info();
• if (err)

• goto out_sess;
  

• err = hwrng_register(&optee_rng);
• if (err) {

• pr_err("registering failed (%d)\n", err);
  

• goto out_sess;
  

• }
• return 0;

+out_sess:

• tee_client_close_session(ctx, ta_rng_session_id);

+out_ctx:

• tee_client_close_context(ctx);
• return err;

+}

+static int optee_rng_remove(struct device *dev) +{

• tee_client_close_session(ctx, ta_rng_session_id);
• tee_client_close_context(ctx);
• hwrng_unregister(&optee_rng);
• return 0;

+}

+const struct tee_client_device_id optee_rng_id_table[] = {

• {UUID_INIT(0xab7a617c, 0xb8e7, 0x4d8f,

•    0x83, 0x01, 0xd0, 0x9b, 0x61, 0x03, 0x6b, 0x64)},
  

• {}

+};

Just so I'm with you here, in the v1 patch set you said, that this could be populated with other platform specific RNG UUID/GUID later. So if I implement another RNG TA for another device in OP-TEE, then I only need to update this array with another corresponding ID? To me it looks like the ta_rng_session_id just stores an id for a single TEE RNG source, correct? I.e., this patch set is not really written to fully support more than a single source in OP-TEE at this point? I.e., my assumption about just adding another UUID to the array is wrong?

+static struct tee_client_driver optee_rng_driver = {

• .id_table = optee_rng_id_table,
• .driver = {

• .name		= DRIVER_NAME,
  

• .bus		= &tee_bus_type,
  

• .probe		= optee_rng_probe,
  

• .remove		= optee_rng_remove,
  

• },

+};

+static int __init mod_init(void) +{

• int rc;
• rc = driver_register(&optee_rng_driver.driver);
• if (rc)

• pr_warn("driver registration failed, err: %d", rc);
  

• return rc;

+}

+static void __exit mod_exit(void) +{

• driver_unregister(&optee_rng_driver.driver);

+}

+module_init(mod_init); +module_exit(mod_exit);

+MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Sumit Garg sumit.garg@linaro.org");

+MODULE_DESCRIPTION("OP-TEE based random number generator driver");

2.7.4

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