Re: [Tee-dev] [PATCH v1 2/2] hwrng: add OP-TEE based rng driver

On Thu, 27 Dec 2018 at 12:08, Sumit Garg sumit.garg@linaro.org 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.

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 | 273 +++++++++++++++++++++++++++++++++++++ 4 files changed, 294 insertions(+) create mode 100644 drivers/char/hw_random/optee-rng.c

Hi Sumit,

I am having some trouble with this driver. Even though the firmware manages to invoke the pseudo-TA, the kernel driver responds with

[ 73.915971] tee_client_open_session failed, error: ffff0008

(note that I need to run teesupplicant or the insmod just hangs)

Also, I have some concerns about the DT dependency (see my comment on the previous patch) I will cc you on some patches I have to expose OP-TEE via ACPI (as well as DT) as a platform device. I'd prefer it if we could do the same for this driver in one way or the other.

diff --git a/MAINTAINERS b/MAINTAINERS index 0767f1d..fe0fb74 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -11100,6 +11100,11 @@ 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..8c63730 --- /dev/null +++ b/drivers/char/hw_random/optee-rng.c @@ -0,0 +1,273 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Copyright (C) 2018 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/tee_drv.h> +#include <linux/uuid.h>

+#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_seesion_id;

session not seesion

+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 */
  

•   inv_arg.func = TA_CMD_GET_ENTROPY;
  

•   inv_arg.session = ta_rng_seesion_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           = "optee-rng",
  

•   .init           = optee_rng_init,
  

•   .cleanup        = optee_rng_cleanup,
  

•   .read           = optee_rng_read,
  

+};

+static const struct of_device_id optee_match[] = {

•   { .compatible = "linaro,optee-tz" },
  

•   {},
  

+};

+static int get_optee_rng_uuid(uuid_t *ta_rng_uuid) +{

•   struct device_node *fw_np;
  

•   struct device_node *np;
  

•   const char *uuid;
  

•   /* Node is supposed to be below /firmware */
  

•   fw_np = of_find_node_by_name(NULL, "firmware");
  

•   if (!fw_np)
  

•           return -ENODEV;
  

•   np = of_find_matching_node(fw_np, optee_match);
  

•   if (!np || !of_device_is_available(np))
  

•           return -ENODEV;
  

•   if (of_property_read_string(np, "rng-uuid", &uuid)) {
  

•           pr_warn("missing \"uuid\" property\n");
  

•           return -ENXIO;
  

•   }
  

So, duplicating all of this is really not a good idea.

•   if (uuid_parse(uuid, ta_rng_uuid)) {
  

•           pr_warn("incorrect rng ta uuid\n");
  

•           return -EINVAL;
  

•   }
  

•   return 0;
  

+}

+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 */
  

•   inv_arg.func = TA_CMD_GET_RNG_INFO;
  

•   inv_arg.session = ta_rng_seesion_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 __init mod_init(void) +{

•   int ret = 0, err = -ENODEV;
  

•   struct tee_ioctl_open_session_arg sess_arg = {0};
  

•   uuid_t ta_rng_uuid = {0};
  

•   err = get_optee_rng_uuid(&ta_rng_uuid);
  

•   if (err)
  

•           return err;
  

•   /* 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, ta_rng_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_seesion_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_seesion_id);
  

+out_ctx:

•   tee_client_close_context(ctx);
  

•   return err;
  

+}

+static void __exit mod_exit(void) +{

•   tee_client_close_session(ctx, ta_rng_seesion_id);
  

•   tee_client_close_context(ctx);
  

•   hwrng_unregister(&optee_rng);
  

+}

+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"); +MODULE_SOFTDEP("pre: optee");

This is also an indicator that the API design needs some work. If the OP-TEE driver becomes a 'bus' driver of some sort, the child RNG device (which is what this driver should bind to) will only exist if a) the OP-TEE driver is loaded, and b) it has actually bound to the /firmware/optee node.

-- 2.7.4