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

Thanks Ard for your comments.

On Thu, 27 Dec 2018 at 23:58, Ard Biesheuvel ard.biesheuvel@linaro.org wrote:

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

Please double check UUID in device tree (probably via dtc dump).

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

Actually OP-TEE tries to find TA in following order:

1. early/pseudo TAs (resident). 2. Dynamic TAs (loaded at runtime).

So if it doesn't find early/pseudo TAs then it tries to load dynamic TAs via tee-supplicant. It seems that its probably stuck in "optee_supp_thrd_req" (drivers/tee/optee/supp.c +85) where it waits for supplicant to fulfil the request.

I think this should be resolved via TEE bus driver approach that I have proposed in previous patch.

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.

Probably via TEE bus driver approach we may get rid of DT or ACPI dependency. BTW, I will switch to platform device as it looks more appropriate.

...

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

Will fix.

...

+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.

Yeah, we may not need this in case we go via TEE bus driver approach.

...

•   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.

Agree.

...

-- 2.7.4