On Thu, 24 Jan 2019 at 18:01, Daniel Thompson
[off-list ref] wrote:

On Thu, Jan 24, 2019 at 11:24:39AM +0530, Sumit Garg wrote:

quoted

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 <redacted>
---
 MAINTAINERS                        |   5 +
 drivers/char/hw_random/Kconfig     |  15 ++
 drivers/char/hw_random/Makefile    |   1 +
 drivers/char/hw_random/optee-rng.c | 274 +++++++++++++++++++++++++++++++++++++
 4 files changed, 295 insertions(+)
 create mode 100644 drivers/char/hw_random/optee-rng.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 51029a4..dcef7e9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -11262,6 +11262,11 @@ 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..4ad0eca
--- /dev/null
+++ b/drivers/char/hw_random/optee-rng.c

@@ -0,0 +1,274 @@
+// 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_ENTROPY function of Trusted App */
+     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);

Why can't these be dev_err()?

See my response below.

quoted

+             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");

This one is slightly annoying. It could be a dev_err() but needs quite
a bit of machinary hooked up (optee_rng_private) to allow you to look up
the device from the hwrng.

It would allow you to move all those statics (like entropy_shm_pool)
into a proper context structure though...

Ok, will create "static struct optee_rng_private" to bundle all the
statics along with device pointer and hwrng struct. And use dev_err()
instead.

-Sumit

Daniel.

quoted

+             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(struct device *dev)
+{
+     u32 ret = 0;
+     struct tee_ioctl_invoke_arg inv_arg = {0};
+     struct tee_param param[4] = {0};
+
+     /* Invoke TA_CMD_GET_RNG_INFO function of Trusted App */
+     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)) {
+             dev_err(dev, "TA_CMD_GET_RNG_INFO invoke func 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)) {
+             dev_err(dev, "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(dev);
+     if (err)
+             goto out_sess;
+
+     err = hwrng_register(&optee_rng);
+     if (err) {
+             dev_err(dev, "hwrng registration 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)
+{
+     hwrng_unregister(&optee_rng);
+     tee_client_close_session(ctx, ta_rng_session_id);
+     tee_client_close_context(ctx);
+
+     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)},
+     {}
+};
+
+MODULE_DEVICE_TABLE(tee, optee_rng_id_table);
+
+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 optee_rng_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 optee_rng_mod_exit(void)
+{
+     driver_unregister(&optee_rng_driver.driver);
+}
+
+module_init(optee_rng_mod_init);
+module_exit(optee_rng_mod_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sumit Garg [off-list ref]");
--
2.7.4

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