Re: [PATCH v5 4/4] hwrng: add OP-TEE based rng driver

From: Sumit Garg
Date: Thu Jan 24 2019 - 09:02:30 EST

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On Thu, 24 Jan 2019 at 18:01, Daniel Thompson
<daniel.thompson@xxxxxxxxxx> wrote:
>
> On Thu, Jan 24, 2019 at 11:24:39AM +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@xxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxx>
> > S: Maintained
> > F: drivers/tee/optee/
> >
> > +OP-TEE RANDOM NUMBER GENERATOR (RNG) DRIVER
> > +M: Sumit Garg <sumit.garg@xxxxxxxxxx>
> > +S: Maintained
> > +F: drivers/char/hw_random/optee-rng.c
> > +
> > OPA-VNIC DRIVER
> > M: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>
> > M: Niranjana Vishwanathapura <niranjana.vishwanathapura@xxxxxxxxx>
> > 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.

>
> > + 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.
>
>
>
> > + 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 <sumit.garg@xxxxxxxxxx>");
> > --
> > 2.7.4
> >

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