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From: Sumit Garg <sumit.garg@linaro.org>
Date: Fri, 28 Dec 2018 15:28:12 +0530
Message-ID: <CAFA6WYN5+NWKpPhnGHRnh_ZOF9A8K=MvbbSQ9uvc2Tv1expXcA@mail.gmail.com>
Subject: Re: [PATCH v1 2/2] hwrng: add OP-TEE based rng driver
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: "open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
        <linux-crypto@vger.kernel.org>,
        Devicetree List <devicetree@vger.kernel.org>, mpm@selenic.com,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jens Wiklander <jens.wiklander@linaro.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Bhupesh Sharma <bhsharma@redhat.com>, tee-dev@lists.linaro.org
Content-Type: text/plain; charset="UTF-8"
Sender: linux-crypto-owner@vger.kernel.org

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
> >