Re: [PATCH] rtc: optee: add RTC driver for OP-TEE RTC PTA

From: Etienne Carriere
Date: Sun Mar 06 2022 - 16:09:19 EST

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Hello Clement,

In the code, rtc-optee driver opens a session with optee and allocates
shared memory from probe to remove time.
This uses resources in the TEE but RTC is not accessed often by Linux I guess.
Would it be interesting if a session is opened and shared memory
allocated only when a RPC command is to be invoked?

Minor comments below.

Br,
etienne

On Wed, 2 Mar 2022 at 16:08, Clément Léger <clement.leger@xxxxxxxxxxx> wrote:
>
> This drivers allows to communicate with a RTC PTA handled by OP-TEE [1].
> This PTA allows to query RTC information, set/get time and set/get
> offset depending on the supported features.
>
> [1] https://github.com/OP-TEE/optee_os/pull/5179
>
> Signed-off-by: Clément Léger <clement.leger@xxxxxxxxxxx>
> ---
> MAINTAINERS | 6 +
> drivers/rtc/Kconfig | 10 +
> drivers/rtc/Makefile | 1 +
> drivers/rtc/rtc-optee.c | 395 ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 412 insertions(+)
> create mode 100644 drivers/rtc/rtc-optee.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 4383949ff654..4449d5ca2e11 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14381,6 +14381,12 @@ L: op-tee@xxxxxxxxxxxxxxxxxxxxxxxxx
> S: Maintained
> F: drivers/char/hw_random/optee-rng.c
>
> +OP-TEE RTC DRIVER
> +M: Clément Léger <clement.leger@xxxxxxxxxxx>
> +L: linux-rtc@xxxxxxxxxxxxxxx
> +S: Maintained
> +F: drivers/rtc/rtc-optee.c
> +
> OPA-VNIC DRIVER
> M: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>
> M: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxxxxxxxxxxxxx>
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index d85a3c31347c..b10d88db8e9c 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -1293,6 +1293,16 @@ config RTC_DRV_OPAL
> This driver can also be built as a module. If so, the module
> will be called rtc-opal.
>
> +config RTC_DRV_OPTEE
> + tristate "OP-TEE based RTC driver"
> + depends on OPTEE
> + help
> + Select this to get support for OP-TEE based RTC control on ARM SoCs

I would remove the Arm SoCs reference. OP-TEE may be available on
other architectures in the future.

> + where RTC are not accessible to the normal world (Linux).
> +
> + This driver can also be built as a module. If so, the module
> + will be called rtc-optee.
> +
> config RTC_DRV_ZYNQMP
> tristate "Xilinx Zynq Ultrascale+ MPSoC RTC"
> depends on OF && HAS_IOMEM
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index e92f3e943245..2d827d8261d5 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -115,6 +115,7 @@ obj-$(CONFIG_RTC_DRV_GAMECUBE) += rtc-gamecube.o
> obj-$(CONFIG_RTC_DRV_NTXEC) += rtc-ntxec.o
> obj-$(CONFIG_RTC_DRV_OMAP) += rtc-omap.o
> obj-$(CONFIG_RTC_DRV_OPAL) += rtc-opal.o
> +obj-$(CONFIG_RTC_DRV_OPTEE) += rtc-optee.o
> obj-$(CONFIG_RTC_DRV_PALMAS) += rtc-palmas.o
> obj-$(CONFIG_RTC_DRV_PCAP) += rtc-pcap.o
> obj-$(CONFIG_RTC_DRV_PCF2123) += rtc-pcf2123.o
> diff --git a/drivers/rtc/rtc-optee.c b/drivers/rtc/rtc-optee.c
> new file mode 100644
> index 000000000000..f265056bf19e
> --- /dev/null
> +++ b/drivers/rtc/rtc-optee.c
> @@ -0,0 +1,395 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2022 Microchip.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/rtc.h>
> +#include <linux/tee_drv.h>
> +
> +#define RTC_INFO_VERSION 0x1
> +
> +#define TA_CMD_RTC_GET_INFO 0x0
> +#define TA_CMD_RTC_GET_TIME 0x1
> +#define TA_CMD_RTC_SET_TIME 0x2
> +#define TA_CMD_RTC_GET_OFFSET 0x3
> +#define TA_CMD_RTC_SET_OFFSET 0x4
> +
> +#define TA_RTC_FEATURE_CORRECTION BIT(0)
> +
> +struct optee_rtc_time {
> + u32 tm_sec;
> + u32 tm_min;
> + u32 tm_hour;
> + u32 tm_mday;
> + u32 tm_mon;
> + u32 tm_year;
> + u32 tm_wday;
> +};
> +
> +struct optee_rtc_info {
> + u64 version;
> + u64 features;
> + struct optee_rtc_time range_min;
> + struct optee_rtc_time range_max;
> +};
> +
> +/**
> + * struct optee_rtc - OP-TEE RTC private data
> + * @dev: OP-TEE based RTC device.
> + * @ctx: OP-TEE context handler.
> + * @session_id: RTC TA session identifier.
> + * @entropy_shm_pool: Memory pool shared with RTC device.
> + * @features: Bitfield of RTC features
> + */
> +struct optee_rtc {
> + struct device *dev;
> + struct tee_context *ctx;
> + u32 session_id;
> + struct tee_shm *entropy_shm_pool;
> + u64 features;
> +};
> +
> +static int optee_rtc_readtime(struct device *dev, struct rtc_time *tm)
> +{
> + struct optee_rtc *priv = dev_get_drvdata(dev);
> + struct tee_ioctl_invoke_arg inv_arg = {0};
> + struct optee_rtc_time *optee_tm;
> + struct tee_param param[4] = {0};
> + int ret = 0;
> +
> + inv_arg.func = TA_CMD_RTC_GET_TIME;
> + inv_arg.session = priv->session_id;
> + inv_arg.num_params = 4;
> +
> + /* Fill invoke cmd params */
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> + param[0].u.memref.shm = priv->entropy_shm_pool;
> + param[0].u.memref.size = sizeof(struct optee_rtc_time);
> + param[0].u.memref.shm_offs = 0;

can remove this line

> +
> + ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(dev, "TA_CMD_RTC_GET_TIME invoke err: %x\n",
> + inv_arg.ret);

print also 'ret' in case error is reported by its value?

> + return ret;

Be careful here to return an errno when ret==0 and inv_arg.ret!=0.
suggestion: return ret ? ret : -EPROTO;

> + }
> +
> + optee_tm = tee_shm_get_va(priv->entropy_shm_pool, 0);
> + if (IS_ERR(optee_tm)) {
> + dev_err(dev, "tee_shm_get_va failed\n");
> + return PTR_ERR(optee_tm);
> + }
> +
> + if (param[0].u.memref.size != sizeof(*optee_tm)) {
> + dev_err(dev, "Invalid read size from OPTEE\n");
> + return -EINVAL;

-EINVAL or -EPROTO.

> + }
> +
> + tm->tm_sec = optee_tm->tm_sec;
> + tm->tm_min = optee_tm->tm_min;
> + tm->tm_hour = optee_tm->tm_hour;
> + tm->tm_mday = optee_tm->tm_mday;
> + tm->tm_mon = optee_tm->tm_mon;
> + tm->tm_year = optee_tm->tm_year - 1900;
> + tm->tm_wday = optee_tm->tm_wday;
> + tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
> +
> + return 0;
> +}
> +
> +static int optee_rtc_settime(struct device *dev, struct rtc_time *tm)
> +{
> + struct optee_rtc *priv = dev_get_drvdata(dev);
> + struct tee_ioctl_invoke_arg inv_arg = {0};
> + struct optee_rtc_time optee_tm;
> + struct tee_param param[4] = {0};
> + void *rtc_data;
> + int ret = 0;
> +
> + optee_tm.tm_sec = tm->tm_sec;
> + optee_tm.tm_min = tm->tm_min;
> + optee_tm.tm_hour = tm->tm_hour;
> + optee_tm.tm_mday = tm->tm_mday;
> + optee_tm.tm_mon = tm->tm_mon;
> + optee_tm.tm_year = tm->tm_year + 1900;
> + optee_tm.tm_wday = tm->tm_wday;
> +
> + inv_arg.func = TA_CMD_RTC_SET_TIME;
> + inv_arg.session = priv->session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
> + param[0].u.memref.shm = priv->entropy_shm_pool;
> + param[0].u.memref.size = sizeof(struct optee_rtc_time);
> + param[0].u.memref.shm_offs = 0;
> +
> + rtc_data = tee_shm_get_va(priv->entropy_shm_pool, 0);
> + if (IS_ERR(rtc_data)) {
> + dev_err(dev, "tee_shm_get_va failed\n");
> + return PTR_ERR(rtc_data);
> + }
> +
> + memcpy(rtc_data, &optee_tm, sizeof(struct optee_rtc_time));
> +
> + ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(dev, "TA_CMD_RTC_GET_TIME invoke err: %x\n",
> + inv_arg.ret);
> + return ret;

Ditto: 'return ret ? ret : -EPROTO;'

> + }
> +
> + return 0;
> +}
> +
> +static int optee_rtc_readoffset(struct device *dev, long *offset)
> +{
> + struct optee_rtc *priv = dev_get_drvdata(dev);
> + struct tee_ioctl_invoke_arg inv_arg = {0};
> + struct tee_param param[4] = {0};
> + int ret = 0;
> +
> + if (!(priv->features & TA_RTC_FEATURE_CORRECTION))
> + return -EOPNOTSUPP;
> +
> + inv_arg.func = TA_CMD_RTC_GET_OFFSET;
> + inv_arg.session = priv->session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT;
> +
> + ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(dev, "TA_CMD_RTC_GET_RNG_INFO invoke err: %x\n",
> + inv_arg.ret);
> + return -EINVAL;
> + }
> +
> + *offset = param[0].u.value.a;
> +
> + return 0;
> +}
> +
> +static int optee_rtc_setoffset(struct device *dev, long offset)
> +{
> + struct optee_rtc *priv = dev_get_drvdata(dev);
> + struct tee_ioctl_invoke_arg inv_arg = {0};
> + struct tee_param param[4] = {0};
> + int ret = 0;
> +
> + if (!(priv->features & TA_RTC_FEATURE_CORRECTION))
> + return -EOPNOTSUPP;
> +
> + inv_arg.func = TA_CMD_RTC_SET_OFFSET;
> + inv_arg.session = priv->session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT;
> + param[0].u.value.a = offset;
> +
> + ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(dev, "TA_CMD_RTC_GET_RNG_INFO invoke err: %x\n",
> + inv_arg.ret);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +static const struct rtc_class_ops optee_rtc_ops = {
> + .read_time = optee_rtc_readtime,
> + .set_time = optee_rtc_settime,
> + .set_offset = optee_rtc_setoffset,
> + .read_offset = optee_rtc_readoffset,
> +};
> +
> +static int optee_rtc_read_info(struct device *dev, struct rtc_device *rtc,
> + u64 *features)
> +{
> + struct optee_rtc *priv = dev_get_drvdata(dev);
> + struct tee_ioctl_invoke_arg inv_arg = {0};
> + struct tee_param param[4] = {0};
> + struct optee_rtc_info *info;
> + struct optee_rtc_time *tm;
> + int ret = 0;
> +
> + inv_arg.func = TA_CMD_RTC_GET_INFO;
> + inv_arg.session = priv->session_id;
> + inv_arg.num_params = 4;
> +
> + param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> + param[0].u.memref.shm = priv->entropy_shm_pool;
> + param[0].u.memref.size = sizeof(*info);
> + param[0].u.memref.shm_offs = 0;
> +
> + ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
> + if ((ret < 0) || (inv_arg.ret != 0)) {
> + dev_err(dev, "TA_CMD_RTC_GET_RNG_INFO invoke err: %x\n",
> + inv_arg.ret);
> + return -EINVAL;
> + }
> +
> + info = tee_shm_get_va(priv->entropy_shm_pool, 0);
> + if (IS_ERR(info)) {
> + dev_err(dev, "tee_shm_get_va failed\n");
> + return PTR_ERR(info);
> + }
> +
> + if (param[0].u.memref.size < sizeof(*info)) {
> + dev_err(dev, "Invalid read size from OPTEE\n");
> + return -EINVAL;

This is also a protocol error. Prefer -EPROTO.

> + }
> +
> + if (info->version != RTC_INFO_VERSION) {
> + dev_err(dev, "Unsupported information version %llu\n",
> + info->version);
> + return -EINVAL;
> + }
> +
> + *features = info->features;
> +
> + tm = &info->range_min;
> + rtc->range_min = mktime64(tm->tm_year, tm->tm_mon, tm->tm_mday,
> + tm->tm_hour, tm->tm_min, tm->tm_sec);
> + tm = &info->range_max;
> + rtc->range_max = mktime64(tm->tm_year, tm->tm_mon, tm->tm_mday,
> + tm->tm_hour, tm->tm_min, tm->tm_sec);
> +
> + 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_rtc_probe(struct device *dev)
> +{
> + struct tee_client_device *rtc_device = to_tee_client_device(dev);
> + struct tee_ioctl_open_session_arg sess_arg;
> + struct tee_shm *entropy_shm_pool = NULL;
> + int ret = 0, err = -ENODEV;
> + struct optee_rtc *priv;
> + struct rtc_device *rtc;
> +
> + memset(&sess_arg, 0, sizeof(sess_arg));
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + rtc = devm_rtc_allocate_device(dev);
> + if (IS_ERR(rtc))
> + return PTR_ERR(rtc);
> +
> + /* Open context with TEE driver */
> + priv->ctx = tee_client_open_context(NULL, optee_ctx_match, NULL,
> + NULL);

Fits in 100 chars. You could get rid of few line breaks in this change.

> + if (IS_ERR(priv->ctx))
> + return -ENODEV;
> +
> + /* Open session with rtc Trusted App */
> + memcpy(sess_arg.uuid, rtc_device->id.uuid.b, TEE_IOCTL_UUID_LEN);
> + sess_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
> + sess_arg.num_params = 0;

not needed.

> +
> + ret = tee_client_open_session(priv->ctx, &sess_arg, NULL);
> + if ((ret < 0) || (sess_arg.ret != 0)) {
> + dev_err(dev, "tee_client_open_session failed, err: %x\n",
> + sess_arg.ret);
> + err = -EINVAL;
> + goto out_ctx;
> + }
> + priv->session_id = sess_arg.session;
> +
> + entropy_shm_pool = tee_shm_alloc(priv->ctx,
> + sizeof(struct optee_rtc_info),
> + TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> + if (IS_ERR(entropy_shm_pool)) {
> + dev_err(priv->dev, "tee_shm_alloc failed\n");
> + err = PTR_ERR(entropy_shm_pool);
> + goto out_sess;
> + }
> +
> + priv->entropy_shm_pool = entropy_shm_pool;
> + priv->dev = dev;
> + dev_set_drvdata(dev, priv);
> +
> + rtc->ops = &optee_rtc_ops;
> +
> + err = optee_rtc_read_info(dev, rtc, &priv->features);
> + if (err) {
> + dev_err(dev, "Failed to get RTC features from OP-TEE\n");
> + goto out_sess;

Should release the allocated shared memory on exit.

> + }
> +
> + err = devm_rtc_register_device(rtc);
> + if (err)
> + goto out_sess;

Ditto.

> +
> + /*
> + * We must clear this bit after registering because rtc_register_device
> + * will set it if it sees that .set_offset is provided.
> + */
> + if (!(priv->features & TA_RTC_FEATURE_CORRECTION))
> + clear_bit(RTC_FEATURE_CORRECTION, rtc->features);
> +
> + return 0;
> +
> +out_sess:
> + tee_client_close_session(priv->ctx, priv->session_id);
> +out_ctx:
> + tee_client_close_context(priv->ctx);
> +
> + return err;
> +}
> +
> +static int optee_rtc_remove(struct device *dev)
> +{
> + struct optee_rtc *priv = dev_get_drvdata(dev);
> +
> + tee_client_close_session(priv->ctx, priv->session_id);
> + tee_client_close_context(priv->ctx);
> +
> + return 0;
> +}
> +
> +static const struct tee_client_device_id optee_rtc_id_table[] = {
> + {UUID_INIT(0xf389f8c8, 0x845f, 0x496c,
> + 0x8b, 0xbe, 0xd6, 0x4b, 0xd2, 0x4c, 0x92, 0xfd)},
> + {}
> +};
> +
> +MODULE_DEVICE_TABLE(tee, optee_rtc_id_table);
> +
> +static struct tee_client_driver optee_rtc_driver = {
> + .id_table = optee_rtc_id_table,
> + .driver = {
> + .name = "optee_rtc",
> + .bus = &tee_bus_type,
> + .probe = optee_rtc_probe,
> + .remove = optee_rtc_remove,
> + },
> +};
> +
> +static int __init optee_rtc_mod_init(void)
> +{
> + return driver_register(&optee_rtc_driver.driver);
> +}
> +
> +static void __exit optee_rtc_mod_exit(void)
> +{
> + driver_unregister(&optee_rtc_driver.driver);
> +}
> +
> +module_init(optee_rtc_mod_init);
> +module_exit(optee_rtc_mod_exit);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Clément Léger <clement.leger@xxxxxxxxxxx>");
> +MODULE_DESCRIPTION("OP-TEE based RTC driver");
> --
> 2.34.1
>

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