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Date: Mon, 1 Jun 2020 09:24:46 +0200
From: "Jorge Ramirez-Ortiz, Foundries" <jorge@...ndries.io>
To: Sumit Garg <sumit.garg@...aro.org>
Cc: Jorge Ramirez-Ortiz <jorge@...ndries.io>,
Jens Wiklander <jens.wiklander@...aro.org>,
"tee-dev @ lists . linaro . org" <tee-dev@...ts.linaro.org>,
ricardo@...ndries.io, mike@...ndries.io,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Tee-dev] [PATCH v2] drivers: optee: allow op-tee to access
devices on the i2c bus
On 01/06/20, Sumit Garg wrote:
> Hi Jorge,
hey
>
> On Mon, 1 Jun 2020 at 04:41, Jorge Ramirez-Ortiz <jorge@...ndries.io> wrote:
> >
> > Some secure elements like NXP's SE050 sit on I2C buses. For OP-TEE to
> > control this type of cryptographic devices it needs coordinated access
> > to the bus, so collisions and RUNTIME_PM dont get in the way.
> >
> > This trampoline driver allow OP-TEE to access them.
> >
>
> This sounds like an interesting use-case but I would like to
> understand how secure is this communication interface with the secure
> element? Like in the case of RPMB, secure world data is encrypted
> which flows via tee-supplicant to RPMB device.
right, the data in the buffer should be encrypted in both directions
(in the case of the SE050 [1] we have the option to operate with or
without encryption which is what I am doing during development
[2]).
But ultimately -before any product can be shipped- all comms must be
encrypted: this means that when OP-TEE uses the SE050 for crypto, it
must encrypt the data on write and decrypt what is comming from the
SE050 on read. I am now looking into how to enable this.
[1] https://www.nxp.com/docs/en/data-sheet/SE050-DATASHEET.pdf
[2] https://github.com/ldts/optee_os/commits/se050
>
> -Sumit
>
> > Signed-off-by: Jorge Ramirez-Ortiz <jorge@...ndries.io>
> > ---
> > drivers/tee/optee/optee_msg.h | 18 +++++++++++
> > drivers/tee/optee/rpc.c | 57 +++++++++++++++++++++++++++++++++++
> > 2 files changed, 75 insertions(+)
> >
> > diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> > index 795bc19ae17a..b6cc964fdeea 100644
> > --- a/drivers/tee/optee/optee_msg.h
> > +++ b/drivers/tee/optee/optee_msg.h
> > @@ -419,4 +419,22 @@ struct optee_msg_arg {
> > */
> > #define OPTEE_MSG_RPC_CMD_SHM_FREE 7
> >
> > +/*
> > + * Access a device on an i2c bus
> > + *
> > + * [in] param[0].u.value.a mode: RD(0), WR(1)
> > + * [in] param[0].u.value.b i2c adapter
> > + * [in] param[0].u.value.c i2c chip
> > + *
> > + * [io] param[1].u.tmem.buf_ptr physical address
> > + * [io] param[1].u.tmem.size transfer size in bytes
> > + * [io] param[1].u.tmem.shm_ref shared memory reference
> > + *
> > + * [out] param[0].u.value.a bytes transferred
> > + *
> > + */
> > +#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER 8
> > +#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD 0
> > +#define OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR 1
> > +
> > #endif /* _OPTEE_MSG_H */
> > diff --git a/drivers/tee/optee/rpc.c b/drivers/tee/optee/rpc.c
> > index b4ade54d1f28..21d452805c6f 100644
> > --- a/drivers/tee/optee/rpc.c
> > +++ b/drivers/tee/optee/rpc.c
> > @@ -9,6 +9,7 @@
> > #include <linux/device.h>
> > #include <linux/slab.h>
> > #include <linux/tee_drv.h>
> > +#include <linux/i2c.h>
> > #include "optee_private.h"
> > #include "optee_smc.h"
> >
> > @@ -48,6 +49,59 @@ static void handle_rpc_func_cmd_get_time(struct optee_msg_arg *arg)
> > bad:
> > arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> > }
> > +static void handle_rpc_func_cmd_i2c_transfer(struct tee_context *ctx,
> > + struct optee_msg_arg *arg)
> > +{
> > + struct i2c_client client;
> > + struct tee_shm *shm;
> > + int i, ret;
> > + char *buf;
> > + uint32_t attr[] = {
> > + OPTEE_MSG_ATTR_TYPE_VALUE_INPUT,
> > + OPTEE_MSG_ATTR_TYPE_TMEM_INOUT,
> > + OPTEE_MSG_ATTR_TYPE_VALUE_OUTPUT,
> > + };
> > +
> > + if (arg->num_params != ARRAY_SIZE(attr))
> > + goto bad;
> > +
> > + for (i = 0; i < ARRAY_SIZE(attr); i++)
> > + if ((arg->params[i].attr & OPTEE_MSG_ATTR_TYPE_MASK) != attr[i])
> > + goto bad;
> > +
> > + shm = (struct tee_shm *)(unsigned long)arg->params[1].u.tmem.shm_ref;
> > + buf = (char *)shm->kaddr;
> > +
> > + client.addr = arg->params[0].u.value.c;
> > + client.adapter = i2c_get_adapter(arg->params[0].u.value.b);
> > + if (!client.adapter)
> > + goto bad;
> > +
> > + snprintf(client.name, I2C_NAME_SIZE, "i2c%d", client.adapter->nr);
> > +
> > + switch (arg->params[0].u.value.a) {
> > + case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_RD:
> > + ret = i2c_master_recv(&client, buf, arg->params[1].u.tmem.size);
> > + break;
> > + case OPTEE_MSG_RPC_CMD_I2C_TRANSFER_WR:
> > + ret = i2c_master_send(&client, buf, arg->params[1].u.tmem.size);
> > + break;
> > + default:
> > + i2c_put_adapter(client.adapter);
> > + goto bad;
> > + }
> > +
> > + if (ret >= 0) {
> > + arg->params[2].u.value.a = ret;
> > + arg->ret = TEEC_SUCCESS;
> > + } else
> > + arg->ret = TEEC_ERROR_COMMUNICATION;
> > +
> > + i2c_put_adapter(client.adapter);
> > + return;
> > +bad:
> > + arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> > +}
> >
> > static struct wq_entry *wq_entry_get(struct optee_wait_queue *wq, u32 key)
> > {
> > @@ -382,6 +436,9 @@ static void handle_rpc_func_cmd(struct tee_context *ctx, struct optee *optee,
> > case OPTEE_MSG_RPC_CMD_SHM_FREE:
> > handle_rpc_func_cmd_shm_free(ctx, arg);
> > break;
> > + case OPTEE_MSG_RPC_CMD_I2C_TRANSFER:
> > + handle_rpc_func_cmd_i2c_transfer(ctx, arg);
> > + break;
> > default:
> > handle_rpc_supp_cmd(ctx, arg);
> > }
> > --
> > 2.17.1
> >
> > _______________________________________________
> > Tee-dev mailing list
> > Tee-dev@...ts.linaro.org
> > https://lists.linaro.org/mailman/listinfo/tee-dev
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