Message-ID: <5f913165-f33e-4d14-8cc3-2e16507aab25@arm.com>
Date: Thu, 13 Feb 2025 16:22:44 -0600
From: Stuart Yoder <stuart.yoder@....com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-integrity@...r.kernel.org, peterhuewe@....de, jgg@...pe.ca,
 sudeep.holla@....com, rafael@...nel.org, lenb@...nel.org,
 linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over
 FF-A



On 2/13/25 4:14 PM, Jarkko Sakkinen wrote:
> On Wed, Feb 12, 2025 at 04:05:44PM -0600, Stuart Yoder wrote:
>> The Arm specification TPM Service CRB over FF-A specification
>> defines the FF-A messages to interact with a CRB-based TPM
>> implemented as an FF-A secure partition.
>>
>> Spec URL:
>> https://developer.arm.com/documentation/den0138/latest/
>>
>> This driver is probed when a TPM Secure Partition is
>> discovered by the FF-A subsystem. It exposes APIs
>> used by the TPM CRB driver to send notifications to
>> the TPM.
>>
>> Signed-off-by: Stuart Yoder <stuart.yoder@....com>
>> ---
>>   drivers/char/tpm/Kconfig       |   9 +
>>   drivers/char/tpm/Makefile      |   1 +
>>   drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
>>   drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
>>   4 files changed, 350 insertions(+)
>>   create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
>>   create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
>>
>> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
>> index 0fc9a510e059..af5ba7c63927 100644
>> --- a/drivers/char/tpm/Kconfig
>> +++ b/drivers/char/tpm/Kconfig
>> @@ -210,6 +210,15 @@ config TCG_CRB
>>   	  from within Linux.  To compile this driver as a module, choose
>>   	  M here; the module will be called tpm_crb.
>>   
>> +config TCG_ARM_FFA_CRB
>> +	tristate "TPM CRB over Arm FF-A Transport"
>> +	depends on ARM_FFA_TRANSPORT
>> +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
>> +	help
>> +	  If the Arm FF-A transport is used to access the TPM say Yes.
>> +	  To compile this driver as a module, choose M here; the module
>> +	  will be called tpm_ffa_crb.
>> +
>>   config TCG_VTPM_PROXY
>>   	tristate "VTPM Proxy Interface"
>>   	depends on TCG_TPM
>> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
>> index 9bb142c75243..21f2eb5a485e 100644
>> --- a/drivers/char/tpm/Makefile
>> +++ b/drivers/char/tpm/Makefile
>> @@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
>>   obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
>>   obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
>>   obj-$(CONFIG_TCG_CRB) += tpm_crb.o
>> +obj-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
>>   obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
>>   obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
>> diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
>> new file mode 100644
>> index 000000000000..56bd77864a47
>> --- /dev/null
>> +++ b/drivers/char/tpm/tpm_ffa_crb.c
>> @@ -0,0 +1,310 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2024 Arm Ltd.
>> + *
>> + * Maintained by: <tpmdd-devel@...ts.sourceforge.net>
>> + *
>> + * This device driver implements the TPM CRB start method
>> + * as defined in the TPM Service Command Response Buffer
>> + * Interface Over FF-A (DEN0138).
>> + */
>> +
>> +#define pr_fmt(fmt) "FFA_CRB: " fmt
>> +
>> +#include <linux/arm_ffa.h>
>> +#include "tpm_ffa_crb.h"
>> +
>> +/* TPM service function status codes */
>> +#define FFA_CRB_OK			0x05000001
>> +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
>> +#define FFA_CRB_NOFUNC			0x8e000001
>> +#define FFA_CRB_NOTSUP			0x8e000002
>> +#define FFA_CRB_INVARG			0x8e000005
>> +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
>> +#define FFA_CRB_ALREADY			0x8e000009
>> +#define FFA_CRB_DENIED			0x8e00000a
>> +#define FFA_CRB_NOMEM			0x8e00000b
>> +
>> +#define FFA_CRB_VERSION_MAJOR	1
>> +#define FFA_CRB_VERSION_MINOR	0
>> +
>> +/* version encoding */
>> +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
>> +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
>> +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
>> +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MINOR_VERSION_MASK, (x))))
>> +
>> +/*
>> + * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
>> + * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
>> + * messages.
>> + *
>> + * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
>> + * are using the AArch32 SMC calling convention with register usage as
>> + * defined in FF-A specification:
>> + * w0:    Function ID (0x8400006F or 0x84000070)
>> + * w1:    Source/Destination IDs
>> + * w2:    Reserved (MBZ)
>> + * w3-w7: Implementation defined, free to be used below
>> + */
>> +
>> +/*
>> + * Returns the version of the interface that is available
>> + * Call register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function ID, FFA_CRB_GET_INTERFACE_VERSION
>> + * w5-w7: Reserved (MBZ)
>> + *
>> + * Return register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function status
>> + * w5:    TPM service interface version
>> + *        Bits[31:16]: major version
>> + *        Bits[15:0]: minor version
>> + * w6-w7: Reserved (MBZ)
>> + *
>> + * Possible function status codes in register w4:
>> + *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
>> + *                                  returned.
>> + */
>> +#define FFA_CRB_GET_INTERFACE_VERSION 0x0f000001
>> +
>> +/*
>> + * Return information on a given feature of the TPM service
>> + * Call register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function ID, FFA_CRB_START
>> + * w5:    Start function qualifier
>> + *            Bits[31:8] (MBZ)
>> + *            Bits[7:0]
>> + *              0: Notifies TPM that a command is ready to be processed
>> + *              1: Notifies TPM that a locality request is ready to be processed
>> + * w6:    TPM locality, one of 0..4
>> + *            -If the start function qualifier is 0, identifies the locality
>> + *             from where the command originated.
>> + *            -If the start function qualifier is 1, identifies the locality
>> + *             of the locality request
>> + * w6-w7: Reserved (MBZ)
>> + *
>> + * Return register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function status
>> + * w5-w7: Reserved (MBZ)
>> + *
>> + * Possible function status codes in register w4:
>> + *     FFA_CRB_OK: the TPM service has been notified successfully
>> + *     FFA_CRB_INVARG: one or more arguments are not valid
>> + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
>> + *         data at the given TPM locality is not valid
>> + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
>> + *         command processing at the given locality
>> + */
>> +#define FFA_CRB_START 0x0f000201
>> +
>> +struct ffa_crb {
>> +	struct ffa_device *ffa_dev;
>> +	u16 major_version;
>> +	u16 minor_version;
>> +	struct mutex msg_data_lock;
>> +	struct ffa_send_direct_data direct_msg_data;
>> +};
>> +
>> +static struct ffa_crb *ffa_crb;
>> +
>> +static int ffa_crb_to_linux_errno(int errno)
>> +{
>> +	int rc;
>> +
>> +	switch (errno) {
>> +	case FFA_CRB_OK:
>> +		rc = 0;
>> +		break;
>> +	case FFA_CRB_OK_RESULTS_RETURNED:
>> +		rc = 0;
>> +		break;
>> +	case FFA_CRB_NOFUNC:
>> +		rc = -ENOENT;
>> +		break;
>> +	case FFA_CRB_NOTSUP:
>> +		rc = -EPERM;
>> +		break;
>> +	case FFA_CRB_INVARG:
>> +		rc = -EINVAL;
>> +		break;
>> +	case FFA_CRB_INV_CRB_CTRL_DATA:
>> +		rc = -ENOEXEC;
>> +		break;
>> +	case FFA_CRB_ALREADY:
>> +		rc = -EEXIST;
>> +		break;
>> +	case FFA_CRB_DENIED:
>> +		rc = -EACCES;
>> +		break;
>> +	case FFA_CRB_NOMEM:
>> +		rc = -ENOMEM;
>> +		break;
>> +	default:
>> +		rc = -EINVAL;
>> +	}
>> +
>> +	return rc;
>> +}
>> +
>> +int ffa_crb_init(void)
>> +{
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_init);
>> +
>> +static int __ffa_crb_send_recieve(unsigned long func_id,
>> +		unsigned long a0, unsigned long a1, unsigned long a2)
>> +{
>> +	int ret;
>> +	const struct ffa_msg_ops *msg_ops;
>> +
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
>> +
>> +	memset(&ffa_crb->direct_msg_data, 0x00,
>> +			sizeof(struct ffa_send_direct_data));
>> +
>> +	ffa_crb->direct_msg_data.data1 = func_id;
>> +	ffa_crb->direct_msg_data.data2 = a0;
>> +	ffa_crb->direct_msg_data.data3 = a1;
>> +	ffa_crb->direct_msg_data.data4 = a2;
>> +
>> +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
>> +			&ffa_crb->direct_msg_data);
>> +	if (!ret)
>> +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
>> +
>> +	return ret;
>> +}
>> +
>> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
>> +{
>> +	int rc;
>> +
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	if (major == NULL || minor == NULL)
>> +		return -EINVAL;
>> +
>> +	guard(mutex)(&ffa_crb->msg_data_lock);
>> +
>> +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
>> +	if (!rc) {
>> +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
>> +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
>> +	}
>> +
>> +	return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
>> +
>> +int ffa_crb_start(int request_type, int locality)
>> +{
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	guard(mutex)(&ffa_crb->msg_data_lock);
>> +
>> +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_start);
>> +
>> +static int ffa_crb_probe(struct ffa_device *ffa_dev)
>> +{
>> +	int rc;
>> +	struct ffa_crb *p;
>> +
>> +	/* only one instance of a TPM partition is supported */
>> +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
>> +		return -EEXIST;
>> +
>> +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
>> +
>> +	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
>> +		pr_err("TPM partition doesn't support direct message receive.\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
>> +	if (!p)
>> +		return -ENOMEM;
>> +	ffa_crb = p;
>> +
>> +	mutex_init(&ffa_crb->msg_data_lock);
>> +	ffa_crb->ffa_dev = ffa_dev;
>> +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
>> +
>> +	/* if TPM is aarch32 use 32-bit SMCs */
>> +	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
>> +		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
>> +
>> +	/* verify compatibility of TPM service version number */
>> +	rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
>> +			&ffa_crb->minor_version);
>> +	if (rc) {
>> +		pr_err("failed to get crb interface version. rc:%d", rc);
>> +		goto out;
>> +	}
>> +
>> +	pr_info("ABI version %u.%u", ffa_crb->major_version,
>> +		ffa_crb->minor_version);
>> +
>> +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
>> +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
>> +		pr_err("Incompatible ABI version");
>> +		goto out;
>> +	}
>> +
>> +	return 0;
>> +
>> +out:
>> +	kfree(ffa_crb);
>> +	ffa_crb = ERR_PTR(-ENODEV);
>> +	return -EINVAL;
>> +}
>> +
>> +static void ffa_crb_remove(struct ffa_device *ffa_dev)
>> +{
>> +	kfree(ffa_crb);
>> +	ffa_crb = NULL;
>> +}
>> +
>> +static const struct ffa_device_id ffa_crb_device_id[] = {
>> +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
>> +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
>> +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
>> +	{}
>> +};
>> +
>> +static struct ffa_driver ffa_crb_driver = {
>> +	.name = "ffa-crb",
>> +	.probe = ffa_crb_probe,
>> +	.remove = ffa_crb_remove,
>> +	.id_table = ffa_crb_device_id,
>> +};
>> +
>> +module_ffa_driver(ffa_crb_driver);
>> +
>> +MODULE_AUTHOR("Arm");
>> +MODULE_DESCRIPTION("FFA CRB driver");
>> +MODULE_VERSION("1.0");
>> +MODULE_LICENSE("GPL");
>> diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
>> new file mode 100644
>> index 000000000000..42327d285165
>> --- /dev/null
>> +++ b/drivers/char/tpm/tpm_ffa_crb.h
>> @@ -0,0 +1,30 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2024 Arm Ltd.
>> + *
>> + * Authors:
>> + * Stuart Yoder <stuart.yoder@....com>
>> + *
>> + * Maintained by: <tpmdd-devel@...ts.sourceforge.net>
>> + *
>> + * This device driver implements the TPM CRB start method
>> + * as defined in the TPM Service Command Response Buffer
>> + * Interface Over FF-A (DEN0138).
>> + */
>> +#ifndef _FFA_CRB_H
>> +#define _FFA_CRB_H
>> +
>> +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
>> +int ffa_crb_init(void);
>> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
>> +int ffa_crb_start(int request_type, int locality);
>> +#else
>> +static inline int ffa_crb_init(void) { return 0; }
>> +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
>> +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
>> +#endif
>> +
>> +#define FFA_CRB_START_TYPE_COMMAND 0
>> +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
>> +
>> +#endif
>> -- 
>> 2.34.1
>>
>>
> 
> tpm_crb_ffa_*

I had renamed the source file to be tpm_ffa_crb.c based on your
previous feedback.  It would be good to be consistent.  Would
you prefer:

tpm_crb_ffa_*
or
tpm_ffa_crb_*

Thanks,
Stuart

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