Add support for the TPM FF-A start method

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 <[email protected]>

---
 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

drivers/char/tpm/Kconfig +9 -0

index 0fc9a510e059..af5ba7c63927 100644
@@ -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

drivers/char/tpm/Makefile +1 -0

index 9bb142c75243..21f2eb5a485e 100644
@@ -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

drivers/char/tpm/tpm_ffa_crb.c new file +310 -0

new file mode 100644
index 000000000000..56bd77864a47
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Maintained by: <[email protected]>
+ *
+ * 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");

drivers/char/tpm/tpm_ffa_crb.h new file +30 -0

new file mode 100644
index 000000000000..42327d285165
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Authors:
+ * Stuart Yoder <[email protected]>
+ *
+ * Maintained by: <[email protected]>
+ *
+ * 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

Signature · 1 line

2.34.1

Quoted 403 lines · Stuart Yoder

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 <[email protected]>

---
  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

drivers/char/tpm/Kconfig +9 -0

index 0fc9a510e059..af5ba7c63927 100644
@@ -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

drivers/char/tpm/Makefile +1 -0

index 9bb142c75243..21f2eb5a485e 100644
@@ -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

drivers/char/tpm/tpm_ffa_crb.c new file +310 -0

new file mode 100644
index 000000000000..56bd77864a47
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Maintained by: <[email protected]>
+ *
+ * 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");

drivers/char/tpm/tpm_ffa_crb.h new file +28 -0

new file mode 100644
index 000000000000..42327d285165
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Authors:
+ * Stuart Yoder <[email protected]>
+ *
+ * Maintained by: <[email protected]>
+ *
+ * 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

Quoted 6 lines

drivers/char/tpm/tpm_ffa_crb.h new file +2 -0

+
+#endif

Signature · 1 line

2.34.1

tpm_crb_ffa_*

Quoted 403 lines · Jarkko Sakkinen

Quoted 402 lines · Stuart Yoder

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 <[email protected]>

---
  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

drivers/char/tpm/Kconfig +9 -0

index 0fc9a510e059..af5ba7c63927 100644
@@ -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

drivers/char/tpm/Makefile +1 -0

index 9bb142c75243..21f2eb5a485e 100644
@@ -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

drivers/char/tpm/tpm_ffa_crb.c new file +310 -0

new file mode 100644
index 000000000000..56bd77864a47
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Maintained by: <[email protected]>
+ *
+ * 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");

drivers/char/tpm/tpm_ffa_crb.h new file +28 -0

new file mode 100644
index 000000000000..42327d285165
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Authors:
+ * Stuart Yoder <[email protected]>
+ *
+ * Maintained by: <[email protected]>
+ *
+ * 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

Quoted 8 lines

Quoted 6 lines

drivers/char/tpm/tpm_ffa_crb.h new file +2 -0

+
+#endif

Signature · 1 line

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_*

Refactor the two checks for whether the TPM supports idle into a single inline function.

Signed-off-by Stuart Yoder <[email protected]>

---
 drivers/char/tpm/tpm_crb.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

drivers/char/tpm/tpm_crb.c +0 -0

index ea085b14ab7c..87d69e990249 100644
@@ -115,6 +115,16 @@ struct tpm2_crb_pluton {
 	u64 reply_addr;
 };
 

drivers/char/tpm/tpm_crb.c +2 -6

 static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
 				unsigned long timeout)
 {

@@ -173,9 +183,7 @@ static int __crb_go_idle(struct device *dev, struct crb_priv *priv)
 {
 	int rc;
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	if (!does_tpm_support_idle(priv->sm))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->regs_t->ctrl_req);

@@ -222,9 +230,7 @@ static int __crb_cmd_ready(struct device *dev, struct crb_priv *priv)
 {
 	int rc;
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	if (!does_tpm_support_idle(priv->sm))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);

Signature · 1 line

2.34.1

Quoted 16 lines · Stuart Yoder

Refactor the two checks for whether the TPM supports idle into a single inline function.

Signed-off-by Stuart Yoder <[email protected]>

---
  drivers/char/tpm/tpm_crb.c | 18 ++++++++++++------
  1 file changed, 12 insertions(+), 6 deletions(-)

drivers/char/tpm/tpm_crb.c +0 -0

index ea085b14ab7c..87d69e990249 100644
@@ -115,6 +115,16 @@ struct tpm2_crb_pluton {
  	u64 reply_addr;
  };
 

drivers/char/tpm/tpm_crb.c struct tpm2_crb_pluton { · line 127

Quoted 10 lines

drivers/char/tpm/tpm_crb.c +10 -0

+static inline bool does_tpm_support_idle(u32 start_method)
+{
+	if ((start_method == ACPI_TPM2_START_METHOD) ||
+	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
+	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+		return false;
+	else
+		return true;
+}
+

I think we could also prefix tpm_crb stuff with tpm_crb_* for the sake of easier grepping etc.

So I'd propose this to be called as: tpm_crb_has_idle()

Add documentation providing details of how the CRB driver interacts with FF-A.

Signed-off-by Stuart Yoder <[email protected]>

---
 Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst

Documentation/security/tpm/tpm_ffa_crb.rst new file +12 -0

new file mode 100644
index 000000000000..c70f8904a93d
@@ -0,0 +1,65 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+TPM CRB over FF-A Driver
+========================
+
+The TPM Command Response Buffer (CRB) interface is a standard TPM interface
+defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
+The CRB provides a structured set of control registers a client uses when
+interacting with a TPM as well as a data buffer for storing TPM commands and
+responses. A CRB interface can be implemented in:
+

Documentation/security/tpm/tpm_ffa_crb.rst new file +43 -0

+
+- Provide a standard interface for software components in the Non-secure
+  state, for example OS and Hypervisors, to communicate with this firmware.
+
+A TPM can be implemented as an FF-A secure service.  This could be a firmware
+TPM or could potentially be a TPM service that acts as a proxy to a discrete
+TPM chip. An FF-A based TPM abstracts hardware details (e.g. bus controller
+and chip selects) away from the OS and can protect locality 4 from access
+by an OS.  The TCG-defined CRB interface is used by clients to interact
+with the TPM service.
+
+The Arm TPM Service Command Response Buffer Interface Over FF-A [3]_
+specification defines FF-A messages that can be used by a client to signal
+when updates have been made to the CRB.
+
+How the Linux CRB driver interacts with FF-A is summarized below:
+
+- The tpm_ffa_crb driver registers with the FF-A subsystem in the kernel
+  with an architected TPM service UUID defined in the CRB over FF-A spec.
+
+- If a TPM service is discovered by FF-A, the probe() function in the
+  tpm_ffa_crb driver runs, and the driver initializes.
+
+- The probing and initialization of the Linux CRB driver is triggered
+  by the discovery of a TPM advertised via ACPI.  The CRB driver can
+  detect the type of TPM through the ACPI 'start' method.  The start
+  method for Arm FF-A was defined in TCG ACPI v1.4 [4]_.
+
+- When the CRB driver performs its normal functions such as signaling 'start'
+  and locality request/relinquish it invokes the ffa_crb_start() funnction
+  in the tpm_ffa_crb driver which handles the FF-A messaging to the TPM.
+
+References
+==========
+
+.. [1] **TCG PC Client Platform TPM Profile (PTP) Specification**
+   https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
+.. [2] **Arm Firmware Framework for Arm A-profile (FF-A)**
+   https://developer.arm.com/documentation/den0077/latest/
+.. [3] **Arm TPM Service Command Response Buffer Interface Over FF-A**
+   https://developer.arm.com/documentation/den0138/latest/
+.. [4] **TCG ACPI Specification**
+   https://trustedcomputinggroup.org/resource/tcg-acpi-specification/

Signature · 1 line

2.34.1

Quoted 31 lines · Stuart Yoder

Add documentation providing details of how the CRB driver interacts with FF-A.

Signed-off-by Stuart Yoder <[email protected]>

---
  Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
  1 file changed, 65 insertions(+)

create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst

Documentation/security/tpm/tpm_ffa_crb.rst new file +16 -0

new file mode 100644
index 000000000000..c70f8904a93d
@@ -0,0 +1,65 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+TPM CRB over FF-A Driver
+========================
+
+The TPM Command Response Buffer (CRB) interface is a standard TPM interface
+defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
+The CRB provides a structured set of control registers a client uses when
+interacting with a TPM as well as a data buffer for storing TPM commands and
+responses. A CRB interface can be implemented in:
+
+- hardware registers in a discrete TPM chip
+
+- in memory for a TPM running in isolated environment where shared memory
+  allows a client to interact with the TPM

Documentation/security/tpm/tpm_ffa_crb.rst line 22

Quoted 6 lines

Documentation/security/tpm/tpm_ffa_crb.rst new file +6 -0

+
+The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
+that defines interfaces and protocols for the following purposes:
+
+- Compartmentalize firmware into software partitions that run in the Arm
+  Secure world environment (also know as TrustZone)

Does that also cover ARM CCA? Just a question (not a review question).

Quoted 32 lines · Jarkko Sakkinen

Quoted 31 lines · Stuart Yoder

Add documentation providing details of how the CRB driver interacts with FF-A.

Signed-off-by Stuart Yoder <[email protected]>

---
  Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
  1 file changed, 65 insertions(+)

create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst

Documentation/security/tpm/tpm_ffa_crb.rst new file +16 -0

new file mode 100644
index 000000000000..c70f8904a93d
@@ -0,0 +1,65 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+TPM CRB over FF-A Driver
+========================
+
+The TPM Command Response Buffer (CRB) interface is a standard TPM interface
+defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
+The CRB provides a structured set of control registers a client uses when
+interacting with a TPM as well as a data buffer for storing TPM commands and
+responses. A CRB interface can be implemented in:
+
+- hardware registers in a discrete TPM chip
+
+- in memory for a TPM running in isolated environment where shared memory
+  allows a client to interact with the TPM

Quoted 8 lines

Documentation/security/tpm/tpm_ffa_crb.rst line 22

Quoted 6 lines

Documentation/security/tpm/tpm_ffa_crb.rst new file +6 -0

+
+The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
+that defines interfaces and protocols for the following purposes:
+
+- Compartmentalize firmware into software partitions that run in the Arm
+  Secure world environment (also know as TrustZone)

Does that also cover ARM CCA? Just a question (not a review question).

No, CCA is for confidential VMs which is a separate trusted execution environment and FF-A is not used there.

Thanks,
Stuart