tpm_crb_ffa.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2024 Arm Ltd.
 *
 * 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) "CRB_FFA: " fmt

#include <linux/arm_ffa.h>
#include <linux/delay.h>
#include <linux/moduleparam.h>
#include "tpm_crb_ffa.h"

static unsigned int busy_timeout_ms = 2000;

module_param(busy_timeout_ms, uint, 0644);
MODULE_PARM_DESC(busy_timeout_ms,
		 "Maximum time in ms to retry before giving up on busy");

/* TPM service function status codes */
#define CRB_FFA_OK			0x05000001
#define CRB_FFA_OK_RESULTS_RETURNED	0x05000002
#define CRB_FFA_NOFUNC			0x8e000001
#define CRB_FFA_NOTSUP			0x8e000002
#define CRB_FFA_INVARG			0x8e000005
#define CRB_FFA_INV_CRB_CTRL_DATA	0x8e000006
#define CRB_FFA_ALREADY			0x8e000009
#define CRB_FFA_DENIED			0x8e00000a
#define CRB_FFA_NOMEM			0x8e00000b

#define CRB_FFA_VERSION_MAJOR	1
#define CRB_FFA_VERSION_MINOR	0

/* version encoding */
#define CRB_FFA_MAJOR_VERSION_MASK  GENMASK(30, 16)
#define CRB_FFA_MINOR_VERSION_MASK  GENMASK(15, 0)
#define CRB_FFA_MAJOR_VERSION(x)    ((u16)(FIELD_GET(CRB_FFA_MAJOR_VERSION_MASK, (x))))
#define CRB_FFA_MINOR_VERSION(x)    ((u16)(FIELD_GET(CRB_FFA_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 or AArch64 SMC calling convention with register usage
 * as defined in FF-A specification:
 * w0:    Function ID
 *          -for 32-bit: 0x8400006F or 0x84000070
 *          -for 64-bit: 0xC400006F or 0xC4000070
 * 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, CRB_FFA_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 CRB_FFA_GET_INTERFACE_VERSION 0x0f000001

/*
 * Notifies the TPM service that a TPM command or TPM locality request is
 * ready to be processed, and allows the TPM service to process it.
 * Call register usage:
 * w3:    Not used (MBZ)
 * w4:    TPM service function ID, CRB_FFA_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:
 *     CRB_FFA_OK: the TPM service has been notified successfully
 *     CRB_FFA_INVARG: one or more arguments are not valid
 *     CRB_FFA_INV_CRB_CTRL_DATA: CRB control data or locality control
 *         data at the given TPM locality is not valid
 *     CRB_FFA_DENIED: the TPM has previously disabled locality requests and
 *         command processing at the given locality
 */
#define CRB_FFA_START 0x0f000201

struct tpm_crb_ffa {
	struct ffa_device *ffa_dev;
	u16 major_version;
	u16 minor_version;
	/* lock to protect sending of FF-A messages: */
	struct mutex msg_data_lock;
	union {
		struct ffa_send_direct_data direct_msg_data;
		struct ffa_send_direct_data2 direct_msg_data2;
	};
};

static struct tpm_crb_ffa *tpm_crb_ffa;
static struct ffa_driver tpm_crb_ffa_driver;

static int tpm_crb_ffa_to_linux_errno(int errno)
{
	int rc;

	switch (errno) {
	case CRB_FFA_OK:
		rc = 0;
		break;
	case CRB_FFA_OK_RESULTS_RETURNED:
		rc = 0;
		break;
	case CRB_FFA_NOFUNC:
		rc = -ENOENT;
		break;
	case CRB_FFA_NOTSUP:
		rc = -EPERM;
		break;
	case CRB_FFA_INVARG:
		rc = -EINVAL;
		break;
	case CRB_FFA_INV_CRB_CTRL_DATA:
		rc = -ENOEXEC;
		break;
	case CRB_FFA_ALREADY:
		rc = -EEXIST;
		break;
	case CRB_FFA_DENIED:
		rc = -EACCES;
		break;
	case CRB_FFA_NOMEM:
		rc = -ENOMEM;
		break;
	default:
		rc = -EINVAL;
	}

	return rc;
}

/**
 * tpm_crb_ffa_init - called by the CRB driver to do any needed initialization
 *
 * This function is called by the tpm_crb driver during the tpm_crb
 * driver's initialization. If the tpm_crb_ffa has not been probed
 * yet, returns -ENOENT in order to force a retry.  If th ffa_crb
 * driver had been probed  but failed with an error, returns -ENODEV
 * in order to prevent further retries.
 *
 * Return: 0 on success, negative error code on failure.
 */
int tpm_crb_ffa_init(void)
{
	int ret = 0;

	if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
		ret = ffa_register(&tpm_crb_ffa_driver);
		if (ret) {
			tpm_crb_ffa = ERR_PTR(-ENODEV);
			return ret;
		}
	}

	if (!tpm_crb_ffa)
		ret = -ENOENT;

	if (IS_ERR_VALUE(tpm_crb_ffa))
		ret = -ENODEV;

	return ret;
}
EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);

static int __tpm_crb_ffa_try_send_receive(unsigned long func_id,
					  unsigned long a0, unsigned long a1,
					  unsigned long a2)
{
	const struct ffa_msg_ops *msg_ops;
	int ret;

	msg_ops = tpm_crb_ffa->ffa_dev->ops->msg_ops;

	if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) {
		tpm_crb_ffa->direct_msg_data2 = (struct ffa_send_direct_data2){
			.data = { func_id, a0, a1, a2 },
		};

		ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev,
				&tpm_crb_ffa->direct_msg_data2);
		if (!ret)
			ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]);
	} else {
		tpm_crb_ffa->direct_msg_data = (struct ffa_send_direct_data){
			.data1 = func_id,
			.data2 = a0,
			.data3 = a1,
			.data4 = a2,
		};

		ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev,
				&tpm_crb_ffa->direct_msg_data);
		if (!ret)
			ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1);
	}

	return ret;
}

static int __tpm_crb_ffa_send_receive(unsigned long func_id, unsigned long a0,
				      unsigned long a1, unsigned long a2)
{
	ktime_t start, stop;
	int ret;

	if (!tpm_crb_ffa)
		return -ENOENT;

	start = ktime_get();
	stop = ktime_add(start, ms_to_ktime(busy_timeout_ms));

	for (;;) {
		ret = __tpm_crb_ffa_try_send_receive(func_id, a0, a1, a2);
		if (ret != -EBUSY)
			break;

		usleep_range(50, 100);
		if (ktime_after(ktime_get(), stop)) {
			dev_warn(&tpm_crb_ffa->ffa_dev->dev,
				 "Busy retry timed out\n");
			break;
		}
	}

	return ret;
}

/**
 * tpm_crb_ffa_get_interface_version() - gets the ABI version of the TPM service
 * @major: Pointer to caller-allocated buffer to hold the major version
 *         number the ABI
 * @minor: Pointer to caller-allocated buffer to hold the minor version
 *         number the ABI
 *
 * Returns the major and minor version of the ABI of the FF-A based TPM.
 * Allows the caller to evaluate its compatibility with the version of
 * the ABI.
 *
 * Return: 0 on success, negative error code on failure.
 */
static int tpm_crb_ffa_get_interface_version(u16 *major, u16 *minor)
{
	int rc;

	if (!tpm_crb_ffa)
		return -ENOENT;

	if (IS_ERR_VALUE(tpm_crb_ffa))
		return -ENODEV;

	if (!major || !minor)
		return -EINVAL;

	guard(mutex)(&tpm_crb_ffa->msg_data_lock);

	rc = __tpm_crb_ffa_send_receive(CRB_FFA_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
	if (!rc) {
		if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) {
			*major = CRB_FFA_MAJOR_VERSION(tpm_crb_ffa->direct_msg_data2.data[1]);
			*minor = CRB_FFA_MINOR_VERSION(tpm_crb_ffa->direct_msg_data2.data[1]);
		} else {
			*major = CRB_FFA_MAJOR_VERSION(tpm_crb_ffa->direct_msg_data.data2);
			*minor = CRB_FFA_MINOR_VERSION(tpm_crb_ffa->direct_msg_data.data2);
		}
	}

	return rc;
}

/**
 * tpm_crb_ffa_start() - signals the TPM that a field has changed in the CRB
 * @request_type: Identifies whether the change to the CRB is in the command
 *                fields or locality fields.
 * @locality: Specifies the locality number.
 *
 * Used by the CRB driver
 * that might be useful to those using or modifying it.  Begins with
 * empty comment line, and may include additional embedded empty
 * comment lines.
 *
 * Return: 0 on success, negative error code on failure.
 */
int tpm_crb_ffa_start(int request_type, int locality)
{
	if (!tpm_crb_ffa)
		return -ENOENT;

	if (IS_ERR_VALUE(tpm_crb_ffa))
		return -ENODEV;

	guard(mutex)(&tpm_crb_ffa->msg_data_lock);

	return __tpm_crb_ffa_send_receive(CRB_FFA_START, request_type, locality, 0x00);
}
EXPORT_SYMBOL_GPL(tpm_crb_ffa_start);

static int tpm_crb_ffa_probe(struct ffa_device *ffa_dev)
{
	struct tpm_crb_ffa *p;
	int rc;

	/* only one instance of a TPM partition is supported */
	if (tpm_crb_ffa && !IS_ERR_VALUE(tpm_crb_ffa))
		return -EEXIST;

	tpm_crb_ffa = ERR_PTR(-ENODEV); // set tpm_crb_ffa so we can detect probe failure

	if (!ffa_partition_supports_direct_recv(ffa_dev) &&
	    !ffa_partition_supports_direct_req2_recv(ffa_dev)) {
		dev_warn(&ffa_dev->dev, "partition doesn't support direct message receive.\n");
		return -EINVAL;
	}

	p = kzalloc(sizeof(*tpm_crb_ffa), GFP_KERNEL);
	if (!p)
		return -ENOMEM;
	tpm_crb_ffa = p;

	mutex_init(&tpm_crb_ffa->msg_data_lock);
	tpm_crb_ffa->ffa_dev = ffa_dev;
	ffa_dev_set_drvdata(ffa_dev, tpm_crb_ffa);

	/* 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 = tpm_crb_ffa_get_interface_version(&tpm_crb_ffa->major_version,
					       &tpm_crb_ffa->minor_version);
	if (rc) {
		dev_err(&ffa_dev->dev, "failed to get crb interface version. rc:%d\n", rc);
		goto out;
	}

	dev_info(&ffa_dev->dev, "ABI version %u.%u\n", tpm_crb_ffa->major_version,
		tpm_crb_ffa->minor_version);

	if (tpm_crb_ffa->major_version != CRB_FFA_VERSION_MAJOR ||
	    (tpm_crb_ffa->minor_version > 0 &&
	    tpm_crb_ffa->minor_version < CRB_FFA_VERSION_MINOR)) {
		dev_warn(&ffa_dev->dev, "Incompatible ABI version\n");
		goto out;
	}

	return 0;

out:
	kfree(tpm_crb_ffa);
	tpm_crb_ffa = ERR_PTR(-ENODEV);
	return -EINVAL;
}

static void tpm_crb_ffa_remove(struct ffa_device *ffa_dev)
{
	kfree(tpm_crb_ffa);
	tpm_crb_ffa = NULL;
}

static const struct ffa_device_id tpm_crb_ffa_device_id[] = {
	/* 17b862a4-1806-4faf-86b3-089a58353861 */
	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
	{}
};

static struct ffa_driver tpm_crb_ffa_driver = {
	.name = "ffa-crb",
	.probe = tpm_crb_ffa_probe,
	.remove = tpm_crb_ffa_remove,
	.id_table = tpm_crb_ffa_device_id,
};

#ifdef MODULE
module_ffa_driver(tpm_crb_ffa_driver);
#endif

MODULE_AUTHOR("Arm");
MODULE_DESCRIPTION("TPM CRB FFA driver");
MODULE_LICENSE("GPL");