firmware: Add Turris Mox rWTM firmware driver

This adds a driver to communicate with the firmware running on the
secure processor of the Turris Mox router, enabling the kernel to
retrieve true random numbers from the Entropy Bit Generator and to read
some information burned into eFuses when device was manufactured:

and to
sign messages with the ECDSA private key burned into each Turris Mox
device when manufacturing.

This also adds support to read other information burned into eFuses:
 - serial number
 - board version
 - MAC addresses
 - RAM size
 - ECDSA public key (this is not read directly from eFuses, rather it
   is computed by the firmware as pair to the burned private key)

The source code of the firmware is open source and can be found at
https://gitlab.labs.nic.cz/turris/mox-boot-builder/tree/master/wtmi

The firmware is also able to, on demand, sign messages with the burned
ECDSA private key, but since Linux's akcipher API is not yet stable
(and therefore not exposed to userspace via netlink), this functionality
is not supported yet.

Link: https://lore.kernel.org/r/20190822014318.19478-3-marek.behun@nic.cz
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -1637,6 +1637,7 @@ F:	Documentation/devicetree/bindings/firmware/cznic,turris-mox-rwtm.txt
 F:	Documentation/devicetree/bindings/gpio/gpio-moxtet.txt
 F:	include/linux/moxtet.h
 F:	drivers/bus/moxtet.c
+F:	drivers/firmware/turris-mox-rwtm.c
 F:	drivers/gpio/gpio-moxtet.c
 
 ARM/EBSA110 MACHINE SUPPORT

drivers/firmware/Kconfig

@@ -270,6 +270,20 @@ config TRUSTED_FOUNDATIONS
 
 	  Choose N if you don't know what this is about.
 
+config TURRIS_MOX_RWTM
+	tristate "Turris Mox rWTM secure firmware driver"
+	depends on ARCH_MVEBU || COMPILE_TEST
+	depends on HAS_DMA && OF
+	depends on MAILBOX
+	select HW_RANDOM
+	select ARMADA_37XX_RWTM_MBOX
+	help
+	  This driver communicates with the firmware on the Cortex-M3 secure
+	  processor of the Turris Mox router. Enable if you are building for
+	  Turris Mox, and you will be able to read the device serial number and
+	  other manufacturing data and also utilize the Entropy Bit Generator
+	  for hardware random number generation.
+
 config HAVE_ARM_SMCCC
 	bool
 

drivers/firmware/Makefile

@@ -22,6 +22,7 @@ obj-$(CONFIG_QCOM_SCM_32)	+= qcom_scm-32.o
 CFLAGS_qcom_scm-32.o :=$(call as-instr,.arch armv7-a\n.arch_extension sec,-DREQUIRES_SEC=1) -march=armv7-a
 obj-$(CONFIG_TI_SCI_PROTOCOL)	+= ti_sci.o
 obj-$(CONFIG_TRUSTED_FOUNDATIONS) += trusted_foundations.o
+obj-$(CONFIG_TURRIS_MOX_RWTM)	+= turris-mox-rwtm.o
 
 obj-$(CONFIG_ARM_SCMI_PROTOCOL)	+= arm_scmi/
 obj-y				+= psci/

drivers/firmware/turris-mox-rwtm.c

@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Turris Mox rWTM firmware driver
+ *
+ * Copyright (C) 2019 Marek Behun <marek.behun@nic.cz>
+ */
+
+#include <linux/armada-37xx-rwtm-mailbox.h>
+#include <linux/completion.h>
+#include <linux/dma-mapping.h>
+#include <linux/hw_random.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define DRIVER_NAME		"turris-mox-rwtm"
+
+/*
+ * The macros and constants below come from Turris Mox's rWTM firmware code.
+ * This firmware is open source and it's sources can be found at
+ * https://gitlab.labs.nic.cz/turris/mox-boot-builder/tree/master/wtmi.
+ */
+
+#define MBOX_STS_SUCCESS	(0 << 30)
+#define MBOX_STS_FAIL		(1 << 30)
+#define MBOX_STS_BADCMD		(2 << 30)
+#define MBOX_STS_ERROR(s)	((s) & (3 << 30))
+#define MBOX_STS_VALUE(s)	(((s) >> 10) & 0xfffff)
+#define MBOX_STS_CMD(s)		((s) & 0x3ff)
+
+enum mbox_cmd {
+	MBOX_CMD_GET_RANDOM	= 1,
+	MBOX_CMD_BOARD_INFO	= 2,
+	MBOX_CMD_ECDSA_PUB_KEY	= 3,
+	MBOX_CMD_HASH		= 4,
+	MBOX_CMD_SIGN		= 5,
+	MBOX_CMD_VERIFY		= 6,
+
+	MBOX_CMD_OTP_READ	= 7,
+	MBOX_CMD_OTP_WRITE	= 8,
+};
+
+struct mox_kobject;
+
+struct mox_rwtm {
+	struct device *dev;
+	struct mbox_client mbox_client;
+	struct mbox_chan *mbox;
+	struct mox_kobject *kobj;
+	struct hwrng hwrng;
+
+	struct armada_37xx_rwtm_rx_msg reply;
+
+	void *buf;
+	dma_addr_t buf_phys;
+
+	struct mutex busy;
+	struct completion cmd_done;
+
+	/* board information */
+	int has_board_info;
+	u64 serial_number;
+	int board_version, ram_size;
+	u8 mac_address1[6], mac_address2[6];
+
+	/* public key burned in eFuse */
+	int has_pubkey;
+	u8 pubkey[135];
+};
+
+struct mox_kobject {
+	struct kobject kobj;
+	struct mox_rwtm *rwtm;
+};
+
+static inline struct kobject *rwtm_to_kobj(struct mox_rwtm *rwtm)
+{
+	return &rwtm->kobj->kobj;
+}
+
+static inline struct mox_rwtm *to_rwtm(struct kobject *kobj)
+{
+	return container_of(kobj, struct mox_kobject, kobj)->rwtm;
+}
+
+static void mox_kobj_release(struct kobject *kobj)
+{
+	kfree(to_rwtm(kobj)->kobj);
+}
+
+static struct kobj_type mox_kobj_ktype = {
+	.release	= mox_kobj_release,
+	.sysfs_ops	= &kobj_sysfs_ops,
+};
+
+static int mox_kobj_create(struct mox_rwtm *rwtm)
+{
+	rwtm->kobj = kzalloc(sizeof(*rwtm->kobj), GFP_KERNEL);
+	if (!rwtm->kobj)
+		return -ENOMEM;
+
+	kobject_init(rwtm_to_kobj(rwtm), &mox_kobj_ktype);
+	if (kobject_add(rwtm_to_kobj(rwtm), firmware_kobj, "turris-mox-rwtm")) {
+		kobject_put(rwtm_to_kobj(rwtm));
+		return -ENXIO;
+	}
+
+	rwtm->kobj->rwtm = rwtm;
+
+	return 0;
+}
+
+#define MOX_ATTR_RO(name, format, cat)				\
+static ssize_t							\
+name##_show(struct kobject *kobj, struct kobj_attribute *a,	\
+	    char *buf)						\
+{								\
+	struct mox_rwtm *rwtm = to_rwtm(kobj);	\
+	if (!rwtm->has_##cat)					\
+		return -ENODATA;				\
+	return sprintf(buf, format, rwtm->name);		\
+}								\
+static struct kobj_attribute mox_attr_##name = __ATTR_RO(name)
+
+MOX_ATTR_RO(serial_number, "%016llX\n", board_info);
+MOX_ATTR_RO(board_version, "%i\n", board_info);
+MOX_ATTR_RO(ram_size, "%i\n", board_info);
+MOX_ATTR_RO(mac_address1, "%pM\n", board_info);
+MOX_ATTR_RO(mac_address2, "%pM\n", board_info);
+MOX_ATTR_RO(pubkey, "%s\n", pubkey);
+
+static int mox_get_status(enum mbox_cmd cmd, u32 retval)
+{
+	if (MBOX_STS_CMD(retval) != cmd ||
+	    MBOX_STS_ERROR(retval) != MBOX_STS_SUCCESS)
+		return -EIO;
+	else if (MBOX_STS_ERROR(retval) == MBOX_STS_FAIL)
+		return -(int)MBOX_STS_VALUE(retval);
+	else
+		return MBOX_STS_VALUE(retval);
+}
+
+static const struct attribute *mox_rwtm_attrs[] = {
+	&mox_attr_serial_number.attr,
+	&mox_attr_board_version.attr,
+	&mox_attr_ram_size.attr,
+	&mox_attr_mac_address1.attr,
+	&mox_attr_mac_address2.attr,
+	&mox_attr_pubkey.attr,
+	NULL
+};
+
+static void mox_rwtm_rx_callback(struct mbox_client *cl, void *data)
+{
+	struct mox_rwtm *rwtm = dev_get_drvdata(cl->dev);
+	struct armada_37xx_rwtm_rx_msg *msg = data;
+
+	rwtm->reply = *msg;
+	complete(&rwtm->cmd_done);
+}
+
+static void reply_to_mac_addr(u8 *mac, u32 t1, u32 t2)
+{
+	mac[0] = t1 >> 8;
+	mac[1] = t1;
+	mac[2] = t2 >> 24;
+	mac[3] = t2 >> 16;
+	mac[4] = t2 >> 8;
+	mac[5] = t2;
+}
+
+static int mox_get_board_info(struct mox_rwtm *rwtm)
+{
+	struct armada_37xx_rwtm_tx_msg msg;
+	struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
+	int ret;
+
+	msg.command = MBOX_CMD_BOARD_INFO;
+	ret = mbox_send_message(rwtm->mbox, &msg);
+	if (ret < 0)
+		return ret;
+
+	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
+	if (ret < 0)
+		return ret;
+
+	ret = mox_get_status(MBOX_CMD_BOARD_INFO, reply->retval);
+	if (ret < 0 && ret != -ENODATA) {
+		return ret;
+	} else if (ret == -ENODATA) {
+		dev_warn(rwtm->dev,
+			 "Board does not have manufacturing information burned!\n");
+	} else {
+		rwtm->serial_number = reply->status[1];
+		rwtm->serial_number <<= 32;
+		rwtm->serial_number |= reply->status[0];
+			rwtm->board_version = reply->status[2];
+		rwtm->ram_size = reply->status[3];
+		reply_to_mac_addr(rwtm->mac_address1, reply->status[4],
+				  reply->status[5]);
+		reply_to_mac_addr(rwtm->mac_address2, reply->status[6],
+				  reply->status[7]);
+		rwtm->has_board_info = 1;
+
+		pr_info("Turris Mox serial number %016llX\n",
+			rwtm->serial_number);
+		pr_info("           board version %i\n", rwtm->board_version);
+		pr_info("           burned RAM size %i MiB\n", rwtm->ram_size);
+	}
+
+	msg.command = MBOX_CMD_ECDSA_PUB_KEY;
+	ret = mbox_send_message(rwtm->mbox, &msg);
+	if (ret < 0)
+		return ret;
+
+	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
+	if (ret < 0)
+		return ret;
+
+	ret = mox_get_status(MBOX_CMD_ECDSA_PUB_KEY, reply->retval);
+	if (ret < 0 && ret != -ENODATA) {
+		return ret;
+	} else if (ret == -ENODATA) {
+		dev_warn(rwtm->dev, "Board has no public key burned!\n");
+	} else {
+		u32 *s = reply->status;
+
+		rwtm->has_pubkey = 1;
+		sprintf(rwtm->pubkey,
+			"%06x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x",
+			ret, s[0], s[1], s[2], s[3], s[4], s[5], s[6], s[7],
+			s[8], s[9], s[10], s[11], s[12], s[13], s[14], s[15]);
+	}
+
+	return 0;
+}
+
+static int mox_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct mox_rwtm *rwtm = (struct mox_rwtm *) rng->priv;
+	struct armada_37xx_rwtm_tx_msg msg;
+	int ret;
+
+	if (max > 4096)
+		max = 4096;
+
+	msg.command = MBOX_CMD_GET_RANDOM;
+	msg.args[0] = 1;
+	msg.args[1] = rwtm->buf_phys;
+	msg.args[2] = (max + 3) & ~3;
+
+	if (!wait) {
+		if (!mutex_trylock(&rwtm->busy))
+			return -EBUSY;
+	} else {
+		mutex_lock(&rwtm->busy);
+	}
+
+	ret = mbox_send_message(rwtm->mbox, &msg);
+	if (ret < 0)
+		goto unlock_mutex;
+
+	ret = wait_for_completion_interruptible(&rwtm->cmd_done);
+	if (ret < 0)
+		goto unlock_mutex;
+
+	ret = mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
+	if (ret < 0)
+		goto unlock_mutex;
+
+	memcpy(data, rwtm->buf, max);
+	ret = max;
+
+unlock_mutex:
+	mutex_unlock(&rwtm->busy);
+	return ret;
+}
+
+static int turris_mox_rwtm_probe(struct platform_device *pdev)
+{
+	struct mox_rwtm *rwtm;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	rwtm = devm_kzalloc(dev, sizeof(*rwtm), GFP_KERNEL);
+	if (!rwtm)
+		return -ENOMEM;
+
+	rwtm->dev = dev;
+	rwtm->buf = dmam_alloc_coherent(dev, PAGE_SIZE, &rwtm->buf_phys,
+					GFP_KERNEL);
+	if (!rwtm->buf)
+		return -ENOMEM;
+
+	ret = mox_kobj_create(rwtm);
+	if (ret < 0) {
+		dev_err(dev, "Cannot create turris-mox-rwtm kobject!\n");
+		return ret;
+	}
+
+	ret = sysfs_create_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
+	if (ret < 0) {
+		dev_err(dev, "Cannot create sysfs files!\n");
+		goto put_kobj;
+	}
+
+	platform_set_drvdata(pdev, rwtm);
+
+	mutex_init(&rwtm->busy);
+
+	rwtm->mbox_client.dev = dev;
+	rwtm->mbox_client.rx_callback = mox_rwtm_rx_callback;
+
+	rwtm->mbox = mbox_request_channel(&rwtm->mbox_client, 0);
+	if (IS_ERR(rwtm->mbox)) {
+		ret = PTR_ERR(rwtm->mbox);
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "Cannot request mailbox channel: %i\n",
+				ret);
+		goto remove_files;
+	}
+
+	init_completion(&rwtm->cmd_done);
+
+	ret = mox_get_board_info(rwtm);
+	if (ret < 0)
+		dev_warn(dev, "Cannot read board information: %i\n", ret);
+
+	rwtm->hwrng.name = DRIVER_NAME "_hwrng";
+	rwtm->hwrng.read = mox_hwrng_read;
+	rwtm->hwrng.priv = (unsigned long) rwtm;
+	rwtm->hwrng.quality = 1024;
+
+	ret = devm_hwrng_register(dev, &rwtm->hwrng);
+	if (ret < 0) {
+		dev_err(dev, "Cannot register HWRNG: %i\n", ret);
+		goto free_channel;
+	}
+
+	return 0;
+
+free_channel:
+	mbox_free_channel(rwtm->mbox);
+remove_files:
+	sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
+put_kobj:
+	kobject_put(rwtm_to_kobj(rwtm));
+	return ret;
+}
+
+static int turris_mox_rwtm_remove(struct platform_device *pdev)
+{
+	struct mox_rwtm *rwtm = platform_get_drvdata(pdev);
+
+	sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
+	kobject_put(rwtm_to_kobj(rwtm));
+	mbox_free_channel(rwtm->mbox);
+
+	return 0;
+}
+
+static const struct of_device_id turris_mox_rwtm_match[] = {
+	{ .compatible = "cznic,turris-mox-rwtm", },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, turris_mox_rwtm_match);
+
+static struct platform_driver turris_mox_rwtm_driver = {
+	.probe	= turris_mox_rwtm_probe,
+	.remove	= turris_mox_rwtm_remove,
+	.driver	= {
+		.name		= DRIVER_NAME,
+		.of_match_table	= turris_mox_rwtm_match,
+	},
+};
+module_platform_driver(turris_mox_rwtm_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Turris Mox rWTM firmware driver");
+MODULE_AUTHOR("Marek Behun <marek.behun@nic.cz>");