tpm_ftpm_tee.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) Microsoft Corporation
  4 *
  5 * Implements a firmware TPM as described here:
  6 * https://www.microsoft.com/en-us/research/publication/ftpm-software-implementation-tpm-chip/
  7 *
  8 * A reference implementation is available here:
  9 * https://github.com/microsoft/ms-tpm-20-ref/tree/master/Samples/ARM32-FirmwareTPM/optee_ta/fTPM
 10 */
 11
 12#include <linux/acpi.h>
 13#include <linux/of.h>
 14#include <linux/platform_device.h>
 15#include <linux/tee_drv.h>
 16#include <linux/tpm.h>
 17#include <linux/uuid.h>
 18
 19#include "tpm.h"
 20#include "tpm_ftpm_tee.h"
 21
 22/*
 23 * TA_FTPM_UUID: BC50D971-D4C9-42C4-82CB-343FB7F37896
 24 *
 25 * Randomly generated, and must correspond to the GUID on the TA side.
 26 * Defined here in the reference implementation:
 27 * https://github.com/microsoft/ms-tpm-20-ref/blob/master/Samples/ARM32-FirmwareTPM/optee_ta/fTPM/include/fTPM.h#L42
 28 */
 29static const uuid_t ftpm_ta_uuid =
 30	UUID_INIT(0xBC50D971, 0xD4C9, 0x42C4,
 31		  0x82, 0xCB, 0x34, 0x3F, 0xB7, 0xF3, 0x78, 0x96);
 32
 33/**
 34 * ftpm_tee_tpm_op_send() - send TPM commands through the TEE shared memory
 35 * and retrieve the response.
 36 * @chip:	the tpm_chip description as specified in driver/char/tpm/tpm.h
 37 * @buf:	the buffer to send and to store the response.
 38 * @bufsiz:	the size of the buffer.
 39 * @cmd_len:	the number of bytes to send.
 40 *
 41 * Return:
 42 *	In case of success, returns the number of bytes received.
 43 *	On failure, -errno
 44 */
 45static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz,
 46				size_t cmd_len)
 47{
 48	struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
 49	size_t resp_len;
 50	int rc;
 51	u8 *temp_buf;
 52	struct tpm_header *resp_header;
 53	struct tee_ioctl_invoke_arg transceive_args;
 54	struct tee_param command_params[4];
 55	struct tee_shm *shm = pvt_data->shm;
 56
 57	if (cmd_len > MAX_COMMAND_SIZE) {
 58		dev_err(&chip->dev,
 59			"%s: len=%zd exceeds MAX_COMMAND_SIZE supported by fTPM TA\n",
 60			__func__, cmd_len);
 61		return -EIO;
 62	}
 63
 64	memset(&transceive_args, 0, sizeof(transceive_args));
 65	memset(command_params, 0, sizeof(command_params));
 66
 67	/* Invoke FTPM_OPTEE_TA_SUBMIT_COMMAND function of fTPM TA */
 68	transceive_args = (struct tee_ioctl_invoke_arg) {
 69		.func = FTPM_OPTEE_TA_SUBMIT_COMMAND,
 70		.session = pvt_data->session,
 71		.num_params = 4,
 72	};
 73
 74	/* Fill FTPM_OPTEE_TA_SUBMIT_COMMAND parameters */
 75	command_params[0] = (struct tee_param) {
 76		.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT,
 77		.u.memref = {
 78			.shm = shm,
 79			.size = cmd_len,
 80			.shm_offs = 0,
 81		},
 82	};
 83
 84	temp_buf = tee_shm_get_va(shm, 0);
 85	if (IS_ERR(temp_buf)) {
 86		dev_err(&chip->dev, "%s: tee_shm_get_va failed for transmit\n",
 87			__func__);
 88		return PTR_ERR(temp_buf);
 89	}
 90	memset(temp_buf, 0, (MAX_COMMAND_SIZE + MAX_RESPONSE_SIZE));
 91	memcpy(temp_buf, buf, cmd_len);
 92
 93	command_params[1] = (struct tee_param) {
 94		.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT,
 95		.u.memref = {
 96			.shm = shm,
 97			.size = MAX_RESPONSE_SIZE,
 98			.shm_offs = MAX_COMMAND_SIZE,
 99		},
100	};
101
102	rc = tee_client_invoke_func(pvt_data->ctx, &transceive_args,
103				    command_params);
104	if ((rc < 0) || (transceive_args.ret != 0)) {
105		dev_err(&chip->dev, "%s: SUBMIT_COMMAND invoke error: 0x%x\n",
106			__func__, transceive_args.ret);
107		return (rc < 0) ? rc : transceive_args.ret;
108	}
109
110	temp_buf = tee_shm_get_va(shm, command_params[1].u.memref.shm_offs);
111	if (IS_ERR(temp_buf)) {
112		dev_err(&chip->dev, "%s: tee_shm_get_va failed for receive\n",
113			__func__);
114		return PTR_ERR(temp_buf);
115	}
116
117	resp_header = (struct tpm_header *)temp_buf;
118	resp_len = be32_to_cpu(resp_header->length);
119
120	/* sanity check resp_len */
121	if (resp_len < TPM_HEADER_SIZE) {
122		dev_err(&chip->dev, "%s: tpm response header too small\n",
123			__func__);
124		return -EIO;
125	}
126	if (resp_len > MAX_RESPONSE_SIZE) {
127		dev_err(&chip->dev,
128			"%s: resp_len=%zd exceeds MAX_RESPONSE_SIZE\n",
129			__func__, resp_len);
130		return -EIO;
131	}
132	if (resp_len > bufsiz) {
133		dev_err(&chip->dev,
134			"%s: resp_len=%zd exceeds bufsiz=%zd\n",
135			__func__, resp_len, bufsiz);
136		return -EIO;
137	}
138
139	memcpy(buf, temp_buf, resp_len);
140
141	return resp_len;
142}
143
144static const struct tpm_class_ops ftpm_tee_tpm_ops = {
145	.flags = TPM_OPS_AUTO_STARTUP,
146	.send = ftpm_tee_tpm_op_send,
147};
148
149/*
150 * Check whether this driver supports the fTPM TA in the TEE instance
151 * represented by the params (ver/data) to this function.
152 */
153static int ftpm_tee_match(struct tee_ioctl_version_data *ver, const void *data)
154{
155	/*
156	 * Currently this driver only support GP Complaint OPTEE based fTPM TA
157	 */
158	if ((ver->impl_id == TEE_IMPL_ID_OPTEE) &&
159		(ver->gen_caps & TEE_GEN_CAP_GP))
160		return 1;
161	else
162		return 0;
163}
164
165/**
166 * ftpm_tee_probe() - initialize the fTPM
167 * @dev: the device description.
168 *
169 * Return:
170 *	On success, 0. On failure, -errno.
171 */
172static int ftpm_tee_probe(struct device *dev)
173{
174	int rc;
175	struct tpm_chip *chip;
176	struct ftpm_tee_private *pvt_data = NULL;
177	struct tee_ioctl_open_session_arg sess_arg;
178
179	pvt_data = devm_kzalloc(dev, sizeof(struct ftpm_tee_private),
180				GFP_KERNEL);
181	if (!pvt_data)
182		return -ENOMEM;
183
184	dev_set_drvdata(dev, pvt_data);
185
186	/* Open context with TEE driver */
187	pvt_data->ctx = tee_client_open_context(NULL, ftpm_tee_match, NULL,
188						NULL);
189	if (IS_ERR(pvt_data->ctx)) {
190		if (PTR_ERR(pvt_data->ctx) == -ENOENT)
191			return -EPROBE_DEFER;
192		dev_err(dev, "%s: tee_client_open_context failed\n", __func__);
193		return PTR_ERR(pvt_data->ctx);
194	}
195
196	/* Open a session with fTPM TA */
197	memset(&sess_arg, 0, sizeof(sess_arg));
198	export_uuid(sess_arg.uuid, &ftpm_ta_uuid);
199	sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
200	sess_arg.num_params = 0;
201
202	rc = tee_client_open_session(pvt_data->ctx, &sess_arg, NULL);
203	if ((rc < 0) || (sess_arg.ret != 0)) {
204		dev_err(dev, "%s: tee_client_open_session failed, err=%x\n",
205			__func__, sess_arg.ret);
206		rc = -EINVAL;
207		goto out_tee_session;
208	}
209	pvt_data->session = sess_arg.session;
210
211	/* Allocate dynamic shared memory with fTPM TA */
212	pvt_data->shm = tee_shm_alloc_kernel_buf(pvt_data->ctx,
213						 MAX_COMMAND_SIZE +
214						 MAX_RESPONSE_SIZE);
215	if (IS_ERR(pvt_data->shm)) {
216		dev_err(dev, "%s: tee_shm_alloc_kernel_buf failed\n", __func__);
217		rc = -ENOMEM;
218		goto out_shm_alloc;
219	}
220
221	/* Allocate new struct tpm_chip instance */
222	chip = tpm_chip_alloc(dev, &ftpm_tee_tpm_ops);
223	if (IS_ERR(chip)) {
224		dev_err(dev, "%s: tpm_chip_alloc failed\n", __func__);
225		rc = PTR_ERR(chip);
226		goto out_chip_alloc;
227	}
228
229	pvt_data->chip = chip;
230	pvt_data->chip->flags |= TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_SYNC;
231
232	/* Create a character device for the fTPM */
233	rc = tpm_chip_register(pvt_data->chip);
234	if (rc) {
235		dev_err(dev, "%s: tpm_chip_register failed with rc=%d\n",
236			__func__, rc);
237		goto out_chip;
238	}
239
240	return 0;
241
242out_chip:
243	put_device(&pvt_data->chip->dev);
244out_chip_alloc:
245	tee_shm_free(pvt_data->shm);
246out_shm_alloc:
247	tee_client_close_session(pvt_data->ctx, pvt_data->session);
248out_tee_session:
249	tee_client_close_context(pvt_data->ctx);
250
251	return rc;
252}
253
254static int ftpm_plat_tee_probe(struct platform_device *pdev)
255{
256	struct device *dev = &pdev->dev;
257
258	return ftpm_tee_probe(dev);
259}
260
261/**
262 * ftpm_tee_remove() - remove the TPM device
263 * @dev: the device description.
264 *
265 * Return:
266 *	0 always.
267 */
268static int ftpm_tee_remove(struct device *dev)
269{
270	struct ftpm_tee_private *pvt_data = dev_get_drvdata(dev);
271
272	/* Release the chip */
273	tpm_chip_unregister(pvt_data->chip);
274
275	/* frees chip */
276	put_device(&pvt_data->chip->dev);
277
278	/* Free the shared memory pool */
279	tee_shm_free(pvt_data->shm);
280
281	/* close the existing session with fTPM TA*/
282	tee_client_close_session(pvt_data->ctx, pvt_data->session);
283
284	/* close the context with TEE driver */
285	tee_client_close_context(pvt_data->ctx);
286
287	/* memory allocated with devm_kzalloc() is freed automatically */
288
289	return 0;
290}
291
292static void ftpm_plat_tee_remove(struct platform_device *pdev)
293{
294	struct device *dev = &pdev->dev;
295
296	ftpm_tee_remove(dev);
297}
298
299/**
300 * ftpm_plat_tee_shutdown() - shutdown the TPM device
301 * @pdev: the platform_device description.
302 */
303static void ftpm_plat_tee_shutdown(struct platform_device *pdev)
304{
305	struct ftpm_tee_private *pvt_data = dev_get_drvdata(&pdev->dev);
306
307	tee_shm_free(pvt_data->shm);
308	tee_client_close_session(pvt_data->ctx, pvt_data->session);
309	tee_client_close_context(pvt_data->ctx);
310}
311
312static const struct of_device_id of_ftpm_tee_ids[] = {
313	{ .compatible = "microsoft,ftpm" },
314	{ }
315};
316MODULE_DEVICE_TABLE(of, of_ftpm_tee_ids);
317
318static struct platform_driver ftpm_tee_plat_driver = {
319	.driver = {
320		.name = "ftpm-tee",
321		.of_match_table = of_ftpm_tee_ids,
322	},
323	.shutdown = ftpm_plat_tee_shutdown,
324	.probe = ftpm_plat_tee_probe,
325	.remove = ftpm_plat_tee_remove,
326};
327
328/* UUID of the fTPM TA */
329static const struct tee_client_device_id optee_ftpm_id_table[] = {
330	{UUID_INIT(0xbc50d971, 0xd4c9, 0x42c4,
331		   0x82, 0xcb, 0x34, 0x3f, 0xb7, 0xf3, 0x78, 0x96)},
332	{}
333};
334
335MODULE_DEVICE_TABLE(tee, optee_ftpm_id_table);
336
337static struct tee_client_driver ftpm_tee_driver = {
338	.id_table	= optee_ftpm_id_table,
339	.driver		= {
340		.name		= "optee-ftpm",
341		.bus		= &tee_bus_type,
342		.probe		= ftpm_tee_probe,
343		.remove		= ftpm_tee_remove,
344	},
345};
346
347static int __init ftpm_mod_init(void)
348{
349	int rc;
350
351	rc = platform_driver_register(&ftpm_tee_plat_driver);
352	if (rc)
353		return rc;
354
355	rc = driver_register(&ftpm_tee_driver.driver);
356	if (rc) {
357		platform_driver_unregister(&ftpm_tee_plat_driver);
358		return rc;
359	}
360
361	return 0;
362}
363
364static void __exit ftpm_mod_exit(void)
365{
366	platform_driver_unregister(&ftpm_tee_plat_driver);
367	driver_unregister(&ftpm_tee_driver.driver);
368}
369
370module_init(ftpm_mod_init);
371module_exit(ftpm_mod_exit);
372
373MODULE_AUTHOR("Thirupathaiah Annapureddy <thiruan@microsoft.com>");
374MODULE_DESCRIPTION("TPM Driver for fTPM TA in TEE");
375MODULE_LICENSE("GPL v2");