Commit f6953f1f authored by Cedric Xing's avatar Cedric Xing Committed by Dan Williams
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tsm-mr: Add tsm-mr sample code 



This sample kernel module demonstrates how to make MRs accessible to user
mode through the tsm-mr library.

Once loaded, this module registers a `miscdevice` that host a set of
emulated measurement registers as shown in the directory tree below.

/sys/class/misc/tsm_mr_sample
└── measurements
    ├── config_mr
    ├── report_digest:sha512
    ├── rtmr0:sha256
    ├── rtmr1:sha384
    ├── rtmr_crypto_agile:sha256
    ├── rtmr_crypto_agile:sha384
    └── static_mr:sha384

Among the MRs in this example:

- `config_mr` demonstrates a hashless MR, like MRCONFIGID in Intel TDX or
  HOSTDATA in AMD SEV.
- `static_mr` demonstrates a static MR. The suffix `:sha384` indicates its
  value is a sha384 digest.
- `rtmr0` is an RTMR with `TSM_MR_F_WRITABLE` **cleared**, preventing
  direct extensions; as a result, the attribute `rtmr0:sha256` is
  read-only.
- `rtmr1` is an RTMR with `TSM_MR_F_WRITABLE` **set**, permitting direct
  extensions; thus, the attribute `rtmr1:sha384` is writable.
- `rtmr_crypto_agile` demonstrates a "single" MR that supports multiple
  hash algorithms. Each supported algorithm has a corresponding digest,
  usually referred to as a "bank" in TCG terminology. In this specific
  sample, the 2 banks are aliased to `rtmr0` and `rtmr1`, respectively.
- `report_digest` contains the digest of the internal report structure
  living in this sample module's memory. It is to demonstrate the use of
  the `TSM_MR_F_LIVE` flag. Its value changes each time an RTMR is
  extended.

Signed-off-by: default avatarCedric Xing <cedric.xing@intel.com>
Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Acked-by: default avatarDionna Amalie Glaze <dionnaglaze@google.com>
Link: https://patch.msgid.link/20250506-tdx-rtmr-v6-2-ac6ff5e9d58a@intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent b9e22b35

MAINTAINERS

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@@ -24651,6 +24651,7 @@ F: Documentation/ABI/testing/configfs-tsm 
F:	Documentation/driver-api/coco/

F:	drivers/virt/coco/tsm*.c

F:	include/linux/tsm*.h

F:	samples/tsm/









TRUSTED SERVICES TEE DRIVER









M:	Balint Dobszay <balint.dobszay@arm.com>

























samples/Kconfig



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@@ -184,6 +184,17 @@ config SAMPLE_TIMER







	bool "Timer sample"









	depends on CC_CAN_LINK && HEADERS_INSTALL



















config SAMPLE_TSM_MR









	tristate "TSM measurement sample"









	select TSM_MEASUREMENTS









	select VIRT_DRIVERS









	help









	  Build a sample module that emulates MRs (Measurement Registers) and









	  exposes them to user mode applications through the TSM sysfs









	  interface (/sys/class/misc/tsm_mr_sample/emulated_mr/).



















	  The module name will be tsm-mr-sample when built as a module.



















config SAMPLE_UHID









	bool "UHID sample"









	depends on CC_CAN_LINK && HEADERS_INSTALL
































samples/Makefile



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@@ -43,3 +43,4 @@ obj-$(CONFIG_SAMPLES_RUST)		+= rust/







obj-$(CONFIG_SAMPLE_DAMON_WSSE)		+= damon/









obj-$(CONFIG_SAMPLE_DAMON_PRCL)		+= damon/









obj-$(CONFIG_SAMPLE_HUNG_TASK)		+= hung_task/









obj-$(CONFIG_SAMPLE_TSM_MR)		+= tsm-mr/
























samples/tsm-mr/Makefile
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# SPDX-License-Identifier: GPL-2.0-only









obj-$(CONFIG_SAMPLE_TSM_MR) += tsm_mr_sample.o
























samples/tsm-mr/tsm_mr_sample.c
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// SPDX-License-Identifier: GPL-2.0-only









/* Copyright(c) 2024-2005 Intel Corporation. All rights reserved. */



















#define pr_fmt(x) KBUILD_MODNAME ": " x



















#include <linux/module.h>









#include <linux/tsm-mr.h>









#include <linux/miscdevice.h>









#include <crypto/hash.h>



















struct {









	u8 static_mr[SHA384_DIGEST_SIZE];









	u8 config_mr[SHA512_DIGEST_SIZE];









	u8 rtmr0[SHA256_DIGEST_SIZE];









	u8 rtmr1[SHA384_DIGEST_SIZE];









	u8 report_digest[SHA512_DIGEST_SIZE];









} sample_report = {









	.static_mr = "static_mr",









	.config_mr = "config_mr",









	.rtmr0 = "rtmr0",









	.rtmr1 = "rtmr1",









};



















static int sample_report_refresh(const struct tsm_measurements *tm)









{









	struct crypto_shash *tfm;









	int rc;



















	tfm = crypto_alloc_shash(hash_algo_name[HASH_ALGO_SHA512], 0, 0);









	if (IS_ERR(tfm)) {









		pr_err("crypto_alloc_shash failed: %ld\n", PTR_ERR(tfm));









		return PTR_ERR(tfm);









	}



















	rc = crypto_shash_tfm_digest(tfm, (u8 *)&sample_report,









				     offsetof(typeof(sample_report),









					      report_digest),









				     sample_report.report_digest);









	crypto_free_shash(tfm);









	if (rc)









		pr_err("crypto_shash_tfm_digest failed: %d\n", rc);









	return rc;









}



















static int sample_report_extend_mr(const struct tsm_measurements *tm,









				   const struct tsm_measurement_register *mr,









				   const u8 *data)









{









	SHASH_DESC_ON_STACK(desc, 0);









	int rc;



















	desc->tfm = crypto_alloc_shash(hash_algo_name[mr->mr_hash], 0, 0);









	if (IS_ERR(desc->tfm)) {









		pr_err("crypto_alloc_shash failed: %ld\n", PTR_ERR(desc->tfm));









		return PTR_ERR(desc->tfm);









	}



















	rc = crypto_shash_init(desc);









	if (!rc)









		rc = crypto_shash_update(desc, mr->mr_value, mr->mr_size);









	if (!rc)









		rc = crypto_shash_finup(desc, data, mr->mr_size, mr->mr_value);









	crypto_free_shash(desc->tfm);









	if (rc)









		pr_err("SHA calculation failed: %d\n", rc);









	return rc;









}



















#define MR_(mr, hash) .mr_value = &sample_report.mr, TSM_MR_(mr, hash)









static const struct tsm_measurement_register sample_mrs[] = {









	/* static MR, read-only */









	{ MR_(static_mr, SHA384) },









	/* config MR, read-only */









	{ MR_(config_mr, SHA512) | TSM_MR_F_NOHASH },









	/* RTMR, direct extension prohibited */









	{ MR_(rtmr0, SHA256) | TSM_MR_F_LIVE },









	/* RTMR, direct extension allowed */









	{ MR_(rtmr1, SHA384) | TSM_MR_F_RTMR },









	/* RTMR, crypto agile, alaised to rtmr0 and rtmr1, respectively */









	{ .mr_value = &sample_report.rtmr0,









	  TSM_MR_(rtmr_crypto_agile, SHA256) | TSM_MR_F_RTMR },









	{ .mr_value = &sample_report.rtmr1,









	  TSM_MR_(rtmr_crypto_agile, SHA384) | TSM_MR_F_RTMR },









	/* sha512 digest of the whole structure */









	{ MR_(report_digest, SHA512) | TSM_MR_F_LIVE },









};









#undef MR_



















static struct tsm_measurements sample_tm = {









	.mrs = sample_mrs,









	.nr_mrs = ARRAY_SIZE(sample_mrs),









	.refresh = sample_report_refresh,









	.write = sample_report_extend_mr,









};



















static const struct attribute_group *sample_groups[] = {









	NULL,









	NULL,









};



















static struct miscdevice sample_misc_dev = {









	.name = KBUILD_MODNAME,









	.minor = MISC_DYNAMIC_MINOR,









	.groups = sample_groups,









};



















static int __init tsm_mr_sample_init(void)









{









	int rc;



















	sample_groups[0] = tsm_mr_create_attribute_group(&sample_tm);









	if (IS_ERR(sample_groups[0]))









		return PTR_ERR(sample_groups[0]);



















	rc = misc_register(&sample_misc_dev);









	if (rc)









		tsm_mr_free_attribute_group(sample_groups[0]);









	return rc;









}



















static void __exit tsm_mr_sample_exit(void)









{









	misc_deregister(&sample_misc_dev);









	tsm_mr_free_attribute_group(sample_groups[0]);









}



















module_init(tsm_mr_sample_init);









module_exit(tsm_mr_sample_exit);



















MODULE_LICENSE("GPL");









MODULE_DESCRIPTION("Sample module using tsm-mr to expose emulated MRs");