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

diff --git a/MAINTAINERS b/MAINTAINERS
index 5d36823d26b28797c1186e7df1eb4d2da612f51c..8bf8a818bce5225bd5e2a18685893efa5a9c5650 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -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>

diff --git a/samples/Kconfig b/samples/Kconfig
index 09011be2391a925bb31b1cf6e6a979599fed30f4..6ade17cb16b441965f0a19d87ddf766c8ee3922c 100644 (file)
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -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

diff --git a/samples/Makefile b/samples/Makefile
index bf6e6fca5410b1b374a287269c24f96de8bb2800..c95bac31851c2cafbbbef3ad8e36bea752e411ea 100644 (file)
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -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/

diff --git a/samples/tsm-mr/Makefile b/samples/tsm-mr/Makefile
new file mode 100644 (file)
index 0000000..587c394
--- /dev/null
+++ b/samples/tsm-mr/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SAMPLE_TSM_MR) += tsm_mr_sample.o

diff --git a/samples/tsm-mr/tsm_mr_sample.c b/samples/tsm-mr/tsm_mr_sample.c
new file mode 100644 (file)
index 0000000..f3e1630
--- /dev/null
+++ b/samples/tsm-mr/tsm_mr_sample.c
@@ -0,0 +1,131 @@
+// 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");