Message-Id: <20241210-tsm-rtmr-v3-1-5997d4dbda73@intel.com>
Date: Tue, 10 Dec 2024 21:22:15 -0600
From: Cedric Xing <cedric.xing@...el.com>
To: Dan Williams <dan.j.williams@...el.com>, 
 Samuel Ortiz <sameo@...osinc.com>, 
 James Bottomley <James.Bottomley@...senPartnership.com>, 
 Lukas Wunner <lukas@...ner.de>, 
 Dionna Amalie Glaze <dionnaglaze@...gle.com>, 
 Qinkun Bao <qinkun@...gle.com>, Mikko Ylinen <mikko.ylinen@...ux.intel.com>, 
 Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev
Subject: [PATCH RFC v3 1/2] tsm: Add TVM Measurement Register Support

This commit extends the TSM core with support for CC measurement registers
(MRs).

The newly added APIs are:

- `tsm_register_measurement(struct tsm_measurement *)`: This API allows a
  CC guest driver to register a set of measurement registers with the TSM
  core.
- `tsm_unregister_measurement(struct tsm_measurement *)`: This API enables
  a CC guest driver to unregister a previously registered set of
  measurement registers.

`struct tsm_measurement` has been defined to encapsulate the details of
CC-specific MRs. It includes an array of `struct tsm_measurement_register`s
and provides operations for reading and updating these registers. For a
comprehensive understanding of the structure and its usage, refer to the
detailed comments in `include/linux/tsm.h`.

Upon successful registration of a measurement provider, the TSM core
exposes the MRs through a directory tree in the sysfs filesystem. The root
of this tree is located at `/sys/kernel/tsm/MR_PROVIDER/`, where
`MR_PROVIDER` is the name of the measurement provider (as specified by
`struct tsm_measurement::name`). Each MR is made accessible as either a
file or a directory of the specified name (i.e.,
`tsm_measurement_register::mr_name`). In the former case, the file content
is the MR value; while in the latter case `HASH_ALG/digest` under the MR
directory contains the MR value, where `HASH_ALG` specifies the hash
algorithm (e.g., sha256, sha384, etc.) used by this MR.

*Crypto Agility* is supported as a set of independent MRs that share a
common name. These MRs will be merged into a single MR directory and each
will be represented by its respective `HASH_ALG/digest` file. Note that
`tsm_measurement_register::mr_hash` must be distinct or the behavior is
undefined.

Signed-off-by: Cedric Xing <cedric.xing@...el.com>
---
 MAINTAINERS                             |   2 +-
 drivers/virt/coco/Kconfig               |   3 +-
 drivers/virt/coco/Makefile              |   2 +
 drivers/virt/coco/{tsm.c => tsm-core.c} |   6 +-
 drivers/virt/coco/tsm-mr.c              | 376 ++++++++++++++++++++++++++++++++
 include/linux/tsm.h                     |  64 ++++++
 6 files changed, 450 insertions(+), 3 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 17daa9ee9384..4c833fa9e388 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23846,7 +23846,7 @@ M:	Dan Williams <dan.j.williams@...el.com>
 L:	linux-coco@...ts.linux.dev
 S:	Maintained
 F:	Documentation/ABI/testing/configfs-tsm
-F:	drivers/virt/coco/tsm.c
+F:	drivers/virt/coco/tsm*.c
 F:	include/linux/tsm.h
 
 TRUSTED SERVICES TEE DRIVER
diff --git a/drivers/virt/coco/Kconfig b/drivers/virt/coco/Kconfig
index ff869d883d95..6f3c0831680b 100644
--- a/drivers/virt/coco/Kconfig
+++ b/drivers/virt/coco/Kconfig
@@ -5,7 +5,8 @@
 
 config TSM_REPORTS
 	select CONFIGFS_FS
-	tristate
+	select CRYPTO_HASH_INFO
+	tristate "Trusted Security Module (TSM) sysfs/configfs support"
 
 source "drivers/virt/coco/efi_secret/Kconfig"
 
diff --git a/drivers/virt/coco/Makefile b/drivers/virt/coco/Makefile
index c3d07cfc087e..4b108d8df1bd 100644
--- a/drivers/virt/coco/Makefile
+++ b/drivers/virt/coco/Makefile
@@ -2,6 +2,8 @@
 #
 # Confidential computing related collateral
 #
+tsm-y				+= tsm-core.o tsm-mr.o
+
 obj-$(CONFIG_TSM_REPORTS)	+= tsm.o
 obj-$(CONFIG_EFI_SECRET)	+= efi_secret/
 obj-$(CONFIG_ARM_PKVM_GUEST)	+= pkvm-guest/
diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm-core.c
similarity index 99%
rename from drivers/virt/coco/tsm.c
rename to drivers/virt/coco/tsm-core.c
index 9432d4e303f1..ab5269db9c13 100644
--- a/drivers/virt/coco/tsm.c
+++ b/drivers/virt/coco/tsm-core.c
@@ -476,6 +476,9 @@ int tsm_unregister(const struct tsm_ops *ops)
 }
 EXPORT_SYMBOL_GPL(tsm_unregister);
 
+int tsm_mr_init(void);
+void tsm_mr_exit(void);
+
 static struct config_group *tsm_report_group;
 
 static int __init tsm_init(void)
@@ -497,12 +500,13 @@ static int __init tsm_init(void)
 	}
 	tsm_report_group = tsm;
 
-	return 0;
+	return tsm_mr_init();
 }
 module_init(tsm_init);
 
 static void __exit tsm_exit(void)
 {
+	tsm_mr_exit();
 	configfs_unregister_default_group(tsm_report_group);
 	configfs_unregister_subsystem(&tsm_configfs);
 }
diff --git a/drivers/virt/coco/tsm-mr.c b/drivers/virt/coco/tsm-mr.c
new file mode 100644
index 000000000000..499d2aa1e6c7
--- /dev/null
+++ b/drivers/virt/coco/tsm-mr.c
@@ -0,0 +1,376 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2024 Intel Corporation. All rights reserved. */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <crypto/hash.h>
+#include <crypto/hash_info.h>
+#include <linux/ctype.h>
+#include <linux/shmem_fs.h>
+#include <linux/tsm.h>
+
+int tsm_mr_init(void);
+void tsm_mr_exit(void);
+
+enum tmr_dir_battr_index {
+	TMR_DIR_BA_DIGEST,
+	TMR_DIR_BA__COUNT,
+
+	TMR_DIR__ALGO_MAX = 4,
+};
+
+struct tmr_dir {
+	struct kobject kobj;
+	struct bin_attribute battrs[TMR_DIR__ALGO_MAX][TMR_DIR_BA__COUNT];
+	int algo;
+};
+
+struct tmr_provider {
+	struct kset kset;
+	struct rw_semaphore rwsem;
+	struct bin_attribute *mrfiles;
+	struct tsm_measurement *tmr;
+	bool in_sync;
+};
+
+static inline struct tmr_provider *tmr_mr_to_provider(const struct tsm_measurement_register *mr,
+						      struct kobject *kobj)
+{
+	if (mr->mr_flags & TSM_MR_F_F)
+		return container_of(kobj, struct tmr_provider, kset.kobj);
+	else
+		return container_of(kobj->kset, struct tmr_provider, kset);
+}
+
+static inline int tmr_call_refresh(struct tmr_provider *pvd,
+				   const struct tsm_measurement_register *mr)
+{
+	int rc;
+
+	rc = pvd->tmr->refresh(pvd->tmr, mr);
+	if (rc)
+		pr_warn("%s.extend(%s) failed %d\n", kobject_name(&pvd->kset.kobj), mr->mr_name,
+			rc);
+	return rc;
+}
+
+static inline int tmr_call_extend(struct tmr_provider *pvd,
+				  const struct tsm_measurement_register *mr, const u8 *data)
+{
+	int rc;
+
+	rc = pvd->tmr->extend(pvd->tmr, mr, data);
+	if (rc)
+		pr_warn("%s.extend(%s) failed %d\n", kobject_name(&pvd->kset.kobj), mr->mr_name,
+			rc);
+	return rc;
+}
+
+static ssize_t tmr_digest_read(struct file *filp, struct kobject *kobj, struct bin_attribute *attr,
+			       char *page, loff_t off, size_t count)
+{
+	const struct tsm_measurement_register *mr;
+	struct tmr_provider *pvd;
+	int rc;
+
+	if (off < 0 || off > attr->size)
+		return -EINVAL;
+
+	count = min(count, attr->size - (size_t)off);
+	if (!count)
+		return count;
+
+	mr = (typeof(mr))attr->private;
+	pvd = tmr_mr_to_provider(mr, kobj);
+	rc = down_read_interruptible(&pvd->rwsem);
+	if (rc)
+		return rc;
+
+	if ((mr->mr_flags & TSM_MR_F_L) && !pvd->in_sync) {
+		up_read(&pvd->rwsem);
+
+		rc = down_write_killable(&pvd->rwsem);
+		if (rc)
+			return rc;
+
+		if (!pvd->in_sync) {
+			rc = tmr_call_refresh(pvd, mr);
+			pvd->in_sync = !rc;
+		}
+
+		downgrade_write(&pvd->rwsem);
+	}
+
+	if (!rc)
+		memcpy(page, mr->mr_value + off, count);
+	else
+		pr_debug("%s.refresh(%s)=%d\n", kobject_name(&pvd->kset.kobj), mr->mr_name, rc);
+
+	up_read(&pvd->rwsem);
+	return rc ?: count;
+}
+
+static ssize_t tmr_digest_write(struct file *filp, struct kobject *kobj, struct bin_attribute *attr,
+				char *page, loff_t off, size_t count)
+{
+	const struct tsm_measurement_register *mr;
+	struct tmr_provider *pvd;
+	ssize_t rc;
+
+	if (off != 0 || count != attr->size)
+		return -EINVAL;
+
+	mr = (typeof(mr))attr->private;
+	pvd = tmr_mr_to_provider(mr, kobj);
+	rc = down_write_killable(&pvd->rwsem);
+	if (rc)
+		return rc;
+
+	if (mr->mr_flags & TSM_MR_F_X)
+		rc = tmr_call_extend(pvd, mr, page);
+	else
+		memcpy(mr->mr_value, page, count);
+
+	if (!rc)
+		pvd->in_sync = false;
+
+	up_write(&pvd->rwsem);
+	return rc ?: count;
+}
+
+static void tmr_dir_release(struct kobject *kobj)
+{
+	struct tmr_dir *mrd;
+
+	mrd = container_of(kobj, typeof(*mrd), kobj);
+	pr_debug("%s(%s)\n", __func__, kobject_name(kobj));
+	kfree(mrd);
+}
+
+static const struct kobj_type tmr_dir_ktype = {
+	.release = tmr_dir_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+};
+
+static struct tmr_dir *tmr_dir_create(const struct tsm_measurement_register *mr,
+				      struct tmr_provider *pvd)
+{
+	struct kobject *kobj;
+	struct tmr_dir *mrd;
+
+	kobj = kset_find_obj(&pvd->kset, mr->mr_name);
+	if (kobj) {
+		mrd = container_of(kobj, typeof(*mrd), kobj);
+		kobject_put(kobj);
+		if (++mrd->algo >= TMR_DIR__ALGO_MAX) {
+			--mrd->algo;
+			return ERR_PTR(-ENOSPC);
+		}
+	} else {
+		int rc;
+
+		mrd = kzalloc(sizeof(*mrd), GFP_KERNEL);
+		if (!mrd)
+			return ERR_PTR(-ENOMEM);
+
+		mrd->kobj.kset = &pvd->kset;
+		rc = kobject_init_and_add(&mrd->kobj, &tmr_dir_ktype, NULL, "%s", mr->mr_name);
+		if (rc) {
+			kfree(mrd);
+			return ERR_PTR(rc);
+		}
+	}
+
+	sysfs_bin_attr_init(&mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST]);
+	mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].attr.name = "digest";
+	if (mr->mr_flags & TSM_MR_F_W)
+		mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].attr.mode |= S_IWUSR | S_IWGRP;
+	if (mr->mr_flags & TSM_MR_F_R)
+		mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].attr.mode |= S_IRUGO;
+
+	mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].size = mr->mr_size;
+	mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].read = tmr_digest_read;
+	mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].write = tmr_digest_write;
+	mrd->battrs[mrd->algo][TMR_DIR_BA_DIGEST].private = (void *)mr;
+
+	return mrd;
+}
+
+static void tmr_provider_release(struct kobject *kobj)
+{
+	struct tmr_provider *pvd;
+
+	pvd = container_of(kobj, typeof(*pvd), kset.kobj);
+	pr_debug("%s(%s)\n", __func__, kobject_name(kobj));
+	if (!WARN_ON(!list_empty(&pvd->kset.list))) {
+		kfree(pvd->mrfiles);
+		kfree(pvd);
+	}
+}
+
+static const struct kobj_type _mr_provider_ktype = {
+	.release = tmr_provider_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+};
+
+static struct kset *tmr_sysfs_root;
+
+static struct tmr_provider *tmr_provider_create(struct tsm_measurement *tmr)
+{
+	struct tmr_provider *pvd __free(kfree);
+	int rc;
+
+	pvd = kzalloc(sizeof(*pvd), GFP_KERNEL);
+	if (!pvd)
+		return ERR_PTR(-ENOMEM);
+
+	if (!tmr->name || !tmr->mrs || !tmr->refresh || !tmr->extend)
+		return ERR_PTR(-EINVAL);
+
+	rc = kobject_set_name(&pvd->kset.kobj, "%s", tmr->name);
+	if (rc)
+		return ERR_PTR(rc);
+
+	pvd->kset.kobj.kset = tmr_sysfs_root;
+	pvd->kset.kobj.ktype = &_mr_provider_ktype;
+	pvd->tmr = tmr;
+
+	init_rwsem(&pvd->rwsem);
+
+	rc = kset_register(&pvd->kset);
+	if (rc)
+		return ERR_PTR(rc);
+
+	return_ptr(pvd);
+}
+
+DEFINE_FREE(_unregister_measurement, struct tmr_provider *,
+	    if (!IS_ERR_OR_NULL(_T)) tsm_unregister_measurement(_T->tmr));
+
+int tsm_register_measurement(struct tsm_measurement *tmr)
+{
+	struct tmr_provider *pvd __free(_unregister_measurement);
+	int rc, nr;
+
+	pvd = tmr_provider_create(tmr);
+	if (IS_ERR(pvd))
+		return PTR_ERR(pvd);
+
+	nr = 0;
+	for (int i = 0; tmr->mrs[i].mr_name; ++i) {
+		// flat files are counted and skipped
+		if (tmr->mrs[i].mr_flags & TSM_MR_F_F) {
+			++nr;
+			continue;
+		}
+
+		struct tmr_dir *mrd;
+		struct bin_attribute *battrs[TMR_DIR_BA__COUNT + 1] = {};
+		struct attribute_group agrp = {
+			.name = hash_algo_name[tmr->mrs[i].mr_hash],
+			.bin_attrs = battrs,
+		};
+
+		mrd = tmr_dir_create(&tmr->mrs[i], pvd);
+		if (IS_ERR(mrd))
+			return PTR_ERR(mrd);
+
+		for (int j = 0; j < TMR_DIR_BA__COUNT; ++j)
+			battrs[j] = &mrd->battrs[mrd->algo][j];
+
+		rc = sysfs_create_group(&mrd->kobj, &agrp);
+		if (rc)
+			return rc;
+	}
+
+	if (nr > 0) {
+		struct bin_attribute *mrfiles __free(kfree);
+		struct bin_attribute **battrs __free(kfree);
+
+		mrfiles = kcalloc(nr, sizeof(*mrfiles), GFP_KERNEL);
+		battrs = kcalloc(nr + 1, sizeof(*battrs), GFP_KERNEL);
+		if (!battrs || !mrfiles)
+			return -ENOMEM;
+
+		for (int i = 0, j = 0; tmr->mrs[i].mr_name; ++i) {
+			if (!(tmr->mrs[i].mr_flags & TSM_MR_F_F))
+				continue;
+
+			mrfiles[j].attr.name = tmr->mrs[i].mr_name;
+			mrfiles[j].read = tmr_digest_read;
+			mrfiles[j].write = tmr_digest_write;
+			mrfiles[j].size = tmr->mrs[i].mr_size;
+			mrfiles[j].private = (void *)&tmr->mrs[i];
+			if (tmr->mrs[i].mr_flags & TSM_MR_F_R)
+				mrfiles[j].attr.mode |= S_IRUGO;
+			if (tmr->mrs[i].mr_flags & TSM_MR_F_W)
+				mrfiles[j].attr.mode |= S_IWUSR | S_IWGRP;
+
+			battrs[j] = &mrfiles[j];
+			++j;
+		}
+
+		struct attribute_group agrp = {
+			.bin_attrs = battrs,
+		};
+		rc = sysfs_create_group(&pvd->kset.kobj, &agrp);
+		if (rc)
+			return rc;
+
+		pvd->mrfiles = no_free_ptr(mrfiles);
+	}
+
+	// set pvd to NULL or it will be freed due to __free(kfree)
+	pvd = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tsm_register_measurement);
+
+static void tmr_put_children(struct kset *kset)
+{
+	struct kobject *p, *n;
+
+	spin_lock(&kset->list_lock);
+	list_for_each_entry_safe(p, n, &kset->list, entry) {
+		spin_unlock(&kset->list_lock);
+		kobject_put(p);
+		spin_lock(&kset->list_lock);
+	}
+	spin_unlock(&kset->list_lock);
+}
+
+int tsm_unregister_measurement(struct tsm_measurement *tmr)
+{
+	struct kobject *kobj;
+	struct tmr_provider *pvd;
+
+	kobj = kset_find_obj(tmr_sysfs_root, tmr->name);
+	if (!kobj)
+		return -ENOENT;
+
+	pvd = container_of(kobj, typeof(*pvd), kset.kobj);
+	if (pvd->tmr != tmr)
+		return -EINVAL;
+
+	tmr_put_children(&pvd->kset);
+	kset_unregister(&pvd->kset);
+	kobject_put(kobj);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tsm_unregister_measurement);
+
+int tsm_mr_init(void)
+{
+	tmr_sysfs_root = kset_create_and_add("tsm", NULL, kernel_kobj);
+	if (!tmr_sysfs_root)
+		return -ENOMEM;
+	return 0;
+}
+
+void tsm_mr_exit(void)
+{
+	kset_unregister(tmr_sysfs_root);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Provide Trusted Security Module measurements via sysfs");
diff --git a/include/linux/tsm.h b/include/linux/tsm.h
index 11b0c525be30..624a7b62b85d 100644
--- a/include/linux/tsm.h
+++ b/include/linux/tsm.h
@@ -5,6 +5,7 @@
 #include <linux/sizes.h>
 #include <linux/types.h>
 #include <linux/uuid.h>
+#include <uapi/linux/hash_info.h>
 
 #define TSM_INBLOB_MAX 64
 #define TSM_OUTBLOB_MAX SZ_32K
@@ -109,4 +110,67 @@ struct tsm_ops {
 
 int tsm_register(const struct tsm_ops *ops, void *priv);
 int tsm_unregister(const struct tsm_ops *ops);
+
+/**
+ * struct tsm_measurement_register - describes an architectural measurement register (MR)
+ * @mr_name: name of the MR
+ * @mr_value: buffer containing the current value of the MR
+ * @mr_size: size of the MR - typically the digest size of @mr_hash
+ * @mr_flags: bitwise OR of flags defined in enum tsm_measurement_register_flag
+ * @mr_hash: optional hash identifier defined in include/uapi/linux/hash_info.h
+ *
+ * A CC guest driver provides this structure to detail the measurement facility supported by the
+ * underlying CC hardware. After registration via `tsm_register_measurement`, the CC guest driver
+ * must retain this structure until it is unregistered using `tsm_unregister_measurement`.
+ */
+struct tsm_measurement_register {
+	const char *mr_name;
+	void *mr_value;
+	u32 mr_size;
+	u32 mr_flags;
+	enum hash_algo mr_hash;
+};
+
+/**
+ * enum tsm_measurement_register_flag - properties of an MR
+ * @TSM_MR_F_X: this MR supports the extension semantics on write
+ * @TSM_MR_F_W: this MR is writable
+ * @TSM_MR_F_R: this MR is readable. This should typically be set
+ * @TSM_MR_F_L: this MR is live - writes to other MRs may change this MR
+ * @TSM_MR_F_F: present this MR as a file (instead of a directory)
+ * @TSM_MR_F_LIVE: shorthand for L (live) and R (readable)
+ * @TSM_MR_F_RTMR: shorthand for LIVE and X (extensible)
+ */
+enum tsm_measurement_register_flag {
+	TSM_MR_F_X = 1,
+	TSM_MR_F_W = 2,
+	TSM_MR_F_R = 4,
+	TSM_MR_F_L = 8,
+	TSM_MR_F_F = 16,
+	TSM_MR_F_LIVE = TSM_MR_F_L | TSM_MR_F_R,
+	TSM_MR_F_RTMR = TSM_MR_F_LIVE | TSM_MR_F_X,
+};
+
+#define TSM_MR_(mr, hash)                                                           \
+	.mr_name = #mr, .mr_size = hash##_DIGEST_SIZE, .mr_hash = HASH_ALGO_##hash, \
+	.mr_flags = TSM_MR_F_R
+
+/**
+ * struct tsm_measurement - define CC specific MRs and methods for updating them
+ * @name: name of the measurement provider
+ * @mrs: array of MR definitions ending with mr_name set to %NULL
+ * @refresh: invoked to update the specified MR
+ * @extend: invoked to extend the specified MR with mr_size bytes
+ */
+struct tsm_measurement {
+	const char *name;
+	const struct tsm_measurement_register *mrs;
+	int (*refresh)(struct tsm_measurement *tmr, const struct tsm_measurement_register *mr);
+	int (*extend)(struct tsm_measurement *tmr, const struct tsm_measurement_register *mr,
+		      const u8 *data);
+};
+
+int tsm_register_measurement(struct tsm_measurement *tmr);
+int tsm_unregister_measurement(struct tsm_measurement *tmr);
+
 #endif /* __TSM_H */

-- 
2.43.0

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