Message-ID: <e6124222-0dd8-46ff-abf7-3fcde963a5bd@linux.intel.com>
Date: Mon, 17 Feb 2025 17:10:02 -0800
From: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Cedric Xing <cedric.xing@...el.com>,
 Dan Williams <dan.j.williams@...el.com>,
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev
Subject: Re: [PATCH 1/4] tsm: Add TVM Measurement Register support

Hi Cedric,

On 2/12/25 6:23 PM, Cedric Xing wrote:
> 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

May be include some info on when a MR can be just a file (like an example)

> 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.

is this required/supported in any of the existing CC providers?

By sharing a common name, you mean internally there will be distinct
registers for every crypto algo supported?

>
> Signed-off-by: Cedric Xing <cedric.xing@...el.com>
> ---
>   Documentation/ABI/testing/sysfs-kernel-tsm |  20 ++
>   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                 | 375 +++++++++++++++++++++++++++++
>   include/linux/tsm.h                        |  64 +++++
>   7 files changed, 469 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-tsm b/Documentation/ABI/testing/sysfs-kernel-tsm
> new file mode 100644
> index 000000000000..99735cf4da5c
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-kernel-tsm
> @@ -0,0 +1,20 @@
> +What:		/sys/kernel/tsm/<measurement_provider>/<register>

Any reason for not using fixed name for registers (like mr[0-n])? May be it
will help if user space use a generic code across vendors.

> +Date:		February 2025
> +Contact:	Cedric Xing <cedric.xing@...el.com>.
> +Description:
> +		This file contains the value of the measurement register
> +		<register>. Depending on the CC architecture, this file may be
> +		writable, in which case the value written will be the new value
> +		of <register>. Each write must start at the beginning and be of
> +		the same size as the file. Partial writes are not permitted.
> +
> +What:		/sys/kernel/tsm/<measurement_provider>/<register>/<hash>/digest
> +Date:		February 2025
> +Contact:	Cedric Xing <cedric.xing@...el.com>.
> +Description:
> +		This file contains the value of the measurement register
> +		<register>. Depending on the CC architecture, this file may be
> +		writable, in which case any value written may be extended to
> +		<register> using <hash>. Each write must start at the beginning
> +		and be of the same size as the file. Partial writes are not
> +		permitted.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 25c86f47353d..c129fccd3d5a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -24098,7 +24098,7 @@ 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"

IMO, sysfs/configfs part is not required in the title.

>   
>   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..8d26e952da6b
> --- /dev/null
> +++ b/drivers/virt/coco/tsm-mr.c
> @@ -0,0 +1,375 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright(c) 2024-2025 Intel Corporation. All rights reserved. */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <crypto/hash.h>
> +#include <crypto/hash_info.h>
> +#include <linux/kobject.h>
> +#include <linux/module.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,

Why not use single underscore uniformly?

> +
> +	TMR_DIR__ALGO_MAX = 4,

Since this is not related to attribute index, why not use #define?

> +};
> +
> +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.refresh(%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;

I think you don't need to cast it.

> +	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) {

Since this path is only taken if in_sync is false, do you need to check 
again?

> +			rc = tmr_call_refresh(pvd, mr);
> +			pvd->in_sync = !rc;
> +		}
> +
> +		downgrade_write(&pvd->rwsem);
> +	}
> +
> +	if (!rc)
> +		memcpy(page, mr->mr_value + off, count);
> +
> +	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);
> +	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";

Since this attribute reflects register value, personally I think "value" 
is more clear
than "digest". But it is fine either way.

> +	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);
> +	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);

Why not add this condition at the top before allocation?

> +
> +	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);
> +	}
> +
> +	// initial refresh of MRs
> +	rc = tmr_call_refresh(pvd, NULL);
> +	pvd->in_sync = !rc;
> +
> +	pvd = NULL; // to avoid being freed automatically
> +	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

Why not use _E? Before reading the help text, I thought _X is for execute.

> + * @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,

It is not clear why you want to differentiate between write and extension.
Please add some help text related to it.

> +	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 */
>
-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

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