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b9e22b35d4
Introduce new TSM Measurement helper library (tsm-mr) for TVM guest drivers
to expose MRs (Measurement Registers) as sysfs attributes, with Crypto
Agility support.
Add the following new APIs (see include/linux/tsm-mr.h for details):
- tsm_mr_create_attribute_group(): Take on input a `struct
tsm_measurements` instance, which includes one `struct
tsm_measurement_register` per MR with properties like `TSM_MR_F_READABLE`
and `TSM_MR_F_WRITABLE`, to determine the supported operations and create
the sysfs attributes accordingly. On success, return a `struct
attribute_group` instance that will typically be included by the guest
driver into `miscdevice.groups` before calling misc_register().
- tsm_mr_free_attribute_group(): Free the memory allocated to the attrubute
group returned by tsm_mr_create_attribute_group().
tsm_mr_create_attribute_group() creates one attribute for each MR, with
names following this pattern:
MRNAME[:HASH]
- MRNAME - Placeholder for the MR name, as specified by
`tsm_measurement_register.mr_name`.
- :HASH - Optional suffix indicating the hash algorithm associated with
this MR, as specified by `tsm_measurement_register.mr_hash`.
Support Crypto Agility by allowing multiple definitions of the same MR
(i.e., with the same `mr_name`) with distinct HASH algorithms.
NOTE: Crypto Agility, introduced in TPM 2.0, allows new hash algorithms to
be introduced without breaking compatibility with applications using older
algorithms. CC architectures may face the same challenge in the future,
needing new hashes for security while retaining compatibility with older
hashes, hence the need for Crypto Agility.
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>
[djbw: fixup bin_attr const conflict]
Link: https://patch.msgid.link/20250509020739.882913-1-dan.j.williams@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
90 lines
3.4 KiB
C
90 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __TSM_MR_H
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#define __TSM_MR_H
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#include <crypto/hash_info.h>
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/**
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* struct tsm_measurement_register - describes an architectural measurement
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* register (MR)
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* @mr_name: name of the MR
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* @mr_value: buffer containing the current value of the MR
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* @mr_size: size of the MR - typically the digest size of @mr_hash
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* @mr_flags: bitwise OR of one or more flags, detailed below
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* @mr_hash: optional hash identifier defined in include/uapi/linux/hash_info.h.
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*
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* A CC guest driver encloses an array of this structure in struct
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* tsm_measurements to detail the measurement facility supported by the
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* underlying CC hardware.
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*
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* @mr_name and @mr_value must stay valid until this structure is no longer in
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* use.
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*
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* @mr_flags is the bitwise-OR of zero or more of the flags below.
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*
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* * %TSM_MR_F_READABLE - the sysfs attribute corresponding to this MR is readable.
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* * %TSM_MR_F_WRITABLE - the sysfs attribute corresponding to this MR is writable.
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* The semantics is typically to extend the MR but could vary depending on the
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* architecture and the MR.
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* * %TSM_MR_F_LIVE - this MR's value may differ from the last value written, so
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* must be read back from the underlying CC hardware/firmware.
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* * %TSM_MR_F_RTMR - bitwise-OR of %TSM_MR_F_LIVE and %TSM_MR_F_WRITABLE.
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* * %TSM_MR_F_NOHASH - this MR does NOT have an associated hash algorithm.
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* @mr_hash will be ignored when this flag is set.
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*/
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struct tsm_measurement_register {
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const char *mr_name;
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void *mr_value;
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u32 mr_size;
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u32 mr_flags;
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enum hash_algo mr_hash;
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};
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#define TSM_MR_F_NOHASH 1
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#define TSM_MR_F_WRITABLE 2
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#define TSM_MR_F_READABLE 4
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#define TSM_MR_F_LIVE 8
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#define TSM_MR_F_RTMR (TSM_MR_F_LIVE | TSM_MR_F_WRITABLE)
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#define TSM_MR_(mr, hash) \
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.mr_name = #mr, .mr_size = hash##_DIGEST_SIZE, \
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.mr_hash = HASH_ALGO_##hash, .mr_flags = TSM_MR_F_READABLE
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/**
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* struct tsm_measurements - defines the CC architecture specific measurement
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* facility and methods for updating measurement registers (MRs)
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* @mrs: Array of MR definitions.
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* @nr_mrs: Number of elements in @mrs.
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* @refresh: Callback function to load/sync all MRs from TVM hardware/firmware
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* into the kernel cache.
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* @write: Callback function to write to the MR specified by the parameter @mr.
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* Typically, writing to an MR extends the input buffer to that MR.
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*
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* The @refresh callback is invoked when an MR with %TSM_MR_F_LIVE set is being
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* read and the cache is stale. It must reload all MRs with %TSM_MR_F_LIVE set.
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* The function parameter @tm is a pointer pointing back to this structure.
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*
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* The @write callback is invoked whenever an MR is being written. It takes two
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* additional parameters besides @tm:
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*
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* * @mr - points to the MR (an element of @tm->mrs) being written.
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* * @data - contains the bytes to write and whose size is @mr->mr_size.
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*
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* Both @refresh and @write should return 0 on success and an appropriate error
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* code on failure.
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*/
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struct tsm_measurements {
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const struct tsm_measurement_register *mrs;
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size_t nr_mrs;
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int (*refresh)(const struct tsm_measurements *tm);
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int (*write)(const struct tsm_measurements *tm,
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const struct tsm_measurement_register *mr, const u8 *data);
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};
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const struct attribute_group *
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tsm_mr_create_attribute_group(const struct tsm_measurements *tm);
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void tsm_mr_free_attribute_group(const struct attribute_group *attr_grp);
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#endif
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