Measurement Registers

struct tsm_measurement_register

describes an architectural measurement register (MR)

Definition:

struct tsm_measurement_register {
    const char *mr_name;
    void *mr_value;
    u32 mr_size;
    u32 mr_flags;
    enum hash_algo mr_hash;
};

Members

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 one or more flags, detailed below

mr_hash

optional hash identifier defined in include/uapi/linux/hash_info.h.

Description

A CC guest driver encloses an array of this structure in struct tsm_measurements to detail the measurement facility supported by the underlying CC hardware.

mr_name and mr_value must stay valid until this structure is no longer in use.

mr_flags is the bitwise-OR of zero or more of the flags below.

• TSM_MR_F_READABLE - the sysfs attribute corresponding to this MR is readable.

• TSM_MR_F_WRITABLE - the sysfs attribute corresponding to this MR is writable. The semantics is typically to extend the MR but could vary depending on the architecture and the MR.

• TSM_MR_F_LIVE - this MR’s value may differ from the last value written, so must be read back from the underlying CC hardware/firmware.

• TSM_MR_F_RTMR - bitwise-OR of TSM_MR_F_LIVE and TSM_MR_F_WRITABLE.

• TSM_MR_F_NOHASH - this MR does NOT have an associated hash algorithm. mr_hash will be ignored when this flag is set.

struct tsm_measurements

defines the CC architecture specific measurement facility and methods for updating measurement registers (MRs)

Definition:

struct tsm_measurements {
    const struct tsm_measurement_register *mrs;
    size_t nr_mrs;
    int (*refresh)(const struct tsm_measurements *tm);
    int (*write)(const struct tsm_measurements *tm, const struct tsm_measurement_register *mr, const u8 *data);
};

Members

mrs

Array of MR definitions.

nr_mrs

Number of elements in mrs.

refresh

Callback function to load/sync all MRs from TVM hardware/firmware into the kernel cache.

write

Callback function to write to the MR specified by the parameter mr. Typically, writing to an MR extends the input buffer to that MR.

Description

The refresh callback is invoked when an MR with TSM_MR_F_LIVE set is being read and the cache is stale. It must reload all MRs with TSM_MR_F_LIVE set. The function parameter tm is a pointer pointing back to this structure.

The write callback is invoked whenever an MR is being written. It takes two additional parameters besides tm:

• mr - points to the MR (an element of tm->mrs) being written.

• data - contains the bytes to write and whose size is mr->mr_size.

Both refresh and write should return 0 on success and an appropriate error code on failure.

const struct attribute_group *tsm_mr_create_attribute_group(const struct tsm_measurements *tm)

creates an attribute group for measurement registers (MRs)

Parameters

const struct tsm_measurements *tm

pointer to struct tsm_measurements containing the MR definitions.

Description

This function creates attributes corresponding to the MR definitions provided by tm->mrs.

The created attributes will reference tm and its members. The caller must not free tm until after tsm_mr_free_attribute_group() is called.

Context

Process context. May sleep due to memory allocation.

Return

• On success, the pointer to a an attribute group is returned; otherwise

• -EINVAL - Invalid MR definitions.

• -ENOMEM - Out of memory.

void tsm_mr_free_attribute_group(const struct attribute_group *attr_grp)

frees the attribute group returned by tsm_mr_create_attribute_group()

Parameters

const struct attribute_group *attr_grp

attribute group returned by tsm_mr_create_attribute_group()

Context

Process context.