Processing Metadata, Policies, and Composite Tags

Patent metadata

Field	Value
Publication number	US-2020387374-A1
Application number	US-202016905680-A
Country	US
Kind code	A1
Filing date	Jun 18, 2020
Priority date	Dec 17, 2015
Publication date	Dec 10, 2020
Grant date	—

Abstract

A method includes receiving, for metadata processing, a current instruction with associated metadata tags. The metadata processing is performed in a metadata processing domain isolated from a code execution domain including the current instruction. Each respective associated metadata tag represents a respective policy of the composite policy. For each respective metadata tag, the method includes determining, in the metadata processing domain and in accordance with the metadata tag and the current instruction, whether a rule exists for the current instruction in a rules cache. The rules cache may include rules on metadata used by the metadata processing to define allowed instructions. The determination of whether a rule exists results in a respective output, which may include generating a new rule and inserting the new rule in the rules cache. Control Status Registers, and associated tags, may be used to accomplish the metadata processing.

First claim

1 . A method of digital processor processing instructions comprising:
receiving, for metadata processing, a current instruction with a plurality of associated metadata tags, the metadata processing being performed in a metadata processing domain isolated from a code execution domain that includes the current instruction, each respective associated metadata tag representing a respective policy of a composite policy, the plurality of associated metadata tags further including pointers to tags of a component policy of the composite policy; for each respective metadata tag of the plurality of associated metadata tags, determining, in the metadata processing domain and in accordance with the metadata tag and the current instruction, whether a rule exists in a rules cache for the current instruction, the rules cache including rules on metadata used by the metadata processing to define allowed instructions, each determination of whether a rule exists resulting in a respective output; responsive to determining no rule exists in the rules cache for the current instruction, performing rule cache miss processing in the metadata processing domain including determining whether execution of the current instruction is one of allowed and disallowed; responsive to determining the current instruction is allowed to be executed in the code execution domain, generating a new rule for the current instruction and, responsive to writing to a register in the metadata processing domain, inserting the new rule into the rules cache; wherein first metadata used to select the rule for the current instruction is stored in a first portion of a plurality of control status registers used by the metadata processing, and wherein the first portion of the plurality of control status registers is used to communicate a plurality of metadata tags for the current instruction to the metadata processing domain, wherein the plurality of metadata tags is used as data in the metadata processing domain.

2 . The method of claim 1 , further comprising:
generating a composite result tag by combining the respective outputs into a single metadata tag representing the composite policy that includes each respective policy; and inserting a new rule into the rules cache, the new rule comprising (i) the current instruction and associated metadata tags, and (ii) the composite result tag.

3 . The method of claim 1 , wherein determining whether a rule exists in a rules cache further includes:
for each metadata tag, determining whether a rule exists in a first level cache; when it is determined that no rule is present in the first level cache, determining whether a rule exists in a second level cache.

4 . The method of claim 1 , wherein the rules cache is at least one of a Unified Component Policy (UCP) cache, composite set of tag (CTAG) cache, or data cache.

5 . The method of claim 1 , wherein:
a composite set of tag (CTAG) cache stores composite results based on combinations of metadata tag values, and generating the composite result tag includes combining the respective outputs into a single metadata tag by looking up a combination of the respective outputs in the CTAG cache.

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Dehon Andre'

Classifications

• G06F21/52 Primary

  during program execution, e.g. stack integrity {; Preventing unwanted data erasure; Buffer overflow} · CPC title

• G06F15/78

  comprising a single central processing unit · CPC title

• G06F9/3867

  using instruction pipelines · CPC title

• G06F2212/452

  Instruction code · CPC title

• G06F12/0875

  with dedicated cache, e.g. instruction or stack · CPC title