Abstract: An apparatus comprises processing circuitry to perform data processing in response to instructions, and memory access circuitry to perform a tag-guarded memory access operation in response to a target address. The tag-guarded memory access operation comprises comparing an address tag associated with the target address with a guard tag stored in a memory system in association with a block of one or more memory locations comprising an addressed location identified by the target address, and generating an indication of whether a match is detected between the guard tag and the address tag. The memory access circuitry determines, according to a programmable mapping, a mapping of guard tag storage locations for storing guard tags for corresponding blocks of memory locations.

Abstract: An apparatus and method are provided for controlling memory accesses. The apparatus has memory access circuitry for performing a tag-guarded memory access operation in response to a target address, the tag-guarded memory access operation by default comprising: comparing an address tag associated with the target address with a guard tag stored in a memory system in association with a block of one or more memory locations comprising an addressed location identified by the target address; and generating an indication of whether a match is detected between the guard tag and the address tag. Further, the apparatus has control tag storage for storing, for each of a plurality of memory regions, configuration control information used to control how the tag-guarded memory access operation is performed by the memory access circuitry when the target address is within that memory region. Each memory region corresponds to multiple of the blocks.

Abstract: In an apparatus with transactional memory support circuitry, for a first type of transaction started using a first type of transaction start instruction, commitment of results of instructions executed speculatively following the first type of transaction start instruction are prevented until a transaction end instruction is reached. An abort is triggered when a conflict is detected between an address of a memory access from another thread and the addresses tracked for the transaction. For a second type of transaction started using a second type of transaction start instruction, an address of the read operation is marked as trackable whilst an address of a write operation is omitted from being marked as trackable. This allows an apparatus that supports transactional memory to also be used for multi-word address watching.

Abstract: An apparatus comprising memory access circuitry to perform a tag-guarded memory access in response to a received target address and methods of operation of the same are disclosed. In the tag-guarded memory access a guard-tag retrieval operation seeks to retrieve a guard tag stored in association with a block of one or more memory locations comprising an addressed location identified by the received target address, and a guard-tag check operation compares an address tag associated with the received target address with the guard tag retrieved by the guard-tag retrieval operation. When the guard-tag retrieval operation is unsuccessful in retrieving the guard tag, a substitute guard tag value is stored as the guard tag in association with the block of one or more memory locations comprising the addressed location identified by the target address.

Abstract: An apparatus comprises: an instruction decoder and processing circuitry. In response to a data structure processing instruction specifying at least one input data structure identifier and an output data structure identifier, the instruction decoder controls the processing circuitry to perform a processing operation on at least one input data structure to generate an output data structure. Each input/output data structure comprises an arrangement of data corresponding to a plurality of memory addresses. The apparatus comprises two or more sets of one or more data structure metadata registers, each set associated with a corresponding data structure identifier and designated to store address-indicating metadata for identifying the memory addresses for the data structure identified by the corresponding data structure identifier.

Abstract: An apparatus and method are provided for controlling use of bounded pointers. The apparatus includes storage to store bounded pointers, where each bounded pointer comprises a pointer value and associated attributes, with the associated attributes including range information indicative of an allowable range of addresses when using the pointer value. Processing circuitry is used to perform a signing operation on an input bounded pointer in order to generate an output bounded pointer in which a signature generated by the signing operation is contained within the output bounded pointer in place of specified bits of the input bounded pointer. In addition, the associated attributes include signing information which is set by the processing circuitry within the output bounded pointer to identify that the output bounded pointer has been signed. Such an approach provides increase resilience to control flow integrity attack when using bounded pointers.

Abstract: An apparatus (2) comprises an instruction decoder (6) and processing circuitry (4). The instruction decoder (6) supports branch instructions for triggering a non-sequential change of program flow to an instruction at a target address, including: a branch-with-link instruction for which a return address is set for a subsequent return of program flow; and at least one target-checking type of branch instruction, for which when the branch is taken an error handling response is triggered when the instruction at the target address is an instruction other than at least one permitted type of branch target instruction. For at least a subset of the at least one target-checking type of branch instruction, a branch target variant of the branch-with-link instruction is a permitted type of branch target instruction.

Abstract: A requester issues a request specifying a target address indicating an addressed location in a memory system. A completer responds to the request. Tag error checking circuitry performs a tag error checking operation when the request issued by the requester is a tag-error-checking request specifying an address tag. The tag error checking operation comprises determining whether the address tag matches an allocation tag stored in the memory system associated with a block of one or more addresses comprising the target address specified by the tag-error-checking request. The requester and the completer communicate via a memory interface having at least one data signal path to exchange read data or write data between the requester and the completer; and at least one tag signal path, provided in parallel with the at least one data signal path, to exchange address tags or allocation tags between the requester and the completer.

Abstract: A requester issues a request specifying a target address indicating an addressed location in a memory system. A completer responds to the request. Tag error checking circuitry performs a tag error checking operation when the request issued by the requester is a tag-error-checking request specifying an address tag. The tag error checking operation comprises determining whether the address tag matches an allocation tag stored in the memory system associated with a block of one or more addresses comprising the target address specified by the tag-error-checking request. The requester and the completer communicate via a memory interface having at least one data signal path to exchange read data or write data between the requester and the completer; and at least one tag signal path, provided in parallel with the at least one data signal path, to exchange address tags or allocation tags between the requester and the completer.

Abstract: A data processing apparatus (20) comprises address translation circuitry (40) to translate a first address into a physical address directly identifying a corresponding location in a data store, and a table (50) comprising one or more entries indexed by the physical address, wherein at least one of the entries specifies the first address from which the corresponding physical address was translated by the address translation circuitry (40).

Abstract: An apparatus (2) comprises processing circuitry (4) to perform speculative execution of instructions; a main cache storage region (30); a speculative cache storage region (32); and cache control circuitry (34) to allocate an entry, for which allocation is caused by a speculative memory access triggered by the processing circuitry, to the speculative cache storage region instead of the main cache storage region while the speculative memory access remains speculative. This can help protect against potential security attacks which exploit cache timing side-channels to gain information about allocations into the cache caused by speculative memory accesses.

Abstract: An apparatus comprises: an instruction decoder and processing circuitry. In response to a data structure processing instruction specifying at least one input data structure identifier and an output data structure identifier, the instruction decoder controls the processing circuitry to perform a processing operation on at least one input data structure to generate an output data structure. Each input/output data structure comprises an arrangement of data corresponding to a plurality of memory addresses. The apparatus comprises two or more sets of one or more data structure metadata registers, each set associated with a corresponding data structure identifier and designated to store address-indicating metadata for identifying the memory addresses for the data structure identified by the corresponding data structure identifier.

Abstract: An apparatus comprises processing circuitry to perform data processing and instruction decoding circuitry to decode instructions to control the processing circuitry to perform the data processing. The instruction decoding circuitry is responsive to a speculation barrier instruction to control the processing circuitry to prevent a subsequent operation, appearing in program order after the speculation barrier instruction, that has an address dependency on an earlier instruction preceding the speculation barrier instruction in the program order, from speculatively influencing allocations of entries in a cache. This provides protection against speculative cache-timing side-channel attacks.

Abstract: A data processing system for processing data comprising: ownership circuitry to enforce ownership rights of memory regions, a given more privileged state memory region having a given owning process specified from among a plurality of processes, said given owning process having exclusive rights to control access to said given memory region; and context switching circuitry responsive to receipt of an interrupt to trigger a context switch from a first active process to a second active process whereby one or more items of state for use in restarting said first process is saved to one or more context data memory regions owned by said first process and one or more items of state accessible to said second process and dependent upon processing by said first process is overwritten prior to commencing execution of said second process.

Abstract: A data processing system comprises ownership circuitry to enforce ownership rights of memory regions within a physical memory address space. A given memory region has a given owning process specified from among a plurality of processes and independently of privilege level. The given owning process has rights to control access to the given memory region. The given owning process designates the given memory region as one of: private to the given owning process and shared between the given owning process and at least one further source of memory access requests. A given owning process may deny access to the given memory region to a process having a greater level of privilege than the given owning process. Data stored within the given memory region may be destructively overwritten, and completion of the overwriting may be tracked by overwrite tracking hardware to ensure completion of the overwriting before the new owner obtains rights to control access.

Abstract: An apparatus 2 has instruction fusing circuitry 50 for fusing two or more instructions fetched from a data store to generate a fused instruction to be processed by processing circuitry 14. A move prefix instruction is provided which indicates to the instruction fusing circuitry 50 that the move prefix instruction can be fused with an immediately following data processing instruction without needing to compare registers specified by the move prefix instruction and the immediately following instruction. This enables the instruction fusing circuitry 50 to be implemented with reduced hardware and energy cost.

Abstract: There is provided an apparatus comprising processing circuitry to execute a transaction comprising a number of program instructions that execute to generate updates to state data, to commit the updates if the transaction completes without a conflict, and to generate trace control signals during execution of the number of program instructions. The processing circuitry uses at least one resource during execution of the program instructions. Transaction trace circuitry generates trace items in response to the trace control signals. In response to the trace control signals indicating that a change in a usage level of the at least one resource has occurred during execution of the program instructions, the transaction trace circuitry generates at least one trace item that indicates the usage level of the at least one resource.

Abstract: A data processing system provides a branch forward instruction (BF) which has programmable parameters specifying a branch target address to be branched to and a branch point identifying a program instruction following the branch forward instruction which, when reached, is followed by a branch to the branch target address.

Abstract: A data processing apparatus has processing circuitry with transactional memory support circuitry to support execution of a transaction using transactional memory. In response to an exception mask updating instruction which updates exception mask information to enable at least one subset of exceptions which was disabled at the start of processing of a transaction, the processing circuitry permits un-aborted processing of one or more subsequent instruction of the transaction that follow the exception mask update instruction.

Abstract: A data processing system (2) supports non-speculative execution of vector load instructions that perform at least one contingent load of a data value. Fault detection circuitry (26) serves to detect whether a contingent load is fault-generating contingent load or a fault-free contingent load. Contingent load suppression circuitry (28) detects and suppresses a fault-free contingent load that matches a predetermined criteria that may result in an undesired change of architectural state (undesired side-effect). Examples of such predetermined criteria are that the contingent load is to a non-memory device or that the contingent load will trigger a diagnostic response such as entry of a halting debug halting mode or triggering of a debug exception.