Abstract: A processor changes the mapping of register addresses to registers dependent on an instruction field. In one particular embodiment, the mapping may be changed for byte addressing of the registers. A register mapping in which each register address maps to either the least significant byte or the next least significant byte of a subset of the registers may be supported, as well as a register mapping in which each register address maps to the least significant byte of each register, in one implementation. In one particular implementation, the instruction field may be a prefix field (e.g. a prefix byte). The processor may provide for uniform addressing of registers (e.g. byte addressing of the registers) responsive to a prefix field, in other embodiments, irrespective of the addressing provided if the prefix field is not included, or is encoded differently than the encoding which results in the uniform addressing.

Abstract: A central processing unit (CPU) is described including a register file and an execution core coupled to the register file. The register file includes a standard register set and an extended register set. The standard register set includes multiple standard registers, and the extended register set include multiple extended registers. The execution core fetches and executes instructions, and receives a signal indicating an operating mode of the CPU. The execution core responds to an instruction by accessing at least one extended register if the signal indicates the CPU is operating in an extended register mode and the instruction includes a prefix portion including information needed to access the at least one extended register. The standard registers may be general purpose registers of a CPU architecture associated with the instruction. The number of extended registers may be greater than the number of general purpose registers defined by the CPU architecture.

Abstract: A processor executes a system call instruction. The processor includes at least two registers in which target addresses may be stored, and selects the target address from one of the registers responsive to the operating mode. Different target addresses may be programmed into the registers, and thus the operating mode of the code sequence may be indicated by which target address is selected.

Abstract: A processor supports at least two different state save formats. Each format stores state in the form that the state exists in one or more operating modes of the processor. The operand size of the state save and state restore instructions may be used to indicate which state format is assumed by the processor during execution of the state save and state restore instructions. In one implementation, the processor implements a processor architecture compatible with the x86 architecture with enhancements to support 64 bit addressing and processing. In modes in which 64 bit addressing is supported, segmentation is not used. In 32 bit and 16 bit modes, segmentation is used. Thus, the address of a floating point instruction and/or operand may be indicated by a segment selector or pointer or by a pointer only.

Abstract: A computer system includes a processor which may initialize a secure execution mode by executing a security initialization instruction. Further, the processor may operate in the secure execution mode by executing a secure operating system code segment. The computer system also includes an input/output (I/O) interface coupled to the processor via an I/O link. The I/O interface may receive transactions performed as a result of the execution of the security initialization instruction. The transactions include at least a portion of the secure operating system code segment. The I/O interface may also determine whether the processor is a source of the transactions. The computer system further includes a security services processor coupled to the I/O interface via a peripheral bus. The I/O interface may convey the transactions to the security services processor dependent upon determining that the processor is the source of the transactions.

Abstract: The initialization of a computer system including a secure execution mode-capable processor includes storing a secure operating system code segment loader to a plurality of locations corresponding to a particular range of addresses within a system memory. The method also includes executing a security initialization instruction. Executing the security initialization instruction may cause several operations to be performed including transmitting a start transaction including a base address of the particular range of addresses. In addition, executing the security instruction may also cause another operation to be performed including retrieving the secure operating system code segment loader from the system memory and transmitting the secure operating system code segment loader for validation as a plurality of data transactions.

Abstract: A processor changes the mapping of register addresses to registers dependent on an instruction field. In one particular embodiment, the mapping may be changed for byte addressing of the registers. A register mapping in which each register address maps to either the least significant byte or the next least significant byte of a subset of the registers may be supported, as well as a register mapping in which each register address maps to the least significant byte of each register, in one implementation. In one particular implementation, the instruction field may be a prefix field (e.g. a prefix byte). The processor may provide for uniform addressing of registers (e.g. byte addressing of the registers) responsive to a prefix field, in other embodiments, irrespective of the addressing provided if the prefix field is not included, or is encoded differently than the encoding which results in the uniform addressing.

Abstract: A processor supports at least two different state save formats. Each format stores state in the form that the state exists in one or more operating modes of the processor. The operand size of the state save and state restore instructions may be used to indicate which state format is assumed by the processor during execution of the state save and state restore instructions. In one implementation, the processor implements a processor architecture compatible with the x86 architecture with enhancements to support 64 bit addressing and processing. In modes in which 64 bit addressing is supported, segmentation is not used. In 32 bit and 16 bit modes, segmentation is used. Thus, the address of a floating point instruction and/or operand may be indicated by a segment selector or pointer or by a pointer only.

Abstract: An apparatus is provided for providing security in a computer system. The apparatus comprises an address generator, a multi-level lookup table, and a cache. The address generator is adapted for producing an address associated with a memory location in the computer system. The multi-level lookup table is adapted for receiving at least a portion of said address and delivering security attributes stored therein associated with said address, wherein the security attributes are associated with each page of memory in the computer system. The cache is a high-speed memory that contains a subset of the information contained in the multi-level lookup table, and may be used to speed the overall retrieval of the requested security attributes when the requested information is present in the cache.

Abstract: A method and mechanism for performing an unconditional stack switch in a processor. A processor includes a processing unit coupled to a memory. The memory includes a plurality of stacks, a special mode task state segment, and a descriptor table. The processor detects interrupts and accesses a descriptor corresponding to the interrupt within the descriptor table. Subsequent to accessing the descriptor, the processor is configured to access an index within the descriptor in order to determine whether or not an interrupt stack table mechanism is enabled. In response to detecting the interrupt stack table mechanism is enabled, the index is used to select an entry in the interrupt stack table. The selected entry in the interrupt stack table indicates a stack pointer which is then used to perform an unconditional stack switch.

Abstract: A processor supports instruction pointer (IP) relative addressing in at least one operating mode of the processor. For example, in some implementations, IP relative addressing is supported in an operating mode or modes in which the address size is greater than 32 bits (e.g. up to 64 bits). In some embodiments, the displacement may be limited to less than the address size (e.g. 32 bits, in one implementation) when such operating modes are active. Code density may be higher than if the displacements were expanded, and flexibility in the placement of variables in memory may be achieved. For example, static variables may be placed in memory with flexibility, and IP relative addressing may be used to locate the static variables.

Abstract: A method and system for performing the method. a method is provided. The method includes executing an insecure routine and receiving a request from the insecure routine. The method also includes performing a first evaluation of the request in hardware, and performing a second evaluation of the request in a secure routine in software. The computer system includes a processor configurable to execute a secure routine and an insecure routine. The computer system also includes hardware coupled to perform a first evaluation of a request associated with the insecure routine. The hardware is further configured to provide a notification of the request to the secure routine. The secure routine is configured to perform a second evaluation of the request. The secure routine is further configured to deny a requested response to the request.

Abstract: A method and system for handling a security exception. The method includes creating a security exception stack frame in secure memory at a base address. The method also includes writing a faulting code sequence address and one or more register values into the security exception stack frame, and executing a plurality of security exception instructions.

Abstract: A mechanism for exception and interrupt handling in multithreaded multiprocessors is provided. The mechanism allows the handling of exceptions and interruptions in a multithreaded multiprocessor computer, while hiding the multiprocessor nature of the computer from the operating system. Generally, when an operating system is cognizant of the multiprocessor nature of a computer, additional overhead may be required when handling exceptions and interruptions. Due to the overhead involved in saving and restoring processing states, the performance of a processor may be significantly impacted. Additional circuitry is provided which allows the multiprocessor nature of the computer to be hidden from the operating system, while minimizing the overhead necessary for proper handling.

Abstract: A processor architecture containing multiple closely coupled processors in a form of symmetric multiprocessing system is provided. The special coupling mechanism allows it to speculatively execute multiple threads in parallel very efficiently. Generally, the operating system is responsible for scheduling various threads of execution among the available processors in a multiprocessor system. One problem with parallel multithreading is that the overhead involved in scheduling the threads for execution by the operating system is such that shorter segments of code cannot efficiently take advantage of parallel multithreading. Consequently, potential performance gains from parallel multithreading are not attainable. Additional circuitry is included in a form of symmetrical multiprocessing system which enables the scheduling and speculative execution of multiple threads on multiple processors without the involvement and inherent overhead of the operating system.

Abstract: A system and method for controlling access to privilege partitioned address space for a model specific register file. A superscalar microprocessor includes a plurality of model specific registers (MSRs). MSRs differ between various implementations of a microprocessor architecture. The MSRs are allocated to access regions within a MSR file. Each access region of the MSR file is assigned access attributes. The MSRs are allocated such that the access region and the access attributes of the MSRs are defined by the address of the MSRs. Access to the MSRs is controlled by comparing the address of the MSR to the current privilege level of the microprocessor. In one embodiment, a validity check circuit is used to control access to the MSRs. If an access is attempted to an MSR that cannot be accessed at the current microprocessor privilege level, access to the register is denied and an exception is generated. In one embodiment, an address checker may be used to verify whether an MSR address is within a valid range.

Abstract: A system and method for transparent handling of extended register states. A set of additional registers, or an extended register file, is added to the base architecture of a microprocessor. The extended register file includes two dedicated registers and a plurality of general-use registers. The extended register file is mapped to a region in main memory. One dedicated register of the extended register file stores the physical base address of the memory region. Another dedicated register of the extended register file is used to store bits to indicate the status of the extended register file. A set of extended instructions is implemented for transferring data to and from the extended register file.

Abstract: An interrupt descriptor cache for a microprocessor is provided which is configured to store interrupt information associated with a plurality of interrupt vectors. Prior to fetching interrupt information from a main memory of a computer system, the microprocessor searches the interrupt descriptor cache. If the interrupt information is stored therein, the address of the interrupt service routine is formed from the stored interrupt information instead of fetching the interrupt information from main memory. The interrupt descriptor cache is additionally configured to monitory memory accesses for updates to the interrupt information stored therein. If a memory location storing interrupt information is updated, then the interrupt descriptor cache invalidates any storage locations which may be storing the information.

Abstract: In a microprocessor system, a program counter circuit generates a program counter value that represents a retrieved instruction and that includes a more significant portion, a less significant portion, and a carry signal for use in determining a next program counter value. An execute program counter circuit generates an execute program counter value from the less significant program counter value and from the carry signal. The execute program counter value represents a program counter value of an executed instruction.

Abstract: A method and mechanism for performing an unconditional stack switch in a processor. A processor includes a processing unit coupled to a memory. The memory is configured to include a plurality of stacks, a special mode task state segment, and a descriptor table including a number of descriptors. The processor is configured to detect interrupts and access a descriptor corresponding to the interrupt within the descriptor table. Each of the descriptors in the descriptor table includes an index corresponding to entries in an interrupt stack table within the task state segment. Subsequent to accessing the descriptor corresponding to the interrupt, the processor is configured to access the index within the descriptor in order to determine whether or not an interrupt stack table mechanism is enabled. In response to detecting the interrupt stack table mechanism is enabled, the index is used to select an entry in the interrupt stack table.