Abstract: A microprocessor is provided with a method for decrypting encrypted instruction data into plain text instruction data and securely executing the same. The microprocessor includes a master key register file comprising a plurality of master keys. Selection logic circuitry in the microprocessor selects a combination of at least two of the plurality of master keys. Key expansion circuitry in the microprocessor performs mathematical operations on the selected master keys to generate a decryption key having a long effective key length. Instruction decryption circuitry performs an efficient mathematical operation on the encrypted instruction data and the decryption key to decrypt the encrypted instruction data into plain text instruction data.

Abstract: An apparatus for generating a decryption key for use to decrypt a block of encrypted instruction data being fetched from an instruction cache in a microprocessor at a fetch address includes a first multiplexer that selects a first key value from a plurality of key values based on a first portion of the fetch address. A second multiplexer selects a second key value from the plurality of key values based on the first portion of the fetch address. A rotater rotates the first key value based on a second portion of the fetch address. An arithmetic unit selectively adds or subtracts the rotated first key value to or from the second key value based on a third portion of the fetch address to generate the decryption key.

Abstract: An apparatus providing for a secure execution environment is presented. The apparatus includes a microprocessor and a secure non-volatile memory. The a microprocessor is configured to execute non-secure application programs and a secure application program, where the non-secure application programs are accessed from a system memory via a system bus. The microprocessor has a plurality of timers which are visible and accessible only by the secure application program when executing in a secure execution mode. The secure non-volatile memory is coupled to the microprocessor via a private bus and is configured to store the secure application program in encrypted form. Transactions over the private bus between the microprocessor and the secure non-volatile memory are isolated from the system bus, the system memory, and corresponding system bus resources within the microprocessor.

Abstract: A microprocessor includes a storage element having a plurality of locations each storing decryption key data associated with an encrypted program. A control register field (may be x86 EFLAGS register reserved field) specifies a storage element location associated with a currently executing encrypted program. The microprocessor restores from memory to the control register a previously saved value of the field in response to executing a return from interrupt instruction. A fetch unit fetches encrypted instructions of the currently executing encrypted program and decrypts them using the decryption key data stored the storage element location specified by the restored field value. A kill bit associated with each storage element location may be employed if the location is clobbered because more encrypted programs are multitasked than available locations in the storage element, in which case an exception is generated to re-load the clobbered decryption key data in response to the return from interrupt instruction.

Abstract: An instruction translator translates a conditional store instruction (specifying data register, base register, and offset register of the register file) into at least two microinstructions. An out-of-order execution pipeline executes the microinstructions. To execute a first microinstruction, an execution unit receives a base value and an offset from the register file and generates a first result as a function of the base value and offset. The first result specifies the memory location address. To execute a second microinstruction, an execution unit receives the first result and writes the first result to an allocated entry in the store queue if the condition flags satisfy the condition (the store queue subsequently writes the data to the memory location specified by the address), and otherwise kills the allocated store queue entry so that the store queue does not write the data to the memory location specified by the address.

Abstract: An instruction translator receives a conditional load/store instruction that specifies a condition, destination/data register, base register, offset source, and memory addressing mode. The instruction instructs the microprocessor to load data from a memory location into the destination register (conditional load) or store data to the memory location from the data register (conditional store) only if the condition flags satisfy the condition. The offset source specifies whether the offset is an immediate value or a value in an offset register. The addressing mode specifies whether the base register is updated when the condition flags satisfy the condition. The instruction translator translates the conditional load instruction into a number of microinstructions, which varies as a function of the offset source, addressing mode, and whether the conditional instruction is a conditional load or store instruction.

Abstract: A fetch unit fetches a sequence of blocks of encrypted instructions of an encrypted program from an instruction cache at a corresponding sequence of fetch address values. While fetching each block of the sequence, the fetch unit generates a decryption key as a function of key values and the corresponding fetch address value, and decrypts the encrypted instructions using the generated decryption key by XORing them together. A switch key instruction instructs the microprocessor to update the key values in the fetch unit while the fetch unit is fetching the sequence of blocks. The fetch unit inherently provides an effective decryption key length that depends upon the function and amount of key values used. Including one or more switch key instructions within the encrypted program increases the effective decryption key length up to the encrypted program length.

Abstract: A microprocessor includes an architected register having a bit (may be x86 EFLAGS register reserved bit) set by the microprocessor. A fetch unit fetches encrypted instructions from an instruction cache and decrypts them (via XOR) prior to executing them, in response to the microprocessor setting the bit. The microprocessor saves the bit value to a stack in memory and then clears the bit in response to receiving an interrupt. The fetch unit fetches unencrypted instructions from the instruction cache and executes them without decrypting them after the microprocessor clears the bit. The microprocessor restores the saved value from the stack in memory to the bit in the architected register (and in one embodiment, also restores decryption key values) in response to executing a return from interrupt instruction. The fetch unit resumes fetching and decrypting the encrypted instructions in response to determining that the restored value of the bit is set.

Abstract: A fetch unit (a) fetches a block of instruction data from an instruction cache of the microprocessor; (b) performs an XOR on the block with a data entity to generate plain text instruction data; and (c) provides the plain text instruction data to an instruction decode unit. In a first instance the block comprises encrypted instruction data and the data entity is a decryption key. In a second instance the block comprises unencrypted instruction data and the data entity is Boolean zeroes. The time required to perform (a), (b), and (c) is the same in the first and second instances regardless of whether the block is encrypted or unencrypted. A decryption key generator selects first and second keys from a plurality of keys, rotates the first key, and adds/subtracts the rotated first key to/from the second key, all based on portions of the fetch address, to generate the decryption key.

Abstract: A microprocessor includes a model specific register (MSR) having an address, fuses manufactured with a first predetermined value, and a control register. The microprocessor initially loads the first predetermined value from fuses into the control register. The microprocessor also receives a second predetermined value into the control register from system software of a computer system comprising the microprocessor subsequent to initially loading the first predetermined value into the control register. The microprocessor prohibits access to the MSR by an instruction that provides a first password generated by encrypting a function of the first predetermined value and the MSR address with a secret key manufactured into the first instance of the microprocessor and enables access to the MSR by an instruction that provides a second password generated by encrypting the function of the second predetermined value and the MSR address with the secret key.

Abstract: A branch target address cache (BTAC) caches history information associated with branch and switch key instructions previously executed by a microprocessor. The history information includes a target address and an identifier (index into a register file) for identifying key values associated with each of the previous branch and switch key instructions. A fetch unit receives from the BTAC a prediction that the fetch unit fetched a previous branch and switch key instruction and receives the target address and identifier associated with the fetched branch and switch key instruction. The fetch unit also fetches encrypted instruction data at the associated target address and decrypts (via XOR) the fetched encrypted instruction data based on the key values identified by the identifier, in response to receiving the prediction. If the BTAC predicts correctly, a pipeline flush normally associated with the branch and switch key instruction is avoided.

Abstract: A microprocessor includes a storage element that stores decryption key data and a fetch unit that fetches and decrypts program instructions using a value of the decryption key data stored in the storage element. The fetch unit fetches an instance of a branch and switch key instruction and decrypts it using a first value of the decryption key data stored in the storage element. If the branch is taken, the microprocessor loads the storage element with a second value of the decryption key data for subsequent use by the fetch unit to decrypt an instruction fetched at a target address specified by the branch and switch key instruction. If the branch is not taken, the microprocessor retains the first value of the decryption key data in the storage element for subsequent use by the fetch unit to decrypt an instruction sequentially following the branch and switch key instruction.

Abstract: A microprocessor includes a memory that stores an exception handler to handle an exception condition. The exception handler is a non-user program private to the microprocessor and includes a conditional branch instruction. A first fetch unit fetches instructions of a user program that includes a user program instruction that causes the exception condition. An execution unit executes the user program instructions fetched by the first fetch unit and executes instructions of the exception handler. The execution unit also saves a state in response to detecting the exception condition caused by the user program instruction. A second fetch unit fetches the exception handler instructions from the memory and resolves the conditional branch instruction based on the saved state without sending the conditional branch instruction to the execution unit to resolve the conditional branch instruction.

Abstract: A microprocessor instruction translator translates a conditional load instruction into at least two microinstructions. An out-of-order execution pipeline executes the microinstructions. To execute a first microinstruction, an execution unit receives source operands from the source registers of a register file and responsively generates a first result using the source operands. To execute a second the microinstruction, an execution unit receives a previous value of the destination register and the first result and responsively reads data from a memory location specified by the first result and provides a second result that is the data if a condition is satisfied and that is the previous destination register value if not. The previous value of the destination register comprises a result produced by execution of a microinstruction that is the most recent in-order previous writer of the destination register with respect to the second microinstruction.

Abstract: An apparatus providing for a secure execution environment. The apparatus includes a microprocessor and a secure non-volatile memory. The microprocessor is configured to execute non-secure application programs and a secure application program, where the non-secure application programs are accessed from a system memory via a system bus. The secure non-volatile memory is coupled to the microprocessor via a private bus. The secure non-volatile memory is configured to store the secure application program, where transactions over the private bus between the microprocessor and the secure non-volatile memory are isolated from the system bus and corresponding system bus resources within the microprocessor.

Abstract: An apparatus including a microprocessor, a system memory, and a secure non-volatile memory. The microprocessor executes non-secure application programs and a secure application program. The secure application program is executed in a secure execution mode. The microprocessor has secure watchdog logic that monitors environmental attributes corresponding to the microprocessor and to the secure application program, and that transfers program control to one of a plurality of event handlers within the secure application program. The system memory has non-secure application programs stored therein. The secure non-volatile memory is coupled to the microprocessor via a private bus.

Abstract: A microprocessor includes an MSR and fuses. The microprocessor encounters an instruction requesting access to the MSR and specifying the MSR address, performs a function of the specified MSR address and a value read from the fuses to generate a first result, encrypts the first result with a secret key to generate a second result, compares the second result with an instruction-specified password, and allows the instruction to access the MSR if the second result matches the password and otherwise denies access MSR. Manufacturing subsequent instances of the microprocessor with a different fuse value effectively revokes the password. Alternatively, a control register of the microprocessor may be written by system software to override the fuse value and thereby revoke the password. The function may be XOR or concatenation, the encryption may be AES, and the secret key is externally invisible.

Abstract: A microprocessor includes a first instruction translator that translates an instruction of an instruction set architecture of a microprocessor. The instruction may specify a first form that writes its result to a destination register or a second form that writes its result to memory. The first instruction translator generates, in response to encountering an instance of the instruction, an indication of whether the instance is of the first form or the second form. A microcode memory stores a tail instruction as part of a microcode routine invoked in response to encountering the instance of the instruction. A second instruction translator receives the tail instruction from the microcode memory and the indication and responsively generates a first micro-operation that writes the result to the destination register if the indication specifies the first form or a second micro-operation that completes a write of the result to memory if the indication specifies the second form.

Abstract: A microprocessor includes a pipeline of stages for processing instructions and first and second types of conditional branch instruction includable by a program. The microprocessor makes a prediction of conditional branch instructions of the first type and flushes the pipeline of instructions if the prediction is subsequently determined to be incorrect, thereby incurring a branch misprediction penalty related to processing of conditional branch instructions of the first type. The microprocessor always correctly resolves conditional branch instructions of the second type without making a prediction of conditional branch instructions of the second type, thereby avoiding ever incurring a branch misprediction penalty related to processing of conditional branch instructions of the second type.

Abstract: An apparatus including a microprocessor and an external crystal. The microprocessor executes non-secure application programs and a secure application program, where the secure application program comprises instructions from a host architecture instruction set, and where the non-secure application programs are accessed from a system memory via a system bus and the secure application program is accessed from a secure non-volatile memory via a private bus coupled to the microprocessor. The microprocessor has a secure real time clock that provides a persistent time, where the secure real time clock is only visible and accessible by the secure application program when the microprocessor is executing in a secure mode. The external crystal is coupled to the secure real time clock within the microprocessor and is configured to cause an oscillator within the secure real time clock to generate an oscillating output voltage that is proportional to the frequency of the external crystal.