Importance

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Abstract

A protection circuit operates in a user or kernel mode. In the kernel mode, a kernel memory is accessible only by a secure kernel. A processor is reset if a security violation occurs, such as by attempting to access kernel memory in user mode. A program fetch supervisor circuit compares addresses to a predetermined address to determine if a security violation has occurred. A data fetch supervisor circuit compares data addresses to a protected memory address range. A security violation occurs if the data address is in protected memory, which resets the processor. A method of kernel mode protection includes fetching a program opcode or data operand. If the program opcode or data operand is from kernel memory and the processor is in user mode, the processor is reset. If an opcode is fetched from user memory while in kernel mode, the processor reverts to user mode.

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First Claim