Meaning
Access attributes assigned to specific blocks of physical or virtual memory dictate the read, write, and execute capabilities allowed for different software processes. This security mechanism, known as memory region permission, prevents application code from overwriting critical kernel data or executing non-executable buffers. Microprocessors enforce these rules at the hardware level during every instruction cycle.
Allocation Rule
Compilation toolchains and operating system kernels define the memory configuration of different software segments during the link phase. The build script assigns a strict memory region permission to the text section containing executable code, designating it as read-only and executable. This configuration prevents malicious software from modifying the core runtime instructions during execution.
Hardware Protection
Memory protection units evaluate every transaction on the system bus to confirm that the requesting peripheral has the correct authorization. If a task attempts to write to a block that lacks the appropriate memory region permission, the hardware generates a memory fault and halts the active process.
Dynamic Enforcement
Real-time systems adjust the access rights of memory pages when transitioning between secure and non-secure execution states. Multi-threaded applications rely on this dynamically adjusted memory region permission to isolate untrusted network drivers from the core system memory.
