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Accessing a control register's content via inline assembly

Among the many fascinating registers on the x86_64 processor, there happen to be six control registers, named CR0 through CR4, and CR8. There's really no need to delve into detail regarding them; suffice it to say that they are crucial to system control. For the purpose of an illustrative example, let's consider the CR0 register for a moment. Intel's manual states: CR0—contains system control flags that control operating mode and states of the processor.

Intel's manuals can be downloaded conveniently as PDF documents from here (includes the Intel® 64 and IA-32 Architectures Software Developer's Manual, Volume 3 (3A, 3B and 3C): System Programming Guide): https://software.intel.com/en-us/articles/intel-sdm ...

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