Linux process 5--real mode and protected mode

The early inter chip only supported 1MB memory, using real mode, with 16bit address. Later, as technology progressed, more memory could be accessed

Protected mode chip with 32bit address. In order to maintain compatibility with the front chip, the Inter supports both of these modes. When the chip starts, the default is in real mode,

Then the OS controls into protected mode.

The biggest difference between real mode and protected mode:

Real mode, the program address is the actual physical address, can access any address space, so that different processes may access to other process programs, causing

Critical error.

Protected mode, the program address is a virtual address, and then the OS system manages memory access so that each process can access only the physical

Memory space, ensuring the security of the program. For example, Linux system address access takes the paging mechanism, and when the program is loaded, the process assigned by the OS can access

Physical page space and set the page Catalog entries and page table entries to ensure that the program runs correctly. This program runtime address is indirectly managed by the OS to prevent

Processes interact with each other, all of which are guaranteed by OS stability.

　　

Linux process 5--real mode and protected mode