Linear Address Space

Reference: http://www.chudov.com/tmp/LinuxVM/html/understand/node30.html


The linear address space is split into two parts, the userspace part which potentially changes with each full context switch and the kernel address space which remains constant.
The location of the split is determined by the value of PAGE_OFFSET which is at 0xC0000000 on the x86.

8MiB (the amount of memory addressed by two PGDs5.3) is reserved at PAGE_OFFSET for loading the kernel image to run. It is placed here during kernel page tables initialisation as discussed in Section 4.6.1.

mem_map: 用來存放struct page的array