The VAX/VMS Address Space

• The code segment never begins at page 0. This page, instead, is marked inaccessible, in order to provide some support for detecting null-pointer accesses.
• the “same” kernel structures are mapped into each user address space.

The Linux Address Space

• Kernel Logical Addresses normal virtual address space of the kernel, allocated by kmalloc
  • Unlike most other memory in the system, kernel logical memory cannot be swapped to disk.
  • there is a direct mapping between kernel logical addresses and the first portion of physical memory.
• Kernel Virtual Addresses allocated by vmalloc
  • usually not contiguous
  • easier to allocate as a result, and thus used for large buffers where finding a contiguous large chunk of physical memory would be challenging.