by Ciro Santilli (@cirosantilli, 32)
The Linux Kernel reserves two zones of virtual memory:
  • one for kernel memory
  • one for programs
The exact split is configured by CONFIG_VMSPLIT_.... By default:
  • on 32-bit:
    • the bottom 3/4 is program space: 00000000 to BFFFFFFF
    • the top 1/4 is kernel memory: C0000000 to FFFFFFFF, like this: 
      ------------------ FFFFFFFF
Kernel
------------------ C0000000
------------------ BFFFFFFF


Process


------------------ 00000000
  • on 64-bit: currently only 48-bits are actually used, split into two equally sized disjoint spaces. The Linux kernel just assigns:
    • the bottom part to processes 00000000 00000000 to 008FFFFF FFFFFFFF
    • the top part to the kernel: FFFF8000 00000000 to FFFFFFFF FFFFFFFF, like this:
      ------------------ FFFFFFFF
Kernel
------------------ C0000000


(not addressable)


------------------ BFFFFFFF
Process
------------------ 00000000
Kernel memory is also paged.

Ancestors

  1. Linux kernel usage
  2. x86 Paging Tutorial
  3. x86
  4. List of instruction set architectures
  5. Instruction set architecture
  6. Computer hardware
  7. Computer
  8. Information technology
  9. Area of technology
  10. Technology
  11. Index

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