INTRO. TO MODERN MICROPROCESSORS

modern CPUs have at least 2 "states" (2 modes of operation):

• priviliged (supervisory):
  • instructions that deal with hardware management
  • writing directly to I/O
  • accessing memory management hardware
  • controlling the hardware that enforces it
  • o.s. abstraction; suid root
  • interrupt management (e.g. when CPU generates an exception, CPU is switched into privileged mode to handle it...)
• non privileged (user):
  • proper subset of privileged
  • if you try to access non-assigned memory then microprocessor will trap it
  • o.s.: all traps are handled by kernel
  • o.s.: usually kernel assigns memory to processes