10-04-2017, 07:26 PM
INSIDE THE LINUX KERNEL
[attachment=17626]
WHAT IS A KERNEL? (1/2)
it s a program that runs in Kernel Mode
CPUs run either in Kernel Mode or in User Mode
when in User Mode, some parts of RAM can t be addressed, some instructions can t be executed, and I/O ports can t be accessed
when in Kernel Mode, no restriction is put on the program
IS AN INSTRUCTION REALLY FAULTY?
faulty instructions may occur for two distinct reasons:
programming error
deferred allocation of some kind of resource
the kernel must be able to identify the reason that caused the exception
WHY IS A KERNEL SO COMPLEX?
large program with many entry points
must offer disk caching to lower average disk access time
must support run nested kernel invocations --> must run with the interrupts enabled most of the time
must be updated quite frequently to support new hardware circuits and devices