about x86 protected mode

well,we only find 2 byte display of segment register in OD, but in fact, the segment register size is 96bit at least. and the protected mode is on segment registers.

there are some data structures very importent:

gdt,idt

gdt→segment descriptor(tss task state segment use it)

idt→ gate descriptor( operating system code use dpl in this to judge it have the right privilege or not)

there are too many rules to make it up. but they r not about the functions, so it is hard to understand, but interesting.

if you just reverse the operating system, you cant understand it. meanwhile you have to know how the cpu works.

so, segmentation and paging is the spirit of the protected mode.

由於看了一些英文資料，因爲慣性吧，用英文表達了一段本身的思考。

相對X86，ARM的尋址方式更像是實模式，至於多任務下的數據保護，由OS來完成。

arm暫時先無論了，到作arm沙箱的時候再研究吧。

to be continue......