Hi, there:
I am a beginer on linux kernel hacking. I am reading this setup.S code
and was puzzled with the sequence:
The kernel loader first switches from real mode into protected mode, and
then moves the loader code from 0x100 to 0x1000.
However, in the linux kernel hacker's guide, it is said the loader first
moves itself from 0x10000 to 0x1000, and then switches into protected
mode. http://kernelnotes.org/guides/KHG/HyperNews/get/tour/tour.html
What I am missing here. I attached a piece of code from setup.S at the
end of email in case you wanna take a look at it.
Fei Liu
starting from setup.S:447.............
seg cs
cmp realmode_swtch,#0
jz rmodeswtch_normal
seg cs
callf far * realmode_swtch
jmp rmodeswtch_end
rmodeswtch_normal:
push cs
call default_switch
rmodeswtch_end:
! we get the code32 start address and modify the below 'jmpi'
! (loader may have changed it)
seg cs
mov eax,code32_start
seg cs
mov code32,eax
! Now we move the system to its rightful place
! ...but we check, if we have a big-kernel.
! in this case we *must* not move it ...
seg cs
test byte ptr loadflags,#LOADED_HIGH
jz do_move0 ! we have a normal low loaded zImage
! we have a high loaded big kernel
jmp end_move ! ... and we skip moving
do_move0:
-
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