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Index > Main > how to jmp far to Long Mode segment?

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fonolite



Joined: 14 Dec 2005
Posts: 32
fonolite
I set up compatibility mode with AMD64 cpu.

I checked LMA=1.
This is compatibility mode.(PML4 paging and LME=1)

I tested as below.
RM16 -> PM16 ->(jmp far)-> PM32 segment (CS.L=0 & CS.D=1)

jmp far FWORD [di] (indirect jmp far is OK!, offset & selector)


But, changed CS.L=1 & CS.D=0 (long mode).

jmp far to PM64 is illegal. it reboots.

I tried direct jmp far such as db 66h, 0EAh, dd offset, dw selector
is illegal, too.


Compatibility mode is OK, but I can't jump to 64bit long mode segment.

What is my problem? Anyone help?
Post 16 Jan 2006, 06:40
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Madis731



Joined: 25 Sep 2003
Posts: 2140
Location: Estonia
Madis731
I think that this topic fits here because of the reason its not any certain OS, but we have a different section for these. Maybe if this topic would be moved to OS, then it would attract the attention of some guys there. I don't know any other way Smile
Post 16 Jan 2006, 07:44
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fonolite



Joined: 14 Dec 2005
Posts: 32
fonolite
OK, I post it again in OS construction section.
Post 16 Jan 2006, 08:13
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fonolite



Joined: 14 Dec 2005
Posts: 32
fonolite
Hi, I made it by myself. Shocked

Entering long mode, the initial base of code segment descriptor becomes zero.

There is no segmentation in long mode. Only flat model.

I re-designed cs64 descriptor with base 0.

It works fine. Really glad to me. Very Happy
Post 16 Jan 2006, 11:41
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CodeWorld



Joined: 15 Nov 2003
Posts: 69
CodeWorld
Hi fonolite!

Can you send me example with going in long mode, please?

Thanks!(codeworld<@>yandex.ru)

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Post 17 Jan 2006, 07:16
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