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Index > Compiler Internals > [bug] EIP-relative addressing cannot get assembled

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MazeGen



Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia
MazeGen
While going back from Kraków with vid, playing with fasm, I noticed that fasm doesn't support EIP-relative addressing.

If I try to assemble the following,
Code:
mov cl,[eip]    

I get
Quote:
error: undefined symbol

It should get assembled to:
Code:
DB 0x67, 0x8A, 0x0D, 0x00, 0x00, 0x00, 0x00    


This addressing is not well documented and it is never referred as "EIP-relative" addressing, but in fact, it is. There are two quotes from the manuls:
AMD wrote:

RIP-relative addressing is enabled by 64-bit mode, not by a 64-
bit address-size. Conversely, use of the address-size prefix
(“Address-Size Override Prefix” on page 6) does not disable
RIP-relative addressing. The effect of the address-size prefix is
to truncate and zero-extend the computed effective address to
32 bits, like any other addressing mode.

Intel wrote:
RIP-relative addressing is enabled by 64-bit mode, not by a 64-bit address-size. The use of the
address-size prefix does not disable RIP-relative addressing. The effect of the address-size
prefix is to truncate and zero-extend the computed effective address to 32 bits.
Post 01 Oct 2006, 20:33
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7756
Location: Kraków, Poland
Tomasz Grysztar
Added. Wink
Post 01 Oct 2006, 21:33
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MazeGen



Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia
MazeGen
Oh how quick you are Smile
Post 01 Oct 2006, 21:51
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
we should have found this earlier... i wanted some real-time streamed FASM coding Smile
Post 01 Oct 2006, 22:12
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