Re: x86-64 asm question
Re: x86-64 asm question
- Subject: Re: x86-64 asm question
- From: Cyrus Harmon <email@hidden>
- Date: Tue, 5 Sep 2006 08:05:55 -0700
Thanks Eric and Scott,
That seems to fix things.
Cyrus
On Sep 4, 2006, at 8:22 PM, Eric Albert wrote:
Scott is right; you do have to make this a RIP-relative reference.
Mac OS X doesn't currently support any non-PIC code models for
x86-64. We don't have any plans to do that in the near term,
either, since non-PIC code wouldn't have any significant
performance benefit for Mac OS X today.
The correct reference here is
mov _all_threads@GOTPCREL(%rip), %rax
If _all_threads is defined in the same translation unit (i.e.
within this .s file), you can write this instead:
mov _all_threads(%rip), %rax
Hope this helps,
Eric
On Sep 4, 2006, at 5:06 PM, Cyrus Harmon wrote:
The linux version of gas (with .global, not just .globl) seems to
handle this code fine. Is it implicitly doing some sort of IP-
relative indexing? Is there something weird about Apple's
assembler going on here? I'm willing to believe that I need to do
some %rip relative addressing, I'm just not convinced that the way
I'm trying to do it is giving me the right results (or, really,
what those should look like).
I tried something similar before, and got it to compile, but
wasn't sure if that was the right approach. Some docs on 1) if
this needs to be done realtive to %rip, and 2) how to properly do
so, would be great.
Thank,
Cyrus
On Sep 4, 2006, at 4:56 PM, Scott Lamb wrote:
On Sep 4, 2006, at 3:57 PM, Cyrus Harmon wrote:
So, using gas I'm trying to port some x86 assembly code that
refers to an external symbol:
.text
.globl _all_threads
...
...
mov _all_threads,%rax
...
the error message I get is:
x86-64-assem.S:133:32-bit absolute addressing is not supported
for x86-64
That works on x86 (well, with �x, of course), but I can't seem
to figure out how to do this on x86-64, or any relevant docs on
Apple's x86-64 assembler.
IIRC, x86_64 uses IP-relative addresses. And in a x64_64-linux
project of mine, I found this line:
movl sigsafe_key_(%rip), �i
--
Scott Lamb <http://www.slamb.org/>
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