Messages in this thread |  | | Date | Sat, 22 Sep 2001 18:01:39 -0400 | From | Brian Gerst <> | Subject | Re: Global Offset Table question.. |
| |
Dave Airlie wrote: > > I've been trying to get dynamic loading on the Linux/VAX project going, > and I've having trouble with the Global Offset Table and how it magically > gets in to the ebx register on x86.. where is this done? > > I think I've looked at the kernel, gcc, binutils, ld.so 1.9, glibc 2.2.3 > and can't see exactly where this happens... > > Anyone care to enlighten my poor brain... > > Thanks, > Dave. >
I assume you are talking about position independant code? On the x86, the only instructions that can use IP-relative addressing are branch instructions. This asm fragment shows how it's done:
call 1f 1: popl %ebx addl $(GOT - 1b), %ebx
If the Vax has better support for IP-relative addressing, this may be easier. On recent x86 procesors, the above code will screw up the call/return cache (branch prediction) and cause performance penalties.
-- Brian Gerst - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |