how to add a new glibc symbol ?

[Net Llama!]

On 12/03/03 02:27, Roger Oberholtzer wrote:

> On Wed, 3 Dec 2003 09:19:48 +0100
> Roger Oberholtzer <roger at opq.se> wrote:
> 
> 
>>
>>The Linux program loader will load a DSO (libxx.so) specified in an
>>environment variable when an application starts. This would allow you to
>>make a dummy library to provide the missing label. I always thought this
>>was both a neat and a dangerous feature. I believe it it the very first
>>thing loaded, so it should be available to libc.
>>
>>Let me know if you are interested and I will relocate the name of the
>>environment variable. It was something like LD_PRELOAD=libxyx.so.
> 
> 
> Oddly, my memory was right. Here is a simple intro:
> 
> 	http://www.uberhip.com/people/godber/interception/html/slide_5.html
> 

OK, i tried this, but either i'm not understanding it, or its not working.

I first did:
gcc -fPIC -rdynamic -g -c -Wall ctype_b.c

which gave me ctype_b.o (no errors, or warnings).  Next I did:
export LD_PRELOAD=~/ctype_b.o

and then I tried to configure rpm again, but it died immediately:
/bin/sh: error while loading shared libraries: /root/ctype_b.o: ELF 
file's phentsize not the expected size

I googled a bit to figure out what a phentsize is, and found this 
explanation:
#####
phentsize is a field in the ELF linking header that specifies the size 
in bytes of one entry in the file's program header table.
#####
The program header table is evidently optional according to the little 
bit I've been able to find on it.  But i don't really understand what 
that all means, or why its blowing up.

Any other ideas?

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
L. Friedman                       	       netllama at linux-sxs.org
Linux Step-by-step & TyGeMo: 		    http://netllama.ipfox.com

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