Re: library fuction calls

[Dwivedi Ajay kumar <ajayd@xxxxxxxxxx>]

On Thu, 22 Feb 2001, Raja Subramanian wrote:

> If your program that you are trying to work with is not available in source,
> and you want to replace the connect calls with your own - you need a library
> interposer. Have a look at 
> http://www.unixinsider.com/swol-09-2000/swol-0929-interposers.html
> for details. This takes advantage of dynamic linking, but does not always work
> (on setuid progs for example).
> 
	Thanks a lot :). This is almost what I wanted. But still there is
a small problem. I tried the malloc interposer from the site. I feel it is
written for solaris cc. So here are my questions (again :)

1. It says cc -o malloc_interposer.so -G -Kpic malloc_interposer.c 
  Now gcc does not have -G and -K option. I feel one of them is for
  -shared (which one and what about the other)

2. Compiled with gcc -shared -o malloc_interposer.so malloc_interposer.c
   and then setting the LD_PRELOAD to the shared lib. Now "ls" gives the
   problem:
   <ajayd:tconn>/bin/ls
   ls: error in loading shared libraries:
    /home/ajayd/tconn/malloc_interposer.so: undefined symbol: dlsym

   However it is working fine for echo
   <ajayd:tconn>/bin/echo
   malloc(176) is called
   malloc(176) is called 
   malloc(52) is called
   <snipped>
   
   It is also working with vi,date etc.. but not ls

	Any ideas ?

PS: I tested the code on a solaris machine, and it worked for everything.

-- 

#!!!	If anything can go wrong, _FIX_ it. (To hell with MURPHY)
	
						Ajay kumar Dwivedi
						 ajayd@xxxxxxxxxx