Register a signal handler in _dl_start

[wuxi]

Hi

I am doing a research project on IA-64 and glibc-2.5. My goal is to 
instrument the program to enable whole-program taint tracking.

For that purpose, I need to register a special handler to handle SIGSEGV 
at the very start of any program, for I use unmapped area as the bitmap 
for taint tracking.

My problem is, when I hook signal handler at _dl_start (very start of 
the library, according to my study of code) to enable taint tracking for 
dynamic linker, the special signal handler seems not work - that is, 
when I run ld.so, it reports Segment fault directly without trapping 
into my signal handler. However, I dump the code and discover the hook 
function has been called before such access.

So, am I missing something here to register a signal handler for dynamic 
linker?

Thanks

yours sincerely

Andrew