About hacking libc

Carlos O'Donell carlos@systemhalted.org
Tue Apr 23 20:35:00 GMT 2013


On Tue, Apr 23, 2013 at 2:37 PM, Xinyang Ge <xxg113@cse.psu.edu> wrote:
> I am a graduate student at Penn State and currently doing some experiments
> on glibc and hoping to put some hooks inside open() library call. However,
> as I examined the source code, I noticed these system call wrappers are
> dynamically generated at compile time from syscall-template.S. I renamed the
> wrapper's name (e.g., from open() to _open()) in syscalls.list and add
> another layer of wrapper to add code beyond _open().

That sounds reasonable.

> Does anyone know some more elegant way in doing the same thing? Thanks a
> lot!

Write a library, preload it, and within your open function dlopen libc
and call the
real open?

Use systemtap to instrument the syscall on the kernel side?

Cheers,
Carlos.



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