DSO: library or PIE

[Kirill A. Shutemov]

Is there any easy way to detect whether DSO is PIE?

I only know about tricky heuristic:

http://git.altlinux.org/people/ldv/packages/rpm.git?p=rpm.git;a=blob;f=sc...

-- 
 Kirill A. Shutemov

[Roland McGrath]

>  Is there any easy way to detect whether DSO is PIE? 
A PIE's dynamic section (SHT_DYNAMIC/PT_DYNAMIC) has a DT_DEBUG entry.
e.g. eu-readelf -d FILE | awk '$1 == "DEBUG" { exit 0 } END { exit 1 }'


Thanks,
Roland

[Kirill A. Shutemov]

On Fri, Nov 12, 2010 at 02:30:03PM -0800, Roland McGrath wrote:
>  > Is there any easy way to detect whether DSO is PIE?
>  
>  A PIE's dynamic section (SHT_DYNAMIC/PT_DYNAMIC) has a DT_DEBUG entry.
>  e.g. eu-readelf -d FILE | awk '$1 == "DEBUG" { exit 0 } END { exit 1 }'
Thanks. It seems works.

Does it specified in some spec or GNU ld just work so?

-- 
 Kirill A. Shutemov

[Roland McGrath]

>  Does it specified in some spec or GNU ld just work so? 
PIE is not part of any formal specification.  
It is a use already permitted by the generic ELF specification.

The essential meaning of a PIE is that it is an ET_DYN object that has an
e_entry address that works normally.  

The presence of a DT_DEBUG is a necessary feature for the well-specified
techniques for debugging dynamically-linked executables to work normally.
Hence, a PIE has a DT_DEBUG.

Since PIE is a GNU invention, what we say it means is what the
specification is.  We say it's an ET_DYN file with a DT_DEBUG entry.


Thanks,
Roland