This is the mail archive of the mailing list for the glibc project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: more prelink

On Sun, Sep 29, 2002 at 11:30:01PM +0200, Jakub Jelinek wrote:
> On Fri, Sep 27, 2002 at 11:39:06PM -0400, Jack Howarth wrote:
> > Jakub,
> >    I think I have stumbled over another issue with prelink that
> > could be problematic unless addressed. Currently the glibc srpms
> > are using a postinst script to prelink with the
> > --reloc-only flag so it is relinked to the specified base address.
> > If I do that on entropy with...
> > 
> > /usr/sbin/prelink --reloc-only=0x40000 /lib/
> I'm terribly sorry to say, but now that I think about it, --reloc-only
> for makes no sense on ppc/x86-64/sparc* etc. Sorry for
> forgotting about this.
> It speeds things up on REL or ELF_MACHINE_REL_RELATIVE arches only.
> ELF_MACHINE_REL_RELATIVE are those where R_*_RELATIVE relocs have the
> addend in *r_offset. ppc/x86-64/sparc* usually have zero there.
> Even if I changed back binutils to put addend to both r_addend and *r_offset
> on ppc, ELF_MACHINE_REL_RELATIVE could not be defined because there are
> already many -z combreloc binaries and libraries out there I think
> and they'd suddenly fail in weird ways.
> R_*_RELATIVE relocs can be skipped on the other
> arches (ppc, x86-64, sparc*, ...) if the library is prelinked, not
> just prelink -r'ed. Then it guarantees *r_offset has the proper value.

How big is the performance difference?  If it's worthwhile, we could
add (say) a dynamic tag which guarantees us that the binary has this

[Didn't you change binutils to do this on PPC a couple of weeks ago? 
When making it put a predictable value there?]

Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]