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Re: more prelink

On Sun, Sep 29, 2002 at 06:24:06PM -0400, Daniel Jacobowitz wrote:
> > Such dynamic tag already exists, DT_GNU_PRELINKED.
> > How big is the performance difference depends on a bunch of things,
> > like how many RELATIVE relocs there are and how many pages
> > normally read-only pages are there with just RELATIVE relocs against
> > it and no other ones.
> > So running prelink (without -r) will make that happen.
> >From what you say above, then, can't we check the presence of
> DT_GNU_PRELINKED and if it is present, use this optimization even on
> Rela architectures?

glibc does that already:
# if !defined DO_RELA || defined ELF_MACHINE_REL_RELATIVE
        /* Rela platforms get the offset from r_addend and this must
           be copied in the relocation address.  Therefore we can skip
           the relative relocations only if this is for rel
           relocations or rela relocations if they are computed as
           memory_loc += l_addr...  */
        if (l_addr != 0)
# else
        /* ...or we know the object has been prelinked.  */
        if (l_addr != 0 || ! map->l_info[VALIDX(DT_GNU_PRELINKED)])
# endif

The --reloc-only=xyz stuff is just a cheap way how to speed things up
even when not prelinking.


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