[Bug ld/12253] .eh_frame_hdr not properly sorted with mixed .eh_frame encodings

[ro at CeBiTec dot Uni-Bielefeld.DE]

http://sourceware.org/bugzilla/show_bug.cgi?id=12253

--- Comment #3 from Rainer Orth <ro at CeBiTec dot Uni-Bielefeld.DE> 2010-11-23 
16:01:49 UTC ---
> --- Comment #2 from Alan Modra <amodra at gmail dot com> 2010-11-23 13:34:02 
> UTC ---
> I took a look at this today.  Besides the sorting problem, elf-eh-frame.c gets
> DW_EH_PE_datarel wrong.  datarel is quite horrible, with behaviour varying 
> from
> one architecture to another, unspecified on most.  For x86, datarel offsets 
> are
> supposed to be relative to .got.plt rather than .got.  On ia64, datarel is
> relative to __gp.

Do you have an idea where this is specified?  I've only found Table 11.6
in the LSB 4.0.0:

   
http://refspecs.freestandards.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/dwarfext.html

which says

DW_EH_PE_datarel    0x30    Value is relative to the beginning of
                                the .got or .eh_frame_hdr section.

A spec which says `do A or B' with no indication when to do one or the
other seems like a joke to me.  I've looked into the architecture
extensions for advise, but found nothing.

I ran into this when trying to get the libgcc unwinder to work with
dl_iterate_phdr on Solaris 11.  While the function works, Sun ld
interpreted DW_EH_PE_datarel relative to .eh_frame_hdr on i386 (apart
from other problems).  It would be good to have a spec to point to for
this, rather than saying `GCC has been doing this' instead.

Thanks.
    Rainer

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