Re: objcopy -j -O binary can't extract debug sections

[Corinna Vinschen <vinschen at redhat dot com>]

Hi Ian,

On Nov 22 11:45, Ian Lance Taylor wrote:
> On Fri, Nov 22, 2013 at 10:40 AM, Corinna Vinschen <...> wrote:
> >
> > Here's the start of the script:
> >
> >   EXE=$1
> >   LONGSECTIONS=".gnu_debuglink \
> >                 .debug_aranges \
> >                 .debug_info \
> >                 .debug_abbrev \
> >                 .debug_line \
> >                 .debug_frame \
> >                 .debug_str \
> >                 .debug_loc \
> >                 .debug_ranges"
> >
> >   for section in ${LONGSECTIONS}
> >   do
> >     objcopy -j "${section}" -O binary "${EXE}" "${EXE}${section}"
> >     objcopy -R "${section}" "${EXE}"
> >   done
> >   [...]
> >
> > So I'm just storing the binary content of the debug sections in separate
> > files and then strip the section from the executable.
> >
> > The problem is, it doesn't work.  The only section which I can export
> > successfully this way is the .gnu_debuglink section.  All the files
> > supposed to contain the Dwarf2 debug sections will have a length of 0.
> > No errors, no warnings, just a size of 0.
> 
> It's because the .debug_XXX sections are marked with SEC_DEBUG in BFD,
> and the BFD "binary" format discards SEC_DEBUG sections.
> 
> Try adding
>     --set-section-flags=".debug*=alloc,load"

Thanks for the hint.  Unfortunately it doesn't work.  It silently ignores
the command.  I also tried without the wildcard:

  $ objdump -h foo.exe
  [...]
   14 .debug_ranges 00000030  0000000100415000  0000000100415000  0000b000  2**0
		    CONTENTS, READONLY, DEBUGGING
  $ objcopy --long-section-names keep --set-section-flags ".debug_ranges=alloc,load" foo.exe
  $ objdump -h foo.exe
  [...]
   14 .debug_ranges 00000030  0000000100415000  0000000100415000  0000b000  2**0
		    CONTENTS, READONLY, DEBUGGING

Nick Clifton gave me the hint to try renaming the sections before
exporting them.  This allows exporting them, but then adding them back
fails:

  $ objcopy --add-section .debug_ranges=foo.exe.debug_ranges --set-section-flags .debug_ranges=contents --adjust-section-vma .debug_ranges=0x100409000 --long-section-names keep foo.exe
  objcopy:foo.exe: File truncated
  objcopy: --change-section-vma .debug_ranges=0x0000000100409000 never used
  objcopy: --change-section-lma .debug_ranges=0x0000000100409000 never used

Even trying to add the section under another name like ".foobar" doesn't
work.  The error is exactly the same.


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat