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Re: [PATCH] elf: Try not pointing empty PT_LOAD segment's offset past EOF


On Fri, Dec 13, 2019 at 10:32:19AM +0100, Bálint Réczey wrote:
> Hi Alan,
> 
> Bálint Réczey <balint@balintreczey.hu> ezt írta (időpont: 2019. dec.
> 11., Sze, 12:44):
> >
> > Alan Modra <amodra@gmail.com> ezt írta (időpont: 2019. dec. 11., Sze, 12:02):
> > >
> ...
> > > "p->p_offset = off % maxpagesize" might be OK, I think.
> >
> > That's perfect, thanks. Attaching the updated patch.
> 
> I have attached the updated patch to to bug, too.
> Would you like me to perform any specific additional testing?

I've run the binutils testsuite over multiple targets without seeing
any problems so will commit the following variant.

	PR 25237
	* elf.c (assign_file_positions_for_load_sections): Attempt to
	keep meaningless p_offset for PT_LOAD segments without file
	contents within file size.

diff --git a/bfd/elf.c b/bfd/elf.c
index 1aa2603ee8..fd447fdb28 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -5752,7 +5752,15 @@ assign_file_positions_for_load_sections (bfd *abfd,
 	  || (p->p_type == PT_NOTE && bfd_get_format (abfd) == bfd_core))
 	{
 	  if (!m->includes_filehdr && !m->includes_phdrs)
-	    p->p_offset = off;
+	    {
+	      p->p_offset = off;
+	      if (no_contents)
+		/* Put meaningless p_offset for PT_LOAD segments
+		   without file contents somewhere within the first
+		   page, in an attempt to not point past EOF.  */
+		p->p_offset = off % (p->p_align > maxpagesize
+				     ? p->p_align : maxpagesize);
+	    }
 	  else
 	    {
 	      file_ptr adjust;


-- 
Alan Modra
Australia Development Lab, IBM


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