Re: [PATCH] [RFC] nios2: Fix initial PLT entry population

[Sandra Loosemore <sandra at codesourcery dot com>]

On 12/08/2015 09:27 AM, Marek Vasut wrote:
> On Tuesday, December 01, 2015 at 02:16:50 PM, Marek Vasut wrote:
> > On Tuesday, December 01, 2015 at 06:11:03 AM, Sandra Loosemore wrote:
> > > On 11/30/2015 07:46 AM, Marek Vasut wrote:
> > > > I can do that, but I didn't find the bug in bugzilla. Shall I create a
> > > > new one? In the meantime, I pushed the whole tarball from the build to
> > > > [1], sha1sum is fe62b3848edf51b6083ca53f861c3dd3af49dd4b
> > > > orc-0.4.23-r0.tar.xz
> > > >
> > > > You can find the entire build log in
> > > > orc-0.4.23-r0/temp/log.do_compile.7916 , the objects are located in
> > > > orc-0.4.23-r0/build/ directory and the source is in the
> > > > orc-0.4.23-r0/orc-0.4.23/ directory.
> > > >
> > > > [1] http://www.bfuser.eu/orc-0.4.23-r0.tar.xz
> > >
> > > I took a look at this, but it seems the set of objects is not complete
> > > (e.g., it's missing the sysroot you are linking against).  If I get you
> > > a patch that I'm more confident is correct, would you be able to test it
> > > on this example?
> >
> > Of course, I'd be happy to help.
> >
> > I can also show you how to prepare the OpenEmbedded/Yocto build for NIOS2,
> > so you can fiddle with it yourself, but that might be a longer process.
> >
> > Please let me know.
>
> Hi,
>
> any news on this please ?

Sorry, I got distracted last week and just finished regression testing 
overnight.  Does the attached patch solve your problem?

-Sandra

2015-12-08  Sandra Loosemore  <sandra@codesourcery.com>

	bfd/
	* elf32-nios2.c (nios2_elf32_finish_dynamic_sections): Correct
	%hiadj/%lo computations for _GLOBAL_OFFSET_TABLE_ in initial
	PLT entries.  Assert alignment requirements.

diff --git a/bfd/elf32-nios2.c b/bfd/elf32-nios2.c
index 6b29d8b..1c54320 100644
--- a/bfd/elf32-nios2.c
+++ b/bfd/elf32-nios2.c
@@ -5383,12 +5383,17 @@ nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 				 + sgotplt->output_offset);
 	  if (bfd_link_pic (info))
 	    {
-	      bfd_vma corrected = got_address - (splt->output_section->vma
-						 + splt->output_offset + 4);
+	      bfd_vma got_pcrel = got_address - (splt->output_section->vma
+						 + splt->output_offset);
+	      /* Both GOT and PLT must be aligned to a 16-byte boundary
+		 for the two loads to share the %hiadj part.  The 4-byte
+		 offset for nextpc is accounted for in the %lo offsets
+		 on the loads.  */
+	      BFD_ASSERT ((got_pcrel & 0xf) == 0);
 	      nios2_elf32_install_data (splt, nios2_so_plt0_entry, 0, 6);
-	      nios2_elf32_install_imm16 (splt, 4, hiadj (corrected));
-	      nios2_elf32_install_imm16 (splt, 12, (corrected & 0xffff) + 4);
-	      nios2_elf32_install_imm16 (splt, 16, (corrected & 0xffff) + 8);
+	      nios2_elf32_install_imm16 (splt, 4, hiadj (got_pcrel));
+	      nios2_elf32_install_imm16 (splt, 12, got_pcrel & 0xffff);
+	      nios2_elf32_install_imm16 (splt, 16, (got_pcrel + 4) & 0xffff);
 	    }
 	  else
 	    {
@@ -5404,6 +5409,10 @@ nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 			    6 | ((res_size - (res_offset + 4)) << 6),
 			    splt->contents + res_offset);
 
+	      /* The GOT must be aligned to a 16-byte boundary for the
+		 two loads to share the same %hiadj part.  */
+	      BFD_ASSERT ((got_address & 0xf) == 0);
+
 	      nios2_elf32_install_data (splt, nios2_plt0_entry, res_size, 7);
 	      nios2_elf32_install_imm16 (splt, res_size, hiadj (res_start));
 	      nios2_elf32_install_imm16 (splt, res_size + 4,
@@ -5411,9 +5420,9 @@ nios2_elf32_finish_dynamic_sections (bfd *output_bfd,
 	      nios2_elf32_install_imm16 (splt, res_size + 12,
 					 hiadj (got_address));
 	      nios2_elf32_install_imm16 (splt, res_size + 16,
-					 (got_address & 0xffff) + 4);
+					 (got_address + 4) & 0xffff);
 	      nios2_elf32_install_imm16 (splt, res_size + 20,
-					 (got_address & 0xffff) + 8);
+					 (got_address + 8) & 0xffff);
 	    }
 	}
     }