[PATCH] Check branch displacement overflow in x86-64 PLT entry

[H.J. Lu]

I checked in this patch.  H.J.

Displacement of branch to PLT0 in x86-64 PLT entry is signed 32-bit.
This patch adds a sanity check.  We will only see the failure when PLT
size is > 2GB.

	* elf64-x86-64.c (elf_x86_64_finish_dynamic_symbol): Check
	branch displacement overflow in PLT entry.
---
 bfd/ChangeLog      |  5 +++++
 bfd/elf64-x86-64.c | 12 ++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 5700c51..040576a 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,8 @@
+2014-11-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* elf64-x86-64.c (elf_x86_64_finish_dynamic_symbol): Check
+	branch displacement overflow in PLT entry.
+
 2014-11-21  Nick Clifton  <nickc@redhat.com>
 
 	PR binutils/17512
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index c64ff4f..8859429 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -4906,11 +4906,19 @@ elf_x86_64_finish_dynamic_symbol (bfd *output_bfd,
       /* Don't fill PLT entry for static executables.  */
       if (plt == htab->elf.splt)
 	{
+	  bfd_vma plt0_offset = h->plt.offset + plt_plt_insn_end;
+
 	  /* Put relocation index.  */
 	  bfd_put_32 (output_bfd, plt_index,
 		      plt->contents + h->plt.offset + abed->plt_reloc_offset);
-	  /* Put offset for jmp .PLT0.  */
-	  bfd_put_32 (output_bfd, - (h->plt.offset + plt_plt_insn_end),
+
+	  /* Put offset for jmp .PLT0 and check for overflow.  We don't
+	     check relocation index for overflow since branch displacement
+	     will overflow first.  */
+	  if (plt0_offset > 0x80000000)
+	    info->callbacks->einfo (_("%F%B: branch displacement overflow in PLT entry for `%s'\n"),
+				    output_bfd, h->root.root.string);
+	  bfd_put_32 (output_bfd, - plt0_offset,
 		      plt->contents + h->plt.offset + plt_plt_offset);
 	}
 
-- 
1.9.3