* elflink.c (get_value): Prevent the use of an undefined shift

operation.  Add sanity checks.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2013-01-03  Nickolai Zeldovich  <nickolai@csail.mit.edu>
+	    Nick Clifton  <nickc@redhat.com>
+
+	* elflink.c (get_value): Prevent the use of an undefined shift
+	operation.  Add sanity checks.
+
 2013-01-02  Kaushik Phatak  <kaushik.phatak@kpitcummins.com>
 
 	* config.bfd (cr16*-*-uclinux*): New target support.

bfd/elflink.c

@@ -1,6 +1,6 @@
 /* ELF linking support for BFD.
    Copyright 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
-   2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
+   2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
    Free Software Foundation, Inc.
 
    This file is part of BFD, the Binary File Descriptor library.
@@ -7917,31 +7917,49 @@ get_value (bfd_vma size,
 	   bfd *input_bfd,
 	   bfd_byte *location)
 {
+  int shift;
   bfd_vma x = 0;
 
+  /* Sanity checks.  */
+  BFD_ASSERT (chunksz <= sizeof (x)
+	      && size >= chunksz
+	      && chunksz != 0
+	      && (size % chunksz) == 0
+	      && input_bfd != NULL
+	      && location != NULL);
+
+  if (chunksz == sizeof (x))
+    {
+      BFD_ASSERT (size == chunksz);
+
+      /* Make sure that we do not perform an undefined shift operation.
+	 We know that size == chunksz so there will only be one iteration
+	 of the loop below.  */
+      shift = 0;
+    }
+  else
+    shift = 8 * chunksz;
+
   for (; size; size -= chunksz, location += chunksz)
     {
       switch (chunksz)
 	{
-	default:
-	case 0:
-	  abort ();
 	case 1:
-	  x = (x << (8 * chunksz)) | bfd_get_8 (input_bfd, location);
+	  x = (x << shift) | bfd_get_8 (input_bfd, location);
 	  break;
 	case 2:
-	  x = (x << (8 * chunksz)) | bfd_get_16 (input_bfd, location);
+	  x = (x << shift) | bfd_get_16 (input_bfd, location);
 	  break;
 	case 4:
-	  x = (x << (8 * chunksz)) | bfd_get_32 (input_bfd, location);
+	  x = (x << shift) | bfd_get_32 (input_bfd, location);
 	  break;
-	case 8:
 #ifdef BFD64
-	  x = (x << (8 * chunksz)) | bfd_get_64 (input_bfd, location);
-#else
-	  abort ();
-#endif
+	case 8:
+	  x = (x << shift) | bfd_get_64 (input_bfd, location);
 	  break;
+#endif
+	default:
+	  abort ();
 	}
     }
   return x;