[mips patch RFA] put back bfd support for pcrel-32 relocs

[cgd at broadcom dot com]

This patch puts back mips elf32 bfd support for pcrel-32 relocs, to
restore compatibility with old mips-linux exception handling data.

with the patch i posted to gcc-patches a bit ago, gcc won't try to
emit code that uses these relocs any longer.  (they were an
embedded-pic extension.)  However, it's desirable to support them at
link time, for compatiblity with existing objects that use them.

tested with binutils sources as of 5/1.  something else has broken
binutils sources badly since then for mips linux shlibs (causing
string table offsets to be way out of bounds, iirc -- it's been a few
dasys since i tried), so i couldn't test w/ very current srcs.

tested compatiblity with old and new objects too (i.e., existing
objects that use pcrel-32 relocs for EH data).


(I would commit this as obvious, but i'd like to hear if this is
considered a reasonable solution to the problem.)


chris
--
[ bfd/ChangeLog ]
2004-06-13  Chris Demetriou  <cgd@broadcom.com>

	* elf32-mips.c (elf_mips_gnu_pcrel32): Add (undoing 2004-04-24
	removal) with updated comment.
	(bfd_elf32_bfd_reloc_type_lookup): Add back case for
	BFD_RELOC_32_PCREL.
	(mips_elf32_rtype_to_howto): Add back case for R_MIPS_PC32.
	* elfxx-mips.c (mips_elf_calculate_relocation): Likewise.

[ include/elf/ChangeLog ]
2004-06-13  Chris Demetriou  <cgd@broadcom.com>

	* mips.h (R_MIPS_PC32): Add back (undoing removal on 2004-04-24),
	with an updated comment.

Index: bfd/elf32-mips.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-mips.c,v
retrieving revision 1.175
diff -u -p -r1.175 elf32-mips.c
--- bfd/elf32-mips.c	24 Apr 2004 22:07:13 -0000	1.175
+++ bfd/elf32-mips.c	14 Jun 2004 06:45:05 -0000
@@ -615,6 +615,25 @@ static reloc_howto_type elf_mips_gnu_rel
 	 0xffff,		/* dst_mask */
 	 TRUE);			/* pcrel_offset */
 
+/* 32 bit pc-relative.  This was a GNU extension used by embedded-PIC.
+   It was co-opted by mips-linux for exception-handling data.  It is no
+   longer used, but should continue to be supported by the linker for
+   backward compatibility.  (GCC stopped using it in May, 2004.)  */
+static reloc_howto_type elf_mips_gnu_pcrel32 =
+  HOWTO (R_MIPS_PC32,		/* type */
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 TRUE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_signed, /* complain_on_overflow */
+	 _bfd_mips_elf_generic_reloc, /* special_function */
+	 "R_MIPS_PC32",		/* name */
+	 TRUE,			/* partial_inplace */
+	 0xffffffff,		/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 TRUE);			/* pcrel_offset */
+
 /* GNU extension to record C++ vtable hierarchy */
 static reloc_howto_type elf_mips_gnu_vtinherit_howto =
   HOWTO (R_MIPS_GNU_VTINHERIT,	/* type */
@@ -1071,6 +1090,8 @@ bfd_elf32_bfd_reloc_type_lookup (bfd *ab
       return &elf_mips_gnu_vtentry_howto;
     case BFD_RELOC_16_PCREL_S2:
       return &elf_mips_gnu_rel16_s2;
+    case BFD_RELOC_32_PCREL:
+      return &elf_mips_gnu_pcrel32;
     }
 }
 
@@ -1092,6 +1113,8 @@ mips_elf32_rtype_to_howto (unsigned int 
       return &elf_mips_gnu_vtentry_howto;
     case R_MIPS_GNU_REL16_S2:
       return &elf_mips_gnu_rel16_s2;
+    case R_MIPS_PC32:
+      return &elf_mips_gnu_pcrel32;
     default:
       BFD_ASSERT (r_type < (unsigned int) R_MIPS_max);
       return &elf_mips_howto_table_rel[r_type];
Index: bfd/elfxx-mips.c
===================================================================
RCS file: /cvs/src/src/bfd/elfxx-mips.c,v
retrieving revision 1.100
diff -u -p -r1.100 elfxx-mips.c
--- bfd/elfxx-mips.c	24 Apr 2004 22:07:13 -0000	1.100
+++ bfd/elfxx-mips.c	14 Jun 2004 06:45:05 -0000
@@ -3335,6 +3335,11 @@ mips_elf_calculate_relocation (bfd *abfd
       value &= howto->dst_mask;
       break;
 
+    case R_MIPS_PC32:
+      value = symbol + addend - p;
+      value &= howto->dst_mask;
+      break;
+
     case R_MIPS_GNU_REL16_S2:
       value = symbol + _bfd_mips_elf_sign_extend (addend, 18) - p;
       overflowed_p = mips_elf_overflow_p (value, 18);
Index: include/elf/mips.h
===================================================================
RCS file: /cvs/src/src/include/elf/mips.h,v
retrieving revision 1.22
diff -u -p -r1.22 mips.h
--- include/elf/mips.h	24 Apr 2004 22:07:14 -0000	1.22
+++ include/elf/mips.h	14 Jun 2004 06:45:06 -0000
@@ -76,6 +76,11 @@ START_RELOC_NUMBERS (elf_mips_reloc_type
   /* These relocs are used for the mips16.  */
   RELOC_NUMBER (R_MIPS16_26, 100)
   RELOC_NUMBER (R_MIPS16_GPREL, 101)
+  /* This was a GNU extension used by embedded-PIC.  It was co-opted by
+     mips-linux for exception-handling data.  It is no longer used, but
+     should continue to be supported by the linker for backward
+     compatibility.  (GCC stopped using it in May, 2004.)  */
+  RELOC_NUMBER (R_MIPS_PC32, 248)
   /* FIXME: this relocation is used internally by gas.  */
   RELOC_NUMBER (R_MIPS_GNU_REL16_S2, 250)
   /* These are GNU extensions to enable C++ vtable garbage collection.  */