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Add an R_MIPS_GLOB_DAT relocation

From: Richard Sandiford <richard at codesourcery dot com>
To: binutils at sourceware dot org
Date: Fri, 27 Oct 2006 15:33:21 +0100
Subject: Add an R_MIPS_GLOB_DAT relocation
Jakub has now committed the (o32) MIPS prelinker port to svn -- thanks!
In order to reduce the number of REL->RELA conversions needed, the port
can convert a prelinked R_MIPS_REL32 relocation against a global symbol
into a R_MIPS_GLOB_DAT relocation if the original addend was zero.
R_MIPS_GLOB_DAT is a new relocation added specifically for this purpose.
It has relocation code 51, is only defined for symbols >= DT_MIPS_GOTSYM,
and has relocation value "S", as for other targets.  It has been blessed
in principle by MTI.

The idea is that, for reasosn of backward compatibility, only the
prelinker should generate this new relocation.  The patch below
therefore just registers R_MIPS_GLOB_DAT with bfd.  Tools like
readelf can then understand the relocations in prelinked objects.

Tested on mips{,64}{,el}-{linux-gnu,elf} and mips-sgi-irix6.5.
OK to install?

Richard


include/elf/
	* mips.h (R_MIPS_GLOB_DAT): Define
	(R_MIPS_max): Bump by 1.

bfd/
	* elf32-mips.c (elf_mips_howto_table_rel): Add R_MIPS_GLOB_DAT.
	* elfn32-mips.c (elf_mips_howto_table_rel): Likewise.
	(elf_mips_howto_table_rela): Likewise.
	* elf64-mips.c (mips_elf64_howto_table_rel): Likewise.
	(mips_elf64_howto_table_rela): Likewise.

Index: include/elf/mips.h
===================================================================
RCS file: /cvs/src/src/include/elf/mips.h,v
retrieving revision 1.31
diff -u -p -r1.31 mips.h
--- include/elf/mips.h	22 Mar 2006 09:28:13 -0000	1.31
+++ include/elf/mips.h	27 Oct 2006 13:26:02 -0000
@@ -87,7 +87,8 @@ START_RELOC_NUMBERS (elf_mips_reloc_type
   RELOC_NUMBER (R_MIPS_TLS_TPREL64, 48)
   RELOC_NUMBER (R_MIPS_TLS_TPREL_HI16, 49)
   RELOC_NUMBER (R_MIPS_TLS_TPREL_LO16, 50)
-  FAKE_RELOC (R_MIPS_max, 51)
+  RELOC_NUMBER (R_MIPS_GLOB_DAT, 51)
+  FAKE_RELOC (R_MIPS_max, 52)
   /* These relocs are used for the mips16.  */
   FAKE_RELOC (R_MIPS16_min, 100)
   RELOC_NUMBER (R_MIPS16_26, 100)
Index: bfd/elf32-mips.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-mips.c,v
retrieving revision 1.192
diff -u -p -r1.192 elf32-mips.c
--- bfd/elf32-mips.c	17 Oct 2006 13:41:47 -0000	1.192
+++ bfd/elf32-mips.c	27 Oct 2006 13:26:02 -0000
@@ -700,6 +700,21 @@ static reloc_howto_type elf_mips_howto_t
 	 0x0000ffff,		/* src_mask */
 	 0x0000ffff,		/* dst_mask */
 	 FALSE),		/* pcrel_offset */
+
+  /* 32 bit relocation with no addend.  */
+  HOWTO (R_MIPS_GLOB_DAT,	/* type */
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 _bfd_mips_elf_generic_reloc, /* special_function */
+	 "R_MIPS_GLOB_DAT",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0x0,			/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 FALSE),		/* pcrel_offset */
 };
 
 /* The reloc used for BFD_RELOC_CTOR when doing a 64 bit link.  This
Index: bfd/elfn32-mips.c
===================================================================
RCS file: /cvs/src/src/bfd/elfn32-mips.c,v
retrieving revision 1.35
diff -u -p -r1.35 elfn32-mips.c
--- bfd/elfn32-mips.c	17 Oct 2006 13:41:47 -0000	1.35
+++ bfd/elfn32-mips.c	27 Oct 2006 13:26:02 -0000
@@ -754,6 +754,21 @@ static reloc_howto_type elf_mips_howto_t
 	 0x0000ffff,		/* src_mask */
 	 0x0000ffff,		/* dst_mask */
 	 FALSE),		/* pcrel_offset */
+
+  /* 32 bit relocation with no addend.  */
+  HOWTO (R_MIPS_GLOB_DAT,	/* type */
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 _bfd_mips_elf_generic_reloc, /* special_function */
+	 "R_MIPS_GLOB_DAT",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0x0,			/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 FALSE),		/* pcrel_offset */
 };
 
 /* The relocation table used for SHT_RELA sections.  */
@@ -1427,6 +1442,21 @@ static reloc_howto_type elf_mips_howto_t
 	 0x0000ffff,		/* src_mask */
 	 0x0000ffff,		/* dst_mask */
 	 FALSE),		/* pcrel_offset */
+
+  /* 32 bit relocation with no addend.  */
+  HOWTO (R_MIPS_GLOB_DAT,	/* type */
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 _bfd_mips_elf_generic_reloc, /* special_function */
+	 "R_MIPS_GLOB_DAT",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0x0,			/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 FALSE),		/* pcrel_offset */
 };
 
 static reloc_howto_type elf_mips16_howto_table_rel[] =
Index: bfd/elf64-mips.c
===================================================================
RCS file: /cvs/src/src/bfd/elf64-mips.c,v
retrieving revision 1.77
diff -u -p -r1.77 elf64-mips.c
--- bfd/elf64-mips.c	17 Oct 2006 13:41:47 -0000	1.77
+++ bfd/elf64-mips.c	27 Oct 2006 13:26:02 -0000
@@ -789,6 +789,21 @@ static reloc_howto_type mips_elf64_howto
 	 0x0000ffff,		/* src_mask */
 	 0x0000ffff,		/* dst_mask */
 	 FALSE),		/* pcrel_offset */
+
+  /* 32 bit relocation with no addend.  */
+  HOWTO (R_MIPS_GLOB_DAT,	/* type */
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 _bfd_mips_elf_generic_reloc, /* special_function */
+	 "R_MIPS_GLOB_DAT",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0x0,			/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 FALSE),		/* pcrel_offset */
 };
 
 /* The relocation table used for SHT_RELA sections.  */
@@ -1421,6 +1436,21 @@ static reloc_howto_type mips_elf64_howto
 	 0x0000ffff,		/* src_mask */
 	 0x0000ffff,		/* dst_mask */
 	 FALSE),		/* pcrel_offset */
+
+  /* 32 bit relocation with no addend.  */
+  HOWTO (R_MIPS_GLOB_DAT,	/* type */
+	 0,			/* rightshift */
+	 2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 FALSE,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_dont, /* complain_on_overflow */
+	 _bfd_mips_elf_generic_reloc, /* special_function */
+	 "R_MIPS_GLOB_DAT",	/* name */
+	 FALSE,			/* partial_inplace */
+	 0x0,			/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 FALSE),		/* pcrel_offset */
 };
 
 static reloc_howto_type mips16_elf64_howto_table_rel[] =
Follow-Ups:
- Re: Add an R_MIPS_GLOB_DAT relocation
  - From: Eric Christopher
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