Re: mips64 elf64 reloc data structures

[Alexandre Oliva <aoliva at redhat dot com>]

On Mar 18, 2003, Roland McGrath <roland at redhat dot com> wrote:

> I think you should make sure that every place for which these macros
> matter uses <ldsodefs.h> and do it in mips/ldsodefs.h instead.

Contrary to my recollections and fears, this seems to have worked.
I've verified that the ELF64_R_ macros defined in elf/elf.h were not
used by building glibc for mips64-linux-gnu after adding syntax errors
to the unwanted definitions, and it still built correctly, so it
appears that the files that include only elf.h do not need these
macros.  I'm still concerned that there is a possibility of errors
being silently introduced by this arrangement, but even my attempt to
avoid taking risks and adding an explicit include of ldsodefs.h
everywhere elf.h was included failed: a number of files just can't
include ldsodefs.h, and I fear some of them may be installed, so I
gave it up.  I still think some of this code belongs in generic code,
but I'm leaving it at this for now.  Ok to install?

Index: ChangeLog
from  Alexandre Oliva  <aoliva at redhat dot com>

	* sysdeps/mips/elf/ldsodefs.h: Add mips-specific elf64 relocation
	data structures and macros.  Protect from multiple inclusion.

Index: sysdeps/mips/elf/ldsodefs.h
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/mips/elf/ldsodefs.h,v
retrieving revision 1.3
diff -u -p -r1.3 ldsodefs.h
--- sysdeps/mips/elf/ldsodefs.h 6 Feb 2002 22:48:35 -0000 1.3
+++ sysdeps/mips/elf/ldsodefs.h 20 Mar 2003 06:07:54 -0000
@@ -1,5 +1,5 @@
 /* Run-time dynamic linker data structures for loaded ELF shared objects.
-   Copyright (C) 2000, 2002 Free Software Foundation, Inc.
+   Copyright (C) 2000, 2002, 2003 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -17,9 +17,93 @@
    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA.  */
 
+#ifndef _MIPS_LDSODEFS_H
+#define _MIPS_LDSODEFS_H
 
 /* The MIPS ABI specifies that the dynamic section has to be read-only.  */
 
 #define DL_RO_DYN_SECTION 1
 
 #include_next <ldsodefs.h>
+
+/* The 64-bit MIPS ELF ABI uses an unusual reloc format.  Each
+   relocation entry specifies up to three actual relocations, all at
+   the same address.  The first relocation which required a symbol
+   uses the symbol in the r_sym field.  The second relocation which
+   requires a symbol uses the symbol in the r_ssym field.  If all
+   three relocations require a symbol, the third one uses a zero
+   value.
+
+   We define these structures in internal headers because we're not
+   sure we want to make them part of the ABI yet.  Eventually, some of
+   this may move into elf/elf.h.  */
+
+/* An entry in a 64 bit SHT_REL section.  */
+
+typedef struct
+{
+  Elf32_Word    r_sym;		/* Symbol index */
+  unsigned char r_ssym;		/* Special symbol for 2nd relocation */
+  unsigned char r_type3;	/* 3rd relocation type */
+  unsigned char r_type2;	/* 2nd relocation type */
+  unsigned char r_type1;	/* 1st relocation type */
+} _Elf64_Mips_R_Info;
+
+typedef union
+{
+  Elf64_Xword	r_info_number;
+  _Elf64_Mips_R_Info r_info_fields;
+} _Elf64_Mips_R_Info_union;
+
+typedef struct
+{
+  Elf64_Addr	r_offset;		/* Address */
+  _Elf64_Mips_R_Info_union r_info;	/* Relocation type and symbol index */
+} Elf64_Mips_Rel;
+
+typedef struct
+{
+  Elf64_Addr	r_offset;		/* Address */
+  _Elf64_Mips_R_Info_union r_info;	/* Relocation type and symbol index */
+  Elf64_Sxword	r_addend;		/* Addend */
+} Elf64_Mips_Rela;
+
+#define ELF64_MIPS_R_SYM(i) \
+  ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_sym)
+#define ELF64_MIPS_R_TYPE(i) \
+  (((_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_type1 \
+   | ((Elf32_Word)(__extension__ (_Elf64_Mips_R_Info_union)(i) \
+		   ).r_info_fields.r_type2 << 8) \
+   | ((Elf32_Word)(__extension__ (_Elf64_Mips_R_Info_union)(i) \
+		   ).r_info_fields.r_type3 << 16) \
+   | ((Elf32_Word)(__extension__ (_Elf64_Mips_R_Info_union)(i) \
+		   ).r_info_fields.r_ssym << 24))
+#define ELF64_MIPS_R_INFO(sym, type) \
+  (__extension__ (_Elf64_Mips_R_Info_union) \
+   (__extension__ (_Elf64_Mips_R_Info) \
+   { (sym), ELF64_MIPS_R_SSYM (type), \
+       ELF64_MIPS_R_TYPE3 (type), \
+       ELF64_MIPS_R_TYPE2 (type), \
+       ELF64_MIPS_R_TYPE1 (type) \
+   }).r_info_number)
+/* These macros decompose the value returned by ELF64_MIPS_R_TYPE, and
+   compose it back into a value that it can be used as an argument to
+   ELF64_MIPS_R_INFO.  */
+#define ELF64_MIPS_R_SSYM(i) (((i) >> 24) & 0xff)
+#define ELF64_MIPS_R_TYPE3(i) (((i) >> 16) & 0xff)
+#define ELF64_MIPS_R_TYPE2(i) (((i) >> 8) & 0xff)
+#define ELF64_MIPS_R_TYPE1(i) ((i) & 0xff)
+#define ELF64_MIPS_R_TYPEENC(type1, type2, type3, ssym) \
+  ((type1) \
+   | ((Elf32_Word)(type2) << 8) \
+   | ((Elf32_Word)(type3) << 16) \
+   | ((Elf32_Word)(ssym) << 24))
+
+#undef ELF64_R_SYM
+#define ELF64_R_SYM(i) ELF64_MIPS_R_SYM (i)
+#undef ELF64_R_TYPE
+#define ELF64_R_TYPE(i) ELF64_MIPS_R_TYPE (i)
+#undef ELF64_R_INFO
+#define ELF64_R_INFO(sym, type) ELF64_MIPS_R_INFO ((sym), (type))
+
+#endif

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                 aoliva at {redhat dot com, gcc.gnu.org}
CS PhD student at IC-Unicamp        oliva at {lsd dot ic dot unicamp dot br, gnu.org}
Free Software Evangelist                Professional serial bug killer