ultrix man page for reloc

reloc(5)							File Formats Manual							  reloc(5)

Name
       reloc - relocation information for a MIPS object file

Syntax
       #include <reloc.h>

Description
       Object  files  have one relocation entry for each relocatable reference in the text or data.  If relocation information is present, it will
       be in the following format:

       struct	reloc
       {
	  long	    r_vaddr ;	       /* (virtual) address of reference */
	  long	    r_symndx ;	       /* index into symbol table */
	  ushort    r_type ;	       /* relocation type */
	  unsigned  r_symndx:24,       /* index into symbol table */
		    r_reserved:3,
		    r_type:4,	       /* relocation type */
		    r_extern:1;        /* if 1 symndx is an index into the
					  external symbol table, else symndx
					  is a section # */
       } ;

       /* Relocation types */

       #define	R_ABS	    0
       #define	R_REFHALF   1
       #define	R_REFWORD   2
       #define	R_JMPADDR   3
       #define	R_REFHI     4
       #define	R_REFLO     5
       #define	R_GPREL     6
       #define	R_LITERAL   7

       /* Section numbers */

       #define	R_SN_NULL   0
       #define	R_SN_TEXT   1
       #define	R_SN_RDATA  2
       #define	R_SN_DATA   3
       #define	R_SN_SDATA  4
       #define	R_SN_SBSS   5
       #define	R_SN_BSS    6
       #define	R_SN_INIT   7
       #define	R_SN_LIT8   8
       #define	R_SN_LIT4   9

       The link editor reads each input section and performs relocation.  The relocation entries direct how references found within the input sec-
       tion are treated.

       If  is zero, it is a local relocation entry and then is a section number (R_SN_*).  For these entries, the starting address for the section
       referenced by the section number is used in place of an external symbol table entry's value.  The assembler and	loader	always	use  local
       relocation entries if the item to be relocated is defined in the object file.

       For  every  external  relocation (except R_ABS) a signed constant is added to the symbol's virtual address that the relocation entry refers
       to.  This constant is assembled at the address being relocated.

       R_ABS	      The reference is absolute and no relocation is necessary.  The entry will be ignored.

       R_REFHALF      A 16-bit reference to the symbol's virtual address.

       R_REFWORD      A 32-bit reference to the symbol's virtual address.

       R_JMPADDR      A 26-bit jump instruction reference to the symbol's virtual address.

       R_REFHI	      A reference to the high 16 bits of the symbol's virtual address.	The  next  relocation  entry  must  be	the  corresponding
		      R_REFLO entry, so the proper value of the constant to be added to the symbol's virtual address can be reconstructed.

       R_REFLO	      A reference to low 16 bits to the symbol's virtual address.

       R_GPREL	      A 16-bit offset to the symbol's virtual address from the global pointer register.

       R_LITERAL      A 16-bit offset to the literal's virtual address from the global pointer register.

       Relocation  entries  are generated automatically by the assembler and automatically used by the link editor.  Link editor options exist for
       both preserving and removing the relocation entries from object files.

       The number of relocation entries for a section is found in the field of the section header.  This field is a C language short and can over-
       flow  with  large objects.  If this field overflows, the section header field has the S_NRELOC_OVFL bit set.  In this case, the true number
       of relocation entries is found in the field of the first relocation entry for that section.  That relocation entry has a type of R_ABS,	so
       it is ignored when the relocation takes place.

See Also
       as(1), ld(1), a.out(5), syms(5), scnhdr(5)

								       RISC								  reloc(5)