Relocations
===========

BFD maintains relocations in much the same way it maintains symbols: they are left alone until required, then read in en-mass and translated into an internal form.  A common routine bfd_perform_relocation acts upon the canonical form to do the fixup.

Relocations are maintained on a per section basis, while symbols are maintained on a per BFD basis.

All that a back end has to do to fit the BFD interface is to create a struct reloc_cache_entry for each relocation in a particular section, and fill in the right bits of the structures.

typedef arelent
---------------

This is the structure of a relocation entry: .

     typedef enum bfd_reloc_status
     {
            /* No errors detected */
       bfd_reloc_ok,

            /* The relocation was performed, but there was an overflow. */
       bfd_reloc_overflow,

            /* The address to relocate was not within the section supplied. */
       bfd_reloc_outofrange,

            /* Used by special functions */
       bfd_reloc_continue,

            /* Unsupported relocation size requested. */
       bfd_reloc_notsupported,

            /* Unused */
       bfd_reloc_other,

            /* The symbol to relocate against was undefined. */
       bfd_reloc_undefined,

            /* The relocation was performed, but may not be ok - presently
               generated only when linking i960 coff files with i960 b.out
               symbols.  If this type is returned, the error_message argument
               to bfd_perform_relocation will be set.  */
       bfd_reloc_dangerous
      }
      bfd_reloc_status_type;

     typedef struct reloc_cache_entry
     {
            /* A pointer into the canonical table of pointers  */
       struct symbol_cache_entry **sym_ptr_ptr;

            /* offset in section */
       bfd_size_type address;

            /* addend for relocation value */
       bfd_vma addend;

            /* Pointer to how to perform the required relocation */
       reloc_howto_type *howto;

     } arelent;

Description

Here is a description of each of the fields within an arelent:

  * sym_ptr_ptr

The symbol table pointer points to a pointer to the symbol associated with the relocation request.  It is the pointer into the table returned by the back end's get_symtab action. See Symbols. The symbol is referenced through a pointer to a pointer so that tools like the linker can fix up all the symbols of the same name by modifying only one pointer. The relocation routine looks in the symbol and uses the base of the section the symbol is attached to and the value of the symbol as the initial relocation offset. If the symbol pointer is zero, then the section provided is looked up.

  * address

The address field gives the offset in bytes from the base of the section data which owns the relocation record to the first byte of relocatable information. The actual data relocated will be relative to this point; for example, a relocation type which modifies the bottom two bytes of a four byte word would not touch the first byte pointed to in a big endian world.

  * addend

The addend is a value provided by the back end to be added (!) to the relocation offset. Its interpretation is dependent upon the howto. For example, on the 68k the code:

             char foo[];
             main()
                     {
                     return foo[0x12345678];
                     }

Could be compiled into:

             linkw fp,#-4
             moveb @#12345678,d0
             extbl d0
             unlk fp
             rts

This could create a reloc pointing to foo, but leave the offset in the data, something like:

     RELOCATION RECORDS FOR [.text]:
     offset   type      value
     00000006 32        _foo

     00000000 4e56 fffc          ; linkw fp,#-4
     00000004 1039 1234 5678     ; moveb @#12345678,d0
     0000000a 49c0               ; extbl d0
     0000000c 4e5e               ; unlk fp
     0000000e 4e75               ; rts

Using coff and an 88k, some instructions don't have enough space in them to represent the full address range, and pointers have to be loaded in two parts. So you'd get something like:

             or.u     r13,r0,hi16(_foo+0x12345678)
             ld.b     r2,r13,lo16(_foo+0x12345678)
             jmp      r1

This should create two relocs, both pointing to _foo, and with 0x12340000 in their addend field. The data would consist of:

     RELOCATION RECORDS FOR [.text]:
     offset   type      value
     00000002 HVRT16    _foo+0x12340000
     00000006 LVRT16    _foo+0x12340000

     00000000 5da05678           ; or.u r13,r0,0x5678
     00000004 1c4d5678           ; ld.b r2,r13,0x5678
     00000008 f400c001           ; jmp r1

The relocation routine digs out the value from the data, adds it to the addend to get the original offset, and then adds the value of _foo. Note that all 32 bits have to be kept around somewhere, to cope with carry from bit 15 to bit 16.

One further example is the sparc and the a.out format. The sparc has a similar problem to the 88k, in that some instructions don't have room for an entire offset, but on the sparc the parts are created in odd sized lumps. The designers of the a.out format chose to not use the data within the section for storing part of the offset; all the offset is kept within the reloc. Anything in the data should be ignored.

             save %sp,-112,%sp
             sethi %hi(_foo+0x12345678),%g2
             ldsb [%g2+%lo(_foo+0x12345678)],%i0
             ret
             restore

Both relocs contain a pointer to foo, and the offsets contain junk.

     RELOCATION RECORDS FOR [.text]:
     offset   type      value
     00000004 HI22      _foo+0x12345678
     00000008 LO10      _foo+0x12345678

     00000000 9de3bf90     ; save %sp,-112,%sp
     00000004 05000000     ; sethi %hi(_foo+0),%g2
     00000008 f048a000     ; ldsb [%g2+%lo(_foo+0)],%i0
     0000000c 81c7e008     ; ret
     00000010 81e80000     ; restore

  * howto

The howto field can be imagined as a relocation instruction. It is a pointer to a structure which contains information on what to do with all of the other information in the reloc record and data section. A back end would normally have a relocation instruction set and turn relocations into pointers to the correct structure on input - but it would be possible to create each howto field on demand.

enum complain_overflow
......................

Indicates what sort of overflow checking should be done when performing a relocation. .

     enum complain_overflow
     {
     	/* Do not complain on overflow. */
       complain_overflow_dont,

     	/* Complain if the bitfield overflows, whether it is considered
     	   as signed or unsigned. */
       complain_overflow_bitfield,

     	/* Complain if the value overflows when considered as signed
     	   number. */
       complain_overflow_signed,

     	/* Complain if the value overflows when considered as an
     	   unsigned number. */
       complain_overflow_unsigned
     };

reloc_howto_type
................

The reloc_howto_type is a structure which contains all the information that libbfd needs to know to tie up a back end's data. .struct symbol_cache_entry;		/* Forward declaration */

     struct reloc_howto_struct
     {
            /*  The type field has mainly a documetary use - the back end can
                do what it wants with it, though normally the back end's
                external idea of what a reloc number is stored
                in this field. For example, a PC relative word relocation
                in a coff environment has the type 023 - because that's
                what the outside world calls a R_PCRWORD reloc. */
       unsigned int type;

            /*  The value the final relocation is shifted right by. This drops
                unwanted data from the relocation.  */
       unsigned int rightshift;

     	/*  The size of the item to be relocated.  This is *not* a
     	    power-of-two measure.  To get the number of bytes operated
     	    on by a type of relocation, use bfd_get_reloc_size.  */
       int size;

            /*  The number of bits in the item to be relocated.  This is used
     	    when doing overflow checking.  */
       unsigned int bitsize;

            /*  Notes that the relocation is relative to the location in the
                data section of the addend. The relocation function will
                subtract from the relocation value the address of the location
                being relocated. */
       boolean pc_relative;

     	/*  The bit position of the reloc value in the destination.
     	    The relocated value is left shifted by this amount. */
       unsigned int bitpos;

     	/* What type of overflow error should be checked for when
     	   relocating. */
       enum complain_overflow complain_on_overflow;

            /* If this field is non null, then the supplied function is
               called rather than the normal function. This allows really
               strange relocation methods to be accomodated (e.g., i960 callj
               instructions). */
       bfd_reloc_status_type (*special_function)
     				    PARAMS ((bfd *abfd,
     					     arelent *reloc_entry,
                                                 struct symbol_cache_entry *symbol,
                                                 PTR data,
                                                 asection *input_section,
                                                 bfd *output_bfd,
                                                 char **error_message));

            /* The textual name of the relocation type. */
       char *name;

            /* When performing a partial link, some formats must modify the
               relocations rather than the data - this flag signals this.*/
       boolean partial_inplace;

            /* The src_mask selects which parts of the read in data
               are to be used in the relocation sum.  E.g., if this was an 8 bit
               bit of data which we read and relocated, this would be
               0x000000ff. When we have relocs which have an addend, such as
               sun4 extended relocs, the value in the offset part of a
               relocating field is garbage so we never use it. In this case
               the mask would be 0x00000000. */
       bfd_vma src_mask;

            /* The dst_mask selects which parts of the instruction are replaced
               into the instruction. In most cases src_mask == dst_mask,
               except in the above special case, where dst_mask would be
               0x000000ff, and src_mask would be 0x00000000.   */
       bfd_vma dst_mask;

            /* When some formats create PC relative instructions, they leave
               the value of the pc of the place being relocated in the offset
               slot of the instruction, so that a PC relative relocation can
               be made just by adding in an ordinary offset (e.g., sun3 a.out).
               Some formats leave the displacement part of an instruction
               empty (e.g., m88k bcs); this flag signals the fact.*/
       boolean pcrel_offset;

     };

The HOWTO Macro
...............

Description

The HOWTO define is horrible and will go away.

     #define HOWTO(C, R,S,B, P, BI, O, SF, NAME, INPLACE, MASKSRC, MASKDST, PC) \
       {(unsigned)C,R,S,B, P, BI, O,SF,NAME,INPLACE,MASKSRC,MASKDST,PC}

Description

And will be replaced with the totally magic way. But for the moment, we are compatible, so do it this way.

     #define NEWHOWTO( FUNCTION, NAME,SIZE,REL,IN) HOWTO(0,0,SIZE,0,REL,0,complain_overflow_dont,FUNCTION, NAME,false,0,0,IN)

Description

Helper routine to turn a symbol into a relocation value.

     #define HOWTO_PREPARE(relocation, symbol)      \
       {                                            \
       if (symbol != (asymbol *)NULL) {             \
         if (bfd_is_com_section (symbol->section)) { \
           relocation = 0;                          \
         }                                          \
         else {                                     \
           relocation = symbol->value;              \
         }                                          \
       }                                            \
     }

bfd_get_reloc_size
..................

Synopsis

     int bfd_get_reloc_size (reloc_howto_type *);

Description

For a reloc_howto_type that operates on a fixed number of bytes, this returns the number of bytes operated on.

arelent_chain
.............

Description

How relocs are tied together in an asection:

     typedef struct relent_chain {
       arelent relent;
       struct   relent_chain *next;
     } arelent_chain;

bfd_perform_relocation
......................

Synopsis

     bfd_reloc_status_type
     bfd_perform_relocation
        (bfd *abfd,
         arelent *reloc_entry,
         PTR data,
         asection *input_section,
         bfd *output_bfd,
         char **error_message);

Description

If OUTPUT_BFD is supplied to this function, the generated image will be relocatable; the relocations are copied to the output file after they have been changed to reflect the new state of the world. There are two ways of reflecting the results of partial linkage in an output file: by modifying the output data in place, and by modifying the relocation record.  Some native formats (e.g., basic a.out and basic coff) have no way of specifying an addend in the relocation type, so the addend has to go in the output data. This is no big deal since in these formats the output data slot will always be big enough for the addend. Complex reloc types with addends were invented to solve just this problem. The ERROR_MESSAGE argument is set to an error message if this return bfd_reloc_dangerous.

bfd_install_relocation
......................

Synopsis

     bfd_reloc_status_type
     bfd_install_relocation
        (bfd *abfd,
         arelent *reloc_entry,
         PTR data, bfd_vma data_start,
         asection *input_section,
         char **error_message);

Description

This looks remarkably like bfd_perform_relocation, except it does not expect that the section contents have been filled in. I.e., it's suitable for use when creating, rather than applying a relocation.

For now, this function should be considered reserved for the assembler.

The howto manager
=================

When an application wants to create a relocation, but doesn't know what the target machine might call it, it can find out by using this bit of code.

bfd_reloc_code_type
...................

Description

The insides of a reloc code.  The idea is that, eventually, there will be one enumerator for every type of relocation we ever do. Pass one of these values to bfd_reloc_type_lookup, and it'll return a howto pointer.

This does mean that the application must determine the correct enumerator value; you can't get a howto pointer from a random set of attributes. Here are the possible values for enum bfd_reloc_code_real:

 -- BFD_RELOC_64:
 -- BFD_RELOC_32:
 -- BFD_RELOC_26:
 -- BFD_RELOC_16:
 -- BFD_RELOC_14:
 -- BFD_RELOC_8:
     Basic absolute relocations of N bits.

 -- BFD_RELOC_64_PCREL:
 -- BFD_RELOC_32_PCREL:
 -- BFD_RELOC_24_PCREL:
 -- BFD_RELOC_16_PCREL:
 -- BFD_RELOC_12_PCREL:
 -- BFD_RELOC_8_PCREL:
     PC-relative relocations.  Sometimes these are relative to the address of the relocation itself; sometimes they are relative to the start of the section containing the relocation.  It depends on the specific target.

     The 24-bit relocation is used in some Intel 960 configurations.

 -- BFD_RELOC_32_GOT_PCREL:
 -- BFD_RELOC_16_GOT_PCREL:
 -- BFD_RELOC_8_GOT_PCREL:
 -- BFD_RELOC_32_GOTOFF:
 -- BFD_RELOC_16_GOTOFF:
 -- BFD_RELOC_LO16_GOTOFF:
 -- BFD_RELOC_HI16_GOTOFF:
 -- BFD_RELOC_HI16_S_GOTOFF:
 -- BFD_RELOC_8_GOTOFF:
 -- BFD_RELOC_32_PLT_PCREL:
 -- BFD_RELOC_24_PLT_PCREL:
 -- BFD_RELOC_16_PLT_PCREL:
 -- BFD_RELOC_8_PLT_PCREL:
 -- BFD_RELOC_32_PLTOFF:
 -- BFD_RELOC_16_PLTOFF:
 -- BFD_RELOC_LO16_PLTOFF:
 -- BFD_RELOC_HI16_PLTOFF:
 -- BFD_RELOC_HI16_S_PLTOFF:
 -- BFD_RELOC_8_PLTOFF:
     For ELF.

 -- BFD_RELOC_68K_GLOB_DAT:
 -- BFD_RELOC_68K_JMP_SLOT:
 -- BFD_RELOC_68K_RELATIVE:
     Relocations used by 68K ELF.

 -- BFD_RELOC_32_BASEREL:
 -- BFD_RELOC_16_BASEREL:
 -- BFD_RELOC_LO16_BASEREL:
 -- BFD_RELOC_HI16_BASEREL:
 -- BFD_RELOC_HI16_S_BASEREL:
 -- BFD_RELOC_8_BASEREL:
 -- BFD_RELOC_RVA:
     Linkage-table relative.

 -- BFD_RELOC_8_FFnn:
     Absolute 8-bit relocation, but used to form an address like 0xFFnn.

 -- BFD_RELOC_32_PCREL_S2:
 -- BFD_RELOC_16_PCREL_S2:
 -- BFD_RELOC_23_PCREL_S2:
     These PC-relative relocations are stored as word displacements -- i.e., byte displacements shifted right two bits.  The 30-bit word displacement (<<32_PCREL_S2>> -- 32 bits, shifted 2) is used on the SPARC.  (SPARC tools generally refer to this as <<WDISP30>>.)  The signed 16-bit displacement is used on the MIPS, and the 23-bit displacement is used on the Alpha.

 -- BFD_RELOC_HI22:
 -- BFD_RELOC_LO10:
     High 22 bits and low 10 bits of 32-bit value, placed into lower bits of the target word.  These are used on the SPARC.

 -- BFD_RELOC_GPREL16:
 -- BFD_RELOC_GPREL32:
     For systems that allocate a Global Pointer register, these are displacements off that register.  These relocation types are handled specially, because the value the register will have is decided relatively late.

 -- BFD_RELOC_SWREL32:
 -- BFD_RELOC_SWREL64:
     For openVMS/Alpha systems, these are displacements for switch tables.

 -- BFD_RELOC_I960_CALLJ:
     Reloc types used for i960/b.out.

 -- BFD_RELOC_NONE:
 -- BFD_RELOC_SPARC_WDISP22:
 -- BFD_RELOC_SPARC22:
 -- BFD_RELOC_SPARC13:
 -- BFD_RELOC_SPARC_GOT10:
 -- BFD_RELOC_SPARC_GOT13:
 -- BFD_RELOC_SPARC_GOT22:
 -- BFD_RELOC_SPARC_PC10:
 -- BFD_RELOC_SPARC_PC22:
 -- BFD_RELOC_SPARC_WPLT30:
 -- BFD_RELOC_SPARC_COPY:
 -- BFD_RELOC_SPARC_GLOB_DAT:
 -- BFD_RELOC_SPARC_JMP_SLOT:
 -- BFD_RELOC_SPARC_RELATIVE:
 -- BFD_RELOC_SPARC_UA32:
     SPARC ELF relocations.  There is probably some overlap with other relocation types already defined.

 -- BFD_RELOC_SPARC_BASE13:
 -- BFD_RELOC_SPARC_BASE22:
     I think these are specific to SPARC a.out (e.g., Sun 4).

 -- BFD_RELOC_SPARC_64:
 -- BFD_RELOC_SPARC_10:
 -- BFD_RELOC_SPARC_11:
 -- BFD_RELOC_SPARC_OLO10:
 -- BFD_RELOC_SPARC_HH22:
 -- BFD_RELOC_SPARC_HM10:
 -- BFD_RELOC_SPARC_LM22:
 -- BFD_RELOC_SPARC_PC_HH22:
 -- BFD_RELOC_SPARC_PC_HM10:
 -- BFD_RELOC_SPARC_PC_LM22:
 -- BFD_RELOC_SPARC_WDISP16:
 -- BFD_RELOC_SPARC_WDISP19:
 -- BFD_RELOC_SPARC_GLOB_JMP:
 -- BFD_RELOC_SPARC_7:
 -- BFD_RELOC_SPARC_6:
 -- BFD_RELOC_SPARC_5:
     Some relocations we're using for SPARC V9 -- subject to change.

 -- BFD_RELOC_ALPHA_GPDISP_HI16:
     Alpha ECOFF and ELF relocations.  Some of these treat the symbol or "addend" in some special way. For GPDISP_HI16 ("gpdisp") relocations, the symbol is ignored when writing; when reading, it will be the absolute section symbol.  The addend is the displacement in bytes of the "lda" instruction from the "ldah" instruction (which is at the address of this reloc).

 -- BFD_RELOC_ALPHA_GPDISP_LO16:
     For GPDISP_LO16 ("ignore") relocations, the symbol is handled as with GPDISP_HI16 relocs.  The addend is ignored when writing the relocations out, and is filled in with the file's GP value on reading, for convenience.

 -- BFD_RELOC_ALPHA_GPDISP:
     The ELF GPDISP relocation is exactly the same as the GPDISP_HI16 relocation except that there is no accompanying GPDISP_LO16 relocation.

 -- BFD_RELOC_ALPHA_LITERAL:
 -- BFD_RELOC_ALPHA_LITUSE:
     The Alpha LITERAL/LITUSE relocs are produced by a symbol reference; the assembler turns it into a LDQ instruction to load the address of the symbol, and then fills in a register in the real instruction.

     The LITERAL reloc, at the LDQ instruction, refers to the .lita section symbol.  The addend is ignored when writing, but is filled in with the file's GP value on reading, for convenience, as with the GPDISP_LO16 reloc.

     The LITUSE reloc, on the instruction using the loaded address, gives information to the linker that it might be able to use to optimize away some literal section references.  The symbol is ignored (read as the absolute section symbol), and the "addend" indicates the type of instruction using the register: 1 - "memory" fmt insn 2 - byte-manipulation (byte offset reg) 3 - jsr (target of branch)

     The GNU linker currently doesn't do any of this optimizing.

 -- BFD_RELOC_ALPHA_HINT:
     The HINT relocation indicates a value that should be filled into the "hint" field of a jmp/jsr/ret instruction, for possible branch- prediction logic which may be provided on some processors.

 -- BFD_RELOC_ALPHA_LINKAGE:
     The LINKAGE relocation outputs a special code in the object file, the rest is handled by the linker.

 -- BFD_RELOC_ALPHA_BASEREG:
     The BASEREG relocation calculates differences to basereg.

 -- BFD_RELOC_MIPS_JMP:
     Bits 27..2 of the relocation address shifted right 2 bits; simple reloc otherwise.

 -- BFD_RELOC_HI16:
     High 16 bits of 32-bit value; simple reloc.

 -- BFD_RELOC_HI16_S:
     High 16 bits of 32-bit value but the low 16 bits will be sign extended and added to form the final result.  If the low 16 bits form a negative number, we need to add one to the high value to compensate for the borrow when the low bits are added.

 -- BFD_RELOC_LO16:
     Low 16 bits.

 -- BFD_RELOC_PCREL_HI16_S:
     Like BFD_RELOC_HI16_S, but PC relative.

 -- BFD_RELOC_PCREL_LO16:
     Like BFD_RELOC_LO16, but PC relative.

 -- BFD_RELOC_MIPS_GPREL:
     Relocation relative to the global pointer.

 -- BFD_RELOC_MIPS_LITERAL:
     Relocation against a MIPS literal section.

 -- BFD_RELOC_MIPS_GOT16:
 -- BFD_RELOC_MIPS_CALL16:
 -- BFD_RELOC_MIPS_GPREL32:
 -- BFD_RELOC_MIPS_GOT_HI16:
 -- BFD_RELOC_MIPS_GOT_LO16:
 -- BFD_RELOC_MIPS_CALL_HI16:
 -- BFD_RELOC_MIPS_CALL_LO16:
     MIPS ELF relocations.

 -- BFD_RELOC_386_GOT32:
 -- BFD_RELOC_386_PLT32:
 -- BFD_RELOC_386_COPY:
 -- BFD_RELOC_386_GLOB_DAT:
 -- BFD_RELOC_386_JUMP_SLOT:
 -- BFD_RELOC_386_RELATIVE:
 -- BFD_RELOC_386_GOTOFF:
 -- BFD_RELOC_386_GOTPC:
     i386/elf relocations

 -- BFD_RELOC_NS32K_IMM_8:
 -- BFD_RELOC_NS32K_IMM_16:
 -- BFD_RELOC_NS32K_IMM_32:
 -- BFD_RELOC_NS32K_IMM_8_PCREL:
 -- BFD_RELOC_NS32K_IMM_16_PCREL:
 -- BFD_RELOC_NS32K_IMM_32_PCREL:
 -- BFD_RELOC_NS32K_DISP_8:
 -- BFD_RELOC_NS32K_DISP_16:
 -- BFD_RELOC_NS32K_DISP_32:
 -- BFD_RELOC_NS32K_DISP_8_PCREL:
 -- BFD_RELOC_NS32K_DISP_16_PCREL:
 -- BFD_RELOC_NS32K_DISP_32_PCREL:
     ns32k relocations

 -- BFD_RELOC_PPC_B26:
 -- BFD_RELOC_PPC_BA26:
 -- BFD_RELOC_PPC_TOC16:
 -- BFD_RELOC_PPC_B16:
 -- BFD_RELOC_PPC_B16_BRTAKEN:
 -- BFD_RELOC_PPC_B16_BRNTAKEN:
 -- BFD_RELOC_PPC_BA16:
 -- BFD_RELOC_PPC_BA16_BRTAKEN:
 -- BFD_RELOC_PPC_BA16_BRNTAKEN:
 -- BFD_RELOC_PPC_COPY:
 -- BFD_RELOC_PPC_GLOB_DAT:
 -- BFD_RELOC_PPC_JMP_SLOT:
 -- BFD_RELOC_PPC_RELATIVE:
 -- BFD_RELOC_PPC_LOCAL24PC:
 -- BFD_RELOC_PPC_EMB_NADDR32:
 -- BFD_RELOC_PPC_EMB_NADDR16:
 -- BFD_RELOC_PPC_EMB_NADDR16_LO:
 -- BFD_RELOC_PPC_EMB_NADDR16_HI:
 -- BFD_RELOC_PPC_EMB_NADDR16_HA:
 -- BFD_RELOC_PPC_EMB_SDAI16:
 -- BFD_RELOC_PPC_EMB_SDA2I16:
 -- BFD_RELOC_PPC_EMB_SDA2REL:
 -- BFD_RELOC_PPC_EMB_SDA21:
 -- BFD_RELOC_PPC_EMB_MRKREF:
 -- BFD_RELOC_PPC_EMB_RELSEC16:
 -- BFD_RELOC_PPC_EMB_RELST_LO:
 -- BFD_RELOC_PPC_EMB_RELST_HI:
 -- BFD_RELOC_PPC_EMB_RELST_HA:
 -- BFD_RELOC_PPC_EMB_BIT_FLD:
 -- BFD_RELOC_PPC_EMB_RELSDA:
     Power(rs6000) and PowerPC relocations.

 -- BFD_RELOC_CTOR:
     The type of reloc used to build a contructor table - at the moment probably a 32 bit wide absolute relocation, but the target can choose. It generally does map to one of the other relocation types.

 -- BFD_RELOC_ARM_PCREL_BRANCH:
     ARM 26 bit pc-relative branch.  The lowest two bits must be zero and are not stored in the instruction.

 -- BFD_RELOC_ARM_IMMEDIATE:
 -- BFD_RELOC_ARM_OFFSET_IMM:
 -- BFD_RELOC_ARM_SHIFT_IMM:
 -- BFD_RELOC_ARM_SWI:
 -- BFD_RELOC_ARM_MULTI:
 -- BFD_RELOC_ARM_CP_OFF_IMM:
 -- BFD_RELOC_ARM_ADR_IMM:
 -- BFD_RELOC_ARM_LDR_IMM:
 -- BFD_RELOC_ARM_LITERAL:
 -- BFD_RELOC_ARM_IN_POOL:
     These relocs are only used within the ARM assembler.  They are not (at present) written to any object files.

.

     typedef enum bfd_reloc_code_real bfd_reloc_code_real_type;

bfd_reloc_type_lookup
.....................

Synopsis

     reloc_howto_type *
     bfd_reloc_type_lookup (bfd *abfd, bfd_reloc_code_real_type code);

Description

Return a pointer to a howto structure which, when invoked, will perform the relocation CODE on data from the architecture noted.

bfd_default_reloc_type_lookup
.............................

Synopsis

     reloc_howto_type *bfd_default_reloc_type_lookup
        (bfd *abfd, bfd_reloc_code_real_type  code);

Description

Provides a default relocation lookup routine for any architecture.

bfd_get_reloc_code_name
.......................

Synopsis

     const char *bfd_get_reloc_code_name (bfd_reloc_code_real_type code);

Description

Provides a printable name for the supplied relocation code. Useful mainly for printing error messages.

bfd_generic_relax_section
.........................

Synopsis

     boolean bfd_generic_relax_section
        (bfd *abfd,
         asection *section,
         struct bfd_link_info *,
         boolean *);

Description

Provides default handling for relaxing for back ends which don't do relaxing -- i.e., does nothing.

bfd_generic_get_relocated_section_contents
..........................................

Synopsis

     bfd_byte *
     bfd_generic_get_relocated_section_contents (bfd *abfd,
         struct bfd_link_info *link_info,
         struct bfd_link_order *link_order,
         bfd_byte *data,
         boolean relocateable,
         asymbol **symbols);

Description

Provides default handling of relocation effort for back ends which can't be bothered to do it efficiently.