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_24

: 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_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_7

: BFD_RELOC_SPARC_6

: BFD_RELOC_SPARC_5

: BFD_RELOC_SPARC_DISP64

: BFD_RELOC_SPARC_PLT64

: BFD_RELOC_SPARC_HIX22

: BFD_RELOC_SPARC_LOX10

: BFD_RELOC_SPARC_H44

: BFD_RELOC_SPARC_M44

: BFD_RELOC_SPARC_L44

: BFD_RELOC_SPARC_REGISTER

SPARC64 relocations

: 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_ELF_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 ELF_LITERAL reloc is somewhere between 16_GOTOFF and GPDISP_LO16. It should refer to the symbol to be referenced, as with 16_GOTOFF, but it generates output not based on the position within the .got section, but relative to the GP value chosen for the file during the final link stage.

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 linkage pair in the object file, which is filled by the linker.

: BFD_RELOC_ALPHA_CODEADDR

The CODEADDR relocation outputs a STO_CA in the object file, which is filled by the linker.

: BFD_RELOC_MIPS_JMP

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

: BFD_RELOC_MIPS16_JMP

The MIPS16 jump instruction.

: BFD_RELOC_MIPS16_GPREL

MIPS16 GP relative reloc.

: 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

: BFD_RELOC_ARM_OFFSET_IMM8

: BFD_RELOC_ARM_HWLITERAL

: BFD_RELOC_ARM_THUMB_ADD

: BFD_RELOC_ARM_THUMB_IMM

: BFD_RELOC_ARM_THUMB_SHIFT

: BFD_RELOC_ARM_THUMB_OFFSET

These relocs are only used within the ARM assembler. They are not (at present) written to any object files.

: BFD_RELOC_SH_PCDISP8BY2

: BFD_RELOC_SH_PCDISP12BY2

: BFD_RELOC_SH_IMM4

: BFD_RELOC_SH_IMM4BY2

: BFD_RELOC_SH_IMM4BY4

: BFD_RELOC_SH_IMM8

: BFD_RELOC_SH_IMM8BY2

: BFD_RELOC_SH_IMM8BY4

: BFD_RELOC_SH_PCRELIMM8BY2

: BFD_RELOC_SH_PCRELIMM8BY4

: BFD_RELOC_SH_SWITCH16

: BFD_RELOC_SH_SWITCH32

: BFD_RELOC_SH_USES

: BFD_RELOC_SH_COUNT

: BFD_RELOC_SH_ALIGN

: BFD_RELOC_SH_CODE

: BFD_RELOC_SH_DATA

: BFD_RELOC_SH_LABEL

Hitachi SH relocs. Not all of these appear in object files.

: BFD_RELOC_THUMB_PCREL_BRANCH9

: BFD_RELOC_THUMB_PCREL_BRANCH12

: BFD_RELOC_THUMB_PCREL_BRANCH23

Thumb 23-, 12- and 9-bit pc-relative branches. The lowest bit must be zero and is not stored in the instruction.

: BFD_RELOC_ARC_B22_PCREL

Argonaut RISC Core (ARC) relocs. ARC 22 bit pc-relative branch. The lowest two bits must be zero and are not stored in the instruction. The high 20 bits are installed in bits 26 through 7 of the instruction.

: BFD_RELOC_ARC_B26

ARC 26 bit absolute branch. The lowest two bits must be zero and are not stored in the instruction. The high 24 bits are installed in bits 23 through 0.

: BFD_RELOC_D10V_10_PCREL_R

Mitsubishi D10V relocs. This is a 10-bit reloc with the right 2 bits assumed to be 0.

: BFD_RELOC_D10V_10_PCREL_L

Mitsubishi D10V relocs. This is a 10-bit reloc with the right 2 bits assumed to be 0. This is the same as the previous reloc except it is in the left container, i.e., shifted left 15 bits.

: BFD_RELOC_D10V_18

This is an 18-bit reloc with the right 2 bits assumed to be 0.

: BFD_RELOC_D10V_18_PCREL

This is an 18-bit reloc with the right 2 bits assumed to be 0.

: BFD_RELOC_M32R_24

Mitsubishi M32R relocs. This is a 24 bit absolute address.

: BFD_RELOC_M32R_10_PCREL

This is a 10-bit pc-relative reloc with the right 2 bits assumed to be 0.

: BFD_RELOC_M32R_18_PCREL

This is an 18-bit reloc with the right 2 bits assumed to be 0.

: BFD_RELOC_M32R_26_PCREL

This is a 26-bit reloc with the right 2 bits assumed to be 0.

: BFD_RELOC_M32R_HI16_ULO

This is a 16-bit reloc containing the high 16 bits of an address used when the lower 16 bits are treated as unsigned.

: BFD_RELOC_M32R_HI16_SLO

This is a 16-bit reloc containing the high 16 bits of an address used when the lower 16 bits are treated as signed.

: BFD_RELOC_M32R_LO16

This is a 16-bit reloc containing the lower 16 bits of an address.

: BFD_RELOC_M32R_SDA16

This is a 16-bit reloc containing the small data area offset for use in add3, load, and store instructions.

: BFD_RELOC_V850_9_PCREL

This is a 9-bit reloc

: BFD_RELOC_V850_22_PCREL

This is a 22-bit reloc

: BFD_RELOC_V850_SDA_16_16_OFFSET

This is a 16 bit offset from the short data area pointer.

: BFD_RELOC_V850_SDA_15_16_OFFSET

This is a 16 bit offset (of which only 15 bits are used) from the short data area pointer.

: BFD_RELOC_V850_ZDA_16_16_OFFSET

This is a 16 bit offset from the zero data area pointer.

: BFD_RELOC_V850_ZDA_15_16_OFFSET

This is a 16 bit offset (of which only 15 bits are used) from the zero data area pointer.

: BFD_RELOC_V850_TDA_6_8_OFFSET

This is an 8 bit offset (of which only 6 bits are used) from the tiny data area pointer.

: BFD_RELOC_V850_TDA_7_8_OFFSET

This is an 8bit offset (of which only 7 bits are used) from the tiny data area pointer.

: BFD_RELOC_V850_TDA_7_7_OFFSET

This is a 7 bit offset from the tiny data area pointer.

: BFD_RELOC_V850_TDA_16_16_OFFSET

This is a 16 bit offset from the tiny data area pointer.

: BFD_RELOC_MN10300_32_PCREL

This is a 32bit pcrel reloc for the mn10300, offset by two bytes in the instruction.

: BFD_RELOC_MN10300_16_PCREL

This is a 16bit pcrel reloc for the mn10300, offset by two bytes in the instruction.

: BFD_RELOC_TIC30_LDP

This is a 8bit DP reloc for the tms320c30, where the most significant 8 bits of a 24 bit word are placed into the least significant 8 bits of the opcode.

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.

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