SPARC: Relocations

On the SPARC platform, relocation entries apply to bytes (byte8), half-words (half16), words (word32), and extended-words (xword64).

The dispn family of relocation fields (disp19, disp22, disp30) are word-aligned, sign-extended, PC-relative displacements. All encode a value with its least significant bit in position 0 of the word, and differ only in the number of bits allocated to the value.

The d2/disp8 and d2/disp14 variants encode 16 and 10-bit displacement values using two non-contiguous bit fields, d2, and dispn.

The immn family of relocation fields (imm5, imm6, imm7, imm10, imm13, imm22) represent unsigned integer constants. All encode a value with its least significant bit in position 0 of the word, and differ only in the number of bits allocated to the value.

The simmn family of relocation fields (simm10, simm11, simm13, simm22) represent signed integer constants. All encode a value with its least significant bit in position 0 of the word, and differ only in the number of bits allocated to the value.

SPARC: Relocation Types

Field names in the following table tell whether the relocation type checks for overflow. A calculated relocation value can be larger than the intended field, and a relocation type can verify (V) the value fits or truncate (T) the result. As an example, V-simm13 means that the computed value can not have significant, nonzero bits outside the simm13 field.

Table 12-16  SPARC: ELF Relocation Types

Name Value Field Calculation R_SPARC_NONE 0 None None R_SPARC_8 1 V-byte8 S + A R_SPARC_16 2 V-half16 S + A R_SPARC_32 3 V-word32 S + A R_SPARC_DISP8 4 V-byte8 S + A - P R_SPARC_DISP16 5 V-half16 S + A - P R_SPARC_DISP32 6 V-disp32 S + A - P R_SPARC_WDISP30 7 V-disp30 (S + A - P) >> 2 R_SPARC_WDISP22 8 V-disp22 (S + A - P) >> 2 R_SPARC_HI22 9 T-imm22 (S + A) >> 10 R_SPARC_22 10 V-imm22 S + A R_SPARC_13 11 V-simm13 S + A R_SPARC_LO10 12 T-simm13 (S + A) & 0x3ff R_SPARC_GOT10 13 T-simm13 G & 0x3ff R_SPARC_GOT13 14 V-simm13 G R_SPARC_GOT22 15 T-simm22 G >> 10 R_SPARC_PC10 16 T-simm13 (S + A - P) & 0x3ff R_SPARC_PC22 17 V-disp22 (S + A - P) >> 10 R_SPARC_WPLT30 18 V-disp30 (L + A - P) >> 2 R_SPARC_COPY 19 None Refer to the explanation following this table. R_SPARC_GLOB_DAT 20 V-word32 S + A R_SPARC_JMP_SLOT 21 None Refer to the explanation following this table. R_SPARC_RELATIVE 22 V-word32 B + A R_SPARC_UA32 23 V-word32 S + A R_SPARC_PLT32 24 V-word32 L + A R_SPARC_HIPLT22 25 T-imm22 (L + A) >> 10 R_SPARC_LOPLT10 26 T-simm13 (L + A) & 0x3ff R_SPARC_PCPLT32 27 V-word32 L + A - P R_SPARC_PCPLT22 28 V-disp22 (L + A - P) >> 10 R_SPARC_PCPLT10 29 V-simm13 (L + A - P) & 0x3ff R_SPARC_10 30 V-simm10 S + A R_SPARC_11 31 V-simm11 S + A R_SPARC_HH22 34 V-imm22 (S + A) >> 42 R_SPARC_HM10 35 T-simm13 ((S + A) >> 32) & 0x3ff R_SPARC_LM22 36 T-imm22 (S + A) >> 10 R_SPARC_PC_HH22 37 V-imm22 (S + A - P) >> 42 R_SPARC_PC_HM10 38 T-simm13 ((S + A - P) >> 32) & 0x3ff R_SPARC_PC_LM22 39 T-imm22 (S + A - P) >> 10 R_SPARC_WDISP16 40 V-d2/disp14 (S + A - P) >> 2 R_SPARC_WDISP19 41 V-disp19 (S + A - P) >> 2 R_SPARC_7 43 V-imm7 S + A R_SPARC_5 44 V-imm5 S + A R_SPARC_6 45 V-imm6 S + A R_SPARC_HIX22 48 V-imm22 ((S + A) ^ 0xffffffffffffffff) >> 10 R_SPARC_LOX10 49 T-simm13 ((S + A) & 0x3ff) | 0x1c00 R_SPARC_H44 50 V-imm22 (S + A) >> 22 R_SPARC_M44 51 T-imm10 ((S + A) >> 12) & 0x3ff R_SPARC_L44 52 T-imm13 (S + A) & 0xfff R_SPARC_REGISTER 53 V-word32 S + A R_SPARC_UA16 55 V-half16 S + A R_SPARC_GOTDATA_HIX22 80 V-imm22 ((S + A - GOT) >> 10) ^ ((S + A - GOT) >> 31) R_SPARC_GOTDATA_LOX10 81 T-imm13 ((S + A - GOT) & 0x3ff) | (((S + A - GOT) >> 31) & 0x1c00) R_SPARC_GOTDATA_OP_HIX22 82 T-imm22 (G >> 10) ^ (G >> 31) R_SPARC_GOTDATA_OP_LOX10 83 T-imm13 (G & 0x3ff) | ((G >> 31) & 0x1c00) R_SPARC_GOTDATA_OP 84 Word32 Refer to the explanation following this table. R_SPARC_SIZE32 86 V-word32 Z + A R_SPARC_WDISP10 88 V-d2/disp8 (S + A - P) >> 2

Some relocation types have semantics beyond simple calculation.

R_SPARC_GOT10

Resembles R_SPARC_LO10, except that the relocation refers to the address of the symbol's GOT entry. Additionally, R_SPARC_GOT10 instructs the link-editor to create a global offset table.

R_SPARC_GOT13

Resembles R_SPARC_13, except that the relocation refers to the address of the symbol's GOT entry. Additionally, R_SPARC_GOT13 instructs the link-editor to create a global offset table.

R_SPARC_GOT22

Resembles R_SPARC_22, except that the relocation refers to the address of the symbol's GOT entry. Additionally, R_SPARC_GOT22 instructs the link-editor to create a global offset table.

R_SPARC_WPLT30

Resembles R_SPARC_WDISP30, except that the relocation refers to the address of the symbol's procedure linkage table entry. Additionally, R_SPARC_WPLT30 instructs the link-editor to create a procedure linkage table.

R_SPARC_COPY

Created by the link-editor for dynamic executables to preserve a read-only text segment. The relocation offset member refers to a location in a writable segment. The symbol table index specifies a symbol that should exist both in the current object file and in a shared object. During execution, the runtime linker copies data associated with the shared object's symbol to the location specified by the offset. See Copy Relocations.

R_SPARC_GLOB_DAT

Resembles R_SPARC_32, except that the relocation sets a GOT entry to the address of the specified symbol. The special relocation type enables you to determine the correspondence between symbols and GOT entries.

R_SPARC_JMP_SLOT

Created by the link-editor for dynamic objects to provide lazy binding. The relocation offset member gives the location of a procedure linkage table entry. The runtime linker modifies the procedure linkage table entry to transfer control to the designated symbol address.

R_SPARC_RELATIVE

Created by the link-editor for dynamic objects. The relocation offset member gives the location within a shared object that contains a value representing a relative address. The runtime linker computes the corresponding virtual address by adding the virtual address at which the shared object is loaded to the relative address. Relocation entries for this type must specify a value of zero for the symbol table index.

R_SPARC_UA32

Resembles R_SPARC_32, except that the relocation refers to an unaligned word. The word to be relocated must be treated as four separate bytes with arbitrary alignment, not as a word aligned according to the architecture requirements.

R_SPARC_LM22

Resembles R_SPARC_HI22, except that the relocation truncates rather than validates.

R_SPARC_PC_LM22

Resembles R_SPARC_PC22, except that the relocation truncates rather than validates.

R_SPARC_HIX22

Used with R_SPARC_LOX10 for executables that are confined to the uppermost 4 gigabytes of the 64–bit address space. Similar to R_SPARC_HI22, but supplies ones complement of linked value.

R_SPARC_LOX10

Used with R_SPARC_HIX22. Similar to R_SPARC_LO10, but always sets bits 10 through 12 of the linked value.

R_SPARC_L44

Used with the R_SPARC_H44 and R_SPARC_M44 relocation types to generate a 44-bit absolute addressing model.

R_SPARC_REGISTER

Used to initialize a register symbol. The relocation offset member contains the register number to be initialized. A corresponding register symbol must exist for this register. The symbol must be of type SHN_ABS.

R_SPARC_GOTDATA_OP_HIX22, R_SPARC_GOTDATA_OP_LOX10, and R_SPARC_GOTDATA_OP

These relocations provide for code transformations.

64-bit SPARC: Relocation Types

The following notation, used in relocation calculation, is unique to 64–bit SPARC.

O

The secondary addend used to compute the value of the relocation field. This addend is extracted from the r_info field by applying the ELF64_R_TYPE_DATA macro.

The relocations that are listed in the following table extend, or alter, the relocations defined for 32–bit SPARC. See Relocation Types.

Table 12-17  64-bit SPARC: ELF Relocation Types

Name Value Field Calculation R_SPARC_HI22 9 V-imm22 (S + A) >> 10 R_SPARC_GLOB_DAT 20 V-xword64 S + A R_SPARC_RELATIVE 22 V-xword64 B + A R_SPARC_64 32 V-xword64 S + A R_SPARC_OLO10 33 V-simm13 ((S + A) & 0x3ff) + O R_SPARC_DISP64 46 V-xword64 S + A - P R_SPARC_PLT64 47 V-xword64 L + A R_SPARC_REGISTER 53 V-xword64 S + A R_SPARC_UA64 54 V-xword64 S + A R_SPARC_H34 85 V-imm22 (S + A) >> 12 R_SPARC_SIZE64 87 V-xword64 Z + A

The following relocation type has semantics beyond simple calculation.

R_SPARC_OLO10

Resembles R_SPARC_LO10, except that an extra offset is added to make full use of the 13-bit signed immediate field.