SPARC: 32-bit Initial Executable (IE) (Linker and Libraries Guide)

Linker and Libraries Guide

SPARC: 32-bit Initial Executable (IE)

This code sequence can only be used in a dynamic executable. It can reference a TLS variable defined in either the executable or any shared libraries loaded at process startup. This model can not reference TLS variables from shared libraries loaded after process startup.

Table 8–4 SPARC: 32-bit Initial Executable Thread-Local Variable Access Codes

Code Sequence	Initial Relocations	Symbol
# %l7 - initialized to GOT pointer 0x00 sethi %hi(@tpoff(x)), %o0 0x04 or %o0,%lo(@tpoff(x)),%o0 0x08 ld [%l7 + %o0], %o0 0x0c add %g7, %o0, %o0 # %o0 - contains address of TLS variable	R_SPARC_TLS_IE_HI22 R_SPARC_TLS_IE_LO10 R_SPARC_TLS_IE_LD R_SPARC_TLS_IE_ADD	x x x x

Code Sequence

Initial Relocations

Symbol

# %l7 - initialized to GOT pointer

0x00 sethi %hi(@tpoff(x)), %o0
0x04 or    %o0,%lo(@tpoff(x)),%o0
0x08 ld    [%l7 + %o0], %o0
0x0c add   %g7, %o0, %o0
 
# %o0 - contains address of TLS variable

 
 
R_SPARC_TLS_IE_HI22
R_SPARC_TLS_IE_LO10
R_SPARC_TLS_IE_LD
R_SPARC_TLS_IE_ADD

 
 
x
x
x
x


	Outstanding Relocations	Symbol
GOT[n]	R_SPARC_TLS_TPOFF32	x

The sethi and or instructions generate R_SPARC_TLS_IE_HI22 and R_SPARC_TLS_IE_LO10 relocations, respectively. These relocations instruct the link-editor to create space in the global offset table to store the static TLS offset for symbol x. A R_SPARC_TLS_TPOFF32 relocation is left outstanding against the GOT for the runtime linker to fill in with the negative static TLS offset for symbol x. The ld and the add instructions are tagged with the R_SPARC_TLS_IE_LD and R_SPARC_TLS_IE_ADD relocations respectively.

Note –

The register used as the GOT-pointer for the add instruction tagged by the R_SPARC_TLS_IE_ADD relocation must be the first register in the instruction. This permits the link-editor to identify the GOT-pointer register during a code transformation.