test

Linker and Libraries Guide

32-bit SPARC: Initial Executable (IE)

This code sequence implements the IE model described in Thread-Local Storage Access Models.

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

Code Sequence

Initial Relocations

Symbol 

# %l7 - initialized to GOT pointer, %g7 - thread 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 instruction and or instruction 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 GOT to store the static TLS offset for symbol x. An 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 requirement permits the link-editor to identify the GOT-pointer register during a code transformation.