glossary.md

Glossary

Section

An area of program address space with a specific kind of content.

Name	Purpose	DOL	REL
init	Program entrypoint	Yes	No
extab	Exception Table	Yes	No
extabindex	Exception Table	Yes	No
text	Program code	Yes	Yes
ctors	Pointers to code to execute on startup	Yes	Yes
dtors	Pointers to code to execute on shutdown	Yes	Yes
rodata	Read-only data	Yes	Yes
data	Mutable data	Yes	Yes
bss	Zero-initialized data	Yes	Yes
sdata	Small mutable data (≤ 8 bytes)	Yes	No
sbss	Small zero-init. data (≤ 8 bytes)	Yes	No
sdata2	Small read-only data (≤ 8 bytes)	Yes	No
sbss2	Small read-only zero bytes	Yes	No

Segment

A part of the binary executable. Gets unpacked into one or more sections.

The BSS segment is special. Since it just contains zeros, only the address and length is saved.

Name	Sections	DOL
init	init	0x00
text	text	0x01
extab	extab	0x07
extabindex	extabindex	0x08
ctors	ctors	0x09
dtors	dtors	0x0a
rodata	rodata	0x0b
data	data	0x0c
sdata	sdata	0x0d
sdata2	sdata2	0x0e
bss	bss, sdata, sbss	bss

Small data area (SDA)

A special area in memory mainly used to load/store global 4 byte values (pointers, floating point literals) with a single instruction. Register r13 points into the middle of the SDA. It is accessed using relative address. The offset is signed:

• Load: lwz <register> <offset>(r13)
• Store: stw <register> <offset>(r13)