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Inside Macintosh: Mac OS Runtime Architectures /

Chapter 10 - Classic 68K Runtime Architecture / How 32-Bit Everything Is Implemented

Relocation Information Format

Relocation information consists of a consecutive list of offsets between longwords that need to be relocated at load time, beginning with the offset of the first such longword from the start of the segment.

Some data compression is used in recording this information. Because instructions start at even addresses, it suffices to record the offset values divided by two. In Table 10-2, the various encodings are shown as bit strings. The part of the value represented by "bbb..." gives, when doubled, the desired offset value.

Table 10-2 Relocation information

Relocation item	Interpretation
00000000 00000000	End of relocation information
0bbbbbbb	Offsets between $02 and $FE
1bbbbbbb bbbbbbbb	Offsets between $0100 and $FFFE
00000000 1bbbbbbb
bbbbbbbb bbbbbbbb
bbbbbbbb	Offsets between $00010000 and $FFFFFFFE