RE: question regarding prelinking (was: (inc. note from dpkg developers) (was:Bug#XXXXXX: (far too many packages) needs rebuilt for prelinking))
Branden,
Packaging prelinked binaries would be considered broken behavior
since the virtual address space assignments that prelink makes will
change for different combinations of binaries. In fact if you prelink
and then install a new build of a shared library, all programs and
shared libraries that are linked against that library are effectively
unprelinked and you must run prelink on them again. The top of the
prelink man page covering this is attached below.
Jack
prelink is a program which modifies ELF shared libraries and ELF dynam-
ically linked binaries, so that the time which dynamic linker needs for
their relocation at startup significantly decreases and also due to
fewer relocations the runtime memory consumption decreases too (espe-
cially number of unshareable pages). Such prelinking information is
only used if all its dependant libraries have not changed since pre-
linking, otherwise programs are relocated normally.
prelink first collects ELF binaries which should be prelinked and all
the ELF shared libraries they depend on. Then it assigns a unique vir-
tual address space slot for each library and relinks the shared library
to that base address. When the dynamic linker attempts to load such a
library, unless that virtual address space slot is already occupied, it
will map it into the given slot. After this is done, prelink with the
help of dynamic linker resolves all relocations in the binary or
library against its dependant libraries and stores the relocations into
the ELF object. It also stores a list of all dependant libraries
together with their checksums into the binary or library. For bina-
ries/libraries, assign them addresses and with v print what
would be prelinked.
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