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96 lines
3.0 KiB
Plaintext
96 lines
3.0 KiB
Plaintext
Fundamental design decision:
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- the sizes of external and internal types are assumed to be the same.
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This leaves byte ordering aside. While assuming this the code can be
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greatly simplified and speed increases. Since no change violating this
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assumption is in sight this is believed to be a worthwhile optimization.
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- the ABI of the backend modules is not guaranteed. Really, no guarantee
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whatsoever. We are enforcing this in the code. The modules and their
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users must match. No third-party EBL module are supported or allowed.
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The only reason there are separate modules is to not have the code for
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all architectures in all the binaries.
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- although the public libraries (libasm, libdw) have a stable API and are
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backwards ABI compatible they, and the elfutils tools, do depend on each
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others internals, and on internals of libelf to provide their interfaces.
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So they should always be upgraded in lockstep when packaging the tools
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and libraries separately. For one example of how to do that, see the
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config/elfutils.spec.
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Some notes:
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- old GNU ld's behavior wrt DSOs seems to be severely broken.
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y.o reference foo()
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y1.o defines foo(), references bar()
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y2.o defines bar()
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libbar.so defines bar()
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Running
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gcc -o y y.o -lbar y1.o y2.o
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uses the bar() definition from libbar.so and does not mention the definition
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in y2.o at all (no duplicate symbol message). Correct is to use the
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definition in y2.o.
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y.o reference foo()
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y1.o defines foo(), references bar()
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y2.o in liby2.a defines bar()
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libbar.so defines bar()
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Running
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gcc -o y y.o -lbar y1.o -ly3
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has to use the definition in -lbar and not pull the definition from liby3.a.
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- the old linker follows DT_NEEDED entries and adds the objects referenced
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this way which define a symbol which is needed as a DT_NEEDED to the
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generated binary. This is wrong since the DT_NEEDED changes the search
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path in the object (which is breadth first).
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- the old linker supported extern "C++", extern "java" in version scripts.
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I believe this implementation is severly broken and needs a redesign
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(how do wildcards work with these languages*?). Therefore it is left
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out for now.
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- what should happen if two sections in different files with the same
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name have different types and/or the flags are different
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- section names in input files are mostly irrelevant. Exceptions:
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.comment/SHT_PROGBITS in strip, ld
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.debug \
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.line |
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.debug_srcinfo |
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.debug_sfnames |
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.debug_aranges |
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.debug_pubnames |
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.debug_info |
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.debug_abbrev |
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.debug_line |
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.debug_abbrev > DWARF sections in ld
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.debug_line |
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.debug_frame |
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.debug_str |
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.debug_loc |
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.debug_macinfo |
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.debug_weaknames |
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.debug_funcnames |
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.debug_typenames |
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.debug_varnames /
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Sections created in output files follow the naming of special section
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from the gABI.
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In no place is a section solely indentified by its name. Internal
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references always use the section index.
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