Our use of --gc-sections causes the linker to discard the symbols
defined by FILE_LICENCE(), meaning that the resulting licence
determination is incomplete.
We must use the KEEP() directive in the linker script to force the
linker to not discard the licence symbols. Using KEEP(*(COMMON))
would be undesirable, since there are some symbols in COMMON which we
may wish to discard.
Fix by placing symbols defined by PROVIDE_SYMBOL() (which is used by
FILE_LICENCE()) into a special ".provided" section, which we then mark
with KEEP(). All such symbols are zero-length, so there is no cost in
terms of the final binary size.
Since the symbols are no longer in COMMON, the linker will reject
symbols with the same name coming from multiple objects. We therefore
append the object name to the licence symbol, to ensure that it is
unique.
Reported-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some binutils versions will drag in an object to satisfy the entry
symbol; some won't. Try to cope with this exciting variety of
behaviour by ensuring that all entry symbols are unique.
Remove the explicit inclusion of the prefix object on the linker
command line, since the entry symbol now provides all the information
needed to identify the prefix.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Use -ffunction-sections, -fdata-sections, and --gc-sections to
automatically prune out any unreferenced sections.
This saves around 744 bytes (uncompressed) from the rtl8139.rom build.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[linker] Expand and correct symbol requirement macros
REQUIRE_SYMBOL() formerly used a formulation of symbol requirement
that would allow a link to succeed despite lacking a required symbol,
because it did not introduce any relocations. Fix by renaming it to
REQUEST_SYMBOL() (since the soft-requirement behavior can be useful)
and add a REQUIRE_SYMBOL() that truly requires.
Add EXPORT_SYMBOL() and IMPORT_SYMBOL() for REQUEST_SYMBOL()-like
behavior that allows one to make use of the symbol, by combining a
weak external on the symbol itself with a REQUEST_SYMBOL() of a second
symbol.
Signed-off-by: Marty Connor <mdc@etherboot.org>
Prevent NULL from ever pointing to some real code or data. (This was
causing the serial console to ignore input, because it happened to end up
linked with serial_ischar() at address 0, which core/console.c decided was
invalid).
Michael Brown