Add support for weak symbols to the kernel linkers. It means that

linkers no longer raise an error when undefined weak symbols are
found, but relocate as if the symbol value was 0.  Note that we do not
repeat the mistake of userspace dynamic linker of making the symbol
lookup prefer non-weak symbol definition over the weak one, if both
are available.  In fact, kernel linker uses the first definition
found, and ignores duplicates.

Signature of the elf_lookup() and elf_obj_lookup() functions changed
to split result/error code and the symbol address returned.
Otherwise, it is impossible to return zero address as the symbol
value, to MD relocation code.  This explains the mechanical changes in
elf_machdep.c sources.

The powerpc64 R_PPC_JMP_SLOT handler did not checked error from the
lookup() call, the patch leaves the code as is (untested).

Reported by:	glebius
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/sys/linker.h b/sys/sys/linker.h
index 5d24f00..7e562a6 100644
--- a/sys/sys/linker.h
+++ b/sys/sys/linker.h
@@ -264,7 +264,7 @@ extern int kld_debug;
 
 #endif
 
-typedef Elf_Addr elf_lookup_fn(linker_file_t, Elf_Size, int);
+typedef int elf_lookup_fn(linker_file_t, Elf_Size, int, Elf_Addr *);
 
 /* Support functions */
 int	elf_reloc(linker_file_t _lf, Elf_Addr base, const void *_rel, int _type, elf_lookup_fn _lu);