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H A D | Makefile | f5948701 Wed Jan 20 16:59:12 CST 2016 Chris Metcalf <cmetcalf@ezchip.com> lib/clz_tab.c: put in lib-y rather than obj-y
The clz table (__clz_tab) in lib/clz_tab.c is also provided as part of libgcc.a, and many architectures link against libgcc. To allow the linker to avoid a multiple-definition link failure, clz_tab.o has to be in lib/lib.a rather than lib/builtin.o. The specific issue is that libgcc.a comes before lib/builtin.o on vmlinux.o's link command line, so its _clz.o is pulled to satisfy __clz_tab, and then when the remainder of lib/builtin.o is pulled in to satisfy all the other dependencies, the __clz_tab symbols conflict. By putting clz_tab.o in lib.a, the linker can simply avoid pulling it into vmlinux.o when this situation arises.
The definitions of __clz_tab are the same in libgcc.a and in the kernel; arguably we could also simply rename the kernel version, but it's unlikely the libgcc version will ever change to become incompatible, so just using it seems reasonably safe.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> f5948701 Wed Jan 20 16:59:12 CST 2016 Chris Metcalf <cmetcalf@ezchip.com> lib/clz_tab.c: put in lib-y rather than obj-y The clz table (__clz_tab) in lib/clz_tab.c is also provided as part of libgcc.a, and many architectures link against libgcc. To allow the linker to avoid a multiple-definition link failure, clz_tab.o has to be in lib/lib.a rather than lib/builtin.o. The specific issue is that libgcc.a comes before lib/builtin.o on vmlinux.o's link command line, so its _clz.o is pulled to satisfy __clz_tab, and then when the remainder of lib/builtin.o is pulled in to satisfy all the other dependencies, the __clz_tab symbols conflict. By putting clz_tab.o in lib.a, the linker can simply avoid pulling it into vmlinux.o when this situation arises. The definitions of __clz_tab are the same in libgcc.a and in the kernel; arguably we could also simply rename the kernel version, but it's unlikely the libgcc version will ever change to become incompatible, so just using it seems reasonably safe. Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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