Back in 2004 we added logic to arch/ppc64/Makefile to pass the --synthetic option to nm, if it was supported by nm. Then in 2005 when arch/ppc64 and arch/ppc were merged, the logic to add --synthetic was moved inside an #ifdef CONFIG_PPC64 block within arch/powerpc/Makefile, and has remained there since. That was fine, though crufty, until recently when a change to init/Kconfig added a config time check that uses $(NM). On powerpc that leads to an infinite loop because Kconfig uses $(NM) to calculate some values, then the powerpc Makefile changes $(NM), which Kconfig notices and restarts. The original commit that added --synthetic simply said: On new toolchains we need to use nm --synthetic or we miss code symbols. And the nm man page says that the --synthetic option causes nm to: Include synthetic symbols in the output. These are special symbols created by the linker for various purposes. So it seems safe to always pass --synthetic if nm supports it, ie. on 32-bit and 64-bit, it just means 32-bit kernels might have more symbols reported (and in practice I see no extra symbols). Making it unconditional avoids the #ifdef CONFIG_PPC64, which in turn avoids the infinite loop. Debugged-by: Peter Collingbourne <pcc@xxxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> --- arch/powerpc/Makefile | 2 -- 1 file changed, 2 deletions(-) See the original discussion here: https://lore.kernel.org/lkml/CAMn1gO6P_VfDRjGZb67ZS4Kh0wjTEQi0cbOkmibTokHQOgP7qw@xxxxxxxxxxxxxx/ diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index c345b79414a9..403f7e193833 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -39,13 +39,11 @@ endif uname := $(shell uname -m) KBUILD_DEFCONFIG := $(if $(filter ppc%,$(uname)),$(uname),ppc64)_defconfig -ifdef CONFIG_PPC64 new_nm := $(shell if $(NM) --help 2>&1 | grep -- '--synthetic' > /dev/null; then echo y; else echo n; fi) ifeq ($(new_nm),y) NM := $(NM) --synthetic endif -endif # BITS is used as extension for files which are available in a 32 bit # and a 64 bit version to simplify shared Makefiles. -- 2.21.0
