From: Michael Ellerman <mpe@ellerman.id.au>
To: will@kernel.org
Cc: linuxppc-dev@ozlabs.org, pcc@google.com,
yamada.masahiro@socionext.com, linux-kernel@vger.kernel.org,
linux-next@vger.kernel.org
Subject: [PATCH] powerpc/Makefile: Always pass --synthetic to nm if supported
Date: Tue, 20 Aug 2019 17:23:19 +1000 [thread overview]
Message-ID: <20190820072319.2884-1-mpe@ellerman.id.au> (raw)
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@google.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/Makefile | 2 --
1 file changed, 2 deletions(-)
See the original discussion here: https://lore.kernel.org/lkml/CAMn1gO6P_VfDRjGZb67ZS4Kh0wjTEQi0cbOkmibTokHQOgP7qw@mail.gmail.com/
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
reply other threads:[~2019-08-20 7:23 UTC|newest]
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