[PATCH] init/Kconfig: Fix infinite Kconfig recursion on PPC

[Will Deacon]

Commit 5cf896fb6be3 ("arm64: Add support for relocating the kernel with
RELR relocations") introduced CONFIG_TOOLS_SUPPORT_RELR, which checks
for RELR support in the toolchain as part of the kernel configuration.
During this procedure, "$(NM)" is invoked to see if it supports the new
relocation format, however PowerPC conditionally overrides this variable
in the architecture Makefile in order to pass '--synthetic' when
targetting PPC64.

This conditional override causes Kconfig to recurse forever, since
CONFIG_TOOLS_SUPPORT_RELR cannot be determined without $(NM) being
defined, but that in turn depends on CONFIG_PPC64:

  $ make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu-
  scripts/kconfig/conf  --syncconfig Kconfig
  scripts/kconfig/conf  --syncconfig Kconfig
  scripts/kconfig/conf  --syncconfig Kconfig
  [...]

In this particular case, it looks like PowerPC may be able to pass
'--synthetic' unconditionally to nm or even drop it altogether. While
that is being resolved, let's just bodge the RELR check by picking up
$(NM) directly from the environment in whatever state it happens to be
in.

Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Suggested-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
 init/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index d96127ebc44e..8b4596edda4e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -31,7 +31,7 @@ config CC_HAS_ASM_GOTO
 	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
 
 config TOOLS_SUPPORT_RELR
-	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
+	def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
 
 config CC_HAS_WARN_MAYBE_UNINITIALIZED
 	def_bool $(cc-option,-Wmaybe-uninitialized)
-- 
2.17.1