Commit 21c54b774744 ("kconfig: show compiler version text in the top comment") was intended to detect the compiler upgrade, but Geert reported a breakage on the m68k build.
The compiler upgrade is detected by the change of the environment variable, CC_VERSION_TEXT, which contains the first line of the output from $(CC) --version. Currently, this works well when CROSS_COMPILE is given via the environment variable or the Make command line. However, some architectures such as m68k can specify CROSS_COMPILE from arch/$(SRCARCH)/Makefile as well. In this case, "make ARCH=m68k" ends up with endless syncconfig loop. $ make ARCH=m68k defconfig *** Default configuration is based on 'multi_defconfig' # # configuration written to .config # $ make ARCH=m68k scripts/kconfig/conf --syncconfig Kconfig scripts/kconfig/conf --syncconfig Kconfig scripts/kconfig/conf --syncconfig Kconfig scripts/kconfig/conf --syncconfig Kconfig Things are happening like this: Because arch/$(SRCARCH)/Makefile is included after CC_VERSION_TEXT is set, it contains the host compiler version in the defconfig phase. To create or update auto.conf, the following line is triggered: include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig This recurses the top Makefile after arch/$(SRCARCH)/Makefile is included. CROSS_COMPILE is set to a m68k toolchain prefix and exported to the recursed Make. Then, syncconfig is invoked with the target compiler version in CC_VERSION_TEXT. The Make will restart because auto.conf and auto.conf.cmd have been updated. At this point, CROSS_COMPILE is reset, so CC_VERSION_TEXT is set to the host compiler version again. Then, syncconfig is triggered due to the change of CC_VERSION_TEXT. This loop continues eternally. To fix this problem, $(CC_VERSION_TEXT) must be evaluated only after arch/$(SRCARCH)/Makefile. Setting it earlier is OK as long as it is defined by using the '=' operator instead of ':='. For the defconfig phase, $(CC_VERSION_TEXT) is evaluated when Kbuild descends into scripts/kconfig/, so it contains the target compiler version correctly. include/config/auto.conf.cmd references $(CC_VERSION_TEXT) as well, so it must be included after arch/$(SRCARCH)/Makefile. Fixes: 21c54b774744 ("kconfig: show compiler version text in the top comment") Reported-by: Geert Uytterhoeven <ge...@linux-m68k.org> Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com> --- Makefile | 54 ++++++++++++++++++++++++++++++------------------------ 1 file changed, 30 insertions(+), 24 deletions(-) diff --git a/Makefile b/Makefile index 019a5a0..747edaf 100644 --- a/Makefile +++ b/Makefile @@ -442,8 +442,6 @@ export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL export KBUILD_ARFLAGS -export CC_VERSION_TEXT := $(shell $(CC) --version | head -n 1) - # When compiling out-of-tree modules, put MODVERDIR in the module # tree rather than in the kernel tree. The kernel tree might # even be read-only. @@ -514,6 +512,12 @@ ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/cc-can-link.sh $(CC)), y) export CC_CAN_LINK endif +# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included. +# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile. +# CC_VERSION_TEXT is referenced from Kconfig (so it needs export), +# and from include/config/auto.conf.cmd to detect the compiler upgrade. +CC_VERSION_TEXT = $(shell $(CC) --version | head -n 1) + ifeq ($(config-targets),1) # =========================================================================== # *config targets only - make sure prerequisites are updated, and descend @@ -523,7 +527,7 @@ ifeq ($(config-targets),1) # KBUILD_DEFCONFIG may point out an alternative default configuration # used for 'make defconfig' include arch/$(SRCARCH)/Makefile -export KBUILD_DEFCONFIG KBUILD_KCONFIG +export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT config: scripts_basic outputmakefile FORCE $(Q)$(MAKE) $(build)=scripts/kconfig $@ @@ -585,12 +589,32 @@ virt-y := virt/ endif # KBUILD_EXTMOD ifeq ($(dot-config),1) -# Read in config -include include/config/auto.conf +endif + +# The all: target is the default when no target is given on the +# command line. +# This allow a user to issue only 'make' to build a kernel including modules +# Defaults to vmlinux, but the arch makefile usually adds further targets +all: vmlinux + +CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \ + $(call cc-option,-fno-tree-loop-im) \ + $(call cc-disable-warning,maybe-uninitialized,) +export CFLAGS_GCOV CFLAGS_KCOV + +# The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default +# values of the respective KBUILD_* variables +ARCH_CPPFLAGS := +ARCH_AFLAGS := +ARCH_CFLAGS := +include arch/$(SRCARCH)/Makefile +ifeq ($(dot-config),1) ifeq ($(KBUILD_EXTMOD),) -# Read in dependencies to all Kconfig* files, make sure to run -# oldconfig if changes are detected. +# Read in dependencies to all Kconfig* files, make sure to run syncconfig if +# changes are detected. This should be included after arch/$(SRCARCH)/Makefile +# because some architectures define CROSS_COMPILE there. -include include/config/auto.conf.cmd # To avoid any implicit rule to kick in, define an empty command @@ -622,24 +646,6 @@ else include/config/auto.conf: ; endif # $(dot-config) -# The all: target is the default when no target is given on the -# command line. -# This allow a user to issue only 'make' to build a kernel including modules -# Defaults to vmlinux, but the arch makefile usually adds further targets -all: vmlinux - -CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \ - $(call cc-option,-fno-tree-loop-im) \ - $(call cc-disable-warning,maybe-uninitialized,) -export CFLAGS_GCOV CFLAGS_KCOV - -# The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default -# values of the respective KBUILD_* variables -ARCH_CPPFLAGS := -ARCH_AFLAGS := -ARCH_CFLAGS := -include arch/$(SRCARCH)/Makefile - KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,) KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html