From: Nick Desaulniers ndesaulniers@google.com
commit d5c8d6e0fa61401a729e9eb6a9c7077b2d3aebb0 upstream.
as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS. This can cause as-option to fail unexpectedly when CONFIG_WERROR is set, because clang will emit -Werror,-Wunused-command-line-argument for various -m and -f flags in KBUILD_CFLAGS for assembler sources.
Callers of as-option and as-instr should be adding flags to KBUILD_AFLAGS / aflags-y, not KBUILD_CFLAGS / cflags-y. Use KBUILD_AFLAGS in all macros to clear up the initial problem.
Unfortunately, -Wunused-command-line-argument can still be triggered with clang by the presence of warning flags or macro definitions because '-x assembler' is used, instead of '-x assembler-with-cpp', which will consume these flags. Switch to '-x assembler-with-cpp' in places where '-x assembler' is used, as the compiler is always used as the driver for out of line assembler sources in the kernel.
Finally, add -Werror to these macros so that they behave consistently whether or not CONFIG_WERROR is set.
[nathan: Reworded and expanded on problems in commit message Use '-x assembler-with-cpp' in a couple more places]
Link: https://github.com/ClangBuiltLinux/linux/issues/1699 Suggested-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Nathan Chancellor nathan@kernel.org Tested-by: Linux Kernel Functional Testing lkft@linaro.org Tested-by: Anders Roxell anders.roxell@linaro.org Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- scripts/Kconfig.include | 2 +- scripts/Makefile.compiler | 8 ++++---- scripts/as-version.sh | 2 +- 3 files changed, 6 insertions(+), 6 deletions(-)
--- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -33,7 +33,7 @@ ld-option = $(success,$(LD) -v $(1))
# $(as-instr,<instr>) # Return y if the assembler supports <instr>, n otherwise -as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -) +as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler-with-cpp -o /dev/null -)
# check if $(CC) and $(LD) exist $(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found) --- a/scripts/Makefile.compiler +++ b/scripts/Makefile.compiler @@ -29,16 +29,16 @@ try-run = $(shell set -e; \ fi)
# as-option -# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,) +# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
as-option = $(call try-run,\ - $(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2)) + $(CC) -Werror $(KBUILD_AFLAGS) $(1) -c -x assembler-with-cpp /dev/null -o "$$TMP",$(1),$(2))
# as-instr -# Usage: cflags-y += $(call as-instr,instr,option1,option2) +# Usage: aflags-y += $(call as-instr,instr,option1,option2)
as-instr = $(call try-run,\ - printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3)) + printf "%b\n" "$(1)" | $(CC) -Werror $(KBUILD_AFLAGS) -c -x assembler-with-cpp -o "$$TMP" -,$(2),$(3))
# __cc-option # Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586) --- a/scripts/as-version.sh +++ b/scripts/as-version.sh @@ -45,7 +45,7 @@ orig_args="$@" # Get the first line of the --version output. IFS=' ' -set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler /dev/null -o /dev/null 2>/dev/null) +set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler-with-cpp /dev/null -o /dev/null 2>/dev/null)
# Split the line on spaces. IFS=' '