2017-10-30 15:50 GMT+09:00 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>: > 2017-10-29 0:00 GMT+09:00 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>: >> 2017-10-28 5:13 GMT+09:00 Nick Desaulniers <ndesaulniers@xxxxxxxxxx>: >>> I was not seeing my linker flags getting added when using ld-option when >>> cross compiling with Clang. Upon investigation, this seems to be due to >>> a difference in how GCC vs Clang handle cross compilation. >>> >>> GCC is configured at build time to support one backend, that is implicit >>> when compiling. Clang is explicit via the use of `-target <triple>` and >>> ships with all supported backends by default. >>> >>> GNU Make feature test macros that compile then link will always fail >>> when cross compiling with Clang unless Clang's triple is passed along to >>> the compiler. For example: >>> >>> $ clang -x c /dev/null -c -o temp.o >>> $ aarch64-linux-android/bin/ld -E temp.o >>> aarch64-linux-android/bin/ld: >>> unknown architecture of input file `temp.o' is incompatible with >>> aarch64 output >>> aarch64-linux-android/bin/ld: >>> warning: cannot find entry symbol _start; defaulting to >>> 0000000000400078 >>> $ echo $? >>> 1 >>> >>> $ clang -target aarch64-linux-android- -x c /dev/null -c -o temp.o >>> $ aarch64-linux-android/bin/ld -E temp.o >>> aarch64-linux-android/bin/ld: >>> warning: cannot find entry symbol _start; defaulting to 00000000004002e4 >>> $ echo $? >>> 0 >>> >>> This causes conditional checks that invoke $(CC) without the target >>> triple, then $(LD) on the result, to always fail. >>> >>> Suggested-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> >>> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> >>> Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> >>> --- >>> Changes since v1: >>> * base patch off of >>> git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git >>> kbuild branch, per Masahiro. >>> * Use $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) rather than $(CLANG_TRIPLE), per >>> Masahiro. >>> >>> scripts/Kbuild.include | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include >>> index 064f477dfdca..0f09e4508554 100644 >>> --- a/scripts/Kbuild.include >>> +++ b/scripts/Kbuild.include >>> @@ -228,12 +228,13 @@ cc-if-fullversion = $(shell [ $(cc-fullversion) $(1) $(2) ] && echo $(3) || echo >>> # cc-ldoption >>> # Usage: ldflags += $(call cc-ldoption, -Wl$(comma)--hash-style=both) >>> cc-ldoption = $(call try-run-cached,\ >>> - $(CC) $(1) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2)) >>> + $(CC) $(1) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2)) >>> >>> # ld-option >>> # Usage: LDFLAGS += $(call ld-option, -X) >>> ld-option = $(call try-run-cached,\ >>> - $(CC) -x c /dev/null -c -o "$$TMPO" ; $(LD) $(1) "$$TMPO" -o "$$TMP",$(1),$(2)) >>> + $(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -x c /dev/null -c -o "$$TMPO"; \ >>> + $(LD) $(1) "$$TMPO" -o "$$TMP",$(1),$(2)) >>> >>> # ar-option >>> # Usage: KBUILD_ARFLAGS := $(call ar-option,D) >>> -- >>> 2.15.0.rc2.357.g7e34df9404-goog >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> Applied to linux-kbuild/kbuild. Thanks! > > > > I do not know the cause of the problem reported by the 0-day bot, but > if the problem happens in the following line, > > ifeq ($(CONFIG_X86_32),y) > LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker) > else > > > > Does the following solve the issue? (adding $(LDFLAGS)) > > ld-option = $(call try-run,\ > $(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -x c /dev/null -c > -o "$$TMPO"; \ > $(LD) $(LDFLAGS) $(1) "$$TMPO" -o "$$TMP",$(1),$(2)) > > I dropped this patch for now. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
