| Message ID | 20171027201345.87383-1-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
2017-10-28 5:13 GMT+09:00 Nick Desaulniers <ndesaulniers@google.com>: > 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@socionext.com> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > Reviewed-by: Matthias Kaehlcke <mka@chromium.org> > --- > 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@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Applied to linux-kbuild/kbuild. Thanks!
2017-10-29 0:00 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > 2017-10-28 5:13 GMT+09:00 Nick Desaulniers <ndesaulniers@google.com>: >> 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@socionext.com> >> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> >> Reviewed-by: Matthias Kaehlcke <mka@chromium.org> >> --- >> 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 := $(call ar-option,D) >> -- >> 2.15.0.rc2.357.g7e34df9404-goog >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > Applied to linux-kbuild/kbuild. Thanks! I do not know the cause of the problem reported by the 0-day bot, but if the problem happens in the following line, ifeq ($(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))
2017-10-30 15:50 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > 2017-10-29 0:00 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: >> 2017-10-28 5:13 GMT+09:00 Nick Desaulniers <ndesaulniers@google.com>: >>> 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@socionext.com> >>> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> >>> Reviewed-by: Matthias Kaehlcke <mka@chromium.org> >>> --- >>> 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 "$$TMP",$(1),$(2)) >>> >>> # ar-option >>> # Usage: KBUILD_ARFLAGS := $(call ar-option,D) >>> -- >>> 2.15.0.rc2.357.g7e34df9404-goog >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> Applied to linux-kbuild/kbuild. Thanks! > > > > I do not know the cause of the problem reported by the 0-day bot, but > if the problem happens in the following line, > > ifeq ($(CONFIG_X86_32),y) > LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker) > else > > > > Does the following solve the issue? (adding $(LDFLAGS)) > > ld-option = $(call try-run,\ > $(CC) $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) -x c /dev/null -c > -o "$$TMPO"; \ > $(LD) $(LDFLAGS) $(1) "$$TMPO" -o "$$TMP",$(1),$(2)) > > I dropped this patch for now.
That's safe to do for now. Here's the 0-day failure thread: https://lists.01.org/pipermail/lkp/2017-October/007427.html If I can sort out the issue, I'll submit a v3. On Mon, Oct 30, 2017 at 8:46 AM, Masahiro Yamada <yamada.masahiro@socionext.com> wrote: > 2017-10-30 15:50 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: >> 2017-10-29 0:00 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: >>> 2017-10-28 5:13 GMT+09:00 Nick Desaulniers <ndesaulniers@google.com>: >>>> 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@socionext.com> >>>> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> >>>> Reviewed-by: Matthias Kaehlcke <mka@chromium.org> >>>> --- >>>> 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 := $(call ar-option,D) >>>> -- >>>> 2.15.0.rc2.357.g7e34df9404-goog >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in >>>> the body of a message to majordomo@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >>> >>> Applied to linux-kbuild/kbuild. Thanks! >> >> >> >> I do not know the cause of the problem reported by the 0-day bot, but >> if the problem happens in the following line, >> >> ifeq ($(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 "$$TMP",$(1),$(2)) >> >> > > > I dropped this patch for now. > > -- > Best Regards > Masahiro Yamada
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 064f477dfdca..0f09e4508554 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -228,12 +228,13 @@ cc-if-fullversion = $(shell [ $(cc-fullversion) $(1) $(2) ] && echo $(3) || echo # cc-ldoption # Usage: ldflags += $(call cc-ldoption, -Wl$(comma)--hash-style=both) cc-ldoption = $(call try-run-cached,\ - $(CC) $(1) -nostdlib -x c /dev/null -o "$$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)