| Message ID | 20210916184017.1881473-3-nathan@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Harden clang against unknown flag options | expand |
On Fri, Sep 17, 2021 at 3:42 AM Nathan Chancellor <nathan@kernel.org> wrote: > > Similar to commit 589834b3a009 ("kbuild: Add > -Werror=unknown-warning-option to CLANG_FLAGS"). > > Clang ignores certain GCC flags that it has not implemented, only > emitting a warning: > > $ echo | clang -fsyntax-only -falign-jumps -x c - > clang-14: warning: optimization flag '-falign-jumps' is not supported > [-Wignored-optimization-argument] > > When one of these flags gets added to KBUILD_CFLAGS unconditionally, all > subsequent cc-{disable-warning,option} calls fail because -Werror was > added to these invocations to turn the above warning and the equivalent > -W flag warning into errors. > > To catch the presence of these flags earlier, turn > -Wignored-optimization-argument into an error so that the flags can > either be implemented or ignored via cc-option and there are no more > weird errors. > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- Applied to linux-kbuild. Thanks. > scripts/Makefile.clang | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > index 4cce8fd0779c..51fc23e2e9e5 100644 > --- a/scripts/Makefile.clang > +++ b/scripts/Makefile.clang > @@ -29,7 +29,12 @@ CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) > else > CLANG_FLAGS += -fintegrated-as > endif > +# By default, clang only warns when it encounters an unknown warning flag or > +# certain optimization flags it knows it has not implemented. > +# Make it behave more like gcc by erroring when these flags are encountered > +# so they can be implemented or wrapped in cc-option. > CLANG_FLAGS += -Werror=unknown-warning-option > +CLANG_FLAGS += -Werror=ignored-optimization-argument > KBUILD_CFLAGS += $(CLANG_FLAGS) > KBUILD_AFLAGS += $(CLANG_FLAGS) > export CLANG_FLAGS > -- > 2.33.0 >
diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang index 4cce8fd0779c..51fc23e2e9e5 100644 --- a/scripts/Makefile.clang +++ b/scripts/Makefile.clang @@ -29,7 +29,12 @@ CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) else CLANG_FLAGS += -fintegrated-as endif +# By default, clang only warns when it encounters an unknown warning flag or +# certain optimization flags it knows it has not implemented. +# Make it behave more like gcc by erroring when these flags are encountered +# so they can be implemented or wrapped in cc-option. CLANG_FLAGS += -Werror=unknown-warning-option +CLANG_FLAGS += -Werror=ignored-optimization-argument KBUILD_CFLAGS += $(CLANG_FLAGS) KBUILD_AFLAGS += $(CLANG_FLAGS) export CLANG_FLAGS
Similar to commit 589834b3a009 ("kbuild: Add -Werror=unknown-warning-option to CLANG_FLAGS"). Clang ignores certain GCC flags that it has not implemented, only emitting a warning: $ echo | clang -fsyntax-only -falign-jumps -x c - clang-14: warning: optimization flag '-falign-jumps' is not supported [-Wignored-optimization-argument] When one of these flags gets added to KBUILD_CFLAGS unconditionally, all subsequent cc-{disable-warning,option} calls fail because -Werror was added to these invocations to turn the above warning and the equivalent -W flag warning into errors. To catch the presence of these flags earlier, turn -Wignored-optimization-argument into an error so that the flags can either be implemented or ignored via cc-option and there are no more weird errors. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- scripts/Makefile.clang | 5 +++++ 1 file changed, 5 insertions(+)