On Thu, Apr 11, 2019 at 1:52 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Thu, Apr 11, 2019 at 12:14 AM 'Nick Desaulniers' via Clang Built > Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote: > > On Wed, Apr 10, 2019 at 1:13 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > > > > The purgatory and boot Makefiles do not inherit the original cflags, > > > so clang falls back to the default target architecture when building it, > > > typically this would be x86 when cross-compiling. > > > > > > Add $(CLANG_FLAGS) everywhere so we pass the correct --target=s390x-linux > > > option when cross-compiling. > > > > > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > > > --- > > > arch/s390/Makefile | 5 +++-- > > > arch/s390/purgatory/Makefile | 1 + > > > 2 files changed, 4 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/s390/Makefile b/arch/s390/Makefile > > > index 9c079a506325..443990791099 100644 > > > --- a/arch/s390/Makefile > > > +++ b/arch/s390/Makefile > > > @@ -17,12 +17,13 @@ KBUILD_CFLAGS_MODULE += -fPIC > > > KBUILD_AFLAGS += -m64 > > > KBUILD_CFLAGS += -m64 > > > aflags_dwarf := -Wa,-gdwarf-2 > > > -KBUILD_AFLAGS_DECOMPRESSOR := -m64 -D__ASSEMBLY__ > > > +KBUILD_AFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -D__ASSEMBLY__ > > > KBUILD_AFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),$(aflags_dwarf)) > > > -KBUILD_CFLAGS_DECOMPRESSOR := -m64 -O2 > > > +KBUILD_CFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -O2 > > > KBUILD_CFLAGS_DECOMPRESSOR += -DDISABLE_BRANCH_PROFILING -D__NO_FORTIFY > > > KBUILD_CFLAGS_DECOMPRESSOR += -fno-delete-null-pointer-checks -msoft-float > > > KBUILD_CFLAGS_DECOMPRESSOR += -fno-asynchronous-unwind-tables > > > > Thanks for the respin with Nathan's suggestion. > > > > > +KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning,pointer-sign) > > > > What's up with this ^ ? Seems like the top level sets it (without > > cc-disable-warning :( ), but then KBUILD_CFLAGS_DECOMPRESSOR discards > > it. Does Clang actually flag code in this arch (that GCC doesn't)? > > Oops, that should have been a separate patch. > > I think what happens is that clang warns more aggressively about pointer sign > bugs than gcc in some cases, and some of those cases happen in s390 > header files that are included by both the kernel and the decompressor. > > The full warning log without this change is rather long, see > https://pastebin.com/KG9xaTNB >From this link, it looks like the definitions of: __atomic64_or __atomic64_and __atomic64_xor and their *_barrier variants are problematic. I think converting those to use unsigned long is the way to go. Shouldn't you be doing bitwise ops on unsigned types anyways? The warnings with __atomic64_add are tougher to read/understand since at that point the log lines look like they start to mix together. > > I also tried patching the code to avoid the warnings, but I'm not entirely > happy with that result either, see > https://pastebin.com/pSMz5eZA That's no terrible, IMO, particularly with the change I suggest above. -- Thanks, ~Nick Desaulniers
