Messages in this thread | | | Date | Wed, 22 Dec 2021 15:17:12 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/boot/compressed: Move CLANG_FLAGS to beginning of KBUILD_CFLAGS |
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On Tue, Dec 21, 2021 at 05:52:45PM -0700, Nathan Chancellor wrote: > When cross compiling i386_defconfig on an arm64 host with clang, there > are a few instances of '-Waddress-of-packed-member' and > '-Wgnu-variable-sized-type-not-at-end' in arch/x86/boot/compressed/, > which should both be disabled with the cc-disable-warning calls in that > directory's Makefile, which indicates that cc-disable-warning is failing > at the point of testing these flags. > > The cc-disable-warning calls fail because at the point that the flags > are tested, KBUILD_CFLAGS has '-march=i386' without $(CLANG_FLAGS), > which has the '--target=' flag to tell clang what architecture it is > targeting. Without the '--target=' flag, the host architecture (arm64) > is used and i386 is not a valid value for '-march=' in that case. This > error can be seen by adding some logging to try-run: > > clang-14: error: the clang compiler does not support '-march=i386' > > Invoking the compiler has to succeed prior to calling cc-option or > cc-disable-warning in order to accurately test whether or not the flag > is supported; if it doesn't, the requested flag can never be added to > the compiler flags. Move $(CLANG_FLAGS) to the beginning of KBUILD_FLAGS > so that any new flags that might be added in the future can be > accurately tested. > > Fixes: d5cbd80e302d ("x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS") > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > arch/x86/boot/compressed/Makefile | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > index 431bf7f846c3..169186dba1d7 100644 > --- a/arch/x86/boot/compressed/Makefile > +++ b/arch/x86/boot/compressed/Makefile > @@ -28,7 +28,7 @@ KCOV_INSTRUMENT := n > targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \ > vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 vmlinux.bin.zst > > -KBUILD_CFLAGS := -m$(BITS) -O2 > +KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS)
I don't mind but this makes the placement of that variable magical so it needs a comment above it that it cannot be moved around freely and why that is the case.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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