On Wed, Jul 06, 2022 at 03:25:51PM -0700, Dave Hansen wrote:
> On 6/17/22 11:08, Nathan Chancellor wrote:
> > When clang is invoked without a '--target' flag, code is generated for
> > the default target, which is usually the host (it is configurable via
> > cmake). As a result, the has-stack-protector scripts will generate code
> > for the default target but check for x86 specific segment registers,
> > which cannot succeed if the default target is not x86.
>
> I guess the real root cause here is the direct use of '$(CC)' without
> any other flags. Adding '$(CLANG_FLAGS)' seems like a pretty normal
> fix, like in scripts/Kconfig.include.
Right, also see the following commits for other areas where this was
addressed.
58d746c119df ("efi/libstub: Add $(CLANG_FLAGS) to x86 flags")
d5cbd80e302d ("x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS")
8abe7fc26ad8 ("x86/build: Propagate $(CLANG_FLAGS) to $(REALMODE_FLAGS)")
> I suspect there's another one of these here:
>
> arch/x86/um/vdso/Makefile: cmd_vdso = $(CC) -nostdlib -o $@
>
> but I wouldn't be surprised if UML doesn't work with clang in the first
> place.
We have started testing UML with clang and it does work but I suspect
there is little value to cross compiling a UML kernel, as it has to run
in an x86 userland anyways, rather than through QEMU or other
virtualization solutions. That is not something I plan to do anyways.
If someone does and a fix similar to this one is needed, it can be done
at that time.
Thank you for picking up this change!
Cheers,
Nathan
