> On Jul 12, 2018, at 3:06 PM, H. Peter Anvin <h...@zytor.com> wrote:
>
>> On 07/12/18 13:37, Alistair Strachan wrote:
>>> On Thu, Jul 12, 2018 at 1:25 PM H. Peter Anvin <h...@zytor.com> wrote:
>>>> On 07/12/18 13:10, Alistair Strachan wrote:
>>>> The vdso{32,64}.so can fail to link with CC=clang when clang tries to
>>>> find a suitable GCC toolchain to link these libraries with.
>>>>
>>>> /usr/bin/ld: arch/x86/entry/vdso/vclock_gettime.o:
>>>> access beyond end of merged section (782)
>>>>
>>>> This happens because the host environment leaked into the cross
>>>> compiler environment due to the way clang searches for suitable GCC
>>>> toolchains.
>>>>
>>>
>>> Is this another clang bug that you want a workaround for in the kernel?
>>
>> Clang is a retargetable compiler (specified with --target=<something>)
>> and so it has a mechanism for searching for suitable binutils (from
>> another "GCC toolchain") to perform assembly and linkage. This
>> mechanism relies on both --target and --gcc-toolchain when
>> cross-compiling, otherwise it will fall back to searching /usr.
>>
>> The --target and --gcc-toolchain flags are already specified correctly
>> in the top level Makefile, but the vdso Makefile rolls its own linker
>> flags and doesn't use KBUILD_CFLAGS. Therefore, these flags get
>> incorrectly dropped from the vdso $CC link command line, and an
>> inconsistency is created between the "GCC toolchain" used to generate
>> the objects for the vdso, and the linker used to link them.
>>
>
> It sounds like there needs to be a more fundamental symbol than
> KBUILD_CFLAGS to contain these kinds of things.
How about $(CC)?
>
> -hpa
