Re: vdso_standalone_test_x86.c build failure on Linus' tree

[Andy Lutomirski]

On Wed, Oct 8, 2014 at 1:46 PM, Chuck Ebbert <cebbert.lkml@xxxxxxxxx> wrote:
> On Wed, 8 Oct 2014 12:16:11 -0700
> Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>
>> On Wed, Oct 8, 2014 at 11:52 AM, Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx> wrote:
>> > I'm seeing the following build failure on a 32-bit x86 build in Fedora
>> > based on Linux v3.17-2860-gef0625b70dac:
>> >
>> > Documentation/vDSO/vdso_standalone_test_x86.o: In function `to_base10':
>> > vdso_standalone_test_x86.c:(.text+0xcc): undefined reference to `__umoddi3'
>> > vdso_standalone_test_x86.c:(.text+0xea): undefined reference to `__udivdi3'
>> > collect2: error: ld returned 1 exit status
>> > scripts/Makefile.host:100: recipe for target
>> > 'Documentation/vDSO/vdso_standalone_test_x86' failed
>> > make[2]: *** [Documentation/vDSO/vdso_standalone_test_x86] Error 1
>> > scripts/Makefile.build:404: recipe for target 'Documentation/vDSO' failed
>> > make[1]: *** [Documentation/vDSO] Error 2
>> > make[1]: *** Waiting for unfinished jobs....
>> > Makefile:922: recipe for target 'vmlinux' failed
>> > make: *** [vmlinux] Error 2
>> >
>> It should build and work on 32-bit.
>>
>> Except that the makefile is totally bogus.  vdso_standalone_test isn't
>> a hostprog at all.  It's a target prog.  But kbuild doesn't understand
>> that, so I have no idea what, if anything, that makefile is supposed
>> to do.
>
> Heh, I was wondering why I got a 64-bit program with ARCH=i386

Once kselftest takes off, we'll have lots of fun.  In principle,
x86_64 kernels should pass the 32-bit tests, too :)

>
>> I would argue that the whole documentation build system should be
>> fixed to cross-compile or should just be disabled for cross-builds if
>> glibc isn't available.
>>
>
> Fedora doesn't cross-compile i686 builds because of problems like
> this. It sets up an i386 chroot and runs all native tools inside of
> it.
>

In this particular case, cross-compiling would have worked around the bug.

--Andy
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