Re: [PATCH] Documentation/vDSO: don't build tests when cross compiling
From: Paul Gortmaker
Date: Mon Jun 22 2015 - 15:09:57 EST
[Re: [PATCH] Documentation/vDSO: don't build tests when cross compiling] On 22/06/2015 (Mon 10:01) Andy Lutomirski wrote:
> On Mon, Jun 22, 2015 at 9:41 AM, Jonathan Corbet <corbet@xxxxxxx> wrote:
> > On Sat, 20 Jun 2015 21:10:28 -0400
> > Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> wrote:
> >> The following was seen in linux-next build coverage, which is somewhat
> >> unique since it uses powerpc host to cross compile x86:
> >> Documentation/vDSO/vdso_standalone_test_x86.c:49:2: error: impossible
> >> register constraint in 'asm'
> >> make: *** [Documentation/vDSO/vdso_standalone_test_x86.o] Error 1
> >> It probably makes sense to just skip building these tests when
> >> we are cross compiling.
> > So I guess I'm not totally averse to applying these; getting rid of build
> > errors is a good thing. But I do get the feeling like it's papering over
> > the real problem. As a general rule, cross-compiling works; what's
> > special about these programs that makes it fail?
> Agreed. What gcc version is this?
Just to re-iterate, this is ppc host, cross compiling x86_64 target.
The linux-next build I saw the errors in this weekend is here:
According to that, it is gcc 4.6.3
It seems that the assumption is that nobody cross compiles x86, so
when people see CONFIG_X86_64 set, they assume HOSTCC can create x86
binaries and will do so by default. Hence the breakdown in creation
of some of these sample programs. We've already a similar fix in
mainline in e9107f88c985bc ("samples/seccomp/Makefile: do not build
tests if cross-compiling for MIPS")
I've added linux-next folks to Cc: -- probably should have done that on
the original send... they know more about the toolchains used for -next.
> > Thanks,
> > jon
> Andy Lutomirski
> AMA Capital Management, LLC
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