Re: samples/seccomp/ broken when cross compiling s390, ppc allyesconfig

[Michal Hocko]

On Wed 14-02-18 09:14:47, Kees Cook wrote:
[...]
> I can send it through my seccomp tree via James Morris.

Could you please do it?

> >
> > From 8d8457e96296538508e478f598d1c8b3406a8626 Mon Sep 17 00:00:00 2001
> > From: Michal Hocko <mhocko@xxxxxxxx>
> > Date: Wed, 14 Feb 2018 10:15:12 +0100
> > Subject: [PATCH] samples/seccomp: do not compile when cross compiled
> > MIME-Version: 1.0
> > Content-Type: text/plain; charset=UTF-8
> > Content-Transfer-Encoding: 8bit
> >
> > samples/seccomp relies on the host setting which is not suitable for
> > crosscompilation and it actually fails when crosscompiling s390 and
> > powerpc all{yes,mod}config on x86_64 with
> >
> > samples/seccomp/bpf-helper.h:135:2: error: #error __BITS_PER_LONG value unusable.
> >  #error __BITS_PER_LONG value unusable.
> >   ^
> > In file included from samples/seccomp/bpf-fancy.c:13:0:
> > samples/seccomp/bpf-fancy.c: In function âmainâ:
> > samples/seccomp/bpf-fancy.c:38:11: error: â__NR_exitâ undeclared (first use in this function)
> >    SYSCALL(__NR_exit, ALLOW),
> >
> > and many others. I am doing these for compile testing and it's been
> > quite useful to catch issues. Crosscompiling sample code on the other
> > hand doesn't seem all that important so it seems like the easiest way to
> > simply disable samples/seccomp when crosscompiling.
> >
> > Fixing this properly is not that easy as Kees explains:
> > : IIRC, one of the problems is with build ordering problems: the kernel
> > : headers used by the samples aren't available when cross compiling.
> >
> > Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> > ---
> >  samples/seccomp/Makefile | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> >
> > diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
> > index 0e349b80686e..ba942e3ead89 100644
> > --- a/samples/seccomp/Makefile
> > +++ b/samples/seccomp/Makefile
> > @@ -1,4 +1,5 @@
> >  # SPDX-License-Identifier: GPL-2.0
> > +ifndef CROSS_COMPILE
> >  hostprogs-$(CONFIG_SAMPLE_SECCOMP) := bpf-fancy dropper bpf-direct
> >
> >  HOSTCFLAGS_bpf-fancy.o += -I$(objtree)/usr/include
> > @@ -16,7 +17,6 @@ HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
> >  bpf-direct-objs := bpf-direct.o
> >
> >  # Try to match the kernel target.
> > -ifndef CROSS_COMPILE
> >  ifndef CONFIG_64BIT
> >
> >  # s390 has -m31 flag to build 31 bit binaries
> > @@ -35,12 +35,4 @@ HOSTLOADLIBES_bpf-fancy += $(MFLAG)
> >  HOSTLOADLIBES_dropper += $(MFLAG)
> >  endif
> >  always := $(hostprogs-m)
> > -else
> > -# MIPS system calls are defined based on the -mabi that is passed
> > -# to the toolchain which may or may not be a valid option
> > -# for the host toolchain. So disable tests if target architecture
> > -# is MIPS but the host isn't.
> > -ifndef CONFIG_MIPS
> > -always := $(hostprogs-m)
> > -endif
> >  endif
> > --
> > 2.15.1
> >
> > --
> > Michal Hocko
> > SUSE Labs
> 
> 
> 
> -- 
> Kees Cook
> Pixel Security

-- 
Michal Hocko
SUSE Labs