On Wed, Feb 14, 2018 at 1:20 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: > On Tue 13-02-18 13:27:30, Kees Cook wrote: >> On Tue, Feb 13, 2018 at 2:32 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: >> > On Tue 13-02-18 21:16:55, Michael Ellerman wrote: >> >> Kees Cook <keescook@xxxxxxxxxxxx> writes: >> >> >> >> > On Mon, Feb 12, 2018 at 7:25 PM, Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote: >> >> >> Michal Hocko <mhocko@xxxxxxxxxx> writes: >> >> >>> Hi, >> >> >>> my build test machinery chokes on samples/seccomp when cross compiling >> >> >>> s390 and ppc64 allyesconfig. This has been the case for quite some >> >> >>> time already but I never found time to look at the problem and report >> >> >>> it. It seems this is not new issue and similar thing happend for >> >> >>> MIPS e9107f88c985 ("samples/seccomp/Makefile: do not build tests if >> >> >>> cross-compiling for MIPS"). >> >> >>> >> >> >>> The build logs are attached. >> >> >>> >> >> >>> What is the best way around this? Should we simply skip compilation on >> >> >>> cross compile or is actually anybody relying on that? Or should I simply >> >> >>> disable it for s390 and ppc? >> >> >> >> >> >> The whole thing seems very confused. It's not building for the target, >> >> >> it's building for the host, ie. the Makefile sets hostprogs-m and >> >> >> HOSTCFLAGS etc. >> >> >> >> >> >> So it can't possibly work with cross compiling as it's currently >> >> >> written. >> >> >> >> >> >> Either the Makefile needs some serious work to properly support cross >> >> >> compiling or it should just be disabled when cross compiling. >> >> > >> >> > Hrm, yeah, the goal was to entirely disable cross compiling, but I >> >> > guess we didn't hit it with a hard enough hammer. :) >> >> >> >> Do you know why it is written that way? Why doesn't it just try to cross >> >> compile like normal code? >> > >> > No idea, sorry. All I know about this code is that it breaks my build >> > testing. >> >> IIRC, one of the problems is with build ordering problems: the kernel >> headers used by the samples aren't available when cross compiling. >> >> I'm happy to kill it entirely with Michal's patch, though. Feel free >> to carry in your tree! >> >> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> > > OK, so let's try to nuke it. How should I route this patch? I'm fine if goes in via ppc (especially if it can land for 4.16). If Michael doesn't want it, I can send it through my seccomp tree via James Morris. -Kees > > 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 ‘main’: > samples/seccomp/bpf-fancy.c:38:11: error: ‘__NR_exit’ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html