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Re: [PATCH 0/8] Improved seccomp-bpf support for MIPS

To: Paul Gortmaker <paul.gortmaker@windriver.com>
Subject: Re: [PATCH 0/8] Improved seccomp-bpf support for MIPS
From: Markos Chandras <Markos.Chandras@imgtec.com>
Date: Wed, 12 Feb 2014 09:39:07 +0000
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On 02/12/2014 12:58 AM, Paul Gortmaker wrote:
On Wed, Jan 22, 2014 at 9:39 AM, Markos Chandras
<markos.chandras@imgtec.com> wrote:
Hi,

This patch improves the existing seccomp-bpf support for MIPS.
It fixes a bug when copying system call arguments for the filter
checks and it also moves away from strict filtering to actually
use the filter supplied by the userspace process.

Hi all,

It seems this causes a build fail on linux-next allmodconfig.  I left
a mindless "git bisect run .." go against it and it came up with:
----------------------------
make[2]: *** [samples/seccomp/bpf-direct.o] Error 1
make[1]: *** [samples/seccomp] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [vmlinux] Error 2
5c5df77172430c6377ec3434ce62f2b14a6799fc is the first bad commit
commit 5c5df77172430c6377ec3434ce62f2b14a6799fc
Author: Markos Chandras <markos.chandras@imgtec.com>
Date:   Wed Jan 22 14:40:04 2014 +0000

     MIPS: Select HAVE_ARCH_SECCOMP_FILTER

     Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
     Reviewed-by: James Hogan <james.hogan@imgtec.com>
     Reviewed-by: Paul Burton <paul.burton@imgtec.com>
     Cc: linux-mips@linux-mips.org
     Patchwork: https://patchwork.linux-mips.org/patch/6401/
     Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
---------------------

The original linux-next fail is at:

http://kisskb.ellerman.id.au/kisskb/buildresult/10601740/

Paul.

Hi Paul,

I don't think this is caused by my patch. My patch just exposed it. To my understanding, the samples/seccomp are not meant to be cross-compiled. The tests use the host toolchain. However, when cross-compiling for MIPS, for example, __NR_write is only defined if

1) _MIPS_SIM == _MIPS_SIM_ABI64
2) _MIPS_SIM == _MIPS_SIM_ABI32
3) _MIPS_SIM == _MIPS_SIM_NABI32

which clearly makes no sense for the x86_64 toolchain. I would propose a fix like this in order to prevent test from being cross-compiled.

diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
index 7203e66..f3a018e 100644
--- a/samples/seccomp/Makefile
+++ b/samples/seccomp/Makefile
@@ -17,9 +17,9 @@ HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
 HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
 bpf-direct-objs := bpf-direct.o

+ifndef CROSS_COMPILE
 # Try to match the kernel target.
 ifndef CONFIG_64BIT
-ifndef CROSS_COMPILE

 # s390 has -m31 flag to build 31 bit binaries
 ifndef CONFIG_S390
@@ -36,7 +36,7 @@ HOSTLOADLIBES_bpf-direct += $(MFLAG)
 HOSTLOADLIBES_bpf-fancy += $(MFLAG)
 HOSTLOADLIBES_dropper += $(MFLAG)
 endif
-endif

 # Tell kbuild to always build the programs
 always := $(hostprogs-y)
+endif


--
markos


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