Re: [Qemu-devel] [PULL 00/05] seccomp branch queue

[Andrew Jones <drjones@redhat.com>]

On Fri, Oct 30, 2015 at 04:30:05PM +0000, Peter Maydell wrote:
> On 30 October 2015 at 13:44, Eduardo Otubo
> <eduardo.otubo@profitbricks.com> wrote:
> > The following changes since commit c49d3411faae8ffaab8f7e5db47405a008411c10:
> >
> >   Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2015-10-12' into staging (2015-10-13 10:42:06 +0100)
> >
> > are available in the git repository at:
> >
> >   git://github.com/otubo/qemu.git tags/pull-seccomp-20151030
> >
> > for you to fetch changes up to b1e1f0bbe7268d0bb8f63da220b41803b2e54081:
> >
> >   seccomp: loosen library version dependency (2015-10-30 14:33:00 +0100)
> >
> > ----------------------------------------------------------------
> > seccomp branch queue
> >
> > ----------------------------------------------------------------
> 
> Hi. I'm afraid this fails to build on x86 Linux:
> 
> /home/petmay01/linaro/qemu-for-merges/qemu-seccomp.c:241:8: error:
> ‘__NR_cacheflush’ undeclared here (not in a function)
>      { SCMP_SYS(cacheflush), 240 },

Ugh...  Of course we can't have a common seccomp syscall table and different
atleast-versions for different architectures... So x86 only requires 2.1.0,
but libseccomp didn't know about cacheflush until 2.2.1, and we require 2.2.3
for other reasons. Ideally, we'd compose the seccomp syscall table by starting
with a common base (something 2.1.0 knows about) and then add an architecture
specific table, and maybe even a machine-type specific table. That's pretty
easy to do, we just need a list of tables, but as it's a framework change and
will touch many places, then I don't expect it to be a super quick job... I
think in the interim the fix for patch 1/5 of this series is something
like shown below. If there are no objections, then I'll send it.

drew

diff --git a/qemu-seccomp.c b/qemu-seccomp.c
index 80d034a8d5190..e76097e958779 100644
--- a/qemu-seccomp.c
+++ b/qemu-seccomp.c
@@ -16,6 +16,10 @@
 #include <seccomp.h>
 #include "sysemu/seccomp.h"
 
+#if SCMP_VER_MAJOR >= 2 && SCMP_VER_MINOR >= 2 && SCMP_VER_MICRO >= 3
+#define HAVE_CACHEFLUSH
+#endif
+
 struct QemuSeccompSyscall {
     int32_t num;
     uint8_t priority;
@@ -238,7 +242,10 @@ static const struct QemuSeccompSyscall
seccomp_whitelist[] = {
     { SCMP_SYS(inotify_init1), 240 },
     { SCMP_SYS(inotify_add_watch), 240 },
-    { SCMP_SYS(mbind), 240 }
+    { SCMP_SYS(mbind), 240 },
+#ifdef HAVE_CACHEFLUSH
+    { SCMP_SYS(cacheflush), 240 },
+#endif
 };
 
 int seccomp_start(void)