From: Kees Cook <keescook@chromium.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, andrii@kernel.org
Subject: Re: [PATCH] treewide: Remove unnamed static initializations to 0
Date: Fri, 10 Sep 2021 19:08:28 -0700 [thread overview]
Message-ID: <202109101845.FF22342@keescook> (raw)
In-Reply-To: <20210910232303.vzwzoo2vvyga6jjs@ast-mbp.dhcp.thefacebook.com>
On Fri, Sep 10, 2021 at 04:23:03PM -0700, Alexei Starovoitov wrote:
> On Fri, Sep 10, 2021 at 03:52:07PM -0700, Kees Cook wrote:
> > GCC 4.9 does not like having struct assignments to 0 when members may be
> > compound types. For example, there are 186 instances of these kinds of
> > errors:
> >
> > drivers/virtio/virtio_vdpa.c:146:9: error: missing braces around initializer [-Werror=missing-braces ]
> > drivers/cxl/core/regs.c:40:17: error: missing braces around initializer [-Werror=missing-braces]
> >
> > Since "= { 0 }" and "= { }" have the same meaning ("incomplete
> > initializer") they will both initialize the given variable to zero
> > (modulo padding games).
> >
> > After this change, I can almost build the "allmodconfig" target with
> > GCC 4.9 again.
> >
> > Signed-off-by: Kees Cook <keescook@chromium.org>
>
> ...
>
> > .../selftests/bpf/prog_tests/perf_branches.c | 4 +-
> > .../selftests/bpf/prog_tests/sk_lookup.c | 12 +-
> > .../selftests/bpf/prog_tests/sockmap_ktls.c | 2 +-
> > .../selftests/bpf/prog_tests/sockmap_listen.c | 4 +-
> > .../selftests/bpf/progs/test_sk_assign.c | 6 +-
> > .../selftests/bpf/progs/test_xdp_vlan.c | 8 +-
>
> Those have nothing to do with GCC. They are compiled with clang with -target bpf.
> Did you check that bpf selftests still pass?
> We've had issues with older clang generating different code with zero and non-zero
> assignments and libbpf was confused.
> It should all work now, but please run the tests.
Sure! I think selftests/bpf/config is missing:
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_INFO_BTF=y
I can't get much further, though:
$ make -C tools/testing/selftests gen_tar TARGETS="bpf" FORMAT=.xz
make: Entering directory '/srv/code/tools/testing/selftests'
make --no-builtin-rules ARCH=x86 -C ../../.. headers_install
make[1]: Entering directory '/srv/code'
INSTALL ./usr/include
make[1]: Leaving directory '/srv/code'
make: *** [Makefile:162: all] Error 1
make: Leaving directory '/srv/code/tools/testing/selftests'
I'm not sure what's breaking ...
--
Kees Cook
next prev parent reply other threads:[~2021-09-11 2:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-10 22:52 [PATCH] treewide: Remove unnamed static initializations to 0 Kees Cook
2021-09-10 23:23 ` Alexei Starovoitov
2021-09-11 2:08 ` Kees Cook [this message]
2021-09-13 19:40 ` Linus Torvalds
2021-09-14 16:50 ` Kees Cook
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