From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antonio Quartulli Subject: Re: [PATCH] Fix ARM BUILD_BUG_ON() errors with batman-adv Date: Sat, 30 Nov 2013 21:12:52 +0100 Message-ID: <529A46C4.9090906@meshcoding.com> References: <20131130191553.GA16735@n2100.arm.linux.org.uk> Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, David Miller , The list for a Better Approach To Mobile Ad-hoc Networking , Marek Lindner To: linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org Return-path: In-Reply-To: <20131130191553.GA16735-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: b.a.t.m.a.n-bounces-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r@public.gmane.org Sender: "B.A.T.M.A.N" List-Id: netdev.vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 30/11/13 20:15, Russell King - ARM Linux wrote: > From: Russell King > > The following errors were observed on ARM during a randconfig > build. This patch addresses them by ensuring that the batadv_header > structure is appropriately packed; this structure contains three > 8-bit elements so there should be no undesired side effect from > this packing. > > net/batman-adv/main.c: In function 'batadv_init': > net/batman-adv/main.c:425:279: error: call to > '__compiletime_assert_425' declared with attribute error: > BUILD_BUG_ON failed: offsetof(struct batadv_unicast_4addr_packet, > src) != 10 net/batman-adv/main.c:426:267: error: call to > '__compiletime_assert_426' declared with attribute error: > BUILD_BUG_ON failed: offsetof(struct batadv_unicast_packet, dest) > != 4 net/batman-adv/main.c:427:275: error: call to > '__compiletime_assert_427' declared with attribute error: > BUILD_BUG_ON failed: offsetof(struct batadv_unicast_tvlv_packet, > dst) != 4 net/batman-adv/main.c:428:261: error: call to > '__compiletime_assert_428' declared with attribute error: > BUILD_BUG_ON failed: offsetof(struct batadv_frag_packet, dest) != > 4 net/batman-adv/main.c:429:271: error: call to > '__compiletime_assert_429' declared with attribute error: > BUILD_BUG_ON failed: offsetof(struct batadv_icmp_packet, icmph.dst) > != 4 net/batman-adv/main.c:430:277: error: call to > '__compiletime_assert_430' declared with attribute error: > BUILD_BUG_ON failed: offsetof(struct batadv_icmp_packet_rr, > icmph.dst) != 4 > > Signed-off-by: Russell King --- > net/batman-adv/packet.h | 2 +- 1 files changed, 1 insertions(+), > 1 deletions(-) > > diff --git a/net/batman-adv/packet.h b/net/batman-adv/packet.h > index 207459b62966..4039f25794e0 100644 --- > a/net/batman-adv/packet.h +++ b/net/batman-adv/packet.h @@ -171,7 > +171,7 @@ struct batadv_header { /* the parent struct has to add a > byte after the header to make * everything 4 bytes aligned again > */ -}; +} __attribute__((packed)); Russell, this attribute was there in the past and then was removed on purpose because on some architectures it makes the compiler generating very inefficient code (you can check http://article.gmane.org/gmane.org.freifunk.batman/8317 for more details). So we removed the __packed attribute and we took care of properly aligning all the structures by adding "alignment/reserved members" when needed. I don't know the ARM architecture at all (I don't know if the other batman-adv developers do), so could you please provide here some more details about why that static check is failing? We would like to address this issue differently rather than re-adding the __packed attribute. Thanks a lot. Best Regards, - -- Antonio Quartulli -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iEYEARECAAYFAlKaRsQACgkQpGgxIkP9cwdDnACeJGU2FXi48yjDwZ2YcPCJBruq vKgAnRc4p1dukczVgFATo2wb+Bflpdom =RrAs -----END PGP SIGNATURE-----