From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Kicinski Subject: Re: [PATCH net] bpf: don't zero out the info struct in bpf_obj_get_info_by_fd() Date: Tue, 25 Jul 2017 16:15:47 -0700 Message-ID: <20170725161547.64d1cba5@cakuba.netronome.com> References: <20170725221612.6937-1-jakub.kicinski@netronome.com> <5977CD65.20504@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, oss-drivers@netronome.com, alexei.starovoitov@gmail.com, kafai@fb.com To: Daniel Borkmann Return-path: Received: from mail-pg0-f42.google.com ([74.125.83.42]:33490 "EHLO mail-pg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750897AbdGYXPu (ORCPT ); Tue, 25 Jul 2017 19:15:50 -0400 Received: by mail-pg0-f42.google.com with SMTP id g14so27268407pgu.0 for ; Tue, 25 Jul 2017 16:15:50 -0700 (PDT) In-Reply-To: <5977CD65.20504@iogearbox.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 26 Jul 2017 00:59:49 +0200, Daniel Borkmann wrote: > > @@ -418,6 +420,8 @@ static void test_bpf_obj_id(void) > > nr_id_found++; > > > > err = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &info_len); > > + prog_infos[i].jited_prog_insns = 0; > > + prog_infos[i].xlated_prog_insns = 0; > > Can you elaborate why this one above is needed? Ah, I removed the comment about it at the last minute. The check below compares the info we get here with info we got reading the programs in the earlier loop - using memcmp(). This call, however, doesn't fill in the pointers for jited and xlated images, so the memcmp() would fail. It used to work when bpf_obj_get_info_by_fd() was zeroing info, since the pointers would be cleared by it, and no dump ever returned, it didn't matter that the call sites differ. > > CHECK(err || info_len != sizeof(struct bpf_prog_info) || > > memcmp(&prog_info, &prog_infos[i], info_len), > > "get-prog-info(next_id->fd)",