From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Kicinski Subject: Re: [PATCH net-next] bpf: add helper capable of reading out instructions Date: Tue, 25 Jul 2017 11:20:06 -0700 Message-ID: <20170725112006.261bf04f@cakuba.netronome.com> References: <20170724212236.21903-2-jakub.kicinski@netronome.com> <59777477.7050609@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, alexei.starovoitov@gmail.com, oss-drivers@netronome.com, kafai@fb.com To: Daniel Borkmann Return-path: Received: from mail-pf0-f171.google.com ([209.85.192.171]:32886 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750861AbdGYSUN (ORCPT ); Tue, 25 Jul 2017 14:20:13 -0400 Received: by mail-pf0-f171.google.com with SMTP id s70so61396476pfs.0 for ; Tue, 25 Jul 2017 11:20:13 -0700 (PDT) In-Reply-To: <59777477.7050609@iogearbox.net> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 25 Jul 2017 18:40:23 +0200, Daniel Borkmann wrote: > [ +Martin ] Sorry, I thought I CCed Martin. > On 07/24/2017 11:22 PM, Jakub Kicinski wrote: > > To read translated and jited instructions from the kernel, > > one has to set certain pointers of struct bpf_prog_info to > > pre-allocated user buffers. Unfortunately, the existing > > bpf_obj_get_info_by_fd() helper zeros struct bpf_prog_info > > before passing it to the kernel. > > > > Keeping the zeroing seems like a good idea in general, since > > kernel will check if the structure was zeroed. Add a new > > helper for those more advanced users who can be trusted to > > take care of zeroing themselves. > > > > Signed-off-by: Jakub Kicinski > > --- > > I'm happy to change the name of the new function. > > > > tools/lib/bpf/bpf.c | 10 ++++++++-- > > tools/lib/bpf/bpf.h | 2 ++ > > 2 files changed, 10 insertions(+), 2 deletions(-) > > > > diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c > > index 412a7c82995a..2703fa282b65 100644 > > --- a/tools/lib/bpf/bpf.c > > +++ b/tools/lib/bpf/bpf.c > > @@ -308,13 +308,12 @@ int bpf_map_get_fd_by_id(__u32 id) > > return sys_bpf(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr)); > > } > > > > -int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len) > > +int __bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len) > > { > > union bpf_attr attr; > > int err; > > > > bzero(&attr, sizeof(attr)); > > - bzero(info, *info_len); > > Looks a bit unintentional to me, e.g. 95b9afd3987f ("bpf: Test for bpf > ID") did set up pointers in test_bpf_obj_id(), but later only checked > for the {jited,xlated}_prog_len. > > Clearing out the pointers looks not to useful. Lets just push the need > for bzero() to call-sites in general in this case. Should I target this at net then? To avoid backwards compatibility issues?