From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Kicinski Subject: Re: [PATCH bpf-next v3 07/10] bpf: fix multi-function JITed dump obtained via syscall Date: Tue, 22 May 2018 12:47:14 -0700 Message-ID: <20180522124714.7a50ada8@cakuba> References: <6f245a366d5a2957e2256f4bd89ab56ade6508d5.1527008647.git.sandipan@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, naveen.n.rao@linux.vnet.ibm.com To: Sandipan Das Return-path: Received: from mail-qt0-f196.google.com ([209.85.216.196]:35449 "EHLO mail-qt0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751559AbeEVTrT (ORCPT ); Tue, 22 May 2018 15:47:19 -0400 Received: by mail-qt0-f196.google.com with SMTP id j1-v6so2056769qtp.2 for ; Tue, 22 May 2018 12:47:18 -0700 (PDT) In-Reply-To: <6f245a366d5a2957e2256f4bd89ab56ade6508d5.1527008647.git.sandipan@linux.vnet.ibm.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 22 May 2018 22:46:10 +0530, Sandipan Das wrote: > Currently, for multi-function programs, we cannot get the JITed > instructions using the bpf system call's BPF_OBJ_GET_INFO_BY_FD > command. Because of this, userspace tools such as bpftool fail > to identify a multi-function program as being JITed or not. > > With the JIT enabled and the test program running, this can be > verified as follows: > > # cat /proc/sys/net/core/bpf_jit_enable > 1 > > Before applying this patch: > > # bpftool prog list > 1: kprobe name foo tag b811aab41a39ad3d gpl > loaded_at 2018-05-16T11:43:38+0530 uid 0 > xlated 216B not jited memlock 65536B > ... > > # bpftool prog dump jited id 1 > no instructions returned > > After applying this patch: > > # bpftool prog list > 1: kprobe name foo tag b811aab41a39ad3d gpl > loaded_at 2018-05-16T12:13:01+0530 uid 0 > xlated 216B jited 308B memlock 65536B > ... > > # bpftool prog dump jited id 1 > 0: nop > 4: nop > 8: mflr r0 > c: std r0,16(r1) > 10: stdu r1,-112(r1) > 14: std r31,104(r1) > 18: addi r31,r1,48 > 1c: li r3,10 > ... > > Signed-off-by: Sandipan Das > --- > kernel/bpf/syscall.c | 36 +++++++++++++++++++++++++++++++++--- > 1 file changed, 33 insertions(+), 3 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index f0ad4b5f0224..1c4cba91e523 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -1970,13 +1970,43 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog, > * for offload. > */ > ulen = info.jited_prog_len; > - info.jited_prog_len = prog->jited_len; > + if (prog->aux->func_cnt) { > + u32 i; > + > + info.jited_prog_len = 0; > + for (i = 0; i < prog->aux->func_cnt; i++) > + info.jited_prog_len += prog->aux->func[i]->jited_len; > + } else { > + info.jited_prog_len = prog->jited_len; > + } > + > if (info.jited_prog_len && ulen) { > if (bpf_dump_raw_ok()) { > uinsns = u64_to_user_ptr(info.jited_prog_insns); > ulen = min_t(u32, info.jited_prog_len, ulen); > - if (copy_to_user(uinsns, prog->bpf_func, ulen)) > - return -EFAULT; > + > + /* for multi-function programs, copy the JITed > + * instructions for all the functions > + */ > + if (prog->aux->func_cnt) { > + u32 len, free, i; > + u8 *img; > + > + free = ulen; > + for (i = 0; i < prog->aux->func_cnt; i++) { > + len = prog->aux->func[i]->jited_len; > + img = (u8 *) prog->aux->func[i]->bpf_func; > + if (len > free) > + break; nit: interesting, the previous code used to fill up the space completely, I would personally vote to keep that behaviour and do: len = min(len, free); copy(); free -= len; if (!free) break; otherwise the user space doesn't know when to stop disassembling truncated output. But that's really a corner case, so not sure we care. > + if (copy_to_user(uinsns, img, len)) > + return -EFAULT; > + uinsns += len; > + free -= len; > + } > + } else { > + if (copy_to_user(uinsns, prog->bpf_func, ulen)) > + return -EFAULT; > + } > } else { > info.jited_prog_insns = 0; > }