From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C0BCC31E4B for ; Fri, 14 Jun 2019 21:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56C7B21473 for ; Fri, 14 Jun 2019 21:07:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726094AbfFNVHz (ORCPT ); Fri, 14 Jun 2019 17:07:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55322 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725808AbfFNVHz (ORCPT ); Fri, 14 Jun 2019 17:07:55 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2982359441; Fri, 14 Jun 2019 21:07:54 +0000 (UTC) Received: from treble (ovpn-121-232.rdu2.redhat.com [10.10.121.232]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4B3CA5C29A; Fri, 14 Jun 2019 21:07:52 +0000 (UTC) Date: Fri, 14 Jun 2019 16:07:45 -0500 From: Josh Poimboeuf To: Alexei Starovoitov Cc: x86@kernel.org, Alexei Starovoitov , linux-kernel@vger.kernel.org, Daniel Borkmann , netdev@vger.kernel.org, bpf@vger.kernel.org, Peter Zijlstra , Song Liu , Kairui Song , Steven Rostedt , David Laight , Thomas Gleixner , Borislav Petkov , Ingo Molnar Subject: Re: [PATCH v2 2/5] objtool: Fix ORC unwinding in non-JIT BPF generated code Message-ID: <20190614210745.kwiqm5pkgabruzuj@treble> References: <20190614205841.s4utbpurntpr6aiq@ast-mbp.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190614205841.s4utbpurntpr6aiq@ast-mbp.dhcp.thefacebook.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 14 Jun 2019 21:07:54 +0000 (UTC) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jun 14, 2019 at 01:58:42PM -0700, Alexei Starovoitov wrote: > On Fri, Jun 14, 2019 at 12:56:41PM -0500, Josh Poimboeuf wrote: > > Objtool currently ignores ___bpf_prog_run() because it doesn't > > understand the jump table. This results in the ORC unwinder not being > > able to unwind through non-JIT BPF code. > > > > Luckily, the BPF jump table resembles a GCC switch jump table, which > > objtool already knows how to read. > > > > Add generic support for reading any static local jump table array named > > "jump_table", and rename the BPF variable accordingly, so objtool can > > generate ORC data for ___bpf_prog_run(). > > > > Fixes: d15d356887e7 ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER") > > Reported-by: Song Liu > > Signed-off-by: Josh Poimboeuf > > Acked-by: Peter Zijlstra (Intel) > > --- > > kernel/bpf/core.c | 5 ++--- > > tools/objtool/check.c | 16 ++++++++++++++-- > > 2 files changed, 16 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > > index 7c473f208a10..aa546ef7dbdc 100644 > > --- a/kernel/bpf/core.c > > +++ b/kernel/bpf/core.c > > @@ -1299,7 +1299,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) > > { > > #define BPF_INSN_2_LBL(x, y) [BPF_##x | BPF_##y] = &&x##_##y > > #define BPF_INSN_3_LBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = &&x##_##y##_##z > > - static const void *jumptable[256] = { > > + static const void *jump_table[256] = { > > [0 ... 255] = &&default_label, > > /* Now overwrite non-defaults ... */ > > BPF_INSN_MAP(BPF_INSN_2_LBL, BPF_INSN_3_LBL), > > @@ -1315,7 +1315,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) > > #define CONT_JMP ({ insn++; goto select_insn; }) > > > > select_insn: > > - goto *jumptable[insn->code]; > > + goto *jump_table[insn->code]; > > > > /* ALU */ > > #define ALU(OPCODE, OP) \ > > @@ -1558,7 +1558,6 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) > > BUG_ON(1); > > return 0; > > } > > -STACK_FRAME_NON_STANDARD(___bpf_prog_run); /* jump table */ > > > > #define PROG_NAME(stack_size) __bpf_prog_run##stack_size > > #define DEFINE_BPF_PROG_RUN(stack_size) \ > > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > > index 172f99195726..8341c2fff14f 100644 > > --- a/tools/objtool/check.c > > +++ b/tools/objtool/check.c > > @@ -18,6 +18,8 @@ > > > > #define FAKE_JUMP_OFFSET -1 > > > > +#define JUMP_TABLE_SYM_PREFIX "jump_table." > > since external tool will be looking at it should it be named > "bpf_jump_table." to avoid potential name conflicts? > Or even more unique name? > Like "bpf_interpreter_jump_table." ? No, the point is that it's a generic feature which can also be used any non-BPF code which might also have a jump table. -- Josh