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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1824C433EF for ; Wed, 9 Feb 2022 19:15:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231133AbiBITO4 (ORCPT ); Wed, 9 Feb 2022 14:14:56 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:39020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232118AbiBITOq (ORCPT ); Wed, 9 Feb 2022 14:14:46 -0500 Received: from mail-wm1-x333.google.com (mail-wm1-x333.google.com [IPv6:2a00:1450:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02D07C00F639; Wed, 9 Feb 2022 11:14:40 -0800 (PST) Received: by mail-wm1-x333.google.com with SMTP id r131so2099212wma.1; Wed, 09 Feb 2022 11:14:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=53AqFhwrg5sf39zbHRlZ7vehLvu2fcixViHXJDSalrM=; b=jsWd78AlHH12GCKj2sM1lGyk7uPOeN2Hbv9zgbd6Jh90rE/VED+SCZQ7MvUbRIpQGQ toDPAuiewlaGeRaYS8OpYAyIo1BRtg9ObuFi66RmkKYrzvRv3f5QIyZwjYyPuwXxwpOO wLXL+aKLyYGe6lUnUuzrFLCypTXYJlj0JcfbJAaiM0DDX+gySER0xQduBFYIxFFt19pQ cLtKzBzncDDqs9mQM+qiR/kcl5dWTIxgfOXz2Be2VG6ssBsjvkqgsjGlwBXcoLt5Pie0 /c9bNrxQltcrKUb24wOJFNrN/p6/GrgN6uBaqTcJAynAOoi2goC8YCjpHmekvKJj0rbE fsMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=53AqFhwrg5sf39zbHRlZ7vehLvu2fcixViHXJDSalrM=; b=cqxw5GPMUzs6sCcP49x0HD1VhkIdJr4qPNYRpbPZTMwoKHLcmsqIPGMGfnBe8LNBjD zeht2ctojXPSmLxb0f5dB47I/T+N6DUVIvj3y7Gzp/xQAXKOruZwMD/HRPzXfjL5ZzNz zFzEWtI/P8N/fQ+htotRx3tBCCYBkF+CzRHy3kmNZABRk14CTAl8+9q7vdc7LdcabzCd 7R6uEUl2Z/+A4SBREwVzk75zKCl8/KgGhYyQW+wU+46Z79//8/5oD6QvOB01pg2AFP7I oCAjDJ4AbaUq7sgk8/Ta4mp3dXPTqE3JyJ8pd7oMIl1SN/kWuXHzEB7+MCTMowITLVID pNRQ== X-Gm-Message-State: AOAM530Wha2/VNScR42hkXWxMQlbETLFBBjE/mIh9cU3ay0++1HatCZ2 vvKL75JbG8+Q2vkhm43KK2Y= X-Google-Smtp-Source: ABdhPJwhmM58FyRk4hJCT5mMbz2jGwH5dhixXieg1tw4oT6/MTcNt7zs5Z0qZofSAHx3/kkf3YsMcw== X-Received: by 2002:a05:600c:2944:: with SMTP id n4mr3393140wmd.190.1644434071348; Wed, 09 Feb 2022 11:14:31 -0800 (PST) Received: from krava ([83.240.63.12]) by smtp.gmail.com with ESMTPSA id l10sm19669970wry.79.2022.02.09.11.14.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Feb 2022 11:14:30 -0800 (PST) Date: Wed, 9 Feb 2022 20:14:28 +0100 From: Jiri Olsa To: Andrii Nakryiko Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Masami Hiramatsu , Networking , bpf , lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Steven Rostedt Subject: Re: [PATCH 2/8] bpf: Add bpf_get_func_ip kprobe helper for fprobe link Message-ID: References: <20220202135333.190761-1-jolsa@kernel.org> <20220202135333.190761-3-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 09, 2022 at 08:05:05AM -0800, Andrii Nakryiko wrote: > On Wed, Feb 9, 2022 at 7:01 AM Jiri Olsa wrote: > > > > On Mon, Feb 07, 2022 at 10:59:18AM -0800, Andrii Nakryiko wrote: > > > On Wed, Feb 2, 2022 at 5:53 AM Jiri Olsa wrote: > > > > > > > > Adding support to call get_func_ip_fprobe helper from kprobe > > > > programs attached by fprobe link. > > > > > > > > Also adding support to inline it, because it's single load > > > > instruction. > > > > > > > > Signed-off-by: Jiri Olsa > > > > --- > > > > kernel/bpf/verifier.c | 19 ++++++++++++++++++- > > > > kernel/trace/bpf_trace.c | 16 +++++++++++++++- > > > > 2 files changed, 33 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > > > index 1ae41d0cf96c..a745ded00635 100644 > > > > --- a/kernel/bpf/verifier.c > > > > +++ b/kernel/bpf/verifier.c > > > > @@ -13625,7 +13625,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env) > > > > continue; > > > > } > > > > > > > > - /* Implement bpf_get_func_ip inline. */ > > > > + /* Implement tracing bpf_get_func_ip inline. */ > > > > if (prog_type == BPF_PROG_TYPE_TRACING && > > > > insn->imm == BPF_FUNC_get_func_ip) { > > > > /* Load IP address from ctx - 16 */ > > > > @@ -13640,6 +13640,23 @@ static int do_misc_fixups(struct bpf_verifier_env *env) > > > > continue; > > > > } > > > > > > > > + /* Implement kprobe/fprobe bpf_get_func_ip inline. */ > > > > + if (prog_type == BPF_PROG_TYPE_KPROBE && > > > > + eatype == BPF_TRACE_FPROBE && > > > > + insn->imm == BPF_FUNC_get_func_ip) { > > > > + /* Load IP address from ctx (struct pt_regs) ip */ > > > > + insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, > > > > + offsetof(struct pt_regs, ip)); > > > > > > Isn't this architecture-specific? I'm starting to dislike this > > > > ugh, it is.. I'm not sure we want #ifdef CONFIG_X86 in here, > > or some arch_* specific function? > > > So not inlining it isn't even considered? this function will be called > once or at most a few times per BPF program invocation. Anyone calling > it in a tight loop is going to use it very-very suboptimally (and even > then useful program logic will dominate). There is no point in > inlining it. I agree that given its usage pattern there won't be too much gain, on the other hand it's simple verifier code changing call/load/ret into simple load, so I thought why not.. also there are just few helpers we can inline so easily but yea.. I can't think of any sane usage of this helper that inlining would matter for.. which doesn't mean there isn't one ;-) jirka > > > > > jirka > > > > > inlining whole more and more. It's just a complication in verifier > > > without clear real-world benefits. We are clearly prematurely > > > optimizing here. In practice you'll just call bpf_get_func_ip() once > > > and that's it. Function call overhead will be negligible compare to > > > other *userful* work you'll be doing in your BPF program. > > > > > > > > > > + > > > > + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1); > > > > + if (!new_prog) > > > > + return -ENOMEM; > > > > + > > > > + env->prog = prog = new_prog; > > > > + insn = new_prog->insnsi + i + delta; > > > > + continue; > > > > + } > > > > + > > > > patch_call_imm: > > > > fn = env->ops->get_func_proto(insn->imm, env->prog); > > > > /* all functions that have prototype and verifier allowed > > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > > > index a2024ba32a20..28e59e31e3db 100644 > > > > --- a/kernel/trace/bpf_trace.c > > > > +++ b/kernel/trace/bpf_trace.c > > > > @@ -1036,6 +1036,19 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = { > > > > .arg1_type = ARG_PTR_TO_CTX, > > > > }; > > > > > > > > +BPF_CALL_1(bpf_get_func_ip_fprobe, struct pt_regs *, regs) > > > > +{ > > > > + /* This helper call is inlined by verifier. */ > > > > + return regs->ip; > > > > +} > > > > + > > > > +static const struct bpf_func_proto bpf_get_func_ip_proto_fprobe = { > > > > + .func = bpf_get_func_ip_fprobe, > > > > + .gpl_only = false, > > > > + .ret_type = RET_INTEGER, > > > > + .arg1_type = ARG_PTR_TO_CTX, > > > > +}; > > > > + > > > > BPF_CALL_1(bpf_get_attach_cookie_trace, void *, ctx) > > > > { > > > > struct bpf_trace_run_ctx *run_ctx; > > > > @@ -1279,7 +1292,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > > > return &bpf_override_return_proto; > > > > #endif > > > > case BPF_FUNC_get_func_ip: > > > > - return &bpf_get_func_ip_proto_kprobe; > > > > + return prog->expected_attach_type == BPF_TRACE_FPROBE ? > > > > + &bpf_get_func_ip_proto_fprobe : &bpf_get_func_ip_proto_kprobe; > > > > case BPF_FUNC_get_attach_cookie: > > > > return &bpf_get_attach_cookie_proto_trace; > > > > default: > > > > -- > > > > 2.34.1 > > > >