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 A64A1C433F5 for ; Thu, 25 Nov 2021 16:39:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237190AbhKYQnA (ORCPT ); Thu, 25 Nov 2021 11:43:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59590 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237194AbhKYQk6 (ORCPT ); Thu, 25 Nov 2021 11:40:58 -0500 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFE62C0613B4; Thu, 25 Nov 2021 08:14:26 -0800 (PST) Received: by mail-pl1-x630.google.com with SMTP id y7so4922374plp.0; Thu, 25 Nov 2021 08:14:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=g3YOy32wAiS4F1wiZhx4eVxL906t+jOLf5KQMas9Kmw=; b=YB8JQFjOo+iWcT2Y8FNFFHiBPDH/Yr/ZAv0K/a1JlFpaVgJuSGElHhwiixpNn5NW3R LXCqkXbY4lqeDlj6SnlUhPGMdy1aTKUMTs3xrWroedi7C7IeZ1N4c1x/hNvof22687Aa Qr0loWvIt0J0v0KlGjlsGOMHA3VIpJ27v9jMQW73l5/50b14QXrOQXyDOdV/7KDnysU6 tJW4qUUwahEFkatJAZ0JCwa5Uzz1X4bwvpAdYwx1Rbm+VNl82ukwPdxadPskidhDmxiy viBj8RSzGpO8G0ckU4aV2Nxe5yKRxzdLMa68kgy64kYJ7S+vQfrNdkv8o/0LevoUkHD2 cSZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=g3YOy32wAiS4F1wiZhx4eVxL906t+jOLf5KQMas9Kmw=; b=7aglaSIBlC6csQ826oqt40wOPQphEjTxx95VUW0aNsmyi/uOaVre5qK3OdYydaF/1m mM1aHUaCw28Y5efU0Zk30EDC/pPYpWkKAzlLfMfy+/qCOcuwd9YdivN2epMzga+Y8NcK 9w5V19e29NPHWfLkBC8XY6F5KavGEtxz5p10dCsqr7VkRewnaQX/xuMt0r8hE9OJ5NR4 lDrH8BQIIaKFJQ2+azss8m48bqxGCivmK39TqyODb7XAyOk02KJJGUkVho7ayRYjLmDJ Mdwz0yy0daNVZF2Q0KIqLbCaJGMA0ILVkL+bMxiosh/0V/oKis3e9JKPl4b2VYU7tpfq FIpQ== X-Gm-Message-State: AOAM533/hzbQ6t2F3eiHklNLAWOZk1XX9+RGlHC5wB1fct9jSlgUh8CT ZRCx2sHmf/GjzD6X3okcugR7rH/pt8J90H4JfWI= X-Google-Smtp-Source: ABdhPJxLbbLPvwFQp2ksuxU2G311B7Nqm5IaIZVNwHEDRDGduXj3iYkMbPHSiy9plbgdK33wHN0GYsL+hMAsDdpKgvA= X-Received: by 2002:a17:90a:17a5:: with SMTP id q34mr8242463pja.122.1637856866419; Thu, 25 Nov 2021 08:14:26 -0800 (PST) MIME-Version: 1.0 References: <20211118112455.475349-1-jolsa@kernel.org> <20211118112455.475349-7-jolsa@kernel.org> In-Reply-To: From: Alexei Starovoitov Date: Thu, 25 Nov 2021 09:14:15 -0700 Message-ID: Subject: Re: [PATCH bpf-next 06/29] bpf: Add bpf_arg/bpf_ret_value helpers for tracing programs To: Andrii Nakryiko Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Networking , bpf , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Nov 24, 2021 at 2:43 PM Andrii Nakryiko wrote: > > + /* Implement bpf_arg inline. */ > > + if (prog_type == BPF_PROG_TYPE_TRACING && > > + insn->imm == BPF_FUNC_arg) { > > + /* Load nr_args from ctx - 8 */ > > + insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8); > > + insn_buf[1] = BPF_JMP32_REG(BPF_JGE, BPF_REG_2, BPF_REG_0, 4); > > + insn_buf[2] = BPF_ALU64_IMM(BPF_MUL, BPF_REG_2, 8); > > + insn_buf[3] = BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1); > > + insn_buf[4] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_2, 0); > > + insn_buf[5] = BPF_JMP_A(1); > > + insn_buf[6] = BPF_MOV64_IMM(BPF_REG_0, 0); > > + > > + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 7); > > + if (!new_prog) > > + return -ENOMEM; > > + > > + delta += 6; > > + env->prog = prog = new_prog; > > + insn = new_prog->insnsi + i + delta; > > + continue; > > nit: this whole sequence of steps and calculations seems like > something that might be abstracted and hidden behind a macro or helper > func? Not related to your change, though. But wouldn't it be easier to > understand if it was just written as: > > PATCH_INSNS( > BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8); > BPF_JMP32_REG(BPF_JGE, BPF_REG_2, BPF_REG_0, 4); > BPF_ALU64_IMM(BPF_MUL, BPF_REG_2, 8); > BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1); > BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_2, 0); > BPF_JMP_A(1); > BPF_MOV64_IMM(BPF_REG_0, 0)); Daniel and myself tried to do similar macro magic in the past, but it suffers unnecessary stack increase and extra copies. So eventually we got rid of it. I suggest staying with Jiri's approach. Independent from anything else... Just noticed BPF_MUL in the above... Please use BPF_LSH instead. JITs don't optimize such things. It's a job of gcc/llvm to do so. JITs assume that all normal optimizations were done by the compiler.