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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 0232BC2D0F0 for ; Mon, 30 Mar 2020 22:23:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C328720784 for ; Mon, 30 Mar 2020 22:23:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="n1H6m0Ic" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729167AbgC3WXH (ORCPT ); Mon, 30 Mar 2020 18:23:07 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:38970 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729035AbgC3WXH (ORCPT ); Mon, 30 Mar 2020 18:23:07 -0400 Received: by mail-pg1-f195.google.com with SMTP id g32so3318873pgb.6; Mon, 30 Mar 2020 15:23:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=BiKAxLOqqm8kt9G/Q7jIDlXTD9R49LyBGIvlpIHtGUk=; b=n1H6m0IcP/NRpqJoT65TmwsjMnLZ6NNhmu9wgguYg1vsX177vLbDMBssdAq95d6QKD if61S88jSC/e+HyL2hg3ikxtDYOfm8JdeDu2Rpsvg8KbYQ51aK6Ecq78Pt/v4n8t3ObB sJgSWAoOjN/rzGZBQkLr+SGu2aZpEV/rUPBO3xTgD4aakVneP+syTRvagyAwnUoRCbA5 klRu7gNiPqu3M0k2zamgqnVBzirbjMtAdlD0foYLChZyI7pIT4uF4/eSHK+RgyY2rRAQ 5S/VTxRw89DFXq2p5xz0tf/iBPNT/6ABDyZ++/AJ1rdjxIAmipS5//Kv7KU6SVsnqc4q tsJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=BiKAxLOqqm8kt9G/Q7jIDlXTD9R49LyBGIvlpIHtGUk=; b=pHIsTrNWybbeFuT9Hc/cOXLUM6JPdwugMtR5Gar3EAGxSB1w3HASwQhLaBIzqOjK4M z0rbVyW0RM5+uqbkW6iXQQWSg4WEWr9vdaWOn6izSirRsX9xqOBQ/g+gM7MrX/O6tHCh 9qaf81W5zN0qlKfkeZ/MIRR2NWatDrgTvuAFMzBje7BsDdBQR9xxxCM3oLVnjM7jYWeH FWafkU/2skdrvjMfeB4qSKiOwYYnwjxX/cchSfQ7Grz6WiHFN6qi9yKmq0TG5ZGK1jog 6Eerk6Y9DKAV0jmWcz0S02DVwHhIA9QrVwdl2J1Fnad8T3VvOhB8YstWeT/AfwyQgdzP Fv7A== X-Gm-Message-State: ANhLgQ0HRU18q+nPTKv3mUx73gbGr5fsroGKK3VPRFa+jq0HvEGvV6Pp Ho+qoSyTXl3wWMzzJqHQRDY= X-Google-Smtp-Source: ADFU+vulXzuZAYYXjvBldJV1/tgm31psAgASpwxS3ocxQk6XszHbfK4Ta5cm5Z+Vy0xkQq2ywAG7nw== X-Received: by 2002:a63:8148:: with SMTP id t69mr14370684pgd.187.1585606985764; Mon, 30 Mar 2020 15:23:05 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:400::5:3558]) by smtp.gmail.com with ESMTPSA id q15sm9480935pfn.89.2020.03.30.15.23.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2020 15:23:04 -0700 (PDT) Date: Mon, 30 Mar 2020 15:23:02 -0700 From: Alexei Starovoitov To: John Fastabend Cc: ecree@solarflare.com, yhs@fb.com, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [bpf-next PATCH v2 2/7] bpf: verifier, do explicit ALU32 bounds tracking Message-ID: <20200330222302.6fhtedyzxfaqmthl@ast-mbp.dhcp.thefacebook.com> References: <158560409224.10843.3588655801186916301.stgit@john-Precision-5820-Tower> <158560419880.10843.11448220440809118343.stgit@john-Precision-5820-Tower> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158560419880.10843.11448220440809118343.stgit@john-Precision-5820-Tower> Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Mar 30, 2020 at 02:36:39PM -0700, John Fastabend wrote: > +static void __scalar64_min_max_lsh(struct bpf_reg_state *dst_reg, > + u64 umin_val, u64 umax_val) > +{ > + /* Special case <<32 because it is a common compiler pattern to zero > + * upper bits by doing <<32 s>>32. In this case if 32bit bounds are > + * positive we know this shift will also be positive so we can track > + * bounds correctly. Otherwise we lose all sign bit information except > + * what we can pick up from var_off. Perhaps we can generalize this > + * later to shifts of any length. > + */ > + if (umin_val == 32 && umax_val == 32 && dst_reg->s32_max_value >= 0) > + dst_reg->smax_value = (s64)dst_reg->s32_max_value << 32; > + else > + dst_reg->smax_value = S64_MAX; I fixed up above comment to say 'sign extend' instead of 'zero upper bit' and applied. Thanks a ton for the awesome work.