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=-2.7 required=3.0 tests=BAYES_00,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 89A2FC433EF for ; Wed, 8 Sep 2021 18:21:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 717BB60E97 for ; Wed, 8 Sep 2021 18:21:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349768AbhIHSWV (ORCPT ); Wed, 8 Sep 2021 14:22:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349745AbhIHSWU (ORCPT ); Wed, 8 Sep 2021 14:22:20 -0400 Received: from mail-pj1-x1035.google.com (mail-pj1-x1035.google.com [IPv6:2607:f8b0:4864:20::1035]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C8EFC061575 for ; Wed, 8 Sep 2021 11:21:10 -0700 (PDT) Received: by mail-pj1-x1035.google.com with SMTP id g13-20020a17090a3c8d00b00196286963b9so1929172pjc.3 for ; Wed, 08 Sep 2021 11:21:10 -0700 (PDT) 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=9Zns6gslyH9a/olbK7XjumGoSBEER/uG5E31IJd9NiA=; b=GFp0C5jqEQgoDtMPCDJ3tpZj88NEjss+AOhG5s1h4dn6UNvfXdwProtzrSCXSaTM6Y S9m2uK14DaE8jwdwI3dTYXQA22aWxZpVCTcKHXv2GfY6j+V4XlmBtmQqnPG55B1jQEmY +RKGwQNV/awJBm2LhDFyBdoWSiSwjB+LtAtedVrDo8Yy19ekUzxHvBUqZ6cocvNDE1Lc JZ9iT8DQthYU/h0Gw+fl07s/pNmcb5JEpUZFhtiTF4SSESjqsTMdAwjByH6a6mkKyQan iWI+SECtwjiwNe1G3zSqawGnCMIIVdB+ArJfQF47locZMYTbkCr+W8V4ouR55YxqlfpX tAWQ== 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=9Zns6gslyH9a/olbK7XjumGoSBEER/uG5E31IJd9NiA=; b=3LeGTvFTrCrRUE4aCC1/ei5DDfBFEqAUiP5D/nAtiheoXHAqWRzim8pWElE2N4IoIY Jhh+Ixo6DZbRRM55Vfx6yR9C+7xpq3Hg1HAY1MMtQ/3Kpk4Snk4A3fx3isuZLENvLyPw 5+POGdlbFHvf9dpu+CwuT7GndLAtvQL8kXKAJXOxS6PQvdOjjGdboHVgkfCYcanXl/In 8aIomriEg18jvqCb8TR8KNwzWG5LR0mgfDJfisfkRlULqCN7mHojzunlSawvE4i5OmDe i3+X9wOJiklZ1r6FHYXdZl1FxOHsjQItzHMkUlwI3XzlO4OlmdhEbdgPiE9jAjkviEav 48ww== X-Gm-Message-State: AOAM531L9AkXRG8sUxnLDPmY8wr28yuUZP/FIVXanUNhl1T/he3d8IWD ZwpU3WvlsmV7rnzKb/tdqVYAVIvgzVg9nv9daR4= X-Google-Smtp-Source: ABdhPJx7bLHsd2Yu88B/rTt2UQp+xh9cyfij6RE7vL9Z6KtZC+b9Fz6AfZ8pnNqwTau96U2T6nZ0ZMhaO1ErkYEUX7w= X-Received: by 2002:a17:90b:4f8e:: with SMTP id qe14mr5583215pjb.122.1631125269538; Wed, 08 Sep 2021 11:21:09 -0700 (PDT) MIME-Version: 1.0 References: <20210908044427.3632119-1-yhs@fb.com> <20210908135326.GZ1200268@ziepe.ca> <20210908151230.m2zyslt4qrufm4bv@revolver> <20210908172118.n2f4w7epm6hh62zf@ast-mbp.dhcp.thefacebook.com> <20210908105259.c47dcc4e4371ebb5e147ee6e@linux-foundation.org> <20210908180258.yjh62e5oouckar5b@ast-mbp.dhcp.thefacebook.com> <20210908111527.9a611426e257d55ccbbf46eb@linux-foundation.org> In-Reply-To: <20210908111527.9a611426e257d55ccbbf46eb@linux-foundation.org> From: Alexei Starovoitov Date: Wed, 8 Sep 2021 11:20:58 -0700 Message-ID: Subject: Re: [PATCH mm/bpf v2] mm: bpf: add find_vma_no_check() without lockdep_assert on mm->mmap_lock To: Andrew Morton Cc: Luigi Rizzo , Yonghong Song , Liam Howlett , Peter Zijlstra , Jason Gunthorpe , Daniel Borkmann , bpf , "linux-mm@kvack.org" , Alexei Starovoitov , Andrii Nakryiko , "kernel-team@fb.com" , walken@fb.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Sep 8, 2021 at 11:15 AM Andrew Morton wrote: > > On Wed, 8 Sep 2021 11:02:58 -0700 Alexei Starovoitov wrote: > > > > Please describe the expected userspace-visible change from Peter's > > > patch in full detail? > > > > User space expects build_id to be available. Peter patch simply removes > > that feature. > > Are you sure? He ends up with More than sure :) Just look at below. > static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > u64 *ips, u32 trace_nr, bool user) > { > int i; > > /* cannot access current->mm, fall back to ips */ > for (i = 0; i < trace_nr; i++) { > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > id_offs[i].ip = ips[i]; > memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX); > } > return; > } > > and you're saying that userspace won't like this because we didn't set > BPF_STACK_BUILD_ID_VALID? The patch forces the "fallback path" that in production is seen 0.001% Meaning that user space doesn't see build_id any more. It sees IPs only. The user space cannot correlate IPs to binaries. That's what build_id enabled. 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=-2.7 required=3.0 tests=BAYES_00,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 5F582C433F5 for ; Wed, 8 Sep 2021 18:21:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0889E60E97 for ; Wed, 8 Sep 2021 18:21:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0889E60E97 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 8D8D06B0071; Wed, 8 Sep 2021 14:21:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 861B26B0072; Wed, 8 Sep 2021 14:21:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7028E6B0073; Wed, 8 Sep 2021 14:21:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0076.hostedemail.com [216.40.44.76]) by kanga.kvack.org (Postfix) with ESMTP id 5619C6B0071 for ; Wed, 8 Sep 2021 14:21:11 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E02BE183E4B93 for ; Wed, 8 Sep 2021 18:21:10 +0000 (UTC) X-FDA: 78565223100.21.4D55B6A Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) by imf27.hostedemail.com (Postfix) with ESMTP id AB5E970000A2 for ; Wed, 8 Sep 2021 18:21:10 +0000 (UTC) Received: by mail-pj1-f47.google.com with SMTP id f3-20020a17090a638300b00199097ddf1aso44338pjj.0 for ; Wed, 08 Sep 2021 11:21:10 -0700 (PDT) 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=9Zns6gslyH9a/olbK7XjumGoSBEER/uG5E31IJd9NiA=; b=GFp0C5jqEQgoDtMPCDJ3tpZj88NEjss+AOhG5s1h4dn6UNvfXdwProtzrSCXSaTM6Y S9m2uK14DaE8jwdwI3dTYXQA22aWxZpVCTcKHXv2GfY6j+V4XlmBtmQqnPG55B1jQEmY +RKGwQNV/awJBm2LhDFyBdoWSiSwjB+LtAtedVrDo8Yy19ekUzxHvBUqZ6cocvNDE1Lc JZ9iT8DQthYU/h0Gw+fl07s/pNmcb5JEpUZFhtiTF4SSESjqsTMdAwjByH6a6mkKyQan iWI+SECtwjiwNe1G3zSqawGnCMIIVdB+ArJfQF47locZMYTbkCr+W8V4ouR55YxqlfpX tAWQ== 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=9Zns6gslyH9a/olbK7XjumGoSBEER/uG5E31IJd9NiA=; b=iJsJpFApMQxoOTz88/Stq5WeQN/nyPJtQjxJLI1jDQ7Md919Rn85YSJvKwB0V2T9lv XA+axmwIpnOIjbrtKrEr6+SgyOzNZkBPCfhm4/3vjh8x/rUPM3VbmTTKr2IbN4vlW14x lINx/hiou3DWLcY/L5IcjzratfgJf4dfE+H5aEnLiw8n9uaJyy7GdRDagbfoiToEmGWV P7I5IDo6iSVJpGDxLYFwNegjq38TbtVZFv+Nm8WCRAGY94uHOqD0qsutD34u+iPR4rwx bA6ZJ4ZvVzQ/f9AvRw4BNtWLpeyb+dcnEp7htN/AvtqztiIz5lTeAUlk3+VwA2rYMTXH VHPA== X-Gm-Message-State: AOAM5316Uuz+EdUBsbmMm9cvkHil/r0Dl3RjMPtSMppZA2SVQYWOUX3p Z+VxR63AexMQWJtOpAMKonrNkADVUFKy+LSzK2E= X-Google-Smtp-Source: ABdhPJx7bLHsd2Yu88B/rTt2UQp+xh9cyfij6RE7vL9Z6KtZC+b9Fz6AfZ8pnNqwTau96U2T6nZ0ZMhaO1ErkYEUX7w= X-Received: by 2002:a17:90b:4f8e:: with SMTP id qe14mr5583215pjb.122.1631125269538; Wed, 08 Sep 2021 11:21:09 -0700 (PDT) MIME-Version: 1.0 References: <20210908044427.3632119-1-yhs@fb.com> <20210908135326.GZ1200268@ziepe.ca> <20210908151230.m2zyslt4qrufm4bv@revolver> <20210908172118.n2f4w7epm6hh62zf@ast-mbp.dhcp.thefacebook.com> <20210908105259.c47dcc4e4371ebb5e147ee6e@linux-foundation.org> <20210908180258.yjh62e5oouckar5b@ast-mbp.dhcp.thefacebook.com> <20210908111527.9a611426e257d55ccbbf46eb@linux-foundation.org> In-Reply-To: <20210908111527.9a611426e257d55ccbbf46eb@linux-foundation.org> From: Alexei Starovoitov Date: Wed, 8 Sep 2021 11:20:58 -0700 Message-ID: Subject: Re: [PATCH mm/bpf v2] mm: bpf: add find_vma_no_check() without lockdep_assert on mm->mmap_lock To: Andrew Morton Cc: Luigi Rizzo , Yonghong Song , Liam Howlett , Peter Zijlstra , Jason Gunthorpe , Daniel Borkmann , bpf , "linux-mm@kvack.org" , Alexei Starovoitov , Andrii Nakryiko , "kernel-team@fb.com" , walken@fb.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: us5e5kzdcymmnidr1ke4mmfed1a58yw5 Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=GFp0C5jq; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf27.hostedemail.com: domain of alexei.starovoitov@gmail.com designates 209.85.216.47 as permitted sender) smtp.mailfrom=alexei.starovoitov@gmail.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: AB5E970000A2 X-HE-Tag: 1631125270-953529 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 8, 2021 at 11:15 AM Andrew Morton wrote: > > On Wed, 8 Sep 2021 11:02:58 -0700 Alexei Starovoitov wrote: > > > > Please describe the expected userspace-visible change from Peter's > > > patch in full detail? > > > > User space expects build_id to be available. Peter patch simply removes > > that feature. > > Are you sure? He ends up with More than sure :) Just look at below. > static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > u64 *ips, u32 trace_nr, bool user) > { > int i; > > /* cannot access current->mm, fall back to ips */ > for (i = 0; i < trace_nr; i++) { > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > id_offs[i].ip = ips[i]; > memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX); > } > return; > } > > and you're saying that userspace won't like this because we didn't set > BPF_STACK_BUILD_ID_VALID? The patch forces the "fallback path" that in production is seen 0.001% Meaning that user space doesn't see build_id any more. It sees IPs only. The user space cannot correlate IPs to binaries. That's what build_id enabled.