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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 20C9CC83013 for ; Fri, 27 Nov 2020 17:58:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF5E72224A for ; Fri, 27 Nov 2020 17:58:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LCxzFfey" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733047AbgK0R6S (ORCPT ); Fri, 27 Nov 2020 12:58:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37824 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732919AbgK0R6R (ORCPT ); Fri, 27 Nov 2020 12:58:17 -0500 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA6CBC0613D2 for ; Fri, 27 Nov 2020 09:58:16 -0800 (PST) Received: by mail-qv1-xf49.google.com with SMTP id b9so3457993qvj.6 for ; Fri, 27 Nov 2020 09:58:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=NXuOTf1MPK8TRE6mj0XMAIGn4tL+u51UNs4Z0qmP7TY=; b=LCxzFfeyElEsmKF10zxjGXjZC+9NCkcHcJd6YRlac2ucNzBm813nhfgUEbO8tX89ls uJr5UW8Z8IRDcmuGXFQ/8rJiigwxIuAKf5yT4AfIY9qJwFSvgKFliJ3NIoQZ83jdEeUq tskA4y84dkkwdYQtTZDEHSU1EPauPDbzchuuBVKw0ZjiSGEoIQImlRJVAbZV3eglnt3D QDmy2ThtjXPWPgev/zPS/yKySFkL6ADja18SIHDYn4IAe7hiaR6j7IWcFtGvZl9mg9JM xEN0wBlt10RwJ6c/Dm+oDBwFniegP0SehwWazCNcDQvnLOQc8D/2sXRRmdlLe8omOh2r tqJQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=NXuOTf1MPK8TRE6mj0XMAIGn4tL+u51UNs4Z0qmP7TY=; b=T0p+RLNrzaIezQ9rIXNM39qeZsgvxqmtzaUeJDvVdrm0M+/GLJFzBkeMhQHxZz4My2 q0VS0Y39VQSXTDucDj9WKC5jpCI0749t/2Gg+mi1/96IFAowZs0fc/oHcYdTLNhC7PDx r5yaZDzT++Q0DW3b9RKDAtjHDuISovsjWdHsIsRzt1cWjsfNS2GMbuX71R+LiqpBOztI zeMBiWnUWb36q9yM3rphg3UT+zTHFk36wZ/eDIvqQP+LwHjjRPRzzQzeQck6De0KCFqo VGFiUKO+YgyZQleUZ8StX81eCPE3Liqx6dSWPcI6CWJdVRRFMh+AkzhOuVrN6Iovdjat fWXw== X-Gm-Message-State: AOAM530xYVR1mPSCUs4GJRz25QuOk/X7tJz2J9FU1SXe38S2raV7iCxM wySTT3WaowF8VH/WD+BW/+SNjhr+HLPCKQ== X-Google-Smtp-Source: ABdhPJxPJl813Avj63aZPEpIBc12NcoU1YbQ5PNvAh5FhZ/HCmrzSxW3HvxObE/cCykzTQtXo1QWJ4L8I0EJ+g== Sender: "jackmanb via sendgmr" X-Received: from beeg.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:11db]) (user=jackmanb job=sendgmr) by 2002:ad4:4725:: with SMTP id l5mr9499075qvz.51.1606499895963; Fri, 27 Nov 2020 09:58:15 -0800 (PST) Date: Fri, 27 Nov 2020 17:57:38 +0000 In-Reply-To: <20201127175738.1085417-1-jackmanb@google.com> Message-Id: <20201127175738.1085417-14-jackmanb@google.com> Mime-Version: 1.0 References: <20201127175738.1085417-1-jackmanb@google.com> X-Mailer: git-send-email 2.29.2.454.gaff20da3a2-goog Subject: [PATCH v2 bpf-next 13/13] bpf: Document new atomic instructions From: Brendan Jackman To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Yonghong Song , Daniel Borkmann , KP Singh , Florent Revest , linux-kernel@vger.kernel.org, Jann Horn , Brendan Jackman Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Brendan Jackman --- Documentation/networking/filter.rst | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst index 1583d59d806d..c86091b8cb0e 100644 --- a/Documentation/networking/filter.rst +++ b/Documentation/networking/filter.rst @@ -1053,6 +1053,33 @@ encoding. .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_W | BPF_STX: lock xadd *(u32 *)(dst_reg + off16) += src_reg .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_DW | BPF_STX: lock xadd *(u64 *)(dst_reg + off16) += src_reg +The basic atomic operations supported (from architecture v4 onwards) are: + + BPF_ADD + BPF_SUB + BPF_AND + BPF_OR + BPF_XOR + +Each having isomorphic semantics with the ``BPF_ADD`` example, that is: the +memory location addresed by ``dst_reg + off`` is atomically modified, with +``src_reg`` as the other operand. If the ``BPF_FETCH`` flag is set in the +immediate, then these operations also overwrite ``src_reg`` with the +pre-modification value from memory. + +The more special operations are: + + BPF_XCHG + +This atomically exchanges ``src_reg`` with the value addressed by ``dst_reg + +off``. + + BPF_CMPXCHG + +This atomically compares the value addressed by ``dst_reg + off`` with +``R0``. If they match it is replaced with ``src_reg``, The pre-modification +value is loaded back to ``R0``. + Note that 1 and 2 byte atomic operations are not supported. You may encounter BPF_XADD - this is a legacy name for BPF_ATOMIC, referring to -- 2.29.2.454.gaff20da3a2-goog