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=-12.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 C7616C433E0 for ; Thu, 30 Jul 2020 21:15:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9E18D2173E for ; Thu, 30 Jul 2020 21:15:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="iSeinaQF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728171AbgG3VPA (ORCPT ); Thu, 30 Jul 2020 17:15:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728849AbgG3VO7 (ORCPT ); Thu, 30 Jul 2020 17:14:59 -0400 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 178D7C061575 for ; Thu, 30 Jul 2020 14:14:59 -0700 (PDT) Received: by mail-ej1-x643.google.com with SMTP id c16so8998062ejx.12 for ; Thu, 30 Jul 2020 14:14:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=HQQ6RdOfI3qK/AtcGyAa3PPfsZ6PvAzcNLL/uW5Ov+c=; b=iSeinaQFf3yOe2lHxw0CJ8uvvymodnA+gZRBuK4XFslunfBv0lKOpua4/qzmJAeEFf CIhT9MTlKcx429Yqx/9BIvA0klhKjSnvGk84//qFwlrkB9ss82m9nN1DLOaLaapcrVBh KwI/PLMaPPLuiVBdfpgbc6+Q6yzAILIrEWmSOzbfKHx359OcZL2Ra3+hiznU8ilKAdgG YM3x9kcYKXXxov8pSZBJMUeEQ2qZIy648K1J3KfS1xgw1u2pwO3Wr8gjFMa+X2vSEiZ+ yNar+F+DxEXNUGQoQlvdbdB6KQ/xGNWe7kHQq4J3/QP3sB0jL/wbrhD+H/8BX/pHIxDw xrHw== 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=HQQ6RdOfI3qK/AtcGyAa3PPfsZ6PvAzcNLL/uW5Ov+c=; b=qQD+8u5qGf1YN5jmoVfn7+BHd2nelONfPgOps5wBz4xAWHZfO2IRl5xiRVjhfdNE76 P0SnHOzDLsCL5rxn7nfsvtymk+a8JTUmLw2fl1KgGJ1GcugSa4207/zJ2JqjWcj+GoZL GqA469qJYdyO1qjmXGaSa9kyaCqPsXpOCgCE6Yb/SBh5ZAIc7gNyDu43DxSYThcosqIP 7+6dlQlFAnzm3nXNEPyrXq1lF3SF5Q64T1NZ2wd2frdl2Fg2xsStvqCNApemjp5NbQJL hDPGAyhBoCQohBPhsxHOOLGRrupMO3qEpH8MZHy9ZXnv4bpwbJrBJbfhiXxi/5ceMs/X dkxQ== X-Gm-Message-State: AOAM5330kI0VFFoiEcDjjb8JMs00P2UJkhr23cqM3T0QU+0YO+sNhfE5 47E8bMqpBXtx9hCkdn/CahTLpn3pfz8u+w== X-Google-Smtp-Source: ABdhPJzlHh02QVVAFLKTB+xoRHb3mqAraUbK6zYudTHxIdHXY8kSsZkO1Rf8FHPFvQ+mk1u0vH6A8A== X-Received: by 2002:a17:906:fb07:: with SMTP id lz7mr991136ejb.49.1596143697686; Thu, 30 Jul 2020 14:14:57 -0700 (PDT) Received: from lophozonia ([2001:1715:4e26:a7e0:f1b0:45a6:cd09:bcd0]) by smtp.gmail.com with ESMTPSA id w20sm7569128eds.21.2020.07.30.14.14.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2020 14:14:57 -0700 (PDT) Date: Thu, 30 Jul 2020 23:14:53 +0200 From: Jean-Philippe Brucker To: Daniel Borkmann Cc: Qian Cai , linux-arm-kernel@lists.infradead.org, bpf@vger.kernel.org, songliubraving@fb.com, andriin@fb.com, catalin.marinas@arm.com, john.fastabend@gmail.com, ast@kernel.org, zlim.lnx@gmail.com, kpsingh@chromium.org, yhs@fb.com, will@kernel.org, kafai@fb.com, sfr@canb.auug.org.au, linux-next@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 1/1] arm64: bpf: Add BPF exception tables Message-ID: <20200730211453.GA79372@lophozonia> References: <20200728152122.1292756-1-jean-philippe@linaro.org> <20200728152122.1292756-2-jean-philippe@linaro.org> <20200730122855.GA3773@lca.pw> <20200730142213.GB1529030@myrica> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Jul 30, 2020 at 09:47:39PM +0200, Daniel Borkmann wrote: > On 7/30/20 4:22 PM, Jean-Philippe Brucker wrote: > > On Thu, Jul 30, 2020 at 08:28:56AM -0400, Qian Cai wrote: > > > On Tue, Jul 28, 2020 at 05:21:26PM +0200, Jean-Philippe Brucker wrote: > > > > When a tracing BPF program attempts to read memory without using the > > > > bpf_probe_read() helper, the verifier marks the load instruction with > > > > the BPF_PROBE_MEM flag. Since the arm64 JIT does not currently recognize > > > > this flag it falls back to the interpreter. > > > > > > > > Add support for BPF_PROBE_MEM, by appending an exception table to the > > > > BPF program. If the load instruction causes a data abort, the fixup > > > > infrastructure finds the exception table and fixes up the fault, by > > > > clearing the destination register and jumping over the faulting > > > > instruction. > > > > > > > > To keep the compact exception table entry format, inspect the pc in > > > > fixup_exception(). A more generic solution would add a "handler" field > > > > to the table entry, like on x86 and s390. > > > > > > > > Signed-off-by: Jean-Philippe Brucker > > > > > > This will fail to compile on arm64, > > > > > > https://gitlab.com/cailca/linux-mm/-/blob/master/arm64.config > > > > > > arch/arm64/mm/extable.o: In function `fixup_exception': > > > arch/arm64/mm/extable.c:19: undefined reference to `arm64_bpf_fixup_exception' > > > > Thanks for the report, I attached a fix. Daniel, can I squash it and > > resend as v2 or is it too late? > > If you want I can squash your attached snippet into the original patch of > yours. If you want to send a v2 that is fine as well of course. Let me know. Yes please squash it into the original patch, sorry for the mess Thanks, Jean