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 D0AC6C43334 for ; Fri, 8 Jul 2022 08:26:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237637AbiGHI01 (ORCPT ); Fri, 8 Jul 2022 04:26:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237586AbiGHI00 (ORCPT ); Fri, 8 Jul 2022 04:26:26 -0400 Received: from mail-wm1-x335.google.com (mail-wm1-x335.google.com [IPv6:2a00:1450:4864:20::335]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39871814A7 for ; Fri, 8 Jul 2022 01:26:25 -0700 (PDT) Received: by mail-wm1-x335.google.com with SMTP id h131-20020a1c2189000000b003a2cc290135so705849wmh.2 for ; Fri, 08 Jul 2022 01:26:25 -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=/OVTFWFueCRPCSOvGcnm5qhmYMmcAYT2qYgKyKk2GrU=; b=QayVImNEczOhK0XOfo/Un1TkE91WIaEh4vd5WGqaoap8Zp3zXyX1dE2P6RqQrpT1XS oy1BzMte5WWi0qpuvNFLbedtjg2n7Za2D4EYGowA6pIDEJpZATtjx7KTCqtGGcRO+0Hm w4Ot42GczZ1AqfqjZNrfsIYwRBv4+h7ReSSB9exmjeAS3NcLvVOm3Cp0vlKsBAUZLeK4 3U0QqPn/SGSigUG8o6BjBZ/4XRXPETHIM0smmMd84MTwqwWFc+HDBmhlrFEZT6wwwNtr wRf5occqwIOBxSXFsjoS+goTKLITad0wByayOqYY9Tj1R8PO6+gn4sR8T1ZFngyCv/Yb FUxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=/OVTFWFueCRPCSOvGcnm5qhmYMmcAYT2qYgKyKk2GrU=; b=ArXVB/abTUlil2gc78e4Kloh8FnhkBtFqzeSV1FZs0tCTPXTKbZluBQj+Ze6gyefaf DQW3VhpBWPo28vYI1h9lWL0cfIk4eIie/N+0afl66DmBVUIllU1mr6/wpR0xJR/uK3pm 0plpeE617D2c4WU3x0ocSiS7yNg+ele67N29Ok4Ttsp4dNnZAwZYH/LxUrzXGWPgiKKj gAT9p8QB6Dmc7ADjHi/es32GSFw8xecxgjpePY+bdNlP0pzX2T/H57XH40VNTjDLYOg0 tio9BdF6B1WQCaaboTNTSS+cJJ+JfcpJXqnY3C6vuDNUO5Tr7H8pK5zxIrutXVPEY3eD zAqQ== X-Gm-Message-State: AJIora9RJZ1dLmrbFHNaF/dca7TE+zwI3KKkhT/TUURiIls7rNXNnBr5 XxY3UN0EPbulUfzvFcvWxkSP4w== X-Google-Smtp-Source: AGRyM1v4J522/CsbJ15YeUOvSaWI8hyF/D8ynhoDdCisWlk5JSxaXP8LbE/H1oMLQMyP+D4lTEzv7Q== X-Received: by 2002:a05:600c:3491:b0:3a0:4d4a:2e2d with SMTP id a17-20020a05600c349100b003a04d4a2e2dmr9448093wmq.4.1657268783790; Fri, 08 Jul 2022 01:26:23 -0700 (PDT) Received: from myrica (cpc92880-cmbg19-2-0-cust679.5-4.cable.virginm.net. [82.27.106.168]) by smtp.gmail.com with ESMTPSA id l1-20020a7bc441000000b003a2cf1535aasm1403895wmi.17.2022.07.08.01.26.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Jul 2022 01:26:23 -0700 (PDT) Date: Fri, 8 Jul 2022 09:25:58 +0100 From: Jean-Philippe Brucker To: Xu Kuohai Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Mark Rutland , Catalin Marinas , Will Deacon , Daniel Borkmann , Alexei Starovoitov , Zi Shen Lim , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , "David S . Miller" , Hideaki YOSHIFUJI , David Ahern , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Jakub Kicinski , Jesper Dangaard Brouer , Russell King , James Morse , Hou Tao , Jason Wang Subject: Re: [PATCH bpf-next v6 3/4] bpf, arm64: Impelment bpf_arch_text_poke() for arm64 Message-ID: References: <20220625161255.547944-1-xukuohai@huawei.com> <20220625161255.547944-4-xukuohai@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jul 08, 2022 at 10:41:46AM +0800, Xu Kuohai wrote: > >> +/* generated prologue: > >> + * bti c // if CONFIG_ARM64_BTI_KERNEL > >> + * mov x9, lr > >> + * nop // POKE_OFFSET > >> + * paciasp // if CONFIG_ARM64_PTR_AUTH_KERNEL > > > > Any reason for the change regarding BTI and pointer auth? We used to put > > 'bti c' at the function entry if (BTI && !PA), or 'paciasp' if (BTI && PA), > > because 'paciasp' is an implicit BTI. > > > > Assuming paciasp is the first instruction if (BTI && PA), when a > trampoline with BPF_TRAMP_F_CALL_ORIG flag attached, we'll encounter the > following scenario. > > bpf_prog: > paciasp // LR1 > mov x9, lr > bl ----> trampoline: > .... > mov x10, > blr x10 > | > CALL_ORIG_entry: | > bti c <------------------| > stp x29, lr, [sp, #- 16]! > ... > autiasp // LR2 > ret > > Because LR1 and LR2 are not equal, the autiasp will fail! > > To make this scenario work properly, the first instruction should be > 'bti c'. Right my mistake, this layout is also what GCC generates for normal kernel functions when (BTI && PA), so it makes sense to use the same Thanks, Jean