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=-10.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 4FD9FC43461 for ; Mon, 14 Sep 2020 12:22:10 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DB95C2226B for ; Mon, 14 Sep 2020 12:22:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dTBsn54W"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="lAyrt8Ms" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB95C2226B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=o8oHM6iD2482vwaDcu4rlC7006ObtQKw1aKPJOz16ls=; b=dTBsn54WFVMiFRoszVEFLWam/ IBsrUymbGHFAyPePjDCgqQIF3ET5XVIVu18u+p08ex3OvnXhjz/RhwKEUvs7ZxYSM1FwPd4QcSlql O5Nmcyi4HQRzuAglD66XEhiWtirKUZqsoUDzuDrz3CH4MIMwik9uor6+MufMsUXEaBU+qkLj3WxTb LceRB2yNxw1qbLmc3fZgWLQtU3McV7cI+J0BaxsDZLO0kV32gNJ9mPw7kySMUwVIumusLVNrbh/hJ 72ZnBsxec4S/p/PliDrOgA95Rjl+X4o22Hb4rYzmPIMXXJovUNCjk6DJRVhzyhiKkfA60o2uK1a8w u87vzytLA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kHnTb-0003cj-0D; Mon, 14 Sep 2020 12:20:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kHnTX-0003c3-CE for linux-arm-kernel@lists.infradead.org; Mon, 14 Sep 2020 12:20:52 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AB9392220E; Mon, 14 Sep 2020 12:20:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600086050; bh=YriLuLaFHzLfRAoXWiSCNiRverNlmw+ZAkR2pmdisCw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lAyrt8Msk+qgwcGynhjL1jG4JJFYSkJICoVwEG5X9Ki7q5+u+PiE6K8WMcPcy+ceH U+kw1F/b3sDTAl7If26HeT3jr9hABXjuKmlYEJWe5CIisAHxCp/aTHbi1ce6fuL/AR RengwapvOITAcODLACP75ilW4+B3IOrCJUaO4k+g= Date: Mon, 14 Sep 2020 13:20:43 +0100 From: Will Deacon To: Ilias Apalodimas Subject: Re: [PATCH] arm64: bpf: Fix branch offset in JIT Message-ID: <20200914122042.GA24441@willie-the-truck> References: <20200914083622.116554-1-ilias.apalodimas@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200914083622.116554-1-ilias.apalodimas@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200914_082051_540542_4238C420 X-CRM114-Status: GOOD ( 17.81 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jean-Philippe Brucker , Song Liu , linux-kernel@vger.kernel.org, Jesper Dangaard Brouer , Daniel Borkmann , Yauheni Kaliuta , Zi Shen Lim , naresh.kamboju@linaro.org, John Fastabend , Alexei Starovoitov , Martin KaFai Lau , netdev@vger.kernel.org, Jakub Kicinski , "David S. Miller" , Catalin Marinas , KP Singh , Yonghong Song , bpf@vger.kernel.org, Andrii Nakryiko , ardb@kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 14, 2020 at 11:36:21AM +0300, Ilias Apalodimas wrote: > Running the eBPF test_verifier leads to random errors looking like this: > > [ 6525.735488] Unexpected kernel BRK exception at EL1 > [ 6525.735502] Internal error: ptrace BRK handler: f2000100 [#1] SMP > [ 6525.741609] Modules linked in: nls_utf8 cifs libdes libarc4 dns_resolver fscache binfmt_misc nls_ascii nls_cp437 vfat fat aes_ce_blk crypto_simd cryptd aes_ce_cipher ghash_ce gf128mul efi_pstore sha2_ce sha256_arm64 sha1_ce evdev efivars efivarfs ip_tables x_tables autofs4 btrfs blake2b_generic xor xor_neon zstd_compress raid6_pq libcrc32c crc32c_generic ahci xhci_pci libahci xhci_hcd igb libata i2c_algo_bit nvme realtek usbcore nvme_core scsi_mod t10_pi netsec mdio_devres of_mdio gpio_keys fixed_phy libphy gpio_mb86s7x > [ 6525.787760] CPU: 3 PID: 7881 Comm: test_verifier Tainted: G W 5.9.0-rc1+ #47 > [ 6525.796111] Hardware name: Socionext SynQuacer E-series DeveloperBox, BIOS build #1 Jun 6 2020 > [ 6525.804812] pstate: 20000005 (nzCv daif -PAN -UAO BTYPE=--) > [ 6525.810390] pc : bpf_prog_c3d01833289b6311_F+0xc8/0x9f4 > [ 6525.815613] lr : bpf_prog_d53bb52e3f4483f9_F+0x38/0xc8c > [ 6525.820832] sp : ffff8000130cbb80 > [ 6525.824141] x29: ffff8000130cbbb0 x28: 0000000000000000 > [ 6525.829451] x27: 000005ef6fcbf39b x26: 0000000000000000 > [ 6525.834759] x25: ffff8000130cbb80 x24: ffff800011dc7038 > [ 6525.840067] x23: ffff8000130cbd00 x22: ffff0008f624d080 > [ 6525.845375] x21: 0000000000000001 x20: ffff800011dc7000 > [ 6525.850682] x19: 0000000000000000 x18: 0000000000000000 > [ 6525.855990] x17: 0000000000000000 x16: 0000000000000000 > [ 6525.861298] x15: 0000000000000000 x14: 0000000000000000 > [ 6525.866606] x13: 0000000000000000 x12: 0000000000000000 > [ 6525.871913] x11: 0000000000000001 x10: ffff8000000a660c > [ 6525.877220] x9 : ffff800010951810 x8 : ffff8000130cbc38 > [ 6525.882528] x7 : 0000000000000000 x6 : 0000009864cfa881 > [ 6525.887836] x5 : 00ffffffffffffff x4 : 002880ba1a0b3e9f > [ 6525.893144] x3 : 0000000000000018 x2 : ffff8000000a4374 > [ 6525.898452] x1 : 000000000000000a x0 : 0000000000000009 > [ 6525.903760] Call trace: > [ 6525.906202] bpf_prog_c3d01833289b6311_F+0xc8/0x9f4 > [ 6525.911076] bpf_prog_d53bb52e3f4483f9_F+0x38/0xc8c > [ 6525.915957] bpf_dispatcher_xdp_func+0x14/0x20 > [ 6525.920398] bpf_test_run+0x70/0x1b0 > [ 6525.923969] bpf_prog_test_run_xdp+0xec/0x190 > [ 6525.928326] __do_sys_bpf+0xc88/0x1b28 > [ 6525.932072] __arm64_sys_bpf+0x24/0x30 > [ 6525.935820] el0_svc_common.constprop.0+0x70/0x168 > [ 6525.940607] do_el0_svc+0x28/0x88 > [ 6525.943920] el0_sync_handler+0x88/0x190 > [ 6525.947838] el0_sync+0x140/0x180 > [ 6525.951154] Code: d4202000 d4202000 d4202000 d4202000 (d4202000) > [ 6525.957249] ---[ end trace cecc3f93b14927e2 ]--- > > The reason seems to be the offset[] creation and usage ctx->offset[] "seems to be"? Are you unsure? > while building the eBPF body. The code currently omits the first > instruction, since build_insn() will increase our ctx->idx before saving > it. When "taken loop with back jump to 1st insn" test runs it will > eventually call bpf2a64_offset(-1, 2, ctx). Since negative indexing is > permitted, the current outcome depends on the value stored in > ctx->offset[-1], which has nothing to do with our array. > If the value happens to be 0 the tests will work. If not this error > triggers. > > So let's fix it by creating the ctx->offset[] correctly in the first > place and account for the extra instruction while calculating the arm > instruction offsets. No Fixes: tag? > Signed-off-by: Ilias Apalodimas > Signed-off-by: Jean-Philippe Brucker > Signed-off-by: Yauheni Kaliuta Non-author signoffs here. What's going on? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel