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 13F08CCA47E for ; Tue, 28 Jun 2022 15:11:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347597AbiF1PLw (ORCPT ); Tue, 28 Jun 2022 11:11:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44538 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346886AbiF1PLw (ORCPT ); Tue, 28 Jun 2022 11:11:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5188E2AC6D; Tue, 28 Jun 2022 08:11:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E125760EAE; Tue, 28 Jun 2022 15:11:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED921C3411D; Tue, 28 Jun 2022 15:11:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656429110; bh=6CRrz5GE3sbPpBNvpOE8bS4r8rF34+JaaCSHcXzLz7U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FgGFKKvuIrmCI31odpnLzLZxivYQQycW+SNotiBpZhqhEy592cZmU5RPF8+Cu3/Vg qADsWEpad00yrFTBKMUKFU6MfFf7XZErZkBgHBKYlEccfAam9HgzjizQiiO20aTu0Z rBy3Wvfv/rz3gkJpniPu55HK43Qraxym3Jo2lOr7I5BrCPlPRR1816zUAB6mVbmKKb vjs7FTztRASVm+SJi7LYR0P6EeRHt/5ENUVgrU8NN8xIt+w08l4H2JLnkgum9fUQ4I Q2j3vkWTOQCoUZmZEf4bV4sUD1oENLFAypIfj51+DyRqden0TlkTNJYQlDuptQgWb4 +XGbWFt3Rtr0Q== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 675E24096F; Tue, 28 Jun 2022 12:11:47 -0300 (-03) Date: Tue, 28 Jun 2022 12:11:47 -0300 From: Arnaldo Carvalho de Melo To: Jiri Olsa Cc: Ian Rogers , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Namhyung Kim , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Dave Marchevsky , Quentin Monnet , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Stephane Eranian Subject: Re: [PATCH] perf bpf: 8 byte align bpil data Message-ID: References: <20220614014714.1407239-1-irogers@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Em Tue, Jun 28, 2022 at 10:14:52AM +0200, Jiri Olsa escreveu: > On Mon, Jun 13, 2022 at 06:47:14PM -0700, Ian Rogers wrote: > > bpil data is accessed assuming 64-bit alignment resulting in undefined > > behavior as the data is just byte aligned. With an -fsanitize=undefined > > build the following errors are observed: > > > > $ sudo perf record -a sleep 1 > > util/bpf-event.c:310:22: runtime error: load of misaligned address 0x55f61084520f for type '__u64', which requires 8 byte alignment > > 0x55f61084520f: note: pointer points here > > a8 fe ff ff 3c 51 d3 c0 ff ff ff ff 04 84 d3 c0 ff ff ff ff d8 aa d3 c0 ff ff ff ff a4 c0 d3 c0 > > ^ > > util/bpf-event.c:311:20: runtime error: load of misaligned address 0x55f61084522f for type '__u32', which requires 4 byte alignment > > 0x55f61084522f: note: pointer points here > > ff ff ff ff c7 17 00 00 f1 02 00 00 1f 04 00 00 58 04 00 00 00 00 00 00 0f 00 00 00 63 02 00 00 > > ^ > > util/bpf-event.c:198:33: runtime error: member access within misaligned address 0x55f61084523f for type 'const struct bpf_func_info', which requires 4 byte alignment > > 0x55f61084523f: note: pointer points here > > 58 04 00 00 00 00 00 00 0f 00 00 00 63 02 00 00 3b 00 00 00 ab 02 00 00 44 00 00 00 14 03 00 00 > > > > Correct this by rouding up the data sizes and aligning the pointers. > > > > Signed-off-by: Ian Rogers > > --- > > tools/perf/util/bpf-utils.c | 5 ++--- > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/tools/perf/util/bpf-utils.c b/tools/perf/util/bpf-utils.c > > index e271e05e51bc..80b1d2b3729b 100644 > > --- a/tools/perf/util/bpf-utils.c > > +++ b/tools/perf/util/bpf-utils.c > > @@ -149,11 +149,10 @@ get_bpf_prog_info_linear(int fd, __u64 arrays) > > count = bpf_prog_info_read_offset_u32(&info, desc->count_offset); > > size = bpf_prog_info_read_offset_u32(&info, desc->size_offset); > > > > - data_len += count * size; > > + data_len += roundup(count * size, sizeof(__u64)); > > } > > > > /* step 3: allocate continuous memory */ > > - data_len = roundup(data_len, sizeof(__u64)); > > info_linear = malloc(sizeof(struct perf_bpil) + data_len); > > if (!info_linear) > > return ERR_PTR(-ENOMEM); > > @@ -180,7 +179,7 @@ get_bpf_prog_info_linear(int fd, __u64 arrays) > > bpf_prog_info_set_offset_u64(&info_linear->info, > > desc->array_offset, > > ptr_to_u64(ptr)); > > - ptr += count * size; > > + ptr += roundup(count * size, sizeof(__u64)); > > this one depends on info_linear->data being alligned(8), right? > > should we make sure it's allways the case like in the patch > below, or it's superfluous? > > thanks, > jirka > > > --- > diff --git a/tools/perf/util/bpf-utils.h b/tools/perf/util/bpf-utils.h > index 86a5055cdfad..1aba76c44116 100644 > --- a/tools/perf/util/bpf-utils.h > +++ b/tools/perf/util/bpf-utils.h > @@ -60,7 +60,7 @@ struct perf_bpil { > /* which arrays are included in data */ > __u64 arrays; > struct bpf_prog_info info; > - __u8 data[]; > + __u8 data[] __attribute__((aligned(8))); > }; > > struct perf_bpil * ⬢[acme@toolbox perf-urgent]$ pahole -C perf_bpil ~/bin/perf struct perf_bpil { __u32 info_len; /* 0 4 */ __u32 data_len; /* 4 4 */ __u64 arrays; /* 8 8 */ struct bpf_prog_info info __attribute__((__aligned__(8))); /* 16 224 */ /* XXX last struct has 4 bytes of padding */ /* --- cacheline 3 boundary (192 bytes) was 48 bytes ago --- */ __u8 data[]; /* 240 0 */ /* size: 240, cachelines: 4, members: 5 */ /* paddings: 1, sum paddings: 4 */ /* forced alignments: 1 */ /* last cacheline: 48 bytes */ } __attribute__((__aligned__(8))); ⬢[acme@toolbox perf-urgent]$ Humm, lotsa explicit alignments already? Looking at the sources: struct perf_bpil { /* size of struct bpf_prog_info, when the tool is compiled */ __u32 info_len; /* total bytes allocated for data, round up to 8 bytes */ __u32 data_len; /* which arrays are included in data */ __u64 arrays; struct bpf_prog_info info; __u8 data[]; }; Interesting, where is pahole finding those aligned attributes? Ok 'struct bpf_prog_info' in tools/include/uapi/linux/bpf.h has aligned(8) for the whole struct, so perf_bpil's info gets that. sp that data right after 'info' is 8 byte alignedas sizeof(bpf_prog_info) is a multiple of 8 bytes. So I think I can apply the patch as-is and leave making sure data is 8-byte aligned for later. Doing that now. - Arnaldo