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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D98CAC433E6 for ; Wed, 17 Feb 2021 12:46:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A98E064E45 for ; Wed, 17 Feb 2021 12:46:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232660AbhBQMqo (ORCPT ); Wed, 17 Feb 2021 07:46:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:54722 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232688AbhBQMqm (ORCPT ); Wed, 17 Feb 2021 07:46:42 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 44E7264E45; Wed, 17 Feb 2021 12:46:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613565961; bh=i4wEVtEtZfNOcsQo3Vb11/Sk+XObvw/m+UYrVSmr96Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FOOlyIsoQRzz7g5o3TQGhYUOHIzAGa1faERXXP90D+p7/W9z6BXPcE8Ft/Hi5G5gj PQlEU5G9HoNBA4yb6eN8mLh2acTfSU1Aoi5NYGnqRvC8KDyIxWs3wjIH8osn3rzI4h V5M+Z4f4WQcUf1X+YvLxK4RalsjsCzOIB52MCCvGxPprGI/qCuKk+RyvoMuvOxOxku SyvrKXYikVVqZ3IbI0cQuCFrgshof7Dds85sDyqMVCd04miGAdvX8B/k3mJydftiu1 bzWGbcUnHHL2vEt/W/Gxrr5hSw9LuC9iWAhBpoaD4+jrnXHik7G6iEI/ZhXpYlDOtp tKQk4I8+HhnRQ== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 5233440CD9; Wed, 17 Feb 2021 09:45:59 -0300 (-03) Date: Wed, 17 Feb 2021 09:45:59 -0300 From: Arnaldo Carvalho de Melo To: Nathan Chancellor Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Andrii Nakryiko , dwarves@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Yonghong Song , Hao Luo , Martin KaFai Lau , Song Liu , John Fastabend , KP Singh , Sedat Dilek Subject: Re: [PATCHv2] btf_encoder: Match ftrace addresses within elf functions Message-ID: References: <20210213164648.1322182-1-jolsa@kernel.org> <20210214023048.GA12132@24bbad8f3778> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210214023048.GA12132@24bbad8f3778> X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Em Sat, Feb 13, 2021 at 07:30:48PM -0700, Nathan Chancellor escreveu: > On Sat, Feb 13, 2021 at 05:46:48PM +0100, Jiri Olsa wrote: > > Currently when processing DWARF function, we check its entrypoint > > against ftrace addresses, assuming that the ftrace address matches > > with function's entrypoint. > > > > This is not the case on some architectures as reported by Nathan > > when building kernel on arm [1]. > > > > Fixing the check to take into account the whole function not > > just the entrypoint. > > > > Most of the is_ftrace_func code was contributed by Andrii. > > > > [1] https://lore.kernel.org/bpf/20210209034416.GA1669105@ubuntu-m3-large-x86/ > > Acked-by: Andrii Nakryiko > > Signed-off-by: Jiri Olsa > > I did several builds with CONFIG_DEBUG_INFO_BTF enabled (arm64, ppc64le, > and x86_64) and saw no build errors. I did not do any runtime testing. > > Tested-by: Nathan Chancellor Thanks, added to the cset, - Arnaldo > > --- > > v2 changes: > > - update functions addr directly [Andrii] > > > > btf_encoder.c | 40 ++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 38 insertions(+), 2 deletions(-) > > > > diff --git a/btf_encoder.c b/btf_encoder.c > > index b124ec20a689..80e896961d4e 100644 > > --- a/btf_encoder.c > > +++ b/btf_encoder.c > > @@ -36,6 +36,7 @@ struct funcs_layout { > > struct elf_function { > > const char *name; > > unsigned long addr; > > + unsigned long size; > > unsigned long sh_addr; > > bool generated; > > }; > > @@ -98,6 +99,7 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym, > > > > functions[functions_cnt].name = name; > > functions[functions_cnt].addr = elf_sym__value(sym); > > + functions[functions_cnt].size = elf_sym__size(sym); > > functions[functions_cnt].sh_addr = sh.sh_addr; > > functions[functions_cnt].generated = false; > > functions_cnt++; > > @@ -236,6 +238,39 @@ get_kmod_addrs(struct btf_elf *btfe, __u64 **paddrs, __u64 *pcount) > > return 0; > > } > > > > +static int is_ftrace_func(struct elf_function *func, __u64 *addrs, __u64 count) > > +{ > > + __u64 start = func->addr; > > + __u64 addr, end = func->addr + func->size; > > + > > + /* > > + * The invariant here is addr[r] that is the smallest address > > + * that is >= than function start addr. Except the corner case > > + * where there is no such r, but for that we have a final check > > + * in the return. > > + */ > > + size_t l = 0, r = count - 1, m; > > + > > + /* make sure we don't use invalid r */ > > + if (count == 0) > > + return false; > > + > > + while (l < r) { > > + m = l + (r - l) / 2; > > + addr = addrs[m]; > > + > > + if (addr >= start) { > > + /* we satisfy invariant, so tighten r */ > > + r = m; > > + } else { > > + /* m is not good enough as l, maybe m + 1 will be */ > > + l = m + 1; > > + } > > + } > > + > > + return start <= addrs[r] && addrs[r] < end; > > +} > > + > > static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > > { > > __u64 *addrs, count, i; > > @@ -283,10 +318,11 @@ static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > > * functions[x]::addr is relative address within section > > * and needs to be relocated by adding sh_addr. > > */ > > - __u64 addr = kmod ? func->addr + func->sh_addr : func->addr; > > + if (kmod) > > + func->addr += func->sh_addr; > > > > /* Make sure function is within ftrace addresses. */ > > - if (bsearch(&addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) { > > + if (is_ftrace_func(func, addrs, count)) { > > /* > > * We iterate over sorted array, so we can easily skip > > * not valid item and move following valid field into > > -- > > 2.29.2 > > -- - Arnaldo