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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 5B606C433E6 for ; Fri, 12 Feb 2021 22:21:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 26A2C64E92 for ; Fri, 12 Feb 2021 22:21:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230307AbhBLWV5 (ORCPT ); Fri, 12 Feb 2021 17:21:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229788AbhBLWV4 (ORCPT ); Fri, 12 Feb 2021 17:21:56 -0500 Received: from mail-yb1-xb33.google.com (mail-yb1-xb33.google.com [IPv6:2607:f8b0:4864:20::b33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E138C061574; Fri, 12 Feb 2021 14:21:16 -0800 (PST) Received: by mail-yb1-xb33.google.com with SMTP id n195so929069ybg.9; Fri, 12 Feb 2021 14:21:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=cKWeJCj4GoLGsmc/rqtRETsvzyNtzdAMI1J104MLKeI=; b=Nm5SGO15yGsQv3nj+NzDaqDGb4zBZ0XnCACa1ALeIMSXVjksV5A2f4ZZlJBMtHgig3 D5PML+gyNEpsEGNC5YjkN8gCZ9wPxLMIt3R4Ntphvt03MaafOGSxwrk2vjC1e/Hqb84a yB32bsww6imVA2Z3sKQr6l5Nf+6x+ciYzQKXOZkTnZnqUQnWbaHy17wNJrjzEx+LQrqa D/V9HrFEb0iKzzZGTnHXvQDgmaXM6Rn2kXiOAkARNwV55aADNe2QrckhU5GfByTnW5uF BL1V9UJNtp/0iW7hNrV2HLKmbibKFUgaZLxVTtafakqIyMD//WYtef7xoNE9y5BXJYR2 1RpA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=cKWeJCj4GoLGsmc/rqtRETsvzyNtzdAMI1J104MLKeI=; b=P6D5B4eRbJJuGUd8vEwjwRmXmZD7lrbpOtoNrhIHiYi6rzfOZRdLoaNcdPBe6MF3ln i7/rRjNy4zi8BVq/5aCGRrGp9cQFQclI/CYY8rilK+ZHXeRl2l4xoze2mYlgwbnceGmB Z+S14HLEukRAYTBUjiehW1CUc4jGJOtNh0m9FTDA3Z1fHewMmk4Czz0eWEZAa/as2CJe hpiidizDX94yIjfgh0wKZtOsQO2cqp5dpdcFDUuibFWbsGhqzrCCGeKhkPg13IhFR8Q/ b4pXdRrxKAa6eSeAp2XzRNiyvHiq1O7ddC4bqR2vUGicLYOm3l1L6ewG7Ru3VKo6PGqf 5Uew== X-Gm-Message-State: AOAM5333bffkG3zzqAOVxuuvOrx3BaucAZXh8PfpygL2QvDi61An6vmy EF/IgUfXcYrWsH3ypEYEVxy2A1NYHe7+nwd6mxI= X-Google-Smtp-Source: ABdhPJwmcNHcG0ISz3V5EdTDWi31kaInHaBkcFJs5Zt/CL7dyC7nbvSbjQCz8CfjlHp0UNiYdyVjEXLVKFpaedyChAc= X-Received: by 2002:a25:4b86:: with SMTP id y128mr6827758yba.403.1613168475253; Fri, 12 Feb 2021 14:21:15 -0800 (PST) MIME-Version: 1.0 References: <20210212135427.1250224-1-jolsa@redhat.com> <20210212220420.1289014-1-jolsa@kernel.org> In-Reply-To: <20210212220420.1289014-1-jolsa@kernel.org> From: Andrii Nakryiko Date: Fri, 12 Feb 2021 14:21:04 -0800 Message-ID: Subject: Re: [PATCH] btf_encoder: Match ftrace addresses within elf functions To: Jiri Olsa Cc: Arnaldo Carvalho de Melo , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , dwarves@vger.kernel.org, Networking , bpf , Yonghong Song , Hao Luo , Martin KaFai Lau , Song Liu , John Fastabend , KP Singh , Nathan Chancellor , Sedat Dilek Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Feb 12, 2021 at 2:05 PM 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/ > Signed-off-by: Jiri Olsa > --- LGTM. But see another suggestion below. In either case: Acked-by: Andrii Nakryiko > btf_encoder.c | 55 +++++++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 45 insertions(+), 10 deletions(-) > > diff --git a/btf_encoder.c b/btf_encoder.c > index b124ec20a689..03242f04c55d 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 +238,48 @@ 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, bool kmod) > +{ > + /* > + * For vmlinux image both addrs[x] and functions[x]::addr > + * values are final address and are comparable. > + * > + * For kernel module addrs[x] is final address, but > + * functions[x]::addr is relative address within section > + * and needs to be relocated by adding sh_addr. > + */ > + __u64 start = kmod ? func->addr + func->sh_addr : 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; > @@ -275,18 +319,9 @@ static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > */ > for (i = 0; i < functions_cnt; i++) { > struct elf_function *func = &functions[i]; > - /* > - * For vmlinux image both addrs[x] and functions[x]::addr > - * values are final address and are comparable. > - * > - * For kernel module addrs[x] is final address, but > - * 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 we just... if (kmod) func->addr += func->sh_addr; ... here, that would make is_ftrace_func() free of kmod knowledge. If there are other places that rely on kmod vs non-kmod address of a function, that would be simplified as well, right? > > /* Make sure function is within ftrace addresses. */ > - if (bsearch(&addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) { > + if (is_ftrace_func(func, addrs, count, kmod)) { > /* > * We iterate over sorted array, so we can easily skip > * not valid item and move following valid field into > -- > 2.29.2 >