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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 3283BC433DF for ; Thu, 18 Jun 2020 02:08:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12FE52193E for ; Thu, 18 Jun 2020 02:08:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592446091; bh=av4bXigQgjGLTBKgKQcAkOoaKU+fXP8Fihq9vCp9qMY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zmKiudc3w6ojTDB4uNQOyHHpmZS52Vr/ZjNi+hxWiDMKwc7IpxCCpkdI+MBuevVj+ KY1jZLsqB0vvNrdO+mJLGHm5kikku/963Kum5gOdWBprtXv75GgwhkA1qeRI2J5f0+ LviwGOI/cYv6Q4b8Sbb2HSFoqzM/Sqj49KMbTiFw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730652AbgFRBWH (ORCPT ); Wed, 17 Jun 2020 21:22:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:54890 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728233AbgFRBWF (ORCPT ); Wed, 17 Jun 2020 21:22:05 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 31A3221974; Thu, 18 Jun 2020 01:22:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592443325; bh=av4bXigQgjGLTBKgKQcAkOoaKU+fXP8Fihq9vCp9qMY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xZCvwK+18qisGGmXUPX9rwGU2eg2PY65Af1Cm/QjJoViWCMqeqT5v0KCardwGert/ NHO0X4cCz1FNmwZG9UByNxCOPFBm2IU1Od2lD3wQDXakQcwnasZ+yePNZ9HU7pvWak jugaz71hDPNA3AdbyiyfUeQEKxzrW5sF8LB/ht/c= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrii Nakryiko , Jean-Philippe Brucker , Daniel Borkmann , Sasha Levin , netdev@vger.kernel.org, bpf@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH AUTOSEL 5.4 258/266] libbpf: Handle GCC noreturn-turned-volatile quirk Date: Wed, 17 Jun 2020 21:16:23 -0400 Message-Id: <20200618011631.604574-258-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200618011631.604574-1-sashal@kernel.org> References: <20200618011631.604574-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org From: Andrii Nakryiko [ Upstream commit 32022fd97ed34f6812802bf1288db27c313576f4 ] Handle a GCC quirk of emitting extra volatile modifier in DWARF (and subsequently preserved in BTF by pahole) for function pointers marked as __attribute__((noreturn)). This was the way to mark such functions before GCC 2.5 added noreturn attribute. Drop such func_proto modifiers, similarly to how it's done for array (also to handle GCC quirk/bug). Such volatile attribute is emitted by GCC only, so existing selftests can't express such test. Simple repro is like this (compiled with GCC + BTF generated by pahole): struct my_struct { void __attribute__((noreturn)) (*fn)(int); }; struct my_struct a; Without this fix, output will be: struct my_struct { voidvolatile (*fn)(int); }; With the fix: struct my_struct { void (*fn)(int); }; Fixes: 351131b51c7a ("libbpf: add btf_dump API for BTF-to-C conversion") Reported-by: Jean-Philippe Brucker Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Tested-by: Jean-Philippe Brucker Link: https://lore.kernel.org/bpf/20200610052335.2862559-1-andriin@fb.com Signed-off-by: Sasha Levin --- tools/lib/bpf/btf_dump.c | 33 ++++++++++++++++++++++++--------- 1 file changed, 24 insertions(+), 9 deletions(-) diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 87f27e2664c5..d9e386b8f47e 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -1141,6 +1141,20 @@ static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack) } } +static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack) +{ + const struct btf_type *t; + __u32 id; + + while (decl_stack->cnt) { + id = decl_stack->ids[decl_stack->cnt - 1]; + t = btf__type_by_id(d->btf, id); + if (!btf_is_mod(t)) + return; + decl_stack->cnt--; + } +} + static void btf_dump_emit_name(const struct btf_dump *d, const char *name, bool last_was_ptr) { @@ -1239,14 +1253,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, * a const/volatile modifier for array, so we are * going to silently skip them here. */ - while (decls->cnt) { - next_id = decls->ids[decls->cnt - 1]; - next_t = btf__type_by_id(d->btf, next_id); - if (btf_is_mod(next_t)) - decls->cnt--; - else - break; - } + btf_dump_drop_mods(d, decls); if (decls->cnt == 0) { btf_dump_emit_name(d, fname, last_was_ptr); @@ -1274,7 +1281,15 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, __u16 vlen = btf_vlen(t); int i; - btf_dump_emit_mods(d, decls); + /* + * GCC emits extra volatile qualifier for + * __attribute__((noreturn)) function pointers. Clang + * doesn't do it. It's a GCC quirk for backwards + * compatibility with code written for GCC <2.5. So, + * similarly to extra qualifiers for array, just drop + * them, instead of handling them. + */ + btf_dump_drop_mods(d, decls); if (decls->cnt) { btf_dump_printf(d, " ("); btf_dump_emit_type_chain(d, decls, fname, lvl); -- 2.25.1