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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 7378EC433DF for ; Tue, 23 Jun 2020 21:28:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B88520724 for ; Tue, 23 Jun 2020 21:28:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592947707; bh=HUrMZuKIgDAI9hf9Xw9LBlkd+lwvmJAtNNHF1cksi4k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Q8sJ0XLv8uYbjl3M7H4CM7P+rgRln4TNK/6eFOiUobK3KPnadIsRWoBZJk0L4KplF SRhQdS+5r5k5Q4f6DjV/iEF27w0NH4Mo1v6X/oCfESufQBGYLYQ5ELdS8dEfRwj179 x0xV0qT6ZBILwh7Di7FCoQ+/NOz0kYqr8c7fWlkU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387774AbgFWV2Q (ORCPT ); Tue, 23 Jun 2020 17:28:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:59364 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389373AbgFWUQE (ORCPT ); Tue, 23 Jun 2020 16:16:04 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 15B572073E; Tue, 23 Jun 2020 20:16:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592943364; bh=HUrMZuKIgDAI9hf9Xw9LBlkd+lwvmJAtNNHF1cksi4k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ls8y08I0VWsPZF1R4NeBvMjkx2yxKe9+NkKlSrxSy/oO6AjpC6eZtRExnMrPLO1zR TtunK1SilbsafDrZBUi8/MRRH5pUSXttjElIRxYs8dP2QR1QfvxxDiIM4Uc8XQe3fl UhpJZJ65V3VFLcFUGMjDhygddhTFfK48EIvSal6A= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jean-Philippe Brucker , Andrii Nakryiko , Daniel Borkmann , Sasha Levin Subject: [PATCH 5.7 363/477] libbpf: Handle GCC noreturn-turned-volatile quirk Date: Tue, 23 Jun 2020 21:56:00 +0200 Message-Id: <20200623195424.690230263@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200623195407.572062007@linuxfoundation.org> References: <20200623195407.572062007@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 0c28ee82834b7..653dbbe2e3663 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -1137,6 +1137,20 @@ 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) { @@ -1235,14 +1249,7 @@ 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); @@ -1270,7 +1277,15 @@ 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