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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 14B66C433DB for ; Sat, 20 Mar 2021 23:33:24 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 53A6561931 for ; Sat, 20 Mar 2021 23:33:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 53A6561931 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40322 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lNl5u-0007Gs-BH for qemu-devel@archiver.kernel.org; Sat, 20 Mar 2021 19:33:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48450) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lNl4t-0006in-3q for qemu-devel@nongnu.org; Sat, 20 Mar 2021 19:32:19 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46144) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lNl4o-00066O-SH for qemu-devel@nongnu.org; Sat, 20 Mar 2021 19:32:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616283133; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iCYYseaEC719ARq0lsD/HuX0KAgDJ59JDw4vcSkw/mE=; b=EGUO/rqVdrcYywsfWonA5A3w8PIkpdMOLoTeeWIlH6B1jkBbh5NepBeDxHqb6aFBnXGlQs LQ9UjXKmMK0B+CIb5LWMR2fxT2KfFaeFcuUVxFyN09X+aqAT3huqJLDyw5qrQ8h6fVLBTa SY0sZsb3bvfe6ttUCl9GUIzIKtNAML0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-7-K6ckKasxPPajUC-jlXHATQ-1; Sat, 20 Mar 2021 19:32:11 -0400 X-MC-Unique: K6ckKasxPPajUC-jlXHATQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 625F651F9; Sat, 20 Mar 2021 23:32:10 +0000 (UTC) Received: from [10.64.54.40] (vpn2-54-40.bne.redhat.com [10.64.54.40]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F115919C79; Sat, 20 Mar 2021 23:32:06 +0000 (UTC) Subject: Re: [PATCH] configure: Improve alias attribute check To: Thomas Huth , qemu-devel@nongnu.org References: <20210320042753.69297-1-gshan@redhat.com> <584e6cec-dd1d-7aa5-5f67-43bfcd9ae66a@redhat.com> From: Gavin Shan Message-ID: <34b8e906-7e3f-197d-78ad-34b973c7b77e@redhat.com> Date: Sun, 21 Mar 2021 10:32:02 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <584e6cec-dd1d-7aa5-5f67-43bfcd9ae66a@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=gshan@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Gavin Shan Cc: richard.henderson@linaro.org, laurent@vivier.eu, qemu-arm@nongnu.org, shan.gavin@gmail.com, pbonzini@redhat.com, philmd@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Thomas, On 3/20/21 3:48 PM, Thomas Huth wrote: > On 20/03/2021 05.27, Gavin Shan wrote: >> It's still possible that the wrong value is returned from the alias >> of variable even if the program can be compiled without issue. This >> improves the check by executing the binary to check the result. >> >> If alias attribute can't be working properly, the @target_page in >> exec-vary.c will always return zeroes when we have the following gcc >> version. >> >>    # gcc --version >>    gcc (GCC) 11.0.0 20210210 (Red Hat 11.0.0-0) >> >> This abstracts the code from exec-vary.c and use it as indicator to >> enable gcc alias attribute or not. >> >> Signed-off-by: Gavin Shan >> --- >>   configure | 34 ++++++++++++++++++++++++++++++---- >>   1 file changed, 30 insertions(+), 4 deletions(-) >> >> diff --git a/configure b/configure >> index f7d022a5db..8321f380d5 100755 >> --- a/configure >> +++ b/configure >> @@ -75,6 +75,7 @@ fi >>   TMPB="qemu-conf" >>   TMPC="${TMPDIR1}/${TMPB}.c" >> +TMPC_B="${TMPDIR1}/${TMPB}_b.c" >>   TMPO="${TMPDIR1}/${TMPB}.o" >>   TMPCXX="${TMPDIR1}/${TMPB}.cxx" >>   TMPE="${TMPDIR1}/${TMPB}.exe" >> @@ -4878,13 +4879,38 @@ fi >>   attralias=no >>   cat > $TMPC << EOF >> -int x = 1; >> +static int x; >>   extern const int y __attribute__((alias("x"))); >> -int main(void) { return 0; } >> +extern int read_y(void); >> +void write_x(int val); >> + >> +void write_x(int val) >> +{ >> +    x = val; >> +} >> + >> +int main(void) >> +{ >> +    return read_y(); >> +} >>   EOF >> -if compile_prog "" "" ; then >> -    attralias=yes >> +cat > $TMPC_B << EOF >> +extern const int y; >> +extern void write_x(int val); >> +int read_y(void); >> + >> +int read_y(void) >> +{ >> +     write_x(1); >> +     return y; >> +} >> +EOF >> + >> +TMPC+=" ${TMPC_B}" >> +if compile_prog "" "" && ! $TMPE; then > > What about cross-compiling? Running an executable won't work if QEMU gets cross-compiled... > Executing the cross-compiled binary returns 126, which means we will disable gcc alias attribute for cross-compiling case with the following changes included into v2: int main(void) { return (read_y() == 1) ? 0 : 1; } if compile_prog "" "" && $TMPE >/dev/null 2>/dev/null; then attralias=yes fi Thanks, Gavin