From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <libc-alpha-return-103087-listarch-libc-alpha=sources.redhat.com@sourceware.org>
Received: (qmail 8167 invoked by alias); 25 Jun 2019 19:47:48 -0000
Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <libc-alpha.sourceware.org>
List-Subscribe: <mailto:libc-alpha-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/libc-alpha/>
List-Post: <mailto:libc-alpha@sourceware.org>
List-Help: <mailto:libc-alpha-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: libc-alpha-owner@sourceware.org
Received: (qmail 8156 invoked by uid 89); 25 Jun 2019 19:47:48 -0000
Authentication-Results: sourceware.org; auth=none
X-Spam-SWARE-Status: No, score=-8.6 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.1 spammy=
X-HELO: mail-qt1-f195.google.com
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=linaro.org; s=google;
        h=subject:to:cc:references:from:openpgp:autocrypt:message-id:date
         :user-agent:mime-version:in-reply-to:content-language
         :content-transfer-encoding;
        bh=/zk5rJ2sMjBA76kztI16aQLq33kJhmp01K2bRCK90Rw=;
        b=umbvAvNPkbLV37yCp4f8d/L2J4E8eS4VKgRnV63lxANZRow7QwlRTe88r3HbwuG1fD
         G5CFOULRwFV9S6LAJaa8u9Sc44P5XEComuSkBM4jfe7X1ql64IXbRbIqEOcoIY7/3S/s
         AgCHZfrTfXvNWiWsTkg6kqs6o+aoI1rsblri919Vmhd2Y6uXcAo9VEGmTUXg6r8pIfWD
         dVavKQdtiRXInH9eiHZLne5CSiaz0JCMzzBVn9Yi7s0NCPePrFRNuvfCJUt1cqZKTnG4
         ihgOKzqBW0AR5fMY9hJpOF5k6/3TBi7A/E0mPzIos1ZW2vncoSp2PHw3V0t7s+3MxOfy
         MDVw==
Return-Path: <adhemerval.zanella@linaro.org>
Subject: Re: [PATCH 11/12] linux: Consolidate time implementation
To: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org
References: <20190614152908.8101-1-adhemerval.zanella@linaro.org>
 <20190614152908.8101-11-adhemerval.zanella@linaro.org>
 <871rzhwmk0.fsf@oldenburg2.str.redhat.com>
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Openpgp: preference=signencrypt
Message-ID: <59a55ae2-f5d1-367c-1882-08b18550bf92@linaro.org>
Date: Tue, 25 Jun 2019 19:47:00 -0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.7.1
MIME-Version: 1.0
In-Reply-To: <871rzhwmk0.fsf@oldenburg2.str.redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
X-SW-Source: 2019-06/txt/msg00696.txt.bz2



On 25/06/2019 15:24, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> 	* include/libc-symbols.h (hidden_def_redir): New macro.
> 
> This macro should have documentation in the large common block above it.
> Its purpose isn't obvious to me.
> 
>> +#if HAVE_IFUNC && defined USE_TIME_VSYSCALL_IFUNC
>> +/* Route externals calls direct to vDSO and static and internal calls to
>> +   fallback implementation (which also might call the vDSO).  */
>> +# ifdef SHARED
>> +#  define INIT_ARCH()
>> +libc_ifunc_redirected (__redirect_time, time,
>> +		       get_vdso_symbol (HAVE_TIME_VSYSCALL)
>> +		       ?: time_syscall);
>> +libc_hidden_def_redir (time_syscall, time)
>> +#  else
>> +strong_alias (time_syscall, time)
>> +#  endif /* SHARED  */
> 
> Does this really work on x86-64?  I don't think it's possible to call
> IFUNCs through hidden aliases.

The idea is to not call an IFUNC in the static case nor on internal 
hidden case for shared case. Only external calls are routes through
iFUNC.