From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_PASS autolearn=ham autolearn_force=no version=3.4.2 Received: (qmail 32336 invoked from network); 16 Apr 2020 15:35:23 -0000 Received-SPF: pass (mother.openwall.net: domain of lists.openwall.com designates 195.42.179.200 as permitted sender) receiver=inbox.vuxu.org; client-ip=195.42.179.200 envelope-from= Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with UTF8ESMTPZ; 16 Apr 2020 15:35:23 -0000 Received: (qmail 7646 invoked by uid 550); 16 Apr 2020 15:35:22 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 7628 invoked from network); 16 Apr 2020 15:35:21 -0000 Date: Thu, 16 Apr 2020 11:35:09 -0400 From: Rich Felker To: Florian Weimer Cc: Nicholas Piggin , libc-alpha@sourceware.org, musl@lists.openwall.com, linuxppc-dev@lists.ozlabs.org, libc-dev@lists.llvm.org Message-ID: <20200416153509.GT11469@brightrain.aerifal.cx> References: <1586931450.ub4c8cq8dj.astroid@bobo.none> <20200415225539.GL11469@brightrain.aerifal.cx> <87k12gf32r.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k12gf32r.fsf@mid.deneb.enyo.de> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] Powerpc Linux 'scv' system call ABI proposal take 2 On Thu, Apr 16, 2020 at 06:48:44AM +0200, Florian Weimer wrote: > * Rich Felker: > > > My preference would be that it work just like the i386 AT_SYSINFO > > where you just replace "int $128" with "call *%%gs:16" and the kernel > > provides a stub in the vdso that performs either scv or the old > > mechanism with the same calling convention. > > The i386 mechanism has received some criticism because it provides an > effective means to redirect execution flow to anyone who can write to > the TCB. I am not sure if it makes sense to copy it. Indeed that's a good point. Do you have ideas for making it equally efficient without use of a function pointer in the TCB? Rich