Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753506Ab2JOQHX (ORCPT ); Mon, 15 Oct 2012 12:07:23 -0400 Received: from service87.mimecast.com ([91.220.42.44]:36489 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751302Ab2JOQHU convert rfc822-to-8bit (ORCPT ); Mon, 15 Oct 2012 12:07:20 -0400 Date: Mon, 15 Oct 2012 17:07:10 +0100 From: Catalin Marinas To: Al Viro Cc: Daniel Mack , Linus Torvalds , Russell King - ARM Linux , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [revert request for commit 9fff2fa] Re: [git pull] signals pile 3 Message-ID: <20121015160710.GC30907@arm.com> References: <20121013005334.GM2616@ZenIV.linux.org.uk> <507ADBBB.9090209@gmail.com> <20121014164020.GV2616@ZenIV.linux.org.uk> <20121014172640.GW2616@ZenIV.linux.org.uk> <20121014192402.GZ2616@ZenIV.linux.org.uk> <20121014195611.GA2616@ZenIV.linux.org.uk> MIME-Version: 1.0 In-Reply-To: <20121014195611.GA2616@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.20 (2009-06-14) X-OriginalArrivalTime: 15 Oct 2012 16:07:13.0952 (UTC) FILETIME=[23E1D200:01CDAAEF] X-MC-Unique: 112101517071700701 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1498 Lines: 33 On Sun, Oct 14, 2012 at 08:56:11PM +0100, Al Viro wrote: > On Sun, Oct 14, 2012 at 08:24:03PM +0100, Al Viro wrote: > > > Russell, could you recall what those had been about? I'm not sure if that > > had been oopsable that far back (again, oops scenario is userland stack > > page getting swapped out before we get to start_thread(), leading to > > direct read from an absent page in start_thread() by plain ldr, without > > anything in exception table about that insn), but it looks very odd > > regardless of that problem. > > BTW, arm64 has copied that logics, so it also seems to be unsafe and very > odd - there we definitely have only ELF to cope with. arm64 folks Cc'd... Good point. We don't need this on arm64 and probably neither on arm (at least since EABI). Setting x0 may cause other issues as well. The dynamic loader simply ignores the startup registers but for static binaries the _start code in glibc expects r0 to contain a function pointer to be registered with atexit() in __libc_start_main() or NULL. Since we pass argc in there, for static binaries the rtld_fini argument to __libc_start_main() is neither NULL nor something meaningful. Russell, do you know whether setting these registers is needed for OABI? -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/