Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753158Ab2JOQ1k (ORCPT ); Mon, 15 Oct 2012 12:27:40 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47503 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752639Ab2JOQ1i (ORCPT ); Mon, 15 Oct 2012 12:27:38 -0400 Date: Mon, 15 Oct 2012 17:27:32 +0100 From: Al Viro To: Catalin Marinas 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: <20121015162732.GG2616@ZenIV.linux.org.uk> 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> <20121015160710.GC30907@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121015160710.GC30907@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1597 Lines: 30 On Mon, Oct 15, 2012 at 05:07:10PM +0100, Catalin Marinas wrote: > 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. The value left there by start_thread() will not reach the userland anyway... -- 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/