From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Metcalf Subject: Re: situation with signals Date: Wed, 27 Oct 2010 18:51:12 -0400 Message-ID: <4CC8ACE0.1040407@tilera.com> References: <20100923221141.GK19804@ZenIV.linux.org.uk> <9lYpY1#WLHA.1516@exchange1.tad.internal.tilera.com> <4CC89352.7020808@tilera.com> <20101027213745.GI19804@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from usmamail.tilera.com ([72.1.168.231]:55759 "EHLO USMAMAIL.TILERA.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751402Ab0J0WvR (ORCPT ); Wed, 27 Oct 2010 18:51:17 -0400 In-Reply-To: <20101027213745.GI19804@ZenIV.linux.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Al Viro Cc: Arnd Bergmann , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org On 10/27/2010 5:37 PM, Al Viro wrote: > On Wed, Oct 27, 2010 at 05:02:10PM -0400, Chris Metcalf wrote >> I set aside this thread to look at when I had a minute, and I believe there >> is just one of the signal issues present in the tile code. The fix is to >> reset regs->fault to something other than the "syscall" fault type when >> exiting from do_signal(), so I'll submit that up for 2.6.37 shortly. > FWIW, I'd do that in handle_signal() when hitting a syscall restart. Right now I'm just doing it unconditionally in handle_signal()'s caller whether or not I actually call handle_signal, to be paranoid: @@ -353,11 +353,11 @@ * clear the TS_RESTORE_SIGMASK flag. */ current_thread_info()->status &= ~TS_RESTORE_SIGMASK; } - return; + goto done; } /* Did we come from a system call? */ if (regs->faultnum == INT_SWINT_1) { /* Restart the system call - no handlers present */ @@ -381,10 +381,14 @@ /* If there's no signal to deliver, just put the saved sigmask back. */ if (current_thread_info()->status & TS_RESTORE_SIGMASK) { current_thread_info()->status &= ~TS_RESTORE_SIGMASK; sigprocmask(SIG_SETMASK, ¤t->saved_sigmask, NULL); } + +done: + /* Avoid double syscall restart if there are nested signals. */ + regs->faultnum = INT_SWINT_1_SIGRETURN; } > BTW, is everything in your pt_regs safe to modify? What an interesting observation. :-) In fact, it would be possible to overwrite the privilege level (the ex1 register) from within the signal handler and then return to run arbitrary code at kernel PL. I'll fix it. -- Chris Metcalf, Tilera Corp. http://www.tilera.com