From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nan.false.org (NaN.false.org [208.75.86.248]) by ozlabs.org (Postfix) with ESMTP id 017ADDDEBA for ; Tue, 24 Jul 2007 02:15:18 +1000 (EST) Date: Mon, 23 Jul 2007 12:15:12 -0400 From: Daniel Jacobowitz To: Bill Gatliff Subject: Re: Gdbserver syscall clobber Message-ID: <20070723161512.GA3235@caradoc.them.org> References: <469B922D.3050701@billgatliff.com> <20070716155348.GA5281@caradoc.them.org> <469E550E.5080905@billgatliff.com> <20070718183143.GA25324@caradoc.them.org> <46A4D1F5.1060005@billgatliff.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <46A4D1F5.1060005@billgatliff.com> Cc: gdb@sourceware.org, linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Jul 23, 2007 at 11:06:13AM -0500, Bill Gatliff wrote: > Daniel Jacobowitz wrote: > > On Wed, Jul 18, 2007 at 12:59:42PM -0500, Bill Gatliff wrote: > > > >> Now, I'm a little rusty on PPC asm (I've been doing a lot of ARM > >> lately), but it looks to me like the kernel is setting bit 0 in CR0 > >> (oris r10, r10, 0x1000) a.k.a LT, but the user side is looking at CR0 > >> (bnslr+) bit 3 a.k.a. SO. Or maybe the other way around, I'm not sure > >> after reading Sections 1.2 and 2.1 of the Programming Environments manual. > >> > > > > It's not checking for restart here - userspace isn't supposed to have to. > > It's probably checking for error. Check for the bit of kernel code > > that's supposed to back you up two instructions. > > > > > > I don't see it in this kernel. What I see is this after the call to the > syscall handler: Look around do_signal: regs->nip -= 4; /* Back up & retry system call */ If your kernel has corrupted the register containing the syscall number at this point, that would explain your problem. It will then do the wrong syscall. I guess PPC only backs up one instruction. -- Daniel Jacobowitz CodeSourcery