Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754233AbbFRJd2 (ORCPT ); Thu, 18 Jun 2015 05:33:28 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:37100 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753109AbbFRJdU (ORCPT ); Thu, 18 Jun 2015 05:33:20 -0400 Date: Thu, 18 Jun 2015 11:33:15 +0200 From: Ingo Molnar To: Denys Vlasenko Cc: Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/5] x86/asm/entry/32: Simplify ptrace register shuffling Message-ID: <20150618093315.GB1094@gmail.com> References: <1433876051-26604-1-git-send-email-dvlasenk@redhat.com> <1433876051-26604-5-git-send-email-dvlasenk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1433876051-26604-5-git-send-email-dvlasenk@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1103 Lines: 28 * Denys Vlasenko wrote: > Before this patch, we were clearing pt_regs->r8..r11 on stack. > We can as well just store actual r8..r11 registers there: > they came from userspace, we leak no information by showing them to ptrace. > This allows to get rid of one insn ("xor %eax,%eax"). > Not a big deal, but still... > > After call to syscall_trace_enter(), before this patch we were restoring > clobbered registers and jump to code which converts 32-bit syscall > ABI to 64-bit C ABI. This is unnecessary work, we can combine both > steps into one (similar to what audit code does already). So this really needs a description about what kind of testing was done, as technically this changes the ABI. Heavy ptrace users should be tried: strace, UML, etc. I don't expect any problems, but still it needs to be tested. Thanks, Ingo -- 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/