From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752040AbaFLSGV (ORCPT ); Thu, 12 Jun 2014 14:06:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34980 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751758AbaFLSGU (ORCPT ); Thu, 12 Jun 2014 14:06:20 -0400 Date: Thu, 12 Jun 2014 20:05:01 +0200 From: Oleg Nesterov To: Anshuman Khandual , "Michael Kerrisk (man-pages)" Cc: Pedro Alves , Peter Zijlstra , linux-kernel@vger.kernel.org, hpa@zytor.com, suresh.b.siddha@intel.com Subject: Re: [PATCH v2] ptrace: Clarify PTRACE_GETREGSET/PTRACE_SETREGSET, documentation in uapi header Message-ID: <20140612180501.GB15795@redhat.com> References: <1398682853-7541-1-git-send-email-khandual@linux.vnet.ibm.com> <53625681.8010905@redhat.com> <53670F35.6010502@linux.vnet.ibm.com> <53725FF6.6060004@redhat.com> <537316DB.4060701@linux.vnet.ibm.com> <53734B7D.4010504@redhat.com> <53996A20.3030300@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53996A20.3030300@linux.vnet.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/12, Anshuman Khandual wrote: > > > --- a/include/uapi/linux/ptrace.h > > +++ b/include/uapi/linux/ptrace.h > > @@ -39,12 +39,17 @@ > > * payload are exactly the same layout. > > * > > * This interface usage is as follows: > > - * struct iovec iov = { buf, len}; > > + * struct iovec iov = { buf, len }; > > * > > * ret = ptrace(PTRACE_GETREGSET/PTRACE_SETREGSET, pid, NT_XXX_TYPE, &iov); > > * > > - * On the successful completion, iov.len will be updated by the kernel, > > - * specifying how much the kernel has written/read to/from the user's iov.buf. > > + * On entry, iov describes the buffer's address and length. The buffer's length > > + * must be a multiple of the size of a single register in the register set. The > > + * kernel never reads or writes more than iov.len, and caps the buffer length to > > + * the register set's size. In other words, the kernel reads or writes > > + * min(iov.len, regset size). I think this should be self-obvious ;) otherwise why do we need to pass the length of the buffer? But of course I won't argue with the additional documentation, perhaps you can re-send this patch to akpm? Usually ptrace changes are routed via -mm tree. But if we update the kernel header, then probably it would be more important to update the man-page. To me the description of GETREGSET looks good, but probably it could also mention that buflen should be multiple of regsize (as you did above). Add Michael. Oleg.