From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: Compat 32-bit syscall entry from 64-bit task!? Date: Fri, 10 Feb 2012 14:56:38 -0800 Message-ID: <4F35A0A6.8020600@zytor.com> References: <20120116183730.GB21112@redhat.com> <4F3007AD.50307@zytor.com> <4F33110D.3050904@zytor.com> <13c2c571244c71c2ba87451987805eed.squirrel@webmail.greenhost.nl> <4F334B8C.2050005@zytor.com> <4F346FB0.9070203@zytor.com> <19ac5d5293110612dc17c514bc7e1ccd.squirrel@webmail.greenhost.nl> <4F353D65.7070705@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: "H.J. Lu" , Linus Torvalds , Andi Kleen , Jamie Lokier , Andrew Lutomirski , Oleg Nesterov , Will Drewry , linux-kernel@vger.kernel.org, keescook@chromium.org, john.johansen@canonical.com, serge.hallyn@canonical.com, coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com, djm@mindrot.org, segoon@openwall.com, rostedt@goodmis.org, jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com, penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, mingo@elte.hu, akpm@linux-foundation.org, khilman@ti.com, borislav.petkov@amd.com, amwang@redhat.com, ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de, dhowells@redhat.com, daniel.lezcano@free.fr, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, olofj@chrom To: Indan Zupancic Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 02/10/2012 02:42 PM, Indan Zupancic wrote: >> #include > > Could you please elaborate? Is it just the stealing of eflags bits that > irks you or are there technical problems too? Yes, I will not accept that unless it gets ok'd by the architecture people, which may take a long time. > I understand some people would prefer a new regset, but that would force > everyone to use PTRACE_GETREGSET instead of whatever they are using now. > The problem with that is that not all archs support PTRACE_GETREGSET, so > the user space ptrace code needs to use different ptrace calls depending > on the architecture for no good reason. If PEEK_USER works then it's less > of a problem, then it's one extra ptrace call compared to the eflag way > if PTRACE_GETREGS is used. If this new info is exposed with a special > regset instead of being appended to normal regs then one extra ptrace > call per system call event needs to be done. You can as well add special > x86 ptrace requests then. Seriously... if you're mucking with registers on this level, youan architecture dependency is not a big deal, and perhaps it's a good sign that the laggard architectures need to catch up. If multiple ptrace requests is a problem, then perhaps this is a good sign that we need a single way to get multiple regsets in a single request? > Or is the main advantage of using a regset that it shows up in coredumps? > That would merit the extra effort at least. That is another plus, which is significant, too. The final advantage is expandability. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.