From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755302AbbAJWAw (ORCPT ); Sat, 10 Jan 2015 17:00:52 -0500 Received: from mail.skyhub.de ([78.46.96.112]:52331 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752198AbbAJWAv (ORCPT ); Sat, 10 Jan 2015 17:00:51 -0500 Date: Sat, 10 Jan 2015 23:00:42 +0100 From: Borislav Petkov To: Denys Vlasenko Cc: Denys Vlasenko , Linux Kernel Mailing List , Linus Torvalds , Oleg Nesterov , "H. Peter Anvin" , Andy Lutomirski , Frederic Weisbecker , X86 ML , Alexei Starovoitov , Will Drewry , Kees Cook Subject: Re: [PATCH 3/4] x86: open-code register save/restore in trace_hardirqs thunks Message-ID: <20150110220042.GG12218@pd.tnic> References: <1420734315-30943-1-git-send-email-dvlasenk@redhat.com> <1420734315-30943-4-git-send-email-dvlasenk@redhat.com> <20150109121950.GD13637@pd.tnic> <20150110142336.GC12218@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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 On Sat, Jan 10, 2015 at 09:14:03PM +0100, Denys Vlasenko wrote: > From 2f636e0a92db898f2bdb592027aa302fcb32a326 Mon Sep 17 00:00:00 2001 > From: Denys Vlasenko > To: linux-kernel@vger.kernel.org > Subject: [PATCH 3/4] x86: open-code register save/restore in trace_hardirqs thunks > > This is a preparatory patch for change in "struct pt_regs" > handling in entry_64.S. > > trace_hardirqs thunks were (ab)using a part of pt_regs > handling code, namely SAVE_ARGS/RESTORE_ARGS macros, > to save/restore registers across C function calls. > > Since SAVE_ARGS is going to be changed, open-code > register saving/restoring here. Take a page from thunk_32.S > and use push/pop insns instead of movq, they are far shorter: > 1 or 2 bytes versus 5, and no need for insns to adjust %rsp: > > text data bss dec hex filename > 333 40 0 373 175 thunk_64_movq.o > 104 40 0 144 90 thunk_64_push_pop.o > > Incidentally, this removes a bit of dead code: > one SAVE_ARGS was used just to emit a CFI annotation, > but it also generated unreachable assembly insns. > > Signed-off-by: Denys Vlasenko > CC: Linus Torvalds > CC: Oleg Nesterov > CC: "H. Peter Anvin" > CC: Borislav Petkov > CC: Andy Lutomirski > CC: Frederic Weisbecker > CC: X86 ML > CC: Alexei Starovoitov > CC: Will Drewry > CC: Kees Cook > CC: linux-kernel@vger.kernel.org > --- > arch/x86/lib/thunk_64.S | 46 ++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 42 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/lib/thunk_64.S b/arch/x86/lib/thunk_64.S > index b30b5eb..8ec443a 100644 > --- a/arch/x86/lib/thunk_64.S > +++ b/arch/x86/lib/thunk_64.S > @@ -17,9 +17,27 @@ > CFI_STARTPROC > > /* this one pushes 9 elems, the next one would be %rIP */ > - SAVE_ARGS > + pushq_cfi %rdi > + CFI_REL_OFFSET rdi, 0 Btw, why the second CFI annotation? pushq_cfi does already CFI_ADJUST_CFA_OFFSET 8. Can't we use one and hide it in the macro? Btw, patch boots fine in the guest. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --