From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933401AbbAIKzr (ORCPT ); Fri, 9 Jan 2015 05:55:47 -0500 Received: from mail.skyhub.de ([78.46.96.112]:50330 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932867AbbAIKzp (ORCPT ); Fri, 9 Jan 2015 05:55:45 -0500 Date: Fri, 9 Jan 2015 11:55:41 +0100 From: Borislav Petkov To: Denys Vlasenko Cc: linux-kernel@vger.kernel.org, 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: <20150109105541.GC13637@pd.tnic> References: <1420734315-30943-1-git-send-email-dvlasenk@redhat.com> <1420734315-30943-4-git-send-email-dvlasenk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1420734315-30943-4-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 On Thu, Jan 08, 2015 at 05:25:14PM +0100, Denys Vlasenko wrote: > 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. > > 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: 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 | 29 ++++++++++++++++++++++++----- > 1 file changed, 24 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/lib/thunk_64.S b/arch/x86/lib/thunk_64.S > index b30b5eb..03a3883 100644 > --- a/arch/x86/lib/thunk_64.S > +++ b/arch/x86/lib/thunk_64.S > @@ -16,10 +16,20 @@ > \name: > CFI_STARTPROC > > - /* this one pushes 9 elems, the next one would be %rIP */ > - SAVE_ARGS > + subq $9*8, %rsp > + CFI_ADJUST_CFA_OFFSET 9*8 > + movq_cfi r11, 0*8 > + movq_cfi r10, 1*8 > + movq_cfi r9, 2*8 > + movq_cfi r8, 3*8 > + movq_cfi rax, 4*8 > + movq_cfi rcx, 5*8 > + movq_cfi rdx, 6*8 > + movq_cfi rsi, 7*8 > + movq_cfi rdi, 8*8 > > .if \put_ret_addr_in_rdi > + /* 9*8(%rsp) is return addr on stack */ > movq_cfi_restore 9*8, rdi > .endif > > @@ -45,11 +55,20 @@ > #endif > #endif > > - /* SAVE_ARGS below is used only for the .cfi directives it contains. */ > CFI_STARTPROC > - SAVE_ARGS > + CFI_ADJUST_CFA_OFFSET 9*8 > restore: > - RESTORE_ARGS > + movq_cfi_restore 0*8, r11 > + movq_cfi_restore 1*8, r10 > + movq_cfi_restore 2*8, r9 > + movq_cfi_restore 3*8, r8 > + movq_cfi_restore 4*8, rax > + movq_cfi_restore 5*8, rcx > + movq_cfi_restore 6*8, rdx > + movq_cfi_restore 7*8, rsi > + movq_cfi_restore 8*8, rdi > + addq 9*8, %rsp > + CFI_ADJUST_CFA_OFFSET -9*8 The only nitpick I'd have with this is can we keep the register saving/restoring order in the code the same as in the SAVE_/RESTORE_ARGS macros? SAVE_ARGS starts with the highest offset 9*8, rdi and ends at 0*8 and r11 and RESTORE_ARGS does that in reverse. Also, can you post the struct pt_regs change too so that we know where this is going? Thanks. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --