From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751475AbbBKCjV (ORCPT ); Tue, 10 Feb 2015 21:39:21 -0500 Received: from mail-lb0-f178.google.com ([209.85.217.178]:43690 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751338AbbBKCjU (ORCPT ); Tue, 10 Feb 2015 21:39:20 -0500 MIME-Version: 1.0 In-Reply-To: <1420927210-19738-4-git-send-email-dvlasenk@redhat.com> References: <1420927210-19738-1-git-send-email-dvlasenk@redhat.com> <1420927210-19738-4-git-send-email-dvlasenk@redhat.com> From: Andy Lutomirski Date: Tue, 10 Feb 2015 18:38:58 -0800 Message-ID: Subject: Re: [PATCH 3/4] x86: open-code register save/restore in trace_hardirqs thunks To: Denys Vlasenko Cc: "linux-kernel@vger.kernel.org" , Linus Torvalds , Oleg Nesterov , "H. Peter Anvin" , Borislav Petkov , Frederic Weisbecker , X86 ML , Alexei Starovoitov , Will Drewry , Kees Cook Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 10, 2015 at 2:00 PM, 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. > > 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 > > 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 > + pushq_cfi %rsi > + CFI_REL_OFFSET rsi, 0 > + pushq_cfi %rdx > + CFI_REL_OFFSET rdx, 0 > + pushq_cfi %rcx > + CFI_REL_OFFSET rcx, 0 > + pushq_cfi %rax > + CFI_REL_OFFSET rax, 0 > + pushq_cfi %r8 > + CFI_REL_OFFSET r8, 0 > + pushq_cfi %r9 > + CFI_REL_OFFSET r9, 0 > + pushq_cfi %r10 > + CFI_REL_OFFSET r10, 0 > + pushq_cfi %r11 > + CFI_REL_OFFSET r11, 0 > > .if \put_ret_addr_in_rdi > + /* 9*8(%rsp) is return addr on stack */ > movq_cfi_restore 9*8, rdi > .endif > > @@ -45,11 +63,31 @@ > #endif > #endif > > - /* SAVE_ARGS below is used only for the .cfi directives it contains. */ > +#if defined(CONFIG_TRACE_IRQFLAGS) \ > + || defined(CONFIG_DEBUG_LOCK_ALLOC) \ > + || defined(CONFIG_PREEMPT) > CFI_STARTPROC > - SAVE_ARGS > + CFI_ADJUST_CFA_OFFSET 9*8 > restore: > - RESTORE_ARGS > + popq_cfi %r11 > + CFI_RESTORE r11 > + popq_cfi %r10 > + CFI_RESTORE r10 > + popq_cfi %r9 > + CFI_RESTORE r9 > + popq_cfi %r8 > + CFI_RESTORE r8 > + popq_cfi %rax > + CFI_RESTORE rax > + popq_cfi %rcx > + CFI_RESTORE rcx > + popq_cfi %rdx > + CFI_RESTORE rdx > + popq_cfi %rsi > + CFI_RESTORE rsi > + popq_cfi %rdi > + CFI_RESTORE rdi > ret > CFI_ENDPROC > _ASM_NOKPROBE(restore) > +#endif Applied. I'll deal with the cleanup as a followup tomorrow.