Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753860AbbB1AaE (ORCPT ); Fri, 27 Feb 2015 19:30:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36966 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbbB1AaC (ORCPT ); Fri, 27 Feb 2015 19:30:02 -0500 From: Denys Vlasenko To: Andy Lutomirski Cc: Denys Vlasenko , Linus Torvalds , Steven Rostedt , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/3] x86: do not save callee-preserved registers around lockdep_sys_exit_thunk Date: Sat, 28 Feb 2015 01:29:18 +0100 Message-Id: <1425083361-7252-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2172 Lines: 59 Recent change to struct pt_regs handling in entry.S, among other things, changed how callee-preserved registers are saved around call to lockdep_sys_exit_thunk: # define LOCKDEP_SYS_EXIT_IRQ \ TRACE_IRQS_ON; \ sti; \ SAVE_EXTRA_REGS; \ <======= HERE LOCKDEP_SYS_EXIT; \ RESTORE_EXTRA_REGS; \ <======= HERE The change is in fact a bit fragile: now we assume that LOCKDEP_SYS_EXIT_IRQ macro is used only when there is a struct pt_regs on the stack. So far this assumption is true, but it is probably a coincidence. We can revert back to pushing registers, but this callee-preserved registers saving appears bogus. It is not necessary: they _are_ callee-preserved, and lockdep_sys_exit() does not touch them on the stack either. First two patches clean up #define maze so that we can see that LOCKDEP_SYS_EXIT macro call above is merely "call lockdep_sys_exit_thunk". Last patch removes SAVE/RESTORE. I tested this patch series and everything seems to run fine on a lockdep-enabled kernel with these lines removed. Denys Vlasenko (3): x86: move ARCH_LOCKDEP_SYS_EXIT[IRQ] defines closer to their users x86: fold ARCH_LOCKDEP_SYS_EXIT defines into their users x86: do not save callee-preserved registers around lockdep_sys_exit_thunk arch/x86/include/asm/irqflags.h | 45 +++++++++++++++++------------------------ 1 file changed, 19 insertions(+), 26 deletions(-) CC: Linus Torvalds CC: Steven Rostedt CC: Ingo Molnar CC: Borislav Petkov CC: "H. Peter Anvin" CC: Andy Lutomirski CC: Oleg Nesterov CC: Frederic Weisbecker CC: Alexei Starovoitov CC: Will Drewry CC: Kees Cook CC: x86@kernel.org CC: linux-kernel@vger.kernel.org -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/