From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751754AbdKVEs1 (ORCPT ); Tue, 21 Nov 2017 23:48:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:36454 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751050AbdKVEoR (ORCPT ); Tue, 21 Nov 2017 23:44:17 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E7F221985 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org From: Andy Lutomirski To: X86 ML Cc: Borislav Petkov , "linux-kernel@vger.kernel.org" , Brian Gerst , Dave Hansen , Linus Torvalds , Josh Poimboeuf , Andy Lutomirski , stable@vger.kernel.org, Boris Ostrovsky , Juergen Gross Subject: [PATCH v2 01/18] x86/entry/64: Fix entry_SYSCALL_64_after_hwframe IRQ tracing Date: Tue, 21 Nov 2017 20:43:56 -0800 Message-Id: <9150aac013b7b95d62c2336751d5b6e91d2722aa.1511325444.git.luto@kernel.org> X-Mailer: git-send-email 2.13.6 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When I added entry_SYSCALL_64_after_hwframe, I left TRACE_IRQS_OFF before it. This means that users of entry_SYSCALL_64_after_hwframe were responsible for invoking TRACE_IRQS_OFF, and the one and only user (added in the same commit) got it wrong. I think this would manifest as a warning if a Xen PV guest with CONFIG_DEBUG_LOCKDEP=y were used with context tracking. (The context tracking bit is to cause lockdep to get invoked before we turn IRQs back on.) I haven't tested that for real yet because I can't get a kernel configured like that to boot at all on Xen PV. I've reported it upstream. The problem seems to be that Xen PV is missing early #UD handling, is hitting some WARN, and we rely on Move TRACE_IRQS_OFF below the label. Cc: stable@vger.kernel.org Cc: Boris Ostrovsky Cc: Juergen Gross Fixes: 8a9949bc71a7 ("x86/xen/64: Rearrange the SYSCALL entries") Signed-off-by: Andy Lutomirski --- arch/x86/entry/entry_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index a2b30ec69497..5063ed1214dd 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -148,8 +148,6 @@ ENTRY(entry_SYSCALL_64) movq %rsp, PER_CPU_VAR(rsp_scratch) movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp - TRACE_IRQS_OFF - /* Construct struct pt_regs on stack */ pushq $__USER_DS /* pt_regs->ss */ pushq PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */ @@ -170,6 +168,8 @@ GLOBAL(entry_SYSCALL_64_after_hwframe) sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */ UNWIND_HINT_REGS extra=0 + TRACE_IRQS_OFF + /* * If we need to do entry work or if we guess we'll need to do * exit work, go straight to the slow path. -- 2.13.6