From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932858AbcAaRdg (ORCPT ); Sun, 31 Jan 2016 12:33:36 -0500 Received: from mail.kernel.org ([198.145.29.136]:36303 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932361AbcAaRde (ORCPT ); Sun, 31 Jan 2016 12:33:34 -0500 From: Andy Lutomirski To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Brian Gerst , Borislav Petkov , Andy Lutomirski Subject: [PATCH 1/3] x86/entry/64: Fix an IRQ state error on ptregs-using syscalls Date: Sun, 31 Jan 2016 09:33:26 -0800 Message-Id: X-Mailer: git-send-email 2.5.0 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 I messed up the IRQ state when jumping off the fast path due to invocation of a ptregs-using syscall. This bug shouldn't have had any impact yet, but it would have caused problems with subsequent context tracking cleanups. Fixes: 1e423bff959e x86/entry/64: ("Migrate the 64-bit syscall slow path to C") Signed-off-by: Andy Lutomirski --- arch/x86/entry/entry_64.S | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 567aa522ac0a..9f7bb808035e 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -191,8 +191,8 @@ entry_SYSCALL_64_fastpath: /* * This call instruction is handled specially in stub_ptregs_64. - * It might end up jumping to the slow path. If it jumps, RAX is - * clobbered. + * It might end up jumping to the slow path. If it jumps, RAX + * and all argument registers are clobbered. */ call *sys_call_table(, %rax, 8) .Lentry_SYSCALL_64_after_fastpath_call: @@ -315,17 +315,24 @@ END(entry_SYSCALL_64) ENTRY(stub_ptregs_64) /* * Syscalls marked as needing ptregs land here. - * If we are on the fast path, we need to save the extra regs. - * If we are on the slow path, the extra regs are already saved. + * If we are on the fast path, we need to save the extra regs, + * which we achieve by trying again on the slow path. If we are on + * the slow path, the extra regs are already saved. * * RAX stores a pointer to the C function implementing the syscall. + * IRQs are on. */ cmpq $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp) jne 1f - /* Called from fast path -- pop return address and jump to slow path */ + /* + * Called from fast path -- disable IRQs again, pop return address + * and jump to slow path + */ + DISABLE_INTERRUPTS(CLBR_NONE) + TRACE_IRQS_OFF popq %rax - jmp entry_SYSCALL64_slow_path /* called from fast path */ + jmp entry_SYSCALL64_slow_path 1: /* Called from C */ -- 2.5.0