From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755395AbaGNLkK (ORCPT ); Mon, 14 Jul 2014 07:40:10 -0400 Received: from mail-we0-f182.google.com ([74.125.82.182]:60478 "EHLO mail-we0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755253AbaGNLj0 (ORCPT ); Mon, 14 Jul 2014 07:39:26 -0400 From: Paolo Bonzini To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org Subject: [PATCH 18/19] KVM: x86: ensure emulator fetches do not span multiple pages Date: Mon, 14 Jul 2014 13:38:42 +0200 Message-Id: <1405337923-4776-19-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1405337923-4776-1-git-send-email-pbonzini@redhat.com> References: <1405337923-4776-1-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When the CS base is not page-aligned, the linear address of the code could get close to the page boundary (e.g. 0x...ffe) even if the EIP value is not. So we need to first linearize the address, and only then compute the number of valid bytes that can be fetched. This happens relatively often when executing real mode code. Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c16314807756..6a1d60956d63 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -711,14 +711,18 @@ static int segmented_read_std(struct x86_emulate_ctxt *ctxt, static int __do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt, int op_size) { int rc; - int size; + unsigned size; unsigned long linear; int cur_size = ctxt->fetch.end - ctxt->fetch.data; struct segmented_address addr = { .seg = VCPU_SREG_CS, .ea = ctxt->eip + cur_size }; - size = min(15UL ^ cur_size, - PAGE_SIZE - offset_in_page(addr.ea)); + size = 15UL ^ cur_size; + rc = __linearize(ctxt, addr, size, false, true, &linear); + if (unlikely(rc != X86EMUL_CONTINUE)) + return rc; + + size = min_t(unsigned, size, PAGE_SIZE - offset_in_page(linear)); /* * One instruction can only straddle two pages, @@ -728,9 +732,6 @@ static int __do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt, int op_size) */ if (unlikely(size < op_size)) return X86EMUL_UNHANDLEABLE; - rc = __linearize(ctxt, addr, size, false, true, &linear); - if (unlikely(rc != X86EMUL_CONTINUE)) - return rc; rc = ctxt->ops->fetch(ctxt, linear, ctxt->fetch.end, size, &ctxt->exception); if (unlikely(rc != X86EMUL_CONTINUE)) -- 1.8.3.1