From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967705AbeCSQ6f (ORCPT ); Mon, 19 Mar 2018 12:58:35 -0400 Received: from mail-qt0-f196.google.com ([209.85.216.196]:39404 "EHLO mail-qt0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935103AbeCSQ6S (ORCPT ); Mon, 19 Mar 2018 12:58:18 -0400 X-Google-Smtp-Source: AG47ELvBzkIhT5IOmLdowr1z2tYx6Mo2SiPRx+jdMYUpqRA3KK9Z7IYGe5UFFuybU9vTfRdmOTIKIw== From: Jason Andryuk To: Boris Ostrovsky , Juergen Gross Cc: Jason Andryuk , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Subject: [PATCH] x86/xen: Delay get_cpu_cap until stack canary is established Date: Mon, 19 Mar 2018 12:58:04 -0400 Message-Id: <20180319165804.10636-1-jandryuk@gmail.com> X-Mailer: git-send-email 2.14.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings") introduced a call to get_cpu_cap, which is fstack-protected. This is works on x86-64 as commit 4f277295e54c ("x86/xen: init %gs very early to avoid page faults with stack protector") ensures the stack protector is configured, but it it did not cover x86-32. Delay calling get_cpu_cap until after xen_setup_gdt has initialized the stack canary. Without this, a 32bit PV machine crashes early in boot. (XEN) Domain 0 (vcpu#0) crashed on cpu#0: (XEN) ----[ Xen-4.6.6-xc x86_64 debug=n Tainted: C ]---- (XEN) CPU: 0 (XEN) RIP: e019:[<00000000c10362f8>] And the PV kernel IP corresponds to init_scattered_cpuid_features 0xc10362f8 <+24>: mov %gs:0x14,%eax Fixes 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings") Signed-off-by: Jason Andryuk --- arch/x86/xen/enlighten_pv.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 3c2c2530737e..c36d23aa6c35 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1259,10 +1259,6 @@ asmlinkage __visible void __init xen_start_kernel(void) */ __userpte_alloc_gfp &= ~__GFP_HIGHMEM; - /* Work out if we support NX */ - get_cpu_cap(&boot_cpu_data); - x86_configure_nx(); - /* Get mfn list */ xen_build_dynamic_phys_to_machine(); @@ -1272,6 +1268,10 @@ asmlinkage __visible void __init xen_start_kernel(void) */ xen_setup_gdt(0); + /* Work out if we support NX */ + get_cpu_cap(&boot_cpu_data); + x86_configure_nx(); + xen_init_irq_ops(); /* Let's presume PV guests always boot on vCPU with id 0. */ -- 2.14.3