From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753582AbdIFVhO (ORCPT ); Wed, 6 Sep 2017 17:37:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:50400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753535AbdIFVhL (ORCPT ); Wed, 6 Sep 2017 17:37:11 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4D51A22A78 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@kernel.org Cc: linux-kernel@vger.kernel.org, Borislav Petkov , Brian Gerst , Andrew Cooper , Juergen Gross , Boris Ostrovsky , Kees Cook , Andy Lutomirski Subject: [RFC 09/17] x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of native_load_sp0() Date: Wed, 6 Sep 2017 14:36:54 -0700 Message-Id: <2c6329543024c4cd53c83833cc31a495797cd07d.1504733277.git.luto@kernel.org> X-Mailer: git-send-email 2.13.5 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 This causees the MSR_IA32_SYSENTER_CS write to move out of the paravirt hook. This shouldn't affect Xen or lgeust: Xen already ignores MSR_IA32_SYSENTER_ESP writes and lguest doesn't support SYSENTER at all. In any event, Xen doesn't support vm86() in a useful way. Signed-off-by: Andy Lutomirski --- arch/x86/include/asm/processor.h | 7 ------- arch/x86/include/asm/switch_to.h | 11 +++++++++++ arch/x86/kernel/process_32.c | 1 + arch/x86/kernel/process_64.c | 2 +- arch/x86/kernel/vm86_32.c | 6 +++++- 5 files changed, 18 insertions(+), 9 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 028245e1c42b..ee37fb86900a 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -513,13 +513,6 @@ static inline void native_load_sp0(struct tss_struct *tss, struct thread_struct *thread) { tss->x86_tss.sp0 = thread->sp0; -#ifdef CONFIG_X86_32 - /* Only happens when SEP is enabled, no need to test "SEP"arately: */ - if (unlikely(tss->x86_tss.ss1 != thread->sysenter_cs)) { - tss->x86_tss.ss1 = thread->sysenter_cs; - wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0); - } -#endif } static inline void native_swapgs(void) diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index fcc5cd387fd1..f3fa19925ae1 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -72,4 +72,15 @@ do { \ ((last) = __switch_to_asm((prev), (next))); \ } while (0) +#ifdef CONFIG_X86_32 +static inline void refresh_sysenter_cs(struct thread_struct *thread) +{ + /* Only happens when SEP is enabled, no need to test "SEP"arately: */ + if (unlikely(this_cpu_read(cpu_tss.x86_tss.ss1) == thread->sysenter_cs)) + return; + + this_cpu_write(cpu_tss.x86_tss.ss1, thread->sysenter_cs); +} +#endif + #endif /* _ASM_X86_SWITCH_TO_H */ diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index c6d6dc5f8bb2..9f217b5ef438 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -287,6 +287,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) * current_thread_info(). */ load_sp0(tss, next); + refresh_sysenter_cs(); /* in case prev or next is vm86 */ this_cpu_write(cpu_current_top_of_stack, (unsigned long)task_stack_page(next_p) + THREAD_SIZE); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index c3169be4c596..985e7569ab57 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -436,7 +436,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) */ this_cpu_write(current_task, next_p); - /* Reload esp0 and ss1. This changes current_thread_info(). */ + /* Reload sp0. */ load_sp0(tss, next); /* diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c index 7924a5356c8a..9edda73dcc90 100644 --- a/arch/x86/kernel/vm86_32.c +++ b/arch/x86/kernel/vm86_32.c @@ -54,6 +54,7 @@ #include #include #include +#include /* * Known problems: @@ -149,6 +150,7 @@ void save_v86_state(struct kernel_vm86_regs *regs, int retval) tsk->thread.sp0 = vm86->saved_sp0; tsk->thread.sysenter_cs = __KERNEL_CS; load_sp0(tss, &tsk->thread); + refresh_sysenter_cs(); vm86->saved_sp0 = 0; put_cpu(); @@ -368,8 +370,10 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus) /* make room for real-mode segments */ tsk->thread.sp0 += 16; - if (static_cpu_has(X86_FEATURE_SEP)) + if (static_cpu_has(X86_FEATURE_SEP)) { tsk->thread.sysenter_cs = 0; + refresh_sysenter_cs(); + } load_sp0(tss, &tsk->thread); put_cpu(); -- 2.13.5