From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932573AbdJZI1z (ORCPT ); Thu, 26 Oct 2017 04:27:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:40906 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932326AbdJZI1u (ORCPT ); Thu, 26 Oct 2017 04:27:50 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DEA7921921 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 , Andy Lutomirski Subject: [PATCH 14/18] x86/boot/64: Stop initializing TSS.sp0 at boot Date: Thu, 26 Oct 2017 01:26:46 -0700 Message-Id: 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 In my quest to get rid of thread_struct::sp0, I want to clean up or remove all of its readers. Two of them are in cpu_init() (32-bit and 64-bit), and they aren't needed. This is because we never enter userspace at all on the threads that CPUs are initialized in. Poison the initial TSS.sp0 and stop initializing it on CPU init. Signed-off-by: Andy Lutomirski --- arch/x86/kernel/cpu/common.c | 12 ++++++++++-- arch/x86/kernel/process.c | 3 ++- 2 files changed, 12 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 079648bd85ed..adc02cb351e0 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1572,9 +1572,13 @@ void cpu_init(void) initialize_tlbstate_and_flush(); enter_lazy_tlb(&init_mm, me); - load_sp0(current->thread.sp0); + /* + * Initialize the TSS. Don't bother initializing sp0, as the initial + * task never enters user mode. + */ set_tss_desc(cpu, t); load_TR_desc(); + load_mm_ldt(&init_mm); clear_all_debug_regs(); @@ -1627,9 +1631,13 @@ void cpu_init(void) initialize_tlbstate_and_flush(); enter_lazy_tlb(&init_mm, curr); - load_sp0(thread->sp0); + /* + * Initialize the TSS. Don't bother initializing sp0, as the initial + * task never enters user mode. + */ set_tss_desc(cpu, t); load_TR_desc(); + load_mm_ldt(&init_mm); t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap); diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index bd6b85fac666..7ece9d4764fb 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -48,7 +48,8 @@ */ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = { .x86_tss = { - .sp0 = TOP_OF_INIT_STACK, + /* Initialize sp0 to a value that is definitely invalid. */ + .sp0 = (1UL << (BITS_PER_LONG-1)) + 1, #ifdef CONFIG_X86_32 .ss0 = __KERNEL_DS, .ss1 = __KERNEL_CS, -- 2.13.6