From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754626AbbCQIrT (ORCPT ); Tue, 17 Mar 2015 04:47:19 -0400 Received: from terminus.zytor.com ([198.137.202.10]:50010 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753032AbbCQIrN (ORCPT ); Tue, 17 Mar 2015 04:47:13 -0400 Date: Tue, 17 Mar 2015 01:46:41 -0700 From: tip-bot for Denys Vlasenko Message-ID: Cc: keescook@chromium.org, wad@chromium.org, hpa@zytor.com, oleg@redhat.com, torvalds@linux-foundation.org, dvlasenk@redhat.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, fweisbec@gmail.com, rostedt@goodmis.org, ast@plumgrid.com, luto@amacapital.net, bp@alien8.de, mingo@kernel.org Reply-To: hpa@zytor.com, torvalds@linux-foundation.org, oleg@redhat.com, tglx@linutronix.de, dvlasenk@redhat.com, wad@chromium.org, keescook@chromium.org, luto@amacapital.net, mingo@kernel.org, bp@alien8.de, linux-kernel@vger.kernel.org, fweisbec@gmail.com, ast@plumgrid.com, rostedt@goodmis.org In-Reply-To: <1425912738-559-2-git-send-email-dvlasenk@redhat.com> References: <1425912738-559-2-git-send-email-dvlasenk@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/asm/entry/32: Document the 32-bit SYSENTER " emergency stack" better Git-Commit-ID: d828c71fba8922b116b4ec56c3e5bca8c822d5ae X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: d828c71fba8922b116b4ec56c3e5bca8c822d5ae Gitweb: http://git.kernel.org/tip/d828c71fba8922b116b4ec56c3e5bca8c822d5ae Author: Denys Vlasenko AuthorDate: Mon, 9 Mar 2015 15:52:18 +0100 Committer: Ingo Molnar CommitDate: Tue, 17 Mar 2015 09:25:29 +0100 x86/asm/entry/32: Document the 32-bit SYSENTER "emergency stack" better Before the patch, the 'tss_struct::stack' field was not referenced anywhere. It was used only to set SYSENTER's stack to point after the last byte of tss_struct, thus the trailing field, stack[64], was used. But grep would not know it. You can comment it out, compile, and kernel will even run until an unlucky NMI corrupts io_bitmap[] (which is also not easily detectable). This patch changes code so that the purpose and usage of this field is not mysterious anymore, and can be easily grepped for. This does change generated code, for a subtle reason: since tss_struct is ____cacheline_aligned, there happens to be 5 longs of padding at the end. Old code was using the padding too; new code will strictly use it only for SYSENTER_stack[]. Signed-off-by: Denys Vlasenko Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/1425912738-559-2-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/processor.h | 4 ++-- arch/x86/kernel/asm-offsets_32.c | 2 +- arch/x86/kernel/cpu/common.c | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 6a5c0ec..5abd9a5 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -291,9 +291,9 @@ struct tss_struct { unsigned long io_bitmap[IO_BITMAP_LONGS + 1]; /* - * .. and then another 0x100 bytes for the emergency kernel stack: + * Space for the temporary SYSENTER stack: */ - unsigned long stack[64]; + unsigned long SYSENTER_stack[64]; } ____cacheline_aligned; diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c index 3b3b9d3..47703ae 100644 --- a/arch/x86/kernel/asm-offsets_32.c +++ b/arch/x86/kernel/asm-offsets_32.c @@ -68,7 +68,7 @@ void foo(void) /* Offset from the sysenter stack to tss.sp0 */ DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) - - sizeof(struct tss_struct)); + offsetofend(struct tss_struct, SYSENTER_stack)); #if defined(CONFIG_LGUEST) || defined(CONFIG_LGUEST_GUEST) || defined(CONFIG_LGUEST_MODULE) BLANK(); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 7634833..7a3dfb1 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -987,7 +987,7 @@ void enable_sep_cpu(void) } tss->x86_tss.ss1 = __KERNEL_CS; - tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss; + tss->x86_tss.sp1 = (unsigned long)tss + offsetofend(struct tss_struct, SYSENTER_stack); wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0); wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);