From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 183C36B000C for ; Fri, 20 Jul 2018 12:22:42 -0400 (EDT) Received: by mail-ed1-f69.google.com with SMTP id w10-v6so4902009eds.7 for ; Fri, 20 Jul 2018 09:22:42 -0700 (PDT) Received: from theia.8bytes.org (8bytes.org. [81.169.241.247]) by mx.google.com with ESMTPS id 5-v6si1931338edo.397.2018.07.20.09.22.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Jul 2018 09:22:40 -0700 (PDT) From: Joerg Roedel Subject: [PATCH 2/3] x86/entry/32: Check for VM86 mode in slow-path check Date: Fri, 20 Jul 2018 18:22:23 +0200 Message-Id: <1532103744-31902-3-git-send-email-joro@8bytes.org> In-Reply-To: <1532103744-31902-1-git-send-email-joro@8bytes.org> References: <1532103744-31902-1-git-send-email-joro@8bytes.org> Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Borislav Petkov , Jiri Kosina , Boris Ostrovsky , Brian Gerst , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , aliguori@amazon.com, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, Andrea Arcangeli , Waiman Long , Pavel Machek , "David H . Gutteridge" , jroedel@suse.de, Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , joro@8bytes.org From: Joerg Roedel The SWITCH_TO_KERNEL_STACK macro only checks for CPL == 0 to go down the slow and paranoid entry path. The problem is that this check also returns true when coming from VM86 mode. This is not a problem by itself, as the paranoid path handles VM86 stack-frames just fine, but it is not necessary as the normal code path handles VM86 mode as well (and faster). Extend the check to include VM86 mode. This also makes an optimization of the paranoid path possible. Signed-off-by: Joerg Roedel --- arch/x86/entry/entry_32.S | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 010cdb4..2767c62 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -414,8 +414,16 @@ andl $(0x0000ffff), PT_CS(%esp) /* Special case - entry from kernel mode via entry stack */ - testl $SEGMENT_RPL_MASK, PT_CS(%esp) - jz .Lentry_from_kernel_\@ +#ifdef CONFIG_VM86 + movl PT_EFLAGS(%esp), %ecx # mix EFLAGS and CS + movb PT_CS(%esp), %cl + andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %ecx +#else + movl PT_CS(%esp), %ecx + andl $SEGMENT_RPL_MASK, %ecx +#endif + cmpl $USER_RPL, %ecx + jb .Lentry_from_kernel_\@ /* Bytes to copy */ movl $PTREGS_SIZE, %ecx -- 2.7.4