Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752715AbbDCLwJ (ORCPT ); Fri, 3 Apr 2015 07:52:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50768 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbbDCLwF (ORCPT ); Fri, 3 Apr 2015 07:52:05 -0400 Message-ID: <551E7EE0.5010901@redhat.com> Date: Fri, 03 Apr 2015 13:52:00 +0200 From: Denys Vlasenko User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Borislav Petkov , Ingo Molnar CC: LKML , Andy Lutomirski , Alexei Starovoitov , Frederic Weisbecker , "H. Peter Anvin" , Kees Cook , Linus Torvalds , Oleg Nesterov , Steven Rostedt , Will Drewry Subject: Re: [PATCH] x86/asm/entry/64: Fix MSR_IA32_SYSENTER_CS MSR value References: <1428054130-25847-1-git-send-email-bp@alien8.de> <20150403112027.GA3418@pd.tnic> In-Reply-To: <20150403112027.GA3418@pd.tnic> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2223 Lines: 63 On 04/03/2015 01:20 PM, Borislav Petkov wrote: > On Fri, Apr 03, 2015 at 11:42:10AM +0200, Borislav Petkov wrote: >> From: Borislav Petkov >> >> Commit >> >> d56fe4bf5f3c ("x86/asm/entry/64: Always set up SYSENTER MSRs") >> >> missed to add "ULL" to the 0 and wrmsrl_safe() complains: >> >> arch/x86/kernel/cpu/common.c: In function ‘syscall_init’: >> arch/x86/kernel/cpu/common.c:1226:2: warning: right shift count >= width of type >> wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0); >> >> Fix it. >> >> Signed-off-by: Borislav Petkov >> Cc: Denys Vlasenko >> Cc: Andy Lutomirski >> Cc: Alexei Starovoitov >> Cc: Frederic Weisbecker >> Cc: H. Peter Anvin >> Cc: Kees Cook >> Cc: Linus Torvalds >> Cc: Oleg Nesterov >> Cc: Steven Rostedt >> Cc: Will Drewry >> Cc: Ingo Molnar >> --- >> arch/x86/kernel/cpu/common.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c >> index bb6633a87a19..2c249b57e4b5 100644 >> --- a/arch/x86/kernel/cpu/common.c >> +++ b/arch/x86/kernel/cpu/common.c >> @@ -1223,7 +1223,7 @@ void syscall_init(void) >> wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target); >> #else >> wrmsrl(MSR_CSTAR, ignore_sysret); >> - wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0); >> + wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0ULL); > > Btw, we probably should define an invalid segment > > #define GDT_ENTRY_INVALID_SEGMENT 0ULL > > and use that value instead of the naked 0. Why? Segment selectors aren't "long long", they are in fact "short" (16-bit ints). The "ULL" is used here in wrmsrl not because it's a segment, but because wrmsrl expects a u64 parameter. We can probably add a cast in its definition... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/