From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758427AbcGKNSQ (ORCPT ); Mon, 11 Jul 2016 09:18:16 -0400 Received: from mga04.intel.com ([192.55.52.120]:17021 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754023AbcGKNR4 (ORCPT ); Mon, 11 Jul 2016 09:17:56 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,346,1464678000"; d="scan'208";a="1019448934" From: "Fenghua Yu" To: "Ingo Molnar" , "Thomas Gleixner" , "H. Peter Anvin" , "Dave Hansen" , "Ravi V Shankar" Cc: Yu-cheng Yu , "Fenghua Yu" , "x86" , "linux-kernel" Subject: [PATCH 3/4] x86/fpu/xstate: Fix fpstate_init() for XRSTORS Date: Mon, 11 Jul 2016 09:18:56 -0700 Message-Id: <1468253937-40008-4-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 1.8.0.1 In-Reply-To: <1468253937-40008-1-git-send-email-fenghua.yu@intel.com> References: <1468253937-40008-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yu-cheng Yu In XSAVES mode if fpstate_init() is used to initialize a task's extended state area, xsave.header.xcomp_bv[63] must be set. Otherwise, when the task is scheduled, a warning is triggered from copy_kernel_to_xregs(). One such test case is: setting an invalid extended state through PTRACE. When xstateregs_set() rejects the syscall and re-initializes the task's extended state area. This triggers the warning mentioned above. Signed-off-by: Yu-cheng Yu Signed-off-by: Fenghua Yu Reviewed-by: Dave Hansen --- arch/x86/include/asm/fpu/types.h | 6 ++++++ arch/x86/kernel/fpu/core.c | 8 ++++++++ 2 files changed, 14 insertions(+) diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index 12dd648..48df486 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -232,6 +232,12 @@ struct xstate_header { } __attribute__((packed)); /* + * xstate_header.xcomp_bv[63] indicates that the extended_state_area + * is in compacted format. + */ +#define XCOMP_BV_COMPACTED_FORMAT ((u64)1 << 63) + +/* * This is our most modern FPU state format, as saved by the XSAVE * and restored by the XRSTOR instructions. * diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index c759bd0..3fc03a0 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include @@ -229,6 +230,13 @@ void fpstate_init(union fpregs_state *state) memset(state, 0, fpu_kernel_xstate_size); + /* + * XRSTORS requires that this bit is set in xcomp_bv, or + * it will #GP. Make sure it is replaced after the memset(). + */ + if (static_cpu_has(X86_FEATURE_XSAVES)) + state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT; + if (static_cpu_has(X86_FEATURE_FXSR)) fpstate_init_fxstate(&state->fxsave); else -- 2.5.0