From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D440C433F5 for ; Thu, 21 Oct 2021 23:05:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3923A6139E for ; Thu, 21 Oct 2021 23:05:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232465AbhJUXHg (ORCPT ); Thu, 21 Oct 2021 19:07:36 -0400 Received: from mga05.intel.com ([192.55.52.43]:58072 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231206AbhJUXHR (ORCPT ); Thu, 21 Oct 2021 19:07:17 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10144"; a="315380045" X-IronPort-AV: E=Sophos;i="5.87,170,1631602800"; d="scan'208";a="315380045" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Oct 2021 16:02:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,170,1631602800"; d="scan'208";a="445033338" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by orsmga006.jf.intel.com with ESMTP; 21 Oct 2021 16:02:23 -0700 From: "Chang S. Bae" To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, tglx@linutronix.de, dave.hansen@linux.intel.com, arjan@linux.intel.com, ravi.v.shankar@intel.com, chang.seok.bae@intel.com Subject: [PATCH 10/23] x86/fpu: Prepare fpu_clone() for dynamically enabled features Date: Thu, 21 Oct 2021 15:55:14 -0700 Message-Id: <20211021225527.10184-11-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211021225527.10184-1-chang.seok.bae@intel.com> References: <20211021225527.10184-1-chang.seok.bae@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner The default portion of the parent's FPU state is saved in a child task. With dynamic features enabled, the non-default portion is not saved in a child's fpstate because these register states are defined to be caller-saved. The new task's fpstate is therefore the default buffer. Fork inherits the permission of the parent. Also, do not use memcpy() when TIF_NEED_FPU_LOAD is set because it is invalid when the parent has dynamic features. Signed-off-by: Thomas Gleixner Signed-off-by: Chang S. Bae --- Changes from the tglx tree: * Add the changelog. * Update comments. (Dave Hansen) --- arch/x86/include/asm/fpu/sched.h | 2 +- arch/x86/kernel/fpu/core.c | 35 +++++++++++++++++++++++--------- arch/x86/kernel/process.c | 2 +- 3 files changed, 27 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sched.h index cdb78d590c86..99a8820e8cc4 100644 --- a/arch/x86/include/asm/fpu/sched.h +++ b/arch/x86/include/asm/fpu/sched.h @@ -11,7 +11,7 @@ extern void save_fpregs_to_fpstate(struct fpu *fpu); extern void fpu__drop(struct fpu *fpu); -extern int fpu_clone(struct task_struct *dst); +extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags); extern void fpu_flush_thread(void); /* diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index ff7d239fe961..177f27687261 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -426,8 +426,20 @@ void fpstate_reset(struct fpu *fpu) fpu->perm.__user_state_size = fpu_user_cfg.default_size; } +static inline void fpu_inherit_perms(struct fpu *dst_fpu) +{ + if (fpu_state_size_dynamic()) { + struct fpu *src_fpu = ¤t->group_leader->thread.fpu; + + spin_lock_irq(¤t->sighand->siglock); + /* Fork also inherits the permissions of the parent */ + dst_fpu->perm = src_fpu->perm; + spin_unlock_irq(¤t->sighand->siglock); + } +} + /* Clone current's FPU state on fork */ -int fpu_clone(struct task_struct *dst) +int fpu_clone(struct task_struct *dst, unsigned long clone_flags) { struct fpu *src_fpu = ¤t->thread.fpu; struct fpu *dst_fpu = &dst->thread.fpu; @@ -458,17 +470,20 @@ int fpu_clone(struct task_struct *dst) } /* - * If the FPU registers are not owned by current just memcpy() the - * state. Otherwise save the FPU registers directly into the - * child's FPU context, without any memory-to-memory copying. + * Save the default portion of the current FPU state into the + * clone. Assume all dynamic features to be defined as caller- + * saved, which enables skipping both the expansion of fpstate + * and the copying of any dynamic state. + * + * Do not use memcpy() when TIF_NEED_FPU_LOAD is set because + * copying is not valid when current uses non-default states. */ fpregs_lock(); - if (test_thread_flag(TIF_NEED_FPU_LOAD)) { - memcpy(&dst_fpu->fpstate->regs, &src_fpu->fpstate->regs, - dst_fpu->fpstate->size); - } else { - save_fpregs_to_fpstate(dst_fpu); - } + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + fpregs_restore_userregs(); + save_fpregs_to_fpstate(dst_fpu); + if (!(clone_flags & CLONE_THREAD)) + fpu_inherit_perms(dst_fpu); fpregs_unlock(); trace_x86_fpu_copy_src(src_fpu); diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 97fea1649a5e..99025e32f105 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -157,7 +157,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, frame->flags = X86_EFLAGS_FIXED; #endif - fpu_clone(p); + fpu_clone(p, clone_flags); /* Kernel thread ? */ if (unlikely(p->flags & PF_KTHREAD)) { -- 2.17.1