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 X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4A49C282CB for ; Wed, 6 Feb 2019 00:12:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92B8F2175B for ; Wed, 6 Feb 2019 00:12:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="NkvOJJO/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729302AbfBFALn (ORCPT ); Tue, 5 Feb 2019 19:11:43 -0500 Received: from mail-ed1-f67.google.com ([209.85.208.67]:33381 "EHLO mail-ed1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729016AbfBFALk (ORCPT ); Tue, 5 Feb 2019 19:11:40 -0500 Received: by mail-ed1-f67.google.com with SMTP id p6so4518416eds.0 for ; Tue, 05 Feb 2019 16:11:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=googlenew; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=miXDyTkaSPpC9go/A5cINAcxSQXOEnI3TLjPTECs36M=; b=NkvOJJO/t7+LS8VTTgDzWs1SFIJJFO5HxvvxMR3d4TPnQ6AbZls8yoLkUNy6Q1bvMs 20prZzgxROOMJDBiDv7k+IUt7FxPAEZ2Xd/IjzjD0T4N+K3x/+Gi2CUJRNEaEJidnMj7 qVLc2NTkYhOCZ3ejBsl9vqO4w3HJ0/PHh0cWcvMvEMVOfcMlUIa2HRFjeX3q5euBqKcm EzUDY/Z0nZK3fiJUhO+Oybc3mRFkVIzJO/kJIQF0LHyXJ1Xr2FNtQbynL6yc47CdbA3e FM/nm/Nu5Zdx+mpQFq/NVGWmZWseKI9Kbbz+eGR4jLcpvnxxgBH5gMTtt+suOkLi3ydg jraw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=miXDyTkaSPpC9go/A5cINAcxSQXOEnI3TLjPTECs36M=; b=g2RWpRp0yY7u6AVhxNabIV1nbSb2l9+fzqnVairJd3FLKalWx+wZfwycKR4pqVY6N9 Fh/XfkClxzCJFgqLCCicbiLqvT8XllzSj5O9CLsk/IxE20UvLxy/7kc19G7aRzXM2XM6 M80GjC2Ku9o9uKmR15FNNnQWtLPq4nrZ8Cb+0usFnKrumA2ZwPlKWB/aKpn0rLm/LoDW raIoN+H7NAdAjqlzurgcOgycN3yJ6i1jbnH8nF0GupK0utW0us0mV7Rxi+jx+EEwPWBj 3bADjYfO6c8gLnrcs8EX94jvT6LtN5Sk7a8WnrmmNgri9j7mzkRYNYyU4nCmABVfVMF3 DkpA== X-Gm-Message-State: AHQUAuZTBjlKYBwMCaTDTtYkmaC0OferqIYCWyqA7g+V622+gg6qcc64 HKGEFz+3gPM4XhNZRyQQJs3wTQAarUQ= X-Google-Smtp-Source: AHgI3IZ/s0OBHnwxlJ6b0XkVIaw3NdlMNFhic6JWMTKyh2y8Ca9/Szz/8P7whPXP6+0hv36e8z1d3w== X-Received: by 2002:a50:fe15:: with SMTP id f21mr5768049edt.116.1549411897797; Tue, 05 Feb 2019 16:11:37 -0800 (PST) Received: from Mindolluin.ire.aristanetworks.com ([217.173.96.166]) by smtp.gmail.com with ESMTPSA id p30sm5489594eda.68.2019.02.05.16.11.36 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 05 Feb 2019 16:11:37 -0800 (PST) From: Dmitry Safonov To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov , Adrian Reber , Andrei Vagin , Andrei Vagin , Andy Lutomirski , Andy Tucker , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , Dmitry Safonov <0x7f454c46@gmail.com>, "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , Thomas Gleixner , containers@lists.linux-foundation.org, criu@openvz.org, linux-api@vger.kernel.org, x86@kernel.org Subject: [PATCH 21/32] x86/vdso: Switch image on setns()/unshare()/clone() Date: Wed, 6 Feb 2019 00:10:55 +0000 Message-Id: <20190206001107.16488-22-dima@arista.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190206001107.16488-1-dima@arista.com> References: <20190206001107.16488-1-dima@arista.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As it has been discussed on timens RFC, adding a new conditional branch `if (inside_time_ns)` on VDSO for all processes is undesirable. It will add a penalty for everybody as branch predictor may mispredict the jump. Also there are instruction cache lines wasted on cmp/jmp. Those effects of introducing time namespace are very much unwanted having in mind how much work have been spent on micro-optimisation vdso code. Addressing those problems, there are two versions of VDSO's .so: for host tasks (without any penalty) and for processes inside of time namespace with clk_to_ns() that subtracts offsets from host's time. Whenever a user does setns()/unshare() or clone() with CLONE_TIMENS, change VDSO image in mm and zap existing VVAR/VDSO page tables. They will be re-faulted with corresponding image and VVAR offsets. Co-developed-by: Andrei Vagin Signed-off-by: Andrei Vagin Signed-off-by: Dmitry Safonov --- arch/x86/entry/vdso/vma.c | 81 +++++++++++++++++++++++++++++++++++++ arch/x86/include/asm/vdso.h | 1 + kernel/time_namespace.c | 11 +++++ 3 files changed, 93 insertions(+) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 56a62076a320..52c1e4c24455 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -25,6 +25,7 @@ #include #include #include +#include #if defined(CONFIG_X86_64) unsigned int __read_mostly vdso64_enabled = 1; @@ -150,6 +151,84 @@ static const struct vm_special_mapping vvar_mapping = { .fault = vvar_fault, }; +#ifdef CONFIG_TIME_NS +static const struct vdso_image *timens_vdso(const struct vdso_image *old_img, + bool in_ns) +{ +#ifdef CONFIG_X86_X32_ABI + if (old_img == &vdso_image_x32) + return NULL; +#endif +#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION + if (old_img == &vdso_image_32 || old_img == &vdso_image_32_timens) + return in_ns ? &vdso_image_32_timens : &vdso_image_32; +#endif +#ifdef CONFIG_X86_64 + if (old_img == &vdso_image_64 || old_img == &vdso_image_64_timens) + return in_ns ? &vdso_image_64_timens : &vdso_image_64; +#endif + return NULL; +} + +static const struct vdso_image *image_to_timens(const struct vdso_image *img) +{ + bool in_ns = (current->nsproxy->time_ns != &init_time_ns); + const struct vdso_image *ns; + + ns = timens_vdso(img, in_ns); + + return ns ?: img; +} + +int vdso_join_timens(struct task_struct *task, bool inside_ns) +{ + const struct vdso_image *new_image, *old_image; + struct mm_struct *mm = task->mm; + struct vm_area_struct *vma; + int ret = 0; + + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + + old_image = mm->context.vdso_image; + new_image = timens_vdso(old_image, inside_ns); + if (!new_image) { + ret = -EOPNOTSUPP; + goto out; + } + + /* Sanity checks, shouldn't happen */ + if (unlikely(old_image->size != new_image->size)) { + ret = -ENXIO; + goto out; + } + + mm->context.vdso_image = new_image; + + for (vma = mm->mmap; vma; vma = vma->vm_next) { + unsigned long size = vma->vm_end - vma->vm_start; + + if (vma_is_special_mapping(vma, &vvar_mapping)) + zap_page_range(vma, vma->vm_start, size); + if (vma_is_special_mapping(vma, &vdso_mapping)) + zap_page_range(vma, vma->vm_start, size); + } + +out: + up_write(&mm->mmap_sem); + return ret; +} +#else /* CONFIG_TIME_NS */ +static const struct vdso_image *image_to_timens(const struct vdso_image *img) +{ + return img; +} +int vdso_join_timens(struct task_struct *task, bool inside_ns) +{ + return -ENXIO; +} +#endif + /* * Add vdso and vvar mappings to current process. * @image - blob to map @@ -165,6 +244,8 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr) if (down_write_killable(&mm->mmap_sem)) return -EINTR; + image = image_to_timens(image); + addr = get_unmapped_area(NULL, addr, image->size - image->sym_vvar_start, 0, 0); if (IS_ERR_VALUE(addr)) { diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h index b6a1a028ac62..c8db853344a0 100644 --- a/arch/x86/include/asm/vdso.h +++ b/arch/x86/include/asm/vdso.h @@ -51,6 +51,7 @@ extern const struct vdso_image vdso_image_32_timens; extern void __init init_vdso_image(const struct vdso_image *image); extern int map_vdso_once(const struct vdso_image *image, unsigned long addr); +extern int vdso_join_timens(struct task_struct *task, bool inside_ns); #endif /* __ASSEMBLER__ */ diff --git a/kernel/time_namespace.c b/kernel/time_namespace.c index 36b31f234472..1d1d1c023ec1 100644 --- a/kernel/time_namespace.c +++ b/kernel/time_namespace.c @@ -14,6 +14,7 @@ #include #include #include +#include static struct ucounts *inc_time_namespaces(struct user_namespace *ns) { @@ -155,11 +156,16 @@ static void timens_put(struct ns_common *ns) static int timens_install(struct nsproxy *nsproxy, struct ns_common *new) { struct time_namespace *ns = to_time_ns(new); + int ret; if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) return -EPERM; + ret = vdso_join_timens(current, ns != &init_time_ns); + if (ret) + return ret; + get_time_ns(ns); get_time_ns(ns); put_time_ns(nsproxy->time_ns); @@ -174,10 +180,15 @@ int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) { struct ns_common *nsc = &nsproxy->time_ns_for_children->ns; struct time_namespace *ns = to_time_ns(nsc); + int ret; if (nsproxy->time_ns == nsproxy->time_ns_for_children) return 0; + ret = vdso_join_timens(tsk, ns != &init_time_ns); + if (ret) + return ret; + get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; -- 2.20.1