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=-9.9 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_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 0A1B0C3A589 for ; Thu, 15 Aug 2019 16:39:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C64A8208C2 for ; Thu, 15 Aug 2019 16:39:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="MYDLo6I1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732504AbfHOQjU (ORCPT ); Thu, 15 Aug 2019 12:39:20 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:39813 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732484AbfHOQjR (ORCPT ); Thu, 15 Aug 2019 12:39:17 -0400 Received: by mail-wm1-f65.google.com with SMTP id i63so1771112wmg.4 for ; Thu, 15 Aug 2019 09:39:15 -0700 (PDT) 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=r/9uyT+mnIHOaH/ccTtg/Nxut5gT2ypiz9lprU+hrks=; b=MYDLo6I1xHd/KR1Jq+sZWa0ONwa92tRKpvfI4g25iKa2lvx2eFR7GcGlcJUhrNEkkH fgSqPDxBa7YWh8Wjvi5A2KVO9M1toYcNRqwY9ORUantp3/6NvYW2ivpFAcm5lVCLCYfh Pxy4X68e1Hco+Tuz3TJpDXgxDFY9R9nNvlnWPcror/fXPTALT8M0G4IJgIw5f+V1k1vH HptVNegpIx+XaYA4kJcQwLPiuhmppOsm4p8OSFLPBFb1g8cKPaNtANUKLEalke7azxAu +jYnnJxROTsSpEcy2VgV8e1eIcJrf55SRUTiuo4dVOQRL3YpM1mcSPBDGcbNoiE0r8+c PsBw== 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=r/9uyT+mnIHOaH/ccTtg/Nxut5gT2ypiz9lprU+hrks=; b=lI6fDwMhqsF/Ge4yU2Ip9zdtKHqfcO3X6Hi7qtknjeS2xU502rqSl8QwJFAb3VLcXG 6+5LVCkT/aTEh8VQA89Qdg0akcq9Va81LOBG82XMTUFiH6Mu0b8S0kvsqreTgmLkf3GA m9gXPJEh+3niumqTP9HqKgAavZEC9gfNVl0ZxwVHLhPIiJY3ZHCxxtEKKjymAlAAUUh1 TJYoljqRGSXnbq1590o7FkG7cXYhTMsMmfS2mvGk9i90huBVX7Js2wGdLd4/2sQ6sx3z Mol/UcBNLL+Dx9AiFkWoEmWhJvpcyVWdmIk2uA1cXJmq8rJcGlR4zPM1Hjw19RQ9WGCE MFPg== X-Gm-Message-State: APjAAAUXfy8qVehYmKN6916M61xb7yyO5MZYG3FV3rcuClfsPE/7A1vS +spuyauMgnNIjpaJc/l9sWjRCbI8grY= X-Google-Smtp-Source: APXvYqyaeGx4F4ZKjGtGiS1uS8X/cbv+de31lrxL5NVHQopePXSDhQC7FYVLZjy5ytMpTUbCFIFDzw== X-Received: by 2002:a1c:9d53:: with SMTP id g80mr3599678wme.103.1565887154182; Thu, 15 Aug 2019 09:39:14 -0700 (PDT) Received: from Mindolluin.ire.aristanetworks.com ([217.173.96.166]) by smtp.gmail.com with ESMTPSA id f7sm5755046wrf.8.2019.08.15.09.39.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Aug 2019 09:39:11 -0700 (PDT) From: Dmitry Safonov To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Dmitry Safonov , Adrian Reber , Andrei Vagin , Andy Lutomirski , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , Thomas Gleixner , Vincenzo Frascino , containers@lists.linux-foundation.org, criu@openvz.org, linux-api@vger.kernel.org, x86@kernel.org, Andrei Vagin Subject: [PATCHv6 24/36] x86/vdso: Switch image on setns()/clone() Date: Thu, 15 Aug 2019 17:38:24 +0100 Message-Id: <20190815163836.2927-25-dima@arista.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190815163836.2927-1-dima@arista.com> References: <20190815163836.2927-1-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() or unshare(CLONE_TIMENS) followed by clone(), change VDSO image in mm and zap 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 | 23 +++++++++++++++++++++++ arch/x86/include/asm/vdso.h | 1 + kernel/time_namespace.c | 11 +++++++++++ 3 files changed, 35 insertions(+) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 8a8211fd4cfc..91cf5a5c8c9e 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; @@ -266,6 +267,28 @@ static const struct vm_special_mapping vvar_mapping = { .mremap = vvar_mremap, }; +#ifdef CONFIG_TIME_NS +int vdso_join_timens(struct task_struct *task) +{ + struct mm_struct *mm = task->mm; + struct vm_area_struct *vma; + + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + + 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) || + vma_is_special_mapping(vma, &vdso_mapping)) + zap_page_range(vma, vma->vm_start, size); + } + + up_write(&mm->mmap_sem); + return 0; +} +#endif + /* * Add vdso and vvar mappings to current process. * @image - blob to map diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h index 03f468c63a24..ccf89dedd04f 100644 --- a/arch/x86/include/asm/vdso.h +++ b/arch/x86/include/asm/vdso.h @@ -45,6 +45,7 @@ extern struct vdso_image vdso_image_32; extern void __init init_vdso_image(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); #endif /* __ASSEMBLER__ */ diff --git a/kernel/time_namespace.c b/kernel/time_namespace.c index ff2c5de7e815..a01c25fe76d5 100644 --- a/kernel/time_namespace.c +++ b/kernel/time_namespace.c @@ -15,6 +15,7 @@ #include #include #include +#include ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, struct timens_offsets *ns_offsets) @@ -201,6 +202,7 @@ 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 (!current_is_single_threaded()) return -EUSERS; @@ -209,6 +211,10 @@ static int timens_install(struct nsproxy *nsproxy, struct ns_common *new) !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) return -EPERM; + ret = vdso_join_timens(current); + if (ret) + return ret; + get_time_ns(ns); get_time_ns(ns); put_time_ns(nsproxy->time_ns); @@ -223,10 +229,15 @@ 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); + if (ret) + return ret; + get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; -- 2.22.0