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=-9.8 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=unavailable 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 7E769ECE58E for ; Thu, 17 Oct 2019 16:43:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52F5421848 for ; Thu, 17 Oct 2019 16:43:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="mq5v6bkc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2503008AbfJQQnB (ORCPT ); Thu, 17 Oct 2019 12:43:01 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:10950 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2502887AbfJQQm5 (ORCPT ); Thu, 17 Oct 2019 12:42:57 -0400 Received: from pps.filterd (m0044010.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id x9HGV6rA003253 for ; Thu, 17 Oct 2019 09:42:56 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=GOJk98uhPyGo6jkczqnhQiMYnPmAVYZKwD5wgDMMEkI=; b=mq5v6bkccQBlRlJBX9JafhKdSkicw458+1tuWO0KANGG+ERtKOKRumkZ6FyPBVBK1iK/ JAFOSfFVL73w7TTKrEscRH6EooQitsFdfISVtp1Q/r+f17ZKiI+GLL3DnDMgccf7mR20 boFB4Aa9xb8DGkGoyzYYjU9GbBQYE/k9rIA= Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 2vp5k0e297-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Thu, 17 Oct 2019 09:42:56 -0700 Received: from 2401:db00:2120:80e1:face:0:29:0 (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::125) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Thu, 17 Oct 2019 09:42:55 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 6F1B362E1477; Thu, 17 Oct 2019 09:42:53 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , , CC: , , , , Song Liu , Srikar Dronamraju , Oleg Nesterov Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v2 5/5] uprobe: only do FOLL_SPLIT_PMD for uprobe register Date: Thu, 17 Oct 2019 09:42:22 -0700 Message-ID: <20191017164223.2762148-6-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191017164223.2762148-1-songliubraving@fb.com> References: <20191017164223.2762148-1-songliubraving@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-17_05:2019-10-17,2019-10-17 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 suspectscore=0 bulkscore=0 clxscore=1015 mlxscore=0 mlxlogscore=770 impostorscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 malwarescore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1908290000 definitions=main-1910170149 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Attaching uprobe to text section in THP splits the PMD mapped page table into PTE mapped entries. On uprobe detach, we would like to regroup PMD mapped page table entry to regain performance benefit of THP. However, the regroup is broken For perf_event based trace_uprobe. This is because perf_event based trace_uprobe calls uprobe_unregister twice on close: first in TRACE_REG_PERF_CLOSE, then in TRACE_REG_PERF_UNREGISTER. The second call will split the PMD mapped page table entry, which is not the desired behavior. Fix this by only use FOLL_SPLIT_PMD for uprobe register case. Add a WARN() to confirm uprobe unregister never work on huge pages, and abort the operation when this WARN() triggers. Fixes: 5a52c9df62b4 ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT") Cc: Kirill A. Shutemov Cc: Srikar Dronamraju Cc: Oleg Nesterov Signed-off-by: Song Liu --- kernel/events/uprobes.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 94d38a39d72e..c74761004ee5 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -474,14 +474,17 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, struct vm_area_struct *vma; int ret, is_register, ref_ctr_updated = 0; bool orig_page_huge = false; + unsigned int gup_flags = FOLL_FORCE; is_register = is_swbp_insn(&opcode); uprobe = container_of(auprobe, struct uprobe, arch); retry: + if (is_register) + gup_flags |= FOLL_SPLIT_PMD; /* Read the page with vaddr into memory */ - ret = get_user_pages_remote(NULL, mm, vaddr, 1, - FOLL_FORCE | FOLL_SPLIT_PMD, &old_page, &vma, NULL); + ret = get_user_pages_remote(NULL, mm, vaddr, 1, gup_flags, + &old_page, &vma, NULL); if (ret <= 0) return ret; @@ -489,6 +492,12 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, if (ret <= 0) goto put_old; + if (WARN(!is_register && PageCompound(old_page), + "uprobe unregister should never work on compound page\n")) { + ret = -EINVAL; + goto put_old; + } + /* We are going to replace instruction, update ref_ctr. */ if (!ref_ctr_updated && uprobe->ref_ctr_offset) { ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1); -- 2.17.1