From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751838AbeB1AlT (ORCPT ); Tue, 27 Feb 2018 19:41:19 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:52248 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521AbeB1AlR (ORCPT ); Tue, 27 Feb 2018 19:41:17 -0500 From: Howard McLauchlan To: CC: Steven Rostedt , Ingo Molnar , , Yonghong Song , Josef Bacik , Omar Sandoval , Howard McLauchlan Subject: [PATCH] uprobe: add support for overlayfs Date: Tue, 27 Feb 2018 16:40:14 -0800 Message-ID: <20180228004014.445-1-hmclauchlan@fb.com> X-Mailer: git-send-email 2.14.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [2620:10d:c090:200::5:5758] X-ClientProxiedBy: SN4PR0201CA0055.namprd02.prod.outlook.com (2603:10b6:803:20::17) To DM3PR15MB0540.namprd15.prod.outlook.com (2a01:111:e400:c477::26) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: ebc9a04a-1a08-4e40-e7e1-08d57e43f485 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(5600026)(4604075)(2017052603307)(7153060)(7193020);SRVR:DM3PR15MB0540; 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To verify, create directories for mounting overlayfs (upper,lower,work,merge), move some binary into merge/ and use readelf to obtain some known instruction of the binary. I used /bin/true and the entry instruction(0x13b0): $ mount -t overlay overlay -o lowerdir=lower,upperdir=upper,workdir=work merge $ cd /sys/kernel/debug/tracing $ echo 'p:true_entry PATH_TO_MERGE/merge/true:0x13b0' > uprobe_events $ echo 1 > events/uprobes/true_entry/enable This returns 'bash: echo: write error: Input/output error' and dmesg tells us 'event trace: Could not enable event true_entry' This change makes create_trace_uprobe() look for the real inode of a dentry. In the case of normal filesystems, this simplifies to just returning the inode. In the case of overlayfs(and similar fs) we will obtain the underlying dentry and corresponding inode, upon which uprobes can successfully register. Running the example above with the patch applied, we can see that the uprobe is enabled and will output to trace as expected. Signed-off-by: Howard McLauchlan --- kernel/trace/trace_uprobe.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 268029ae1be6..8b86d76c55ee 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -446,7 +446,7 @@ static int create_trace_uprobe(int argc, char **argv) if (ret) goto fail_address_parse; - inode = igrab(d_inode(path.dentry)); + inode = igrab(d_real_inode(path.dentry)); path_put(&path); if (!inode || !S_ISREG(inode->i_mode)) { -- 2.14.1