From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755424AbeDJXK6 (ORCPT ); Tue, 10 Apr 2018 19:10:58 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:49548 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752735AbeDJXKz (ORCPT ); Tue, 10 Apr 2018 19:10:55 -0400 From: Howard McLauchlan To: CC: Steven Rostedt , Ingo Molnar , , Howard McLauchlan Subject: [PATCH] uprobe: add support for overlayfs Date: Tue, 10 Apr 2018 16:10:30 -0700 Message-ID: <20180410231030.2720-1-hmclauchlan@fb.com> X-Mailer: git-send-email 2.17.0 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [2620:10d:c090:200::5:53e8] X-ClientProxiedBy: CO2PR05CA0097.namprd05.prod.outlook.com (2603:10b6:104:1::23) To BN4PR15MB0532.namprd15.prod.outlook.com (2a01:111:e400:59c3::26) X-MS-PublicTrafficType: Email X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(5600026)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7153060)(7193020);SRVR:BN4PR15MB0532; 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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. Reviewed-by: Josef Bacik 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 2014f4351ae0..17c65fa4136d 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)) { -- 2.17.0