From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752279AbeDKABE (ORCPT ); Tue, 10 Apr 2018 20:01:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:59594 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751960AbeDKABD (ORCPT ); Tue, 10 Apr 2018 20:01:03 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E6DFE21722 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Tue, 10 Apr 2018 20:00:59 -0400 From: Steven Rostedt To: Howard McLauchlan Cc: , Ingo Molnar , , Masami Hiramatsu , Srikar Dronamraju Subject: Re: [PATCH] uprobe: add support for overlayfs Message-ID: <20180410200059.731d87fe@gandalf.local.home> In-Reply-To: <20180410231030.2720-1-hmclauchlan@fb.com> References: <20180410231030.2720-1-hmclauchlan@fb.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 10 Apr 2018 16:10:30 -0700 Howard McLauchlan wrote: > uprobes cannot successfully attach to binaries located in a directory > mounted with overlayfs. > > 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' I tried the above and verified that it is a problem and your patch solves it. Thanks, I'll apply it and start my tests on it. -- Steve > > 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)) {