From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752754AbeDKCN0 (ORCPT ); Tue, 10 Apr 2018 22:13:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:45422 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752295AbeDKCNZ (ORCPT ); Tue, 10 Apr 2018 22:13:25 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0126921785 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org Date: Wed, 11 Apr 2018 11:13:22 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Howard McLauchlan , , Ingo Molnar , , Masami Hiramatsu , Srikar Dronamraju Subject: Re: [PATCH] uprobe: add support for overlayfs Message-Id: <20180411111322.14b5a21ea61ad968f8375427@kernel.org> In-Reply-To: <20180410200059.731d87fe@gandalf.local.home> References: <20180410231030.2720-1-hmclauchlan@fb.com> <20180410200059.731d87fe@gandalf.local.home> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-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 20:00:59 -0400 Steven Rostedt wrote: > 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. This looks good to me. Reviewed-by: Masami Hiramatsu Thanks! > > -- 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)) { > -- Masami Hiramatsu