linux-kernel - Re: [PATCH 2/2] selftests/ftrace: Make uprobe test more robust against binary name

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Message-ID: <20250217125949.24d52997@gandalf.local.home>
Date: Mon, 17 Feb 2025 12:59:49 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Heiko Carstens <hca@...ux.ibm.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Shuah Khan
 <shuah@...nel.org>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/2] selftests/ftrace: Make uprobe test more robust
 against binary name

On Mon, 17 Feb 2025 14:42:44 +0100
Heiko Carstens <hca@...ux.ibm.com> wrote:

> > +REALBIN=`readlink -f /bin/sh`
> > +
> >  echo 'cat /proc/$$/maps' | /bin/sh | \
> > -	grep "r-xp .*/bin/.*sh$" | \
> > +	grep "r-xp .*${REALBIN}$" | \
> >  	awk '{printf "p:myevent %s:0x%s\n", $6,$3 }' >> uprobe_events  
> 
> This test fails on s390, not because of this change, but since the
> test seems to assume that the entry point of /bin/sh is at offset 0;
> or at least there is some code that is executed at least once at
> offset 0; but that is not the case (at least) for s390.
> 
> Not sure how this can be addressed. Using "readelf -f" to get the
> entry point address of the executable and use that for the uprobe
> would work, but it would also add a dependency to binutils for the
> ftrace selftests, which doesn't exist yet, as far as I can tell.
> 
> Would it maybe an option for architectures to opt-in to use readelf
> and skip the test (exit_unsupported) if readelf is not available?

I'm OK for adding a dependency on readelf existing on the test system, as
it is part of binutils.

Masami and Shuah,

Are you OK with that?

-- Steve