From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Kees Cook <keescook@chromium.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
kbuild-all@lists.01.org, linux-kernel@vger.kernel.org,
kernel test robot <lkp@intel.com>
Subject: Re: vmlinux.o: warning: objtool: stackleak_erase()+0x35: call to ftrace_likely_update() leaves .noinstr.text section
Date: Tue, 5 Apr 2022 10:03:35 +0200 [thread overview]
Message-ID: <20220405080335.GC30877@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220404152502.0621caf9@gandalf.local.home>
On Mon, Apr 04, 2022 at 03:25:02PM -0400, Steven Rostedt wrote:
> On Mon, 4 Apr 2022 11:27:47 -0700
> Kees Cook <keescook@chromium.org> wrote:
>
> > I got CCed on this because of stackleak_erase() triggering, this, but it
> > appears to be an existing issue for other callers too. It looks like
> > __branch_check__() shouldn't be emitting ftrace_likely_update() calls
> > for noinstr functions...
> >
> > I have no idea how a macro is meant to check for function attributes,
> > though... :(
>
> Ignore it. It's the branch tracer enabled (that is, every "if ()" is being
> traced).
>
> Although I still use the branch profiler, I do not believe anyone uses the
> branch tracer. The branch profiler updates an array of counters that tells
> when the branch was true or false, the branch tracer actually traces
> (records an event) for every branch in the system!
\o/
> I think I'll just send a patch to nuke the tracer. I'm sure Peter Zijlstra
> will be happy when I do that. But I still want the profiler, as I find that
> useful.
It'll explode the moment Lai's entry rework goes through. That'll make
us run C code before we switch to the kernel address space, so your
counters will not exist/be-mapped and *BOOM*.
next prev parent reply other threads:[~2022-04-05 12:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-04 12:22 vmlinux.o: warning: objtool: stackleak_erase()+0x35: call to ftrace_likely_update() leaves .noinstr.text section kernel test robot
2022-04-04 18:27 ` Kees Cook
2022-04-04 19:25 ` Steven Rostedt
2022-04-05 8:03 ` Peter Zijlstra [this message]
2022-04-05 13:38 ` Steven Rostedt
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