[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20230323144220.2729561c@gandalf.local.home>
Date: Thu, 23 Mar 2023 14:42:20 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org,
mhiramat@...nel.org, "Jose E. Marchesi" <jose.marchesi@...cle.com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] tracepoint: Fix CFI failures with tp_stub_func
On Thu, 23 Mar 2023 14:37:15 -0400
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> > Repeated again so Mathieu doesn't have to search for it.
> >
> > [ Note, this version does use undefined compiler behavior (assuming that
> > a stub function with no parameters or return, can be called by a location
> > that thinks it has parameters but still no return value. Static calls
> > do the same thing, so this trick is not without precedent.
> >
> > There's another solution that uses RCU tricks and is more complex, but
> > can be an alternative if this solution becomes an issue.
> >
> > Link: https://lore.kernel.org/lkml/20210127170721.58bce7cc@gandalf.local.home/
> > ]
>
> Ugh. The last thing we need there is more RCU complexity. My brain is still recovering
> from fixing the last time the introduction of static calls special-cases ended up subtly
> breaking tracepoints.
Well, we can go back to your approach with doing the check in the iterator.
Setting it to 0x1UL I think is what you wanted (to know it's a removed
function and not a random NULL).
I could write that up if you want.
-- Steve
Powered by blists - more mailing lists