From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnd Bergmann <arnd@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jason Baron <jbaron@akamai.com>, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Ard Biesheuvel <ardb@kernel.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] static_call: fix function type mismatch
Date: Tue, 23 Mar 2021 08:47:50 +0100 [thread overview]
Message-ID: <YFmdJlESrCh4iC9A@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210322172921.56350a69@gandalf.local.home>
On Mon, Mar 22, 2021 at 05:29:21PM -0400, Steven Rostedt wrote:
> On Mon, 22 Mar 2021 22:18:17 +0100
> Arnd Bergmann <arnd@kernel.org> wrote:
>
> > I think the code works correctly on all architectures we support because
> > both 'int' and 'long' are returned in a register with any unused bits cleared.
> > It is however undefined behavior in C because 'int' and 'long' are not
> > compatible types, and the calling conventions don't have to allow this.
>
> Static calls (and so do tracepoints) currently rely on these kind of
> "undefined behavior" in C. This isn't the only UB that it relies on.
Right, most of the kernel lives in UB. That's what we have -fwrapv
-fno-strict-aliassing and lots of other bits for, to 'fix' the stupid C
standard.
This is one more of them, so just ignore the warning and make it go
away:
-Wno-cast-function-type
seems to be the magic knob.
next prev parent reply other threads:[~2021-03-23 7:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 17:06 [PATCH] static_call: fix function type mismatch Arnd Bergmann
2021-03-22 19:32 ` Steven Rostedt
2021-03-22 20:47 ` Peter Zijlstra
2021-03-22 21:18 ` Arnd Bergmann
2021-03-22 21:29 ` Steven Rostedt
2021-03-23 7:47 ` Peter Zijlstra [this message]
2021-03-24 12:46 ` Rasmus Villemoes
2021-03-24 16:01 ` Sami Tolvanen
2021-03-24 16:45 ` Rasmus Villemoes
2021-03-24 17:33 ` Peter Zijlstra
2021-03-24 19:16 ` Peter Zijlstra
2021-03-24 21:51 ` Rasmus Villemoes
2021-03-24 22:34 ` Sami Tolvanen
2021-03-24 22:53 ` Rasmus Villemoes
2021-03-24 23:40 ` Sami Tolvanen
2021-03-25 0:42 ` Rasmus Villemoes
2021-03-25 7:42 ` Peter Zijlstra
2021-03-25 7:45 ` Ard Biesheuvel
2021-03-25 8:27 ` Rasmus Villemoes
2021-03-23 7:35 ` Peter Zijlstra
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