linux-kernel - Re: violating function pointer signature

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Message-ID: <874klmwxxm.fsf@mid.deneb.enyo.de>
Date:   Wed, 18 Nov 2020 15:18:29 +0100
From:   Florian Weimer <fw@...eb.enyo.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Matt Mullins <mmullins@...x.us>,
        Ingo Molnar <mingo@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        linux-toolchains@...r.kernel.org
Subject: Re: violating function pointer signature

* Peter Zijlstra:

>> The default Linux calling conventions are all of the cdecl family,
>> where the caller pops the argument off the stack.  You didn't quote
>> enough to context to tell whether other calling conventions matter in
>> your case.
>
> This is strictly in-kernel, and I think we're all cdecl, of which the
> important part is caller-cleanup. The function compiles to:
>
> 	RET
>
> so whatever the arguments are is irrelevant.

Yes, then the stub is ABI-compatible, as far as I know.