linux-kernel - Re: [PATCH] samples/ftrace: mark my

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Message-ID: <CABCJKudNGa2=65vATJMqo--8guvWHZ6-wMWHZQy-ZaH32dXdnA@mail.gmail.com>
Date:   Mon, 16 Nov 2020 12:10:10 -0800
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Colin Ian King <colin.king@...onical.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] samples/ftrace: mark my_tramp[12]? global

On Mon, Nov 16, 2020 at 8:39 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Fri, 13 Nov 2020 10:34:14 -0800
> Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> > my_tramp[12]? are declared as global functions in C, but they are not
> > marked global in the inline assembly definition. This mismatch confuses
> > Clang's Control-Flow Integrity checking. Fix the definitions by adding
> > .globl.
> >
>
> Actually, since that function is not really global, would it work if you
> removed the "extern" from the my_tramp declaration?

Unfortunately not, removing the "extern" doesn't seem to change anything.

> In other words, is there a way to tell C that a function is declared in an
> inline assembly block?

I'm not sure if there's a way to tell C that a static function is
declared in inline assembly. At least I couldn't find a way that would
make the compiler happy.

Sami