linux-hardening - Re: [PATCH v4 06/15] ftrace: Use an opaque type for functions not callable from C

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Message-ID: <CABCJKudTuheEd5jyhXmfJHup7iYzOz3_OcO92hFnpRK1MapJSg@mail.gmail.com>
Date:   Wed, 6 Oct 2021 10:45:41 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, X86 ML <x86@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        linux-hardening@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, llvm@...ts.linux.dev
Subject: Re: [PATCH v4 06/15] ftrace: Use an opaque type for functions not
 callable from C

On Wed, Oct 6, 2021 at 9:58 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 6 Oct 2021 09:31:04 -0700
> Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> > > > On Thu, Sep 30, 2021 at 11:05:22AM -0700, Sami Tolvanen wrote:
> > > > > With CONFIG_CFI_CLANG, the compiler changes function references to point
> > > > > to the CFI jump table. As ftrace_call, ftrace_regs_call, and mcount_call
> > > > > are not called from C, use DECLARE_ASM_FUNC_SYMBOL to declare them.
> > >
> > > "not called from C" is a bit confusing.
> >
> > Any thoughts on how to make this less confusing?
>
>  "Not called by C code, but injected by the compiler."
>
> ?

Sure, sounds good to me. I'll update this in v5.

Sami