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From: Sami Tolvanen <samitolvanen@google.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, X86 ML <x86@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	linux-hardening@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	llvm@lists.linux.dev
Subject: Re: [PATCH v4 06/15] ftrace: Use an opaque type for functions not callable from C
Date: Wed, 6 Oct 2021 16:14:17 -0700	[thread overview]
Message-ID: <CABCJKufCaOXOUF43a-PQshO8aEsMNhZ2EiyGMSOp9ZGn57G=pg@mail.gmail.com> (raw)
In-Reply-To: <20211006212355.mfuyci3pnsdlbp3w@treble>

On Wed, Oct 6, 2021 at 2:24 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Wed, Oct 06, 2021 at 05:10:16PM -0400, Steven Rostedt wrote:
> > On Wed, 6 Oct 2021 13:43:35 -0700
> > Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > > On Wed, Oct 06, 2021 at 10:45:41AM -0700, Sami Tolvanen wrote:
> > > > On Wed, Oct 6, 2021 at 9:58 AM Steven Rostedt <rostedt@goodmis.org> wrote:
> > > > >
> > > > > On Wed, 6 Oct 2021 09:31:04 -0700
> > > > > Sami Tolvanen <samitolvanen@google.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.
> > >
> > > "injected by the compiler" sounds even more confusing.  It almost sounds
> > > like those functions are generated by GCC, which they are most
> > > definitely not.
> > >
> >
> > Heh, I was thinking of the locations that are injected (mcount / fentry) as
> > these are just replacements for them. Those injections are added by GCC.
> >
> > So, continuing the bikeshedding, what about "not called by C code, but are
> > trampolines injected as calls replacing the nops at the start of
> > functions added by the compiler." ?
>
> I'm not quite sure what that means, but I'll allow it ;-)

Alright, I'll go with the updated version then. I'll also rename
DECLARE_ASM_FUNC_SYMBOL() to DECLARE_NOT_CALLED_FROM_C() unless
someone has strong objections about that.

Sami

  reply	other threads:[~2021-10-06 23:14 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-30 18:05 [PATCH v4 00/15] x86: Add support for Clang CFI Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 01/15] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-09-30 18:40   ` Nick Desaulniers
2021-10-06  3:36   ` Josh Poimboeuf
2021-10-06 16:18     ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 02/15] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-10-06  3:37   ` Josh Poimboeuf
2021-09-30 18:05 ` [PATCH v4 03/15] linkage: Add DECLARE_ASM_FUNC_SYMBOL Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB Sami Tolvanen
2021-09-30 18:50   ` Nick Desaulniers
2021-10-01 20:07     ` Sami Tolvanen
2021-10-04 13:50   ` Peter Zijlstra
2021-10-04 19:10     ` Sami Tolvanen
2021-10-05  6:59       ` Peter Zijlstra
2021-10-05 20:29         ` Sami Tolvanen
2021-10-05 20:56           ` Peter Zijlstra
2021-10-05 21:53             ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 05/15] tracepoint: Exclude tp_stub_func from CFI checking Sami Tolvanen
2021-09-30 18:50   ` Nick Desaulniers
2021-10-01 20:08     ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 06/15] ftrace: Use an opaque type for functions not callable from C Sami Tolvanen
2021-10-06  3:29   ` Josh Poimboeuf
2021-10-06 13:02     ` Steven Rostedt
2021-10-06 13:54       ` Josh Poimboeuf
2021-10-06 14:16         ` Steven Rostedt
2021-10-06 16:31       ` Sami Tolvanen
2021-10-06 16:58         ` Steven Rostedt
2021-10-06 17:45           ` Sami Tolvanen
2021-10-06 20:43             ` Josh Poimboeuf
2021-10-06 21:10               ` Steven Rostedt
2021-10-06 21:23                 ` Josh Poimboeuf
2021-10-06 23:14                   ` Sami Tolvanen [this message]
2021-10-07  0:56                     ` Steven Rostedt
2021-09-30 18:05 ` [PATCH v4 07/15] lkdtm: Disable UNSET_SMEP with CFI Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 08/15] lkdtm: Use an opaque type for lkdtm_rodata_do_nothing Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 09/15] x86: Use an opaque type for functions not callable from C Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 10/15] x86/purgatory: Disable CFI Sami Tolvanen
2021-09-30 19:05   ` Nick Desaulniers
2021-09-30 18:05 ` [PATCH v4 11/15] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-10-06  3:31   ` Josh Poimboeuf
2021-10-06 16:17     ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 12/15] x86, module: " Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 13/15] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 14/15] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 15/15] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
2021-09-30 18:38 ` [PATCH v4 00/15] x86: Add support for Clang CFI Nick Desaulniers
2021-10-05 20:36 ` Josh Poimboeuf
2021-10-05 21:52   ` Sami Tolvanen
2021-10-06  2:42     ` Josh Poimboeuf

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