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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Sami Tolvanen <samitolvanen@google.com>, 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 14:23:55 -0700	[thread overview]
Message-ID: <20211006212355.mfuyci3pnsdlbp3w@treble> (raw)
In-Reply-To: <20211006171016.07d90b59@gandalf.local.home>

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 ;-)

-- 
Josh


  reply	other threads:[~2021-10-06 21:24 UTC|newest]

Thread overview: 74+ 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 ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 01/15] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-09-30 18:05   ` Sami Tolvanen
2021-09-30 18:40   ` Nick Desaulniers
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
2021-09-30 18:05   ` 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   ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB Sami Tolvanen
2021-09-30 18:05   ` Sami Tolvanen
2021-09-30 18:50   ` Nick Desaulniers
2021-09-30 18:50     ` Nick Desaulniers
2021-10-01 20:07     ` Sami Tolvanen
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 18:05   ` Sami Tolvanen
2021-09-30 18:50   ` Nick Desaulniers
2021-09-30 18:50     ` Nick Desaulniers
2021-10-01 20:08     ` Sami Tolvanen
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
2021-09-30 18:05   ` 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 [this message]
2021-10-06 23:14                   ` Sami Tolvanen
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   ` 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   ` 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   ` Sami Tolvanen
2021-09-30 18:05 ` [PATCH v4 10/15] x86/purgatory: Disable CFI Sami Tolvanen
2021-09-30 18:05   ` Sami Tolvanen
2021-09-30 19:05   ` Nick Desaulniers
2021-09-30 19:05     ` Nick Desaulniers
2021-09-30 18:05 ` [PATCH v4 11/15] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-09-30 18:05   ` 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   ` 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   ` 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   ` 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 18:05   ` Sami Tolvanen
2021-09-30 18:38 ` [PATCH v4 00/15] x86: Add support for Clang CFI Nick Desaulniers
2021-09-30 18:38   ` Nick Desaulniers
2021-10-01 20:55   ` Sedat Dilek
2021-10-01 20:55     ` Sedat Dilek
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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