From: Steven Rostedt <rostedt@goodmis.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Sami Tolvanen <samitolvanen@google.com>,
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, 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 09:02:49 -0400 [thread overview]
Message-ID: <20211006090249.248c65b0@gandalf.local.home> (raw)
In-Reply-To: <20211006032945.axlqh3vehgar6adr@treble>
On Tue, 5 Oct 2021 20:29:45 -0700
Josh Poimboeuf <jpoimboe@redhat.com> wrote:
Thanks for Cc'ing me, as I should have been Cc'd on the original patch.
> 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.
> >
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > ---
> > include/linux/ftrace.h | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 832e65f06754..67de28464aeb 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -578,9 +578,10 @@ extern void ftrace_replace_code(int enable);
> > extern int ftrace_update_ftrace_func(ftrace_func_t func);
> > extern void ftrace_caller(void);
> > extern void ftrace_regs_caller(void);
> > -extern void ftrace_call(void);
> > -extern void ftrace_regs_call(void);
> > -extern void mcount_call(void);
> > +
> > +DECLARE_ASM_FUNC_SYMBOL(ftrace_call);
> > +DECLARE_ASM_FUNC_SYMBOL(ftrace_regs_call);
> > +DECLARE_ASM_FUNC_SYMBOL(mcount_call);
>
> I'm thinking DECLARE_ASM_FUNC_SYMBOL needs a better name. It's not clear
> from reading it why some asm symbols need the macro and others don't.
>
> I guess it means "an asm text symbol which isn't callable from C code
> (not including alternatives)"?
>
> DECLARE_UNCALLED_SYMBOL() maybe?
>
That's even worse ;-) Because "called" is an assembler command in x86, and
it is "called" from assembly (when you look at an objdump, it is most
definitely "called").
Perhaps DECLARE_ASM_INTERNAL_SYMBOL() ?
Or call it "DECLARE_ASM_MCOUNT_SYMBOL()" as "mcount" is the original name
of what a compiler does when passed the -pg option, and that's exactly what
those functions are.
-- Steve
next prev parent reply other threads:[~2021-10-06 13:02 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 [this message]
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
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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