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From: Andy Lutomirski <luto@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	David Laight <David.Laight@aculab.com>,
	Borislav Petkov <bp@alien8.de>,
	Sami Tolvanen <samitolvanen@google.com>, X86 ML <x86@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	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>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH 05/15] x86: Implement function_nocfi
Date: Sun, 18 Apr 2021 15:57:19 -0700	[thread overview]
Message-ID: <CALCETrXRHhEivNK0hqEdRz+gN8c9jhdsjJC=4EQKMWB1roYw3A@mail.gmail.com> (raw)
In-Reply-To: <871rb7sh31.ffs@nanos.tec.linutronix.de>

On Sun, Apr 18, 2021 at 9:17 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Sat, Apr 17 2021 at 17:11, Andy Lutomirski wrote:
> > On Sat, Apr 17, 2021 at 4:53 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >> which works for
> >>
> >>       foo = function_nocfi(bar);
> >
> > I agree in general.  But right now, we have, in asm/proto.h:
> >
> > void entry_SYSCALL_64(void);
> >
> > and that's pure nonsense.  Depending on your point of view,
> > entry_SYSCALL_64 is a symbol that resolves to an integer or it's an
> > array of bytes containing instructions, but it is most definitely not
> > a function void (void).  So, regardless of any CFI stuff, I propose
> > that we standardize our handling of prototypes of symbols that are
> > opaque to the C compiler.  Here are a couple of choices:
> >
> > Easy one:
> >
> > extern u8 entry_SYSCALL_64[];
> >
> > Slightly more complicated:
> >
> > struct opaque_symbol;
> > extern struct opaque_symbol entry_SYSCALL_64;
> >
> > The opaque_symbol variant avoids any possible confusion over the weird
> > status of arrays in C, and it's hard to misuse, since struct
> > opaque_symbol is an incomplete type.
>
> Makes sense.

Sami, do you want to do this as part of your series or should I write a patch?

  reply	other threads:[~2021-04-18 22:57 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 20:38 [PATCH 00/15] x86: Add support for Clang CFI Sami Tolvanen
2021-04-16 20:38 ` [PATCH 01/15] objtool: Find a destination for jumps beyond the section end Sami Tolvanen
2021-04-20 18:14   ` Josh Poimboeuf
2021-04-20 20:25     ` Sami Tolvanen
2021-04-20 22:55       ` Josh Poimboeuf
2021-04-20 22:58         ` Nick Desaulniers
2021-04-16 20:38 ` [PATCH 02/15] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-04-20 19:47   ` Josh Poimboeuf
2021-04-20 20:45     ` Sami Tolvanen
2021-04-16 20:38 ` [PATCH 03/15] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-04-16 20:38 ` [PATCH 04/15] static_call: Use global functions for the self-test Sami Tolvanen
2021-04-16 21:37   ` Thomas Gleixner
2021-04-17  0:16     ` Thomas Gleixner
2021-04-16 20:38 ` [PATCH 05/15] x86: Implement function_nocfi Sami Tolvanen
2021-04-16 21:18   ` Borislav Petkov
2021-04-16 21:49     ` Sami Tolvanen
2021-04-16 22:02       ` Borislav Petkov
2021-04-16 22:06         ` Andy Lutomirski
2021-04-16 22:14           ` Borislav Petkov
2021-04-16 22:20             ` Andy Lutomirski
2021-04-16 22:37               ` Kees Cook
2021-04-16 23:02                 ` Thomas Gleixner
2021-04-17 10:16                   ` Thomas Gleixner
2021-04-19 15:13                     ` Sami Tolvanen
2021-04-16 22:28           ` Kees Cook
2021-04-16 22:52             ` Andy Lutomirski
2021-04-16 22:58               ` Kees Cook
2021-04-16 23:40               ` Kees Cook
2021-04-17 23:19                 ` Andy Lutomirski
2021-04-17 23:53                   ` Thomas Gleixner
2021-04-18  0:11                     ` Andy Lutomirski
2021-04-18 16:17                       ` Thomas Gleixner
2021-04-18 22:57                         ` Andy Lutomirski [this message]
2021-04-19 15:20                           ` Sami Tolvanen
2021-04-19 15:26                       ` David Laight
2021-04-19 17:46                         ` Andy Lutomirski
2021-04-17 14:20             ` David Laight
2021-04-17 15:48               ` Andy Lutomirski
2021-04-19  8:40             ` Rasmus Villemoes
2021-04-19 16:45               ` Joao Moreira
2021-04-19 21:52               ` David Laight
2021-04-16 22:16         ` Kees Cook
2021-04-16 22:13       ` Thomas Gleixner
2021-04-16 20:38 ` [PATCH 06/15] x86: Avoid CFI jump tables in IDT and entry points Sami Tolvanen
2021-04-16 22:26   ` Thomas Gleixner
2021-04-16 23:56     ` Kees Cook
2021-04-17  0:02       ` Thomas Gleixner
2021-04-16 20:38 ` [PATCH 07/15] x86/ftrace: Use function_nocfi in MCOUNT_ADDR Sami Tolvanen
2021-04-16 20:38 ` [PATCH 08/15] x86/extable: Do not mark exception callback as CFI Sami Tolvanen
2021-04-16 20:38 ` [PATCH 09/15] x86/alternatives: Use C int3 selftest but disable KASAN Sami Tolvanen
2021-04-17 11:37   ` Peter Zijlstra
2021-04-19 15:26     ` Sami Tolvanen
2021-04-20  7:19       ` Peter Zijlstra
2021-04-16 20:38 ` [PATCH 10/15] x86/purgatory: Disable CFI Sami Tolvanen
2021-04-16 20:38 ` [PATCH 11/15] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-04-16 20:38 ` [PATCH 12/15] x86, module: " Sami Tolvanen
2021-04-16 20:38 ` [PATCH 13/15] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-04-16 20:38 ` [PATCH 14/15] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-04-16 20:38 ` [PATCH 15/15] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen

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