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From: Nick Desaulniers <ndesaulniers@google.com>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: x86@kernel.org, Kees Cook <keescook@chromium.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
	clang-built-linux@googlegroups.com
Subject: Re: [PATCH v3 14/16] x86, cpu: Use LTO for cpu.c with CFI
Date: Tue, 14 Sep 2021 12:46:08 -0700	[thread overview]
Message-ID: <CAKwvOdm1dy7RiSfP1Ra1ek08OQ=8o8FDnrMdW44e6ZssgPbCAw@mail.gmail.com> (raw)
In-Reply-To: <20210914191045.2234020-15-samitolvanen@google.com>

On Tue, Sep 14, 2021 at 12:11 PM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> Allow LTO to be used for cpu.c when CONFIG_CFI_CLANG is enabled to avoid
> indirect call failures. CFI requires Clang >= 13, which doesn't have the
> stack protector inlining bug.

True, that was fixed in clang-12. I hope to one day use
__attribute__((no_stack_protector)) to clean up this chem spill.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Technically, GCC still has this bug.

>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
>  arch/x86/power/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/power/Makefile b/arch/x86/power/Makefile
> index 379777572bc9..a0532851fed7 100644
> --- a/arch/x86/power/Makefile
> +++ b/arch/x86/power/Makefile
> @@ -4,9 +4,11 @@
>  # itself be stack-protected
>  CFLAGS_cpu.o   := -fno-stack-protector
>
> +ifndef CONFIG_CFI_CLANG
>  # Clang may incorrectly inline functions with stack protector enabled into
>  # __restore_processor_state(): https://bugs.llvm.org/show_bug.cgi?id=47479
>  CFLAGS_REMOVE_cpu.o := $(CC_FLAGS_LTO)
> +endif
>
>  obj-$(CONFIG_PM_SLEEP)         += cpu.o
>  obj-$(CONFIG_HIBERNATION)      += hibernate_$(BITS).o hibernate_asm_$(BITS).o hibernate.o
> --
> 2.33.0.309.g3052b89438-goog
>


-- 
Thanks,
~Nick Desaulniers

  parent reply	other threads:[~2021-09-14 19:46 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14 19:10 [PATCH v3 00/16] x86: Add support for Clang CFI Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 01/16] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-09-14 19:29   ` Nick Desaulniers
2021-09-14 21:01     ` Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 02/16] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 03/16] linkage: Add DECLARE_ASM_FUNC_SYMBOL Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 04/16] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB Sami Tolvanen
2021-09-14 19:36   ` Nick Desaulniers
2021-09-14 20:32     ` Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 05/16] tracepoint: Exclude tp_stub_func from CFI checking Sami Tolvanen
2021-09-14 19:39   ` Nick Desaulniers
2021-09-14 19:10 ` [PATCH v3 06/16] ftrace: Use an opaque type for functions not callable from C Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 07/16] lkdtm: Disable UNSET_SMEP with CFI Sami Tolvanen
2021-09-14 19:30   ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 08/16] lkdtm: Use an opaque type for lkdtm_rodata_do_nothing Sami Tolvanen
2021-09-14 19:32   ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 09/16] x86: Use an opaque type for functions not callable from C Sami Tolvanen
2021-09-14 19:33   ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 10/16] x86/extable: Mark handlers __cficanonical Sami Tolvanen
2021-09-14 19:37   ` Kees Cook
2021-09-14 20:38     ` Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 11/16] x86/purgatory: Disable CFI Sami Tolvanen
2021-09-14 20:02   ` Nick Desaulniers
2021-09-14 20:30     ` Sami Tolvanen
2021-09-14 22:31       ` Nick Desaulniers
2021-09-15  6:24         ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 12/16] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 13/16] x86, module: " Sami Tolvanen
2021-09-14 19:10 ` [PATCH v3 14/16] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-09-14 19:44   ` Kees Cook
2021-09-14 19:46   ` Nick Desaulniers [this message]
2021-09-14 19:10 ` [PATCH v3 15/16] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-09-14 19:40   ` Kees Cook
2021-09-14 19:10 ` [PATCH v3 16/16] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen

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