From: Mark Rutland <mark.rutland@arm.com>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Masahiro Yamada <masahiroy@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH 3/3] arm64: Drop the inline assembly implementation of function_nocfi
Date: Tue, 5 Apr 2022 17:23:13 +0100 [thread overview]
Message-ID: <Ykxs8YmNBtst8DM5@FVFF77S0Q05N> (raw)
In-Reply-To: <20220401201916.1487500-4-samitolvanen@google.com>
On Fri, Apr 01, 2022 at 01:19:16PM -0700, Sami Tolvanen wrote:
> Drop the inline assembly version of function_nocfi() now that
> CONFIG_CFI_CLANG depends on __builtin_function_start(), which allows
> this macro to be implemented more cleanly and in a way that works also
> with static initializers.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
> arch/arm64/include/asm/compiler.h | 16 ----------------
> 1 file changed, 16 deletions(-)
It's very nice to see the asm go here!
I grabbed the LLVM 14.0.0 binary release from llvm.org and gave this a spin. I
tested with ThinLTO and CFI_CLANG, and verified that CPU hotplug and ftrace
worked as expected (given those rely on function_nocfi()), and that the LKDTM
CFI_FORWARD_PROTO caught the mismatched prototype as expected.
FWIW:
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
As noted on patch 2 I think we should squash the series together, but those
tags apply either way.
Thanks,
Mark.
>
> diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h
> index dc3ea4080e2e..6fb2e6bcc392 100644
> --- a/arch/arm64/include/asm/compiler.h
> +++ b/arch/arm64/include/asm/compiler.h
> @@ -23,20 +23,4 @@
> #define __builtin_return_address(val) \
> (void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val)))
>
> -#ifdef CONFIG_CFI_CLANG
> -/*
> - * With CONFIG_CFI_CLANG, the compiler replaces function address
> - * references with the address of the function's CFI jump table
> - * entry. The function_nocfi macro always returns the address of the
> - * actual function instead.
> - */
> -#define function_nocfi(x) ({ \
> - void *addr; \
> - asm("adrp %0, " __stringify(x) "\n\t" \
> - "add %0, %0, :lo12:" __stringify(x) \
> - : "=r" (addr)); \
> - addr; \
> -})
> -#endif
> -
> #endif /* __ASM_COMPILER_H */
> --
> 2.35.0
>
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next prev parent reply other threads:[~2022-04-05 16:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-01 20:19 [PATCH 0/3] cfi: Use __builtin_function_start Sami Tolvanen
2022-04-01 20:19 ` [PATCH 1/3] kbuild: Change CFI_CLANG to depend on __builtin_function_start Sami Tolvanen
2022-04-02 13:31 ` Masahiro Yamada
2022-04-04 19:40 ` Sami Tolvanen
2022-04-04 22:52 ` Nathan Chancellor
2022-04-05 2:53 ` Kees Cook
2022-04-01 20:19 ` [PATCH 2/3] linux/compiler-clang.h: define function_nocfi Sami Tolvanen
2022-04-05 16:16 ` Mark Rutland
2022-04-01 20:19 ` [PATCH 3/3] arm64: Drop the inline assembly implementation of function_nocfi Sami Tolvanen
2022-04-04 9:03 ` Will Deacon
2022-04-05 16:23 ` Mark Rutland [this message]
2022-04-01 20:49 ` [PATCH 0/3] cfi: Use __builtin_function_start Nick Desaulniers
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