linux-kernel - Re: [PATCH v3 01/60] arm64: kernel: Disable latent

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Date:   Fri, 28 Apr 2023 11:37:49 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Ryan Roberts <ryan.roberts@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v3 01/60] arm64: kernel: Disable latent_entropy GCC
 plugin in early C runtime

On Tue, Mar 07, 2023 at 03:04:23PM +0100, Ard Biesheuvel wrote:
> Avoid build issues in the early C code related to the latent_entropy GCC
> plugin, by incorporating the C flags fragment that disables it.
> 
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>

Just to check, are you seeing issues today? IIUC the plugin only instruments
functions which are explicitly marked with __latent_entropy, and if we're
seeing that happen unexpectedly (or due to that being applying to __meminit /
__init), we might need to do likewise for other noinstr code.

Regardless, for this patch:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/pi/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/kernel/pi/Makefile b/arch/arm64/kernel/pi/Makefile
> index 4c0ea3cd4ea406b6..c844a0546d7f0e62 100644
> --- a/arch/arm64/kernel/pi/Makefile
> +++ b/arch/arm64/kernel/pi/Makefile
> @@ -3,6 +3,7 @@
>  
>  KBUILD_CFLAGS	:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \
>  		   -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \
> +		   $(DISABLE_LATENT_ENTROPY_PLUGIN) \
>  		   $(call cc-option,-mbranch-protection=none) \
>  		   -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
>  		   -include $(srctree)/include/linux/hidden.h \
> -- 
> 2.39.2
> 
>