linux-kernel - Re: [RFC PATCH v3 13/13] objtool: arm64: Enable stack validation for arm64

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Date:   Thu, 7 Apr 2022 14:19:19 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Chen Zhongjin <chenzhongjin@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        jthierry@...hat.com, catalin.marinas@....com, will@...nel.org,
        mark.rutland@....com, ardb@...nel.org, masahiroy@...nel.org,
        jpoimboe@...hat.com, ycote@...hat.com
Subject: Re: [RFC PATCH v3 13/13] objtool: arm64: Enable stack validation for
 arm64

On Thu, Apr 07, 2022 at 08:01:41PM +0800, Chen Zhongjin wrote:
> From: Raphael Gault <raphael.gault@....com>
> 
> Add build option to run stack validation at compile time.
> 
> When requiring stack validation, jump tables are disabled as it
> simplifies objtool analysis (without having to introduce unreliable
> artifacs). In local testing, this does not appear to significaly
> affect final binary size nor system performance.
> 
> Signed-off-by: Raphael Gault <raphael.gault@....com>
> Signed-off-by: Julien Thierry <jthierry@...hat.com>
> ---
>  arch/arm64/Kconfig  | 1 +
>  arch/arm64/Makefile | 4 ++++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 23048be0333b..119cfce4117f 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -201,6 +201,7 @@ config ARM64
>  	select MMU_GATHER_RCU_TABLE_FREE
>  	select HAVE_RSEQ
>  	select HAVE_STACKPROTECTOR
> +	select HAVE_STACK_VALIDATION
>  	select HAVE_SYSCALL_TRACEPOINTS
>  	select HAVE_KPROBES
>  	select HAVE_KRETPROBES
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 2f1de88651e6..ad2f4a5e8f6c 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -133,6 +133,10 @@ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y)
>    CC_FLAGS_FTRACE := -fpatchable-function-entry=2
>  endif
>  
> +ifeq ($(CONFIG_STACK_VALIDATION),y)
> +KBUILD_CFLAGS	+= -fno-jump-tables
> +endif

IIRC this is a sore spot for the whole endeavour..