linux-kernel - Re: [PATCH] scs: add CONFIG_MMU dependency for vfree

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Date: Mon, 22 Jan 2024 11:21:04 -0800
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Samuel Holland <samuel.holland@...ive.com>
Cc: Will Deacon <will@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scs: add CONFIG_MMU dependency for vfree_atomic()

Hi Samuel,

On Mon, Jan 22, 2024 at 9:52 AM Samuel Holland
<samuel.holland@...ive.com> wrote:
>
> The shadow call stack implementation fails to build without CONFIG_MMU:
>
>   ld.lld: error: undefined symbol: vfree_atomic
>   >>> referenced by scs.c
>   >>>               kernel/scs.o:(scs_free) in archive vmlinux.a
>
> Fixes: a2abe7cbd8fe ("scs: switch to vmapped shadow stacks")
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
> ---
>
>  arch/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index c91917b50873..a5af0edd3eb8 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -673,6 +673,7 @@ config SHADOW_CALL_STACK
>         bool "Shadow Call Stack"
>         depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
>         depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
> +       depends on MMU
>         help
>           This option enables the compiler's Shadow Call Stack, which
>           uses a shadow stack to protect function return addresses from

Looks good to me. Thanks for the patch!

Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>

Sami