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Subject: Re: [PATCH v3 3/3] um: allow static linking for non-glibc
 implementations
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Ignat Korchagin <ignat@cloudflare.com>, jdike@addtoit.com,
        richard@nod.at, anton.ivanov@cambridgegreys.com,
        brendanhiggins@google.com, masahiroy@kernel.org,
        linux-um@lists.infradead.org, linux-kernel@vger.kernel.org
Cc:     kernel-team@cloudflare.com
Date:   Thu, 16 Jul 2020 11:10:19 +0200
In-Reply-To: <20200715201159.54166-4-ignat@cloudflare.com>
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         <20200715201159.54166-4-ignat@cloudflare.com>
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On Wed, 2020-07-15 at 21:11 +0100, Ignat Korchagin wrote:
> It is possible to produce a statically linked UML binary with UML_NET_VECTOR,
> UML_NET_VDE and UML_NET_PCAP options enabled using alternative libc
> implementations, which do not rely on NSS, such as musl.
> 
> Allow static linking in this case.
> 
> Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
> Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
> Tested-by: Brendan Higgins <brendanhiggins@google.com>
> ---
>  arch/um/Kconfig         | 5 +----
>  arch/um/drivers/Kconfig | 3 ---
>  2 files changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/arch/um/Kconfig b/arch/um/Kconfig
> index 9318dc6d1a0c..beb98b3b9f75 100644
> --- a/arch/um/Kconfig
> +++ b/arch/um/Kconfig
> @@ -62,12 +62,9 @@ config NR_CPUS
>  
>  source "arch/$(HEADER_ARCH)/um/Kconfig"
>  
> -config FORBID_STATIC_LINK
> -	bool
> -
>  config STATIC_LINK
>  	bool "Force a static link"
> -	depends on !FORBID_STATIC_LINK
> +	depends on CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS || (!UML_NET_VECTOR && !UML_NET_VDE && !UML_NET_PCAP)

Come to think of it, in a way "FORBID_STATIC_LINK" was nicer because
there didn't need to be a single list of "what has dynamic dependencies"
like here the list of UML_NET_VECTOR, UML_NET_VDE, UML_NET_PCAP.

Maybe it could be

config MAY_HAVE_NON_STATIC_RUNTIME_DEPS
	bool

config STATIC_LINK
	...
	depends on !MAY_HAVE_NON_STATIC_RUNTIME_DEPS || CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS


and then UML_NET_VECTOR et al can

	select MAY_HAVE_NON_STATIC_RUNTIME_DEPS

so that the knowledge is still distributed to the corresponding options?

johannes