From: Masahiro Yamada <masahiroy@kernel.org>
Date: Sat, 9 May 2020 16:39:15 +0900
Subject: bpfilter: check if $(CC) can link static libc in Kconfig
Patch-mainline: v5.8-rc1
Git-commit: b1183b6dca3e0d59ce8fa81767def6ea6188e8ec
References: bsc#1177028

On Fedora, linking static glibc requires the glibc-static RPM package,
which is not part of the glibc-devel package.

CONFIG_CC_CAN_LINK does not check the capability of static linking,
so you can enable CONFIG_BPFILTER_UMH, then fail to build:

    HOSTLD  net/bpfilter/bpfilter_umh
  /usr/bin/ld: cannot find -lc
  collect2: error: ld returned 1 exit status

Add CONFIG_CC_CAN_LINK_STATIC, and make CONFIG_BPFILTER_UMH depend
on it.

Reported-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Gary Lin <glin@suse.com>
---
 init/Kconfig         |    5 +++++
 net/bpfilter/Kconfig |    2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

--- a/init/Kconfig
+++ b/init/Kconfig
@@ -27,6 +27,11 @@ config CLANG_VERSION
 config CC_CAN_LINK
 	def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
 
+config CC_CAN_LINK_STATIC
+	bool
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m64-flag)) if 64BIT
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m32-flag))
+
 config CC_HAS_ASM_GOTO
 	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
 
--- a/net/bpfilter/Kconfig
+++ b/net/bpfilter/Kconfig
@@ -9,7 +9,7 @@ menuconfig BPFILTER
 if BPFILTER
 config BPFILTER_UMH
 	tristate "bpfilter kernel module with user mode helper"
-	depends on CC_CAN_LINK
+	depends on CC_CAN_LINK_STATIC
 	default m
 	help
 	  This builds bpfilter kernel module with embedded user mode helper