linux-kernel - [PATCH] bpfilter: document build requirements for bpfilter

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Date:   Sat, 09 May 2020 00:47:19 -0400
From:   "Valdis Klētnieks" <valdis.kletnieks@...edu>
To:     Masahiro Yamada <masahiroy@...nel.org>
cc:     Sam Ravnborg <sam@...nborg.org>,
        "David S. Miller" <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] bpfilter: document build requirements for bpfilter_umh

It's not intuitively obvious that bpfilter_umh is a statically linked binary.
Mention the toolchain requirement in the Kconfig help, so people
have an easier time figuring out what's needed.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@...edu>

diff --git a/net/bpfilter/Kconfig b/net/bpfilter/Kconfig
index fed9290e3b41..0ec6c7958c20 100644
--- a/net/bpfilter/Kconfig
+++ b/net/bpfilter/Kconfig
@@ -13,4 +13,8 @@ config BPFILTER_UMH
 	default m
 	help
 	  This builds bpfilter kernel module with embedded user mode helper
+
+	  Note: your toolchain must support building static binaries, since
+	  rootfs isn't mounted at the time when __init functions are called
+	  and do_execv won't be able to find the elf interpreter.
 endif