[PATCH] bpfilter: document build requirements for bpfilter_umh

[Valdis KlÄtnieks]

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@xxxxxx>

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