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@vt.edu>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

diff --git a/net/bpfilter/Kconfig b/net/bpfilter/Kconfig
index 045144d..84015ef 100644 (file)
--- 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