Originally, bpfilter_umh was linked with -static only when
CONFIG_BPFILTER_UMH=y.
Commit 8a2cc0505c ("bpfilter: use 'userprogs' syntax to build
bpfilter_umh") silently, accidentally dropped the CONFIG_BPFILTER_UMH=y
test in the Makefile. Revive it in order to link it dynamically when
CONFIG_BPFILTER_UMH=m.
Since commit b1183b6dca ("bpfilter: check if $(CC) can link static
libc in Kconfig"), the compiler must be capable of static linking to
enable CONFIG_BPFILTER_UMH, but it requires more than needed.
To loosen the compiler requirement, I changed the dependency as follows:
depends on CC_CAN_LINK
depends on m || CC_CAN_LINK_STATIC
If CONFIG_CC_CAN_LINK_STATIC in unset, CONFIG_BPFILTER_UMH is restricted
to 'm' or 'n'.
In theory, CONFIG_CC_CAN_LINK is not required for CONFIG_BPFILTER_UMH=y,
but I did not come up with a good way to describe it.
Fixes: 8a2cc0505c ("bpfilter: use 'userprogs' syntax to build bpfilter_umh")
Reported-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Michal Kubecek <mkubecek@suse.cz>
Link: https://lore.kernel.org/bpf/20200701092644.762234-1-masahiroy@kernel.org
9326e0f85b