From 9326e0f85bfaf0578d40f5357f8143ec857469f5 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Wed, 1 Jul 2020 18:26:44 +0900 Subject: [PATCH] bpfilter: Allow to build bpfilter_umh as a module without static library Originally, bpfilter_umh was linked with -static only when CONFIG_BPFILTER_UMH=y. Commit 8a2cc0505cc4 ("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 b1183b6dca3e ("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: 8a2cc0505cc4 ("bpfilter: use 'userprogs' syntax to build bpfilter_umh") Reported-by: Michal Kubecek Signed-off-by: Masahiro Yamada Signed-off-by: Alexei Starovoitov Tested-by: Michal Kubecek Link: https://lore.kernel.org/bpf/20200701092644.762234-1-masahiroy@kernel.org --- net/bpfilter/Kconfig | 10 ++++++---- net/bpfilter/Makefile | 2 ++ 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/net/bpfilter/Kconfig b/net/bpfilter/Kconfig index 84015ef3ee27..73d0b12789f1 100644 --- a/net/bpfilter/Kconfig +++ b/net/bpfilter/Kconfig @@ -9,12 +9,14 @@ menuconfig BPFILTER if BPFILTER config BPFILTER_UMH tristate "bpfilter kernel module with user mode helper" - depends on CC_CAN_LINK_STATIC + depends on CC_CAN_LINK + depends on m || CC_CAN_LINK_STATIC 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. + Note: To compile this as built-in, 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 diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile index f23b53294fba..cdac82b8c53a 100644 --- a/net/bpfilter/Makefile +++ b/net/bpfilter/Makefile @@ -7,10 +7,12 @@ userprogs := bpfilter_umh bpfilter_umh-objs := main.o userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi +ifeq ($(CONFIG_BPFILTER_UMH), y) # builtin bpfilter_umh should be linked with -static # since rootfs isn't mounted at the time of __init # function is called and do_execv won't find elf interpreter userldflags += -static +endif $(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh