On Wed, Jul 01, 2020 at 06:26:44PM +0900, Masahiro Yamada wrote:
> 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 <mkubecek@xxxxxxx>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Tested-by: Michal Kubecek <mkubecek@xxxxxxx>
Thank you,
Michal
> ---
>
> 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
>
> --
> 2.25.1
>
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