bpfilter: allow to build bpfilter_umh as a module without static library
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Message ID 20200701092644.762234-1-masahiroy@kernel.org
State New
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  • bpfilter: allow to build bpfilter_umh as a module without static library
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Commit Message

Masahiro Yamada July 1, 2020, 9:26 a.m. UTC
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@suse.cz>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 net/bpfilter/Kconfig  | 10 ++++++----
 net/bpfilter/Makefile |  2 ++
 2 files changed, 8 insertions(+), 4 deletions(-)

Comments

Michal Kubecek July 1, 2020, 12:57 p.m. UTC | #1
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@suse.cz>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Tested-by: Michal Kubecek <mkubecek@suse.cz>

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
>
Alexei Starovoitov July 1, 2020, 5:46 p.m. UTC | #2
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@suse.cz>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

lgtm
Do you mind I'll take it into bpf-next tree?
Eric is working on a bunch of patches in this area. I'll take his set
into bpf-next as well and then can apply this patch.
Just to make sure there are no conflicts.
Masahiro Yamada July 1, 2020, 5:50 p.m. UTC | #3
On Thu, Jul 2, 2020 at 2:46 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> 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@suse.cz>
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>
> lgtm
> Do you mind I'll take it into bpf-next tree?
> Eric is working on a bunch of patches in this area. I'll take his set
> into bpf-next as well and then can apply this patch.
> Just to make sure there are no conflicts.

Please go ahead.

Thank you.
Alexei Starovoitov July 14, 2020, 7:39 p.m. UTC | #4
On Wed, Jul 1, 2020 at 10:50 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Thu, Jul 2, 2020 at 2:46 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > 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@suse.cz>
> > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> >
> > lgtm
> > Do you mind I'll take it into bpf-next tree?
> > Eric is working on a bunch of patches in this area. I'll take his set
> > into bpf-next as well and then can apply this patch.
> > Just to make sure there are no conflicts.
>
> Please go ahead.

I've merged Eric's set and applied yours on top.
Thanks

Patch
diff mbox series

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