[PATCH v2 0/3] net: bpfilter: clean-up build rules

[PATCH v2 0/3] net: bpfilter: clean-up build rules

[Masahiro Yamada]

Clean-up from Kbuild/Kconfig point of view.

I confirmed this series can apply and compile
based on today's Linus tree.
(commit 2837461dbe6f)



Masahiro Yamada (3):
  bpfilter: add bpfilter_umh to .gitignore
  bpfilter: include bpfilter_umh in assembly instead of using objcopy
  bpfilter: check compiler capability in Kconfig

 Makefile                         |  5 -----
 net/Makefile                     |  4 ----
 net/bpfilter/.gitignore          |  1 +
 net/bpfilter/Kconfig             |  2 +-
 net/bpfilter/Makefile            | 15 ++-------------
 net/bpfilter/bpfilter_kern.c     | 11 +++++------
 net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
 scripts/cc-can-link.sh           |  2 +-
 8 files changed, 17 insertions(+), 30 deletions(-)
 create mode 100644 net/bpfilter/.gitignore
 create mode 100644 net/bpfilter/bpfilter_umh_blob.S

-- 
2.7.4

[PATCH v2 1/3] bpfilter: add bpfilter_umh to .gitignore

[Masahiro Yamada]

bpfilter_umh is a generated file.  It should be ignored by git.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v2: None

 net/bpfilter/.gitignore | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 net/bpfilter/.gitignore

diff --git a/net/bpfilter/.gitignore b/net/bpfilter/.gitignore
new file mode 100644
index 0000000..e97084e
--- /dev/null
+++ b/net/bpfilter/.gitignore
@@ -0,0 +1 @@
+bpfilter_umh
-- 
2.7.4

[PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy

[Masahiro Yamada]

What we want here is to embed a user-space program into the kernel.
Instead of the complex ELF magic, let's simply wrap it in the assembly
with the '.incbin' directive.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v2:
  - Rebase

 net/bpfilter/Makefile            | 15 ++-------------
 net/bpfilter/bpfilter_kern.c     | 11 +++++------
 net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
 3 files changed, 14 insertions(+), 19 deletions(-)
 create mode 100644 net/bpfilter/bpfilter_umh_blob.S

diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
index e0bbe75..39c6980 100644
--- a/net/bpfilter/Makefile
+++ b/net/bpfilter/Makefile
@@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y)
 HOSTLDFLAGS += -static
 endif
 
-# a bit of elf magic to convert bpfilter_umh binary into a binary blob
-# inside bpfilter_umh.o elf file referenced by
-# _binary_net_bpfilter_bpfilter_umh_start symbol
-# which bpfilter_kern.c passes further into umh blob loader at run-time
-quiet_cmd_copy_umh = GEN $@
-      cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \
-      $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \
-      -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \
-      --rename-section .data=.init.rodata $< $@
-
-$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh
-	$(call cmd,copy_umh)
+$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
 
 obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o
-bpfilter-objs += bpfilter_kern.o bpfilter_umh.o
+bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o
diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 0952257..6de3ae5 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -10,11 +10,8 @@
 #include <linux/file.h>
 #include "msgfmt.h"
 
-#define UMH_start _binary_net_bpfilter_bpfilter_umh_start
-#define UMH_end _binary_net_bpfilter_bpfilter_umh_end
-
-extern char UMH_start;
-extern char UMH_end;
+extern char bpfilter_umh_start;
+extern char bpfilter_umh_end;
 
 static struct umh_info info;
 /* since ip_getsockopt() can run in parallel, serialize access to umh */
@@ -93,7 +90,9 @@ static int __init load_umh(void)
 	int err;
 
 	/* fork usermode process */
-	err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info);
+	err = fork_usermode_blob(&bpfilter_umh_end,
+				 &bpfilter_umh_end - &bpfilter_umh_start,
+				 &info);
 	if (err)
 		return err;
 	pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
new file mode 100644
index 0000000..40311d1
--- /dev/null
+++ b/net/bpfilter/bpfilter_umh_blob.S
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+	.section .init.rodata, "a"
+	.global bpfilter_umh_start
+bpfilter_umh_start:
+	.incbin "net/bpfilter/bpfilter_umh"
+	.global bpfilter_umh_end
+bpfilter_umh_end:
-- 
2.7.4

[PATCH v2 3/3] bpfilter: check compiler capability in Kconfig

[Masahiro Yamada]

With the brand-new syntax extension of Kconfig, we can directly
check the compiler capability in the configuration phase.

If the cc-can-link.sh fails, the BPFILTER_UMH is automatically
hidden by the dependency.

I deleted 'default n', which is no-op.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v2:
  - newly added

 Makefile               | 5 -----
 net/Makefile           | 4 ----
 net/bpfilter/Kconfig   | 2 +-
 scripts/cc-can-link.sh | 2 +-
 4 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/Makefile b/Makefile
index 8a26b59..9ada673 100644
--- a/Makefile
+++ b/Makefile
@@ -507,11 +507,6 @@ ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLA
   KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO
 endif
 
-ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/cc-can-link.sh $(CC)), y)
-  CC_CAN_LINK := y
-  export CC_CAN_LINK
-endif
-
 # The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
 # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
 # CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
diff --git a/net/Makefile b/net/Makefile
index 13ec0d5..bdaf539 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -20,11 +20,7 @@ obj-$(CONFIG_TLS)		+= tls/
 obj-$(CONFIG_XFRM)		+= xfrm/
 obj-$(CONFIG_UNIX)		+= unix/
 obj-$(CONFIG_NET)		+= ipv6/
-ifneq ($(CC_CAN_LINK),y)
-$(warning CC cannot link executables. Skipping bpfilter.)
-else
 obj-$(CONFIG_BPFILTER)		+= bpfilter/
-endif
 obj-$(CONFIG_PACKET)		+= packet/
 obj-$(CONFIG_NET_KEY)		+= key/
 obj-$(CONFIG_BRIDGE)		+= bridge/
diff --git a/net/bpfilter/Kconfig b/net/bpfilter/Kconfig
index a948b07..76deb66 100644
--- a/net/bpfilter/Kconfig
+++ b/net/bpfilter/Kconfig
@@ -1,6 +1,5 @@
 menuconfig BPFILTER
 	bool "BPF based packet filtering framework (BPFILTER)"
-	default n
 	depends on NET && BPF && INET
 	help
 	  This builds experimental bpfilter framework that is aiming to
@@ -9,6 +8,7 @@ menuconfig BPFILTER
 if BPFILTER
 config BPFILTER_UMH
 	tristate "bpfilter kernel module with user mode helper"
+	depends on $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
 	default m
 	help
 	  This builds bpfilter kernel module with embedded user mode helper
diff --git a/scripts/cc-can-link.sh b/scripts/cc-can-link.sh
index 208eb28..6efcead 100755
--- a/scripts/cc-can-link.sh
+++ b/scripts/cc-can-link.sh
@@ -1,7 +1,7 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 
-cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1 && echo "y"
+cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1
 #include <stdio.h>
 int main(void)
 {
-- 
2.7.4

Re: [PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy

[Alexei Starovoitov]

On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote:
> What we want here is to embed a user-space program into the kernel.
> Instead of the complex ELF magic, let's simply wrap it in the assembly
> with the '.incbin' directive.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
> Changes in v2:
>   - Rebase
> 
>  net/bpfilter/Makefile            | 15 ++-------------
>  net/bpfilter/bpfilter_kern.c     | 11 +++++------
>  net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
>  3 files changed, 14 insertions(+), 19 deletions(-)
>  create mode 100644 net/bpfilter/bpfilter_umh_blob.S
> 
> diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
> index e0bbe75..39c6980 100644
> --- a/net/bpfilter/Makefile
> +++ b/net/bpfilter/Makefile
> @@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y)
>  HOSTLDFLAGS += -static
>  endif
>  
> -# a bit of elf magic to convert bpfilter_umh binary into a binary blob
> -# inside bpfilter_umh.o elf file referenced by
> -# _binary_net_bpfilter_bpfilter_umh_start symbol
> -# which bpfilter_kern.c passes further into umh blob loader at run-time
> -quiet_cmd_copy_umh = GEN $@
> -      cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \
> -      $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \
> -      -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \
> -      --rename-section .data=.init.rodata $< $@
> -
> -$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh
> -	$(call cmd,copy_umh)
> +$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
>  
>  obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o
> -bpfilter-objs += bpfilter_kern.o bpfilter_umh.o
> +bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o
> diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> index 0952257..6de3ae5 100644
> --- a/net/bpfilter/bpfilter_kern.c
> +++ b/net/bpfilter/bpfilter_kern.c
> @@ -10,11 +10,8 @@
>  #include <linux/file.h>
>  #include "msgfmt.h"
>  
> -#define UMH_start _binary_net_bpfilter_bpfilter_umh_start
> -#define UMH_end _binary_net_bpfilter_bpfilter_umh_end
> -
> -extern char UMH_start;
> -extern char UMH_end;
> +extern char bpfilter_umh_start;
> +extern char bpfilter_umh_end;
>  
>  static struct umh_info info;
>  /* since ip_getsockopt() can run in parallel, serialize access to umh */
> @@ -93,7 +90,9 @@ static int __init load_umh(void)
>  	int err;
>  
>  	/* fork usermode process */
> -	err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info);
> +	err = fork_usermode_blob(&bpfilter_umh_end,
> +				 &bpfilter_umh_end - &bpfilter_umh_start,
> +				 &info);
>  	if (err)
>  		return err;
>  	pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
> diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
> new file mode 100644
> index 0000000..40311d1
> --- /dev/null
> +++ b/net/bpfilter/bpfilter_umh_blob.S
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +	.section .init.rodata, "a"
> +	.global bpfilter_umh_start
> +bpfilter_umh_start:
> +	.incbin "net/bpfilter/bpfilter_umh"
> +	.global bpfilter_umh_end
> +bpfilter_umh_end:

for some reason it doesn't work.
fork_usermode_blob() returns ENOEXEC
You should be able to test it simply running 'iptables -L'.
Without this patch you should see:
[   12.696937] bpfilter: Loaded bpfilter_umh pid 225
Started bpfilter

where first line comes from kernel module and second from umh.

Re: [PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy

[Masahiro Yamada]

Hi Alexei,


2018-06-15 9:47 GMT+09:00 Alexei Starovoitov <alexei.starovoitov@gmail.com>:
> On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote:
>> What we want here is to embed a user-space program into the kernel.
>> Instead of the complex ELF magic, let's simply wrap it in the assembly
>> with the '.incbin' directive.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> ---
>>
>> Changes in v2:
>>   - Rebase
>>
>>  net/bpfilter/Makefile            | 15 ++-------------
>>  net/bpfilter/bpfilter_kern.c     | 11 +++++------
>>  net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
>>  3 files changed, 14 insertions(+), 19 deletions(-)
>>  create mode 100644 net/bpfilter/bpfilter_umh_blob.S
>>
>> diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
>> index e0bbe75..39c6980 100644
>> --- a/net/bpfilter/Makefile
>> +++ b/net/bpfilter/Makefile
>> @@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y)
>>  HOSTLDFLAGS += -static
>>  endif
>>
>> -# a bit of elf magic to convert bpfilter_umh binary into a binary blob
>> -# inside bpfilter_umh.o elf file referenced by
>> -# _binary_net_bpfilter_bpfilter_umh_start symbol
>> -# which bpfilter_kern.c passes further into umh blob loader at run-time
>> -quiet_cmd_copy_umh = GEN $@
>> -      cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \
>> -      $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \
>> -      -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \
>> -      --rename-section .data=.init.rodata $< $@
>> -
>> -$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh
>> -     $(call cmd,copy_umh)
>> +$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
>>
>>  obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o
>> -bpfilter-objs += bpfilter_kern.o bpfilter_umh.o
>> +bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o
>> diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
>> index 0952257..6de3ae5 100644
>> --- a/net/bpfilter/bpfilter_kern.c
>> +++ b/net/bpfilter/bpfilter_kern.c
>> @@ -10,11 +10,8 @@
>>  #include <linux/file.h>
>>  #include "msgfmt.h"
>>
>> -#define UMH_start _binary_net_bpfilter_bpfilter_umh_start
>> -#define UMH_end _binary_net_bpfilter_bpfilter_umh_end
>> -
>> -extern char UMH_start;
>> -extern char UMH_end;
>> +extern char bpfilter_umh_start;
>> +extern char bpfilter_umh_end;
>>
>>  static struct umh_info info;
>>  /* since ip_getsockopt() can run in parallel, serialize access to umh */
>> @@ -93,7 +90,9 @@ static int __init load_umh(void)
>>       int err;
>>
>>       /* fork usermode process */
>> -     err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info);
>> +     err = fork_usermode_blob(&bpfilter_umh_end,
>> +                              &bpfilter_umh_end - &bpfilter_umh_start,
>> +                              &info);
>>       if (err)
>>               return err;
>>       pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
>> diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
>> new file mode 100644
>> index 0000000..40311d1
>> --- /dev/null
>> +++ b/net/bpfilter/bpfilter_umh_blob.S
>> @@ -0,0 +1,7 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +     .section .init.rodata, "a"
>> +     .global bpfilter_umh_start
>> +bpfilter_umh_start:
>> +     .incbin "net/bpfilter/bpfilter_umh"
>> +     .global bpfilter_umh_end
>> +bpfilter_umh_end:
>
> for some reason it doesn't work.
> fork_usermode_blob() returns ENOEXEC
> You should be able to test it simply running 'iptables -L'.
> Without this patch you should see:
> [   12.696937] bpfilter: Loaded bpfilter_umh pid 225
> Started bpfilter
>
> where first line comes from kernel module and second from umh.


Sorry for the late reply.

Unfortunately, I will be busy for a while.

I will come back eventually
to check it out, but I cannot tell when.


Somebody else sent a patch equivalent to 1/3, so it is fine.

3/3 can go independently, so it will send it as a separate patch for now.





-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy

[Janne Karhunen]

Hi,

Hmm, does this approach work if the code is not in a kernel module? I
tried to use it as part of the kernel image and looks to me the
bounding symbols _start and _end are not correctly relocated?

--
Janne

On Fri, Jun 15, 2018 at 3:48 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote:
> > What we want here is to embed a user-space program into the kernel.
> > Instead of the complex ELF magic, let's simply wrap it in the assembly
> > with the '.incbin' directive.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> > Changes in v2:
> >   - Rebase
> >
> >  net/bpfilter/Makefile            | 15 ++-------------
> >  net/bpfilter/bpfilter_kern.c     | 11 +++++------
> >  net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
> >  3 files changed, 14 insertions(+), 19 deletions(-)
> >  create mode 100644 net/bpfilter/bpfilter_umh_blob.S
> >
> > diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
> > index e0bbe75..39c6980 100644
> > --- a/net/bpfilter/Makefile
> > +++ b/net/bpfilter/Makefile
> > @@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y)
> >  HOSTLDFLAGS += -static
> >  endif
> >
> > -# a bit of elf magic to convert bpfilter_umh binary into a binary blob
> > -# inside bpfilter_umh.o elf file referenced by
> > -# _binary_net_bpfilter_bpfilter_umh_start symbol
> > -# which bpfilter_kern.c passes further into umh blob loader at run-time
> > -quiet_cmd_copy_umh = GEN $@
> > -      cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \
> > -      $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \
> > -      -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \
> > -      --rename-section .data=.init.rodata $< $@
> > -
> > -$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh
> > -     $(call cmd,copy_umh)
> > +$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
> >
> >  obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o
> > -bpfilter-objs += bpfilter_kern.o bpfilter_umh.o
> > +bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o
> > diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> > index 0952257..6de3ae5 100644
> > --- a/net/bpfilter/bpfilter_kern.c
> > +++ b/net/bpfilter/bpfilter_kern.c
> > @@ -10,11 +10,8 @@
> >  #include <linux/file.h>
> >  #include "msgfmt.h"
> >
> > -#define UMH_start _binary_net_bpfilter_bpfilter_umh_start
> > -#define UMH_end _binary_net_bpfilter_bpfilter_umh_end
> > -
> > -extern char UMH_start;
> > -extern char UMH_end;
> > +extern char bpfilter_umh_start;
> > +extern char bpfilter_umh_end;
> >
> >  static struct umh_info info;
> >  /* since ip_getsockopt() can run in parallel, serialize access to umh */
> > @@ -93,7 +90,9 @@ static int __init load_umh(void)
> >       int err;
> >
> >       /* fork usermode process */
> > -     err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info);
> > +     err = fork_usermode_blob(&bpfilter_umh_end,
> > +                              &bpfilter_umh_end - &bpfilter_umh_start,
> > +                              &info);
> >       if (err)
> >               return err;
> >       pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
> > diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
> > new file mode 100644
> > index 0000000..40311d1
> > --- /dev/null
> > +++ b/net/bpfilter/bpfilter_umh_blob.S
> > @@ -0,0 +1,7 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +     .section .init.rodata, "a"
> > +     .global bpfilter_umh_start
> > +bpfilter_umh_start:
> > +     .incbin "net/bpfilter/bpfilter_umh"
> > +     .global bpfilter_umh_end
> > +bpfilter_umh_end:
>
> for some reason it doesn't work.
> fork_usermode_blob() returns ENOEXEC
> You should be able to test it simply running 'iptables -L'.
> Without this patch you should see:
> [   12.696937] bpfilter: Loaded bpfilter_umh pid 225
> Started bpfilter
>
> where first line comes from kernel module and second from umh.
>
>

Re: [PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy

[Janne Karhunen]

Hi,

Never mind, not enough coffee for the morning. Looks good addressing
wise, but something goes haywire with the copy. Some size limitation?

[   84.402647] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1ubuntu1 04/01/2014
[   84.403899] RIP: 0010:__memcpy+0x12/0x20
[   84.404441] Code: c1 e2 20 48 09 d0 48 31 c3 e9 76 ff ff ff 90 90
90 90 90 90 90 90 90 90 0f 1f 44 00 00 48 89 f8 48 89 d1 48 c1 e9 03
83 e2 07 <f3> 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1
f3 a4
[   84.407004] RSP: 0018:ffffc90000ac39c0 EFLAGS: 00010246
[   84.407714] RAX: ffff888041709000 RBX: 0000000000001000 RCX: 0000000000000200
[   84.408667] RDX: 0000000000000000 RSI: ffffffff82a7cb4d RDI: ffff888041709000
[   84.409668] RBP: ffffc90000ac3a08 R08: ffff888041709000 R09: 0000000000000000
[   84.410621] R10: 0000000000000000 R11: 000015fffefa3dbf R12: 0000000000001000
[   84.411710] R13: 0000000000001000 R14: ffffc90000ac3b28 R15: 0000000000001000
[   84.412675] FS:  00007f6cd3a35740(0000) GS:ffff88807da00000(0000)
knlGS:0000000000000000
[   84.413805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   84.414655] CR2: ffffffff82a7cb4d CR3: 0000000031344000 CR4: 00000000000006f0
[   84.415656] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   84.416647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   84.417619] Call Trace:
[   84.417996]  ? iov_iter_copy_from_user_atomic+0x21b/0x360
[   84.418754]  ? shmem_write_begin+0x4a/0x80
[   84.419396]  generic_perform_write+0xdd/0x1b0
[   84.419897]  __generic_file_write_iter+0x1ab/0x1d0
[   84.420453]  ? apparmor_file_alloc_security+0x4c/0x230
[   84.421082]  ? kmem_cache_alloc+0x1b5/0x1d0
[   84.421677]  generic_file_write_iter+0xb3/0x150
[   84.422353]  __vfs_write+0x145/0x1d0
[   84.422907]  vfs_write+0xae/0x1a0
[   84.423435]  kernel_write+0x55/0x70
[   84.423996]  fork_usermode_blob+0x85/0x11b
..

ret = fork_usermode_blob(&test_umh_start,
&test_umh_end - &test_umh_start, &um_info);

Addresses indeed seem ok and the '-fpic -fpie -fPIE -static' compiled
user mode blob sits in between those symbols correctly. Hummm ?


--
Janne

On Thu, Jan 31, 2019 at 12:48 PM Janne Karhunen
<janne.karhunen@gmail.com> wrote:
>
> Hi,
>
> Hmm, does this approach work if the code is not in a kernel module? I
> tried to use it as part of the kernel image and looks to me the
> bounding symbols _start and _end are not correctly relocated?
>
> --
> Janne
>
> On Fri, Jun 15, 2018 at 3:48 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote:
> > > What we want here is to embed a user-space program into the kernel.
> > > Instead of the complex ELF magic, let's simply wrap it in the assembly
> > > with the '.incbin' directive.
> > >
> > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > > ---
> > >
> > > Changes in v2:
> > >   - Rebase
> > >
> > >  net/bpfilter/Makefile            | 15 ++-------------
> > >  net/bpfilter/bpfilter_kern.c     | 11 +++++------
> > >  net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
> > >  3 files changed, 14 insertions(+), 19 deletions(-)
> > >  create mode 100644 net/bpfilter/bpfilter_umh_blob.S
> > >
> > > diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
> > > index e0bbe75..39c6980 100644
> > > --- a/net/bpfilter/Makefile
> > > +++ b/net/bpfilter/Makefile
> > > @@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y)
> > >  HOSTLDFLAGS += -static
> > >  endif
> > >
> > > -# a bit of elf magic to convert bpfilter_umh binary into a binary blob
> > > -# inside bpfilter_umh.o elf file referenced by
> > > -# _binary_net_bpfilter_bpfilter_umh_start symbol
> > > -# which bpfilter_kern.c passes further into umh blob loader at run-time
> > > -quiet_cmd_copy_umh = GEN $@
> > > -      cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \
> > > -      $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \
> > > -      -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \
> > > -      --rename-section .data=.init.rodata $< $@
> > > -
> > > -$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh
> > > -     $(call cmd,copy_umh)
> > > +$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
> > >
> > >  obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o
> > > -bpfilter-objs += bpfilter_kern.o bpfilter_umh.o
> > > +bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o
> > > diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> > > index 0952257..6de3ae5 100644
> > > --- a/net/bpfilter/bpfilter_kern.c
> > > +++ b/net/bpfilter/bpfilter_kern.c
> > > @@ -10,11 +10,8 @@
> > >  #include <linux/file.h>
> > >  #include "msgfmt.h"
> > >
> > > -#define UMH_start _binary_net_bpfilter_bpfilter_umh_start
> > > -#define UMH_end _binary_net_bpfilter_bpfilter_umh_end
> > > -
> > > -extern char UMH_start;
> > > -extern char UMH_end;
> > > +extern char bpfilter_umh_start;
> > > +extern char bpfilter_umh_end;
> > >
> > >  static struct umh_info info;
> > >  /* since ip_getsockopt() can run in parallel, serialize access to umh */
> > > @@ -93,7 +90,9 @@ static int __init load_umh(void)
> > >       int err;
> > >
> > >       /* fork usermode process */
> > > -     err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info);
> > > +     err = fork_usermode_blob(&bpfilter_umh_end,
> > > +                              &bpfilter_umh_end - &bpfilter_umh_start,
> > > +                              &info);
> > >       if (err)
> > >               return err;
> > >       pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
> > > diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
> > > new file mode 100644
> > > index 0000000..40311d1
> > > --- /dev/null
> > > +++ b/net/bpfilter/bpfilter_umh_blob.S
> > > @@ -0,0 +1,7 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +     .section .init.rodata, "a"
> > > +     .global bpfilter_umh_start
> > > +bpfilter_umh_start:
> > > +     .incbin "net/bpfilter/bpfilter_umh"
> > > +     .global bpfilter_umh_end
> > > +bpfilter_umh_end:
> >
> > for some reason it doesn't work.
> > fork_usermode_blob() returns ENOEXEC
> > You should be able to test it simply running 'iptables -L'.
> > Without this patch you should see:
> > [   12.696937] bpfilter: Loaded bpfilter_umh pid 225
> > Started bpfilter
> >
> > where first line comes from kernel module and second from umh.
> >
> >

Re: [PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy

[Janne Karhunen]

Hi,

Okay my bad, proper __initconst declarations would do the trick, cool stuff.


--
Janne

On Thu, Jan 31, 2019 at 1:09 PM Janne Karhunen <janne.karhunen@gmail.com> wrote:
>
> Hi,
>
> Never mind, not enough coffee for the morning. Looks good addressing
> wise, but something goes haywire with the copy. Some size limitation?
>
> [   84.402647] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.10.2-1ubuntu1 04/01/2014
> [   84.403899] RIP: 0010:__memcpy+0x12/0x20
> [   84.404441] Code: c1 e2 20 48 09 d0 48 31 c3 e9 76 ff ff ff 90 90
> 90 90 90 90 90 90 90 90 0f 1f 44 00 00 48 89 f8 48 89 d1 48 c1 e9 03
> 83 e2 07 <f3> 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1
> f3 a4
> [   84.407004] RSP: 0018:ffffc90000ac39c0 EFLAGS: 00010246
> [   84.407714] RAX: ffff888041709000 RBX: 0000000000001000 RCX: 0000000000000200
> [   84.408667] RDX: 0000000000000000 RSI: ffffffff82a7cb4d RDI: ffff888041709000
> [   84.409668] RBP: ffffc90000ac3a08 R08: ffff888041709000 R09: 0000000000000000
> [   84.410621] R10: 0000000000000000 R11: 000015fffefa3dbf R12: 0000000000001000
> [   84.411710] R13: 0000000000001000 R14: ffffc90000ac3b28 R15: 0000000000001000
> [   84.412675] FS:  00007f6cd3a35740(0000) GS:ffff88807da00000(0000)
> knlGS:0000000000000000
> [   84.413805] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   84.414655] CR2: ffffffff82a7cb4d CR3: 0000000031344000 CR4: 00000000000006f0
> [   84.415656] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   84.416647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   84.417619] Call Trace:
> [   84.417996]  ? iov_iter_copy_from_user_atomic+0x21b/0x360
> [   84.418754]  ? shmem_write_begin+0x4a/0x80
> [   84.419396]  generic_perform_write+0xdd/0x1b0
> [   84.419897]  __generic_file_write_iter+0x1ab/0x1d0
> [   84.420453]  ? apparmor_file_alloc_security+0x4c/0x230
> [   84.421082]  ? kmem_cache_alloc+0x1b5/0x1d0
> [   84.421677]  generic_file_write_iter+0xb3/0x150
> [   84.422353]  __vfs_write+0x145/0x1d0
> [   84.422907]  vfs_write+0xae/0x1a0
> [   84.423435]  kernel_write+0x55/0x70
> [   84.423996]  fork_usermode_blob+0x85/0x11b
> ..
>
> ret = fork_usermode_blob(&test_umh_start,
> &test_umh_end - &test_umh_start, &um_info);
>
> Addresses indeed seem ok and the '-fpic -fpie -fPIE -static' compiled
> user mode blob sits in between those symbols correctly. Hummm ?
>
>
> --
> Janne
>
> On Thu, Jan 31, 2019 at 12:48 PM Janne Karhunen
> <janne.karhunen@gmail.com> wrote:
> >
> > Hi,
> >
> > Hmm, does this approach work if the code is not in a kernel module? I
> > tried to use it as part of the kernel image and looks to me the
> > bounding symbols _start and _end are not correctly relocated?
> >
> > --
> > Janne
> >
> > On Fri, Jun 15, 2018 at 3:48 AM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote:
> > > > What we want here is to embed a user-space program into the kernel.
> > > > Instead of the complex ELF magic, let's simply wrap it in the assembly
> > > > with the '.incbin' directive.
> > > >
> > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > > > ---
> > > >
> > > > Changes in v2:
> > > >   - Rebase
> > > >
> > > >  net/bpfilter/Makefile            | 15 ++-------------
> > > >  net/bpfilter/bpfilter_kern.c     | 11 +++++------
> > > >  net/bpfilter/bpfilter_umh_blob.S |  7 +++++++
> > > >  3 files changed, 14 insertions(+), 19 deletions(-)
> > > >  create mode 100644 net/bpfilter/bpfilter_umh_blob.S
> > > >
> > > > diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
> > > > index e0bbe75..39c6980 100644
> > > > --- a/net/bpfilter/Makefile
> > > > +++ b/net/bpfilter/Makefile
> > > > @@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y)
> > > >  HOSTLDFLAGS += -static
> > > >  endif
> > > >
> > > > -# a bit of elf magic to convert bpfilter_umh binary into a binary blob
> > > > -# inside bpfilter_umh.o elf file referenced by
> > > > -# _binary_net_bpfilter_bpfilter_umh_start symbol
> > > > -# which bpfilter_kern.c passes further into umh blob loader at run-time
> > > > -quiet_cmd_copy_umh = GEN $@
> > > > -      cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \
> > > > -      $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \
> > > > -      -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \
> > > > -      --rename-section .data=.init.rodata $< $@
> > > > -
> > > > -$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh
> > > > -     $(call cmd,copy_umh)
> > > > +$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
> > > >
> > > >  obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o
> > > > -bpfilter-objs += bpfilter_kern.o bpfilter_umh.o
> > > > +bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o
> > > > diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> > > > index 0952257..6de3ae5 100644
> > > > --- a/net/bpfilter/bpfilter_kern.c
> > > > +++ b/net/bpfilter/bpfilter_kern.c
> > > > @@ -10,11 +10,8 @@
> > > >  #include <linux/file.h>
> > > >  #include "msgfmt.h"
> > > >
> > > > -#define UMH_start _binary_net_bpfilter_bpfilter_umh_start
> > > > -#define UMH_end _binary_net_bpfilter_bpfilter_umh_end
> > > > -
> > > > -extern char UMH_start;
> > > > -extern char UMH_end;
> > > > +extern char bpfilter_umh_start;
> > > > +extern char bpfilter_umh_end;
> > > >
> > > >  static struct umh_info info;
> > > >  /* since ip_getsockopt() can run in parallel, serialize access to umh */
> > > > @@ -93,7 +90,9 @@ static int __init load_umh(void)
> > > >       int err;
> > > >
> > > >       /* fork usermode process */
> > > > -     err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info);
> > > > +     err = fork_usermode_blob(&bpfilter_umh_end,
> > > > +                              &bpfilter_umh_end - &bpfilter_umh_start,
> > > > +                              &info);
> > > >       if (err)
> > > >               return err;
> > > >       pr_info("Loaded bpfilter_umh pid %d\n", info.pid);
> > > > diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S
> > > > new file mode 100644
> > > > index 0000000..40311d1
> > > > --- /dev/null
> > > > +++ b/net/bpfilter/bpfilter_umh_blob.S
> > > > @@ -0,0 +1,7 @@
> > > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > > +     .section .init.rodata, "a"
> > > > +     .global bpfilter_umh_start
> > > > +bpfilter_umh_start:
> > > > +     .incbin "net/bpfilter/bpfilter_umh"
> > > > +     .global bpfilter_umh_end
> > > > +bpfilter_umh_end:
> > >
> > > for some reason it doesn't work.
> > > fork_usermode_blob() returns ENOEXEC
> > > You should be able to test it simply running 'iptables -L'.
> > > Without this patch you should see:
> > > [   12.696937] bpfilter: Loaded bpfilter_umh pid 225
> > > Started bpfilter
> > >
> > > where first line comes from kernel module and second from umh.
> > >
> > >