Do not build lib/bpf/bpf.o with this Makefile but use the one from the
library directory. This avoid making a buggy bpf.o file (e.g. missing
symbols).
This patch is useful if some code (e.g. Landlock tests) needs both the
bpf.o (from tools/lib/bpf) and the bpf_load.o (from samples/bpf).
Signed-off-by: Mickaël Salaün <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Daniel Borkmann <[email protected]>
---
This is not a complet fix because the call to multi_depend with
$(host-cmulti) from scripts/Makefile.host force the build of bpf.o
anyway. I'm not sure how to completely avoid this automatic build
though.
---
samples/bpf/Makefile | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 7f61a3d57fa7..64335bb94f9f 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -201,13 +201,16 @@ CLANG_ARCH_ARGS = -target $(ARCH)
endif
# Trick to allow make to be run from this directory
-all:
+all: $(LIBBPF)
$(MAKE) -C ../../ $(CURDIR)/
clean:
$(MAKE) -C ../../ M=$(CURDIR) clean
@rm -f *~
+$(LIBBPF): FORCE
+ $(MAKE) -C $(dir $@) $(notdir $@)
+
$(obj)/syscall_nrs.s: $(src)/syscall_nrs.c
$(call if_changed_dep,cc_s_c)
--
2.15.1
On Fri, Jan 26, 2018 at 01:39:30AM +0100, Micka?l Sala?n wrote:
> Do not build lib/bpf/bpf.o with this Makefile but use the one from the
> library directory. This avoid making a buggy bpf.o file (e.g. missing
> symbols).
could you provide an example?
What symbols will be missing?
I don't think there is an issue with existing Makefile.
> This patch is useful if some code (e.g. Landlock tests) needs both the
> bpf.o (from tools/lib/bpf) and the bpf_load.o (from samples/bpf).
is that some future patches?
we're trying to move everything form samples/bpf/ into selftests/bpf/
and convert to use libbpf.a instead of obsolete bpf_load.c
Please use this approach for landlock as well.
> Signed-off-by: Micka?l Sala?n <[email protected]>
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Daniel Borkmann <[email protected]>
> ---
>
> This is not a complet fix because the call to multi_depend with
> $(host-cmulti) from scripts/Makefile.host force the build of bpf.o
> anyway. I'm not sure how to completely avoid this automatic build
> though.
> ---
> samples/bpf/Makefile | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 7f61a3d57fa7..64335bb94f9f 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -201,13 +201,16 @@ CLANG_ARCH_ARGS = -target $(ARCH)
> endif
>
> # Trick to allow make to be run from this directory
> -all:
> +all: $(LIBBPF)
> $(MAKE) -C ../../ $(CURDIR)/
>
> clean:
> $(MAKE) -C ../../ M=$(CURDIR) clean
> @rm -f *~
>
> +$(LIBBPF): FORCE
> + $(MAKE) -C $(dir $@) $(notdir $@)
> +
> $(obj)/syscall_nrs.s: $(src)/syscall_nrs.c
> $(call if_changed_dep,cc_s_c)
>
> --
> 2.15.1
>
On 26/01/2018 03:16, Alexei Starovoitov wrote:
> On Fri, Jan 26, 2018 at 01:39:30AM +0100, Micka?l Sala?n wrote:
>> Do not build lib/bpf/bpf.o with this Makefile but use the one from the
>> library directory. This avoid making a buggy bpf.o file (e.g. missing
>> symbols).
>
> could you provide an example?
> What symbols will be missing?
> I don't think there is an issue with existing Makefile.
You can run this commands:
make -C samples/bpf; nm tools/lib/bpf/bpf.o > a; make -C tools/lib/bpf;
nm tools/lib/bpf/bpf.o > b; diff -u a b
Symbols like bzero and sys_bpf are missing with the samples/bpf
Makefile, which makes the bpf.o shrink from 25K to 7K.
>
>> This patch is useful if some code (e.g. Landlock tests) needs both the
>> bpf.o (from tools/lib/bpf) and the bpf_load.o (from samples/bpf).
>
> is that some future patches?
Yes, I'll send them next week.
>
> we're trying to move everything form samples/bpf/ into selftests/bpf/
> and convert to use libbpf.a instead of obsolete bpf_load.c
> Please use this approach for landlock as well.
Ok, it should be better with this lib.
>
>> Signed-off-by: Micka?l Sala?n <[email protected]>
>> Cc: Alexei Starovoitov <[email protected]>
>> Cc: Daniel Borkmann <[email protected]>
>> ---
>>
>> This is not a complet fix because the call to multi_depend with
>> $(host-cmulti) from scripts/Makefile.host force the build of bpf.o
>> anyway. I'm not sure how to completely avoid this automatic build
>> though.
>> ---
>> samples/bpf/Makefile | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
>> index 7f61a3d57fa7..64335bb94f9f 100644
>> --- a/samples/bpf/Makefile
>> +++ b/samples/bpf/Makefile
>> @@ -201,13 +201,16 @@ CLANG_ARCH_ARGS = -target $(ARCH)
>> endif
>>
>> # Trick to allow make to be run from this directory
>> -all:
>> +all: $(LIBBPF)
>> $(MAKE) -C ../../ $(CURDIR)/
>>
>> clean:
>> $(MAKE) -C ../../ M=$(CURDIR) clean
>> @rm -f *~
>>
>> +$(LIBBPF): FORCE
>> + $(MAKE) -C $(dir $@) $(notdir $@)
>> +
>> $(obj)/syscall_nrs.s: $(src)/syscall_nrs.c
>> $(call if_changed_dep,cc_s_c)
>>
>> --
>> 2.15.1
>>
>
On 01/26/2018 09:30 AM, Micka?l Sala?n wrote:
> On 26/01/2018 03:16, Alexei Starovoitov wrote:
>> On Fri, Jan 26, 2018 at 01:39:30AM +0100, Micka?l Sala?n wrote:
>>> Do not build lib/bpf/bpf.o with this Makefile but use the one from the
>>> library directory. This avoid making a buggy bpf.o file (e.g. missing
>>> symbols).
>>
>> could you provide an example?
>> What symbols will be missing?
>> I don't think there is an issue with existing Makefile.
>
> You can run this commands:
> make -C samples/bpf; nm tools/lib/bpf/bpf.o > a; make -C tools/lib/bpf;
> nm tools/lib/bpf/bpf.o > b; diff -u a b
>
> Symbols like bzero and sys_bpf are missing with the samples/bpf
> Makefile, which makes the bpf.o shrink from 25K to 7K.
I've applied it to bpf-next, thanks Micka?l!