diff mbox series

[3/3] bpftool: Allow to link libbpf dynamically

Message ID 20191127094837.4045-4-jolsa@kernel.org
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series perf/bpftool: Allow to link libbpf dynamically | expand

Commit Message

Jiri Olsa Nov. 27, 2019, 9:48 a.m. UTC
Currently we support only static linking with kernel's libbpf
(tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable
that triggers libbpf detection and bpf dynamic linking:

  $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1

If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with:

  $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1
    Auto-detecting system features:
    ...                        libbfd: [ on  ]
    ...        disassembler-four-args: [ on  ]
    ...                          zlib: [ on  ]
    ...                        libbpf: [ OFF ]

  Makefile:102: *** Error: libbpf-devel is missing, please install it.  Stop.

Adding specific bpftool's libbpf check for libbpf_netlink_open (LIBBPF_0.0.6)
which is the latest we need for bpftool at the moment.

Adding LIBBPF_DIR compile variable to allow linking with
libbpf installed into specific directory:

  $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers
  $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/

It might be needed to clean build tree first because features
framework does not detect the change properly:

  $ make -C tools/build/feature clean
  $ make -C tools/bpf/bpftool/ clean

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/bpf/bpftool/Makefile        | 40 ++++++++++++++++++++++++++++++-
 tools/build/feature/test-libbpf.c |  9 +++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

Comments

Quentin Monnet Nov. 27, 2019, 1:38 p.m. UTC | #1
2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
> Currently we support only static linking with kernel's libbpf
> (tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable
> that triggers libbpf detection and bpf dynamic linking:
> 
>   $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1
> 
> If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with:
> 
>   $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1
>     Auto-detecting system features:
>     ...                        libbfd: [ on  ]
>     ...        disassembler-four-args: [ on  ]
>     ...                          zlib: [ on  ]
>     ...                        libbpf: [ OFF ]
> 
>   Makefile:102: *** Error: libbpf-devel is missing, please install it.  Stop.
> 
> Adding specific bpftool's libbpf check for libbpf_netlink_open (LIBBPF_0.0.6)
> which is the latest we need for bpftool at the moment.
> 
> Adding LIBBPF_DIR compile variable to allow linking with
> libbpf installed into specific directory:
> 
>   $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers
>   $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/
> 
> It might be needed to clean build tree first because features
> framework does not detect the change properly:
> 
>   $ make -C tools/build/feature clean
>   $ make -C tools/bpf/bpftool/ clean
> 
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/bpf/bpftool/Makefile        | 40 ++++++++++++++++++++++++++++++-
>  tools/build/feature/test-libbpf.c |  9 +++++++
>  2 files changed, 48 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 39bc6f0f4f0b..2b6ed08cb31e 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile

> @@ -55,7 +64,7 @@ ifneq ($(EXTRA_LDFLAGS),)
>  LDFLAGS += $(EXTRA_LDFLAGS)
>  endif
>  
> -LIBS = $(LIBBPF) -lelf -lz
> +LIBS = -lelf -lz

Hi Jiri,

This change seems to be breaking the build with the static library for
me. I know you add back $(LIBBPF) later in the Makefile, see at the end
of this email...

>  
>  INSTALL ?= install
>  RM ?= rm -f
> @@ -64,6 +73,23 @@ FEATURE_USER = .bpftool
>  FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib
>  FEATURE_DISPLAY = libbfd disassembler-four-args zlib
>  
> +ifdef LIBBPF_DYNAMIC
> +  # Add libbpf check with the flags to ensure bpftool
> +  # specific version is detected.

Nit: We do not check for a specific bpftool version, we check for a
recent enough libbpf version?

> +  FEATURE_CHECK_CFLAGS-libbpf := -DBPFTOOL
> +  FEATURE_TESTS   += libbpf
> +  FEATURE_DISPLAY += libbpf
> +
> +  # for linking with debug library run:
> +  # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf
> +  ifdef LIBBPF_DIR
> +    LIBBPF_CFLAGS  := -I$(LIBBPF_DIR)/include
> +    LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative)
> +    FEATURE_CHECK_CFLAGS-libbpf  := $(LIBBPF_CFLAGS)
> +    FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS)
> +  endif
> +endif
> +
>  check_feat := 1
>  NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
>  ifdef MAKECMDGOALS
> @@ -88,6 +114,18 @@ ifeq ($(feature-reallocarray), 0)
>  CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
>  endif
>  
> +ifdef LIBBPF_DYNAMIC
> +  ifeq ($(feature-libbpf), 1)
> +    LIBS    += -lbpf
> +    CFLAGS  += $(LIBBPF_CFLAGS)
> +    LDFLAGS += $(LIBBPF_LDFLAGS)
> +  else
> +    dummy := $(error Error: No libbpf devel library found, please install libbpf-devel)

libbpf-devel sounds like a RH/Fedora package name, but other
distributions might have different names (Debian/Ubuntu would go by
libbpf-dev I suppose, although I don't believe such package exists at
the moment). Maybe use a more generic message?

> +  endif
> +else
> +  LIBS += $(LIBBPF)

... I believe the order of the libraries is relevant, and it seems the
static libbpf should be passed before the dynamic libs. Here I could fix
the build with the static library on my setup by prepending the library
path instead, like this:

	LIBS := $(LIBBPF) $(LIBS)

On the plus side, all build attempts from
tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
my setup with dynamic linking from your branch.

> +endif
> +
>  include $(wildcard $(OUTPUT)*.d)
>  
>  all: $(OUTPUT)bpftool

Thanks,
Quentin
Jiri Olsa Nov. 27, 2019, 2:15 p.m. UTC | #2
On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
> 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
> > Currently we support only static linking with kernel's libbpf
> > (tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable
> > that triggers libbpf detection and bpf dynamic linking:
> > 
> >   $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1
> > 
> > If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with:
> > 
> >   $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1
> >     Auto-detecting system features:
> >     ...                        libbfd: [ on  ]
> >     ...        disassembler-four-args: [ on  ]
> >     ...                          zlib: [ on  ]
> >     ...                        libbpf: [ OFF ]
> > 
> >   Makefile:102: *** Error: libbpf-devel is missing, please install it.  Stop.
> > 
> > Adding specific bpftool's libbpf check for libbpf_netlink_open (LIBBPF_0.0.6)
> > which is the latest we need for bpftool at the moment.
> > 
> > Adding LIBBPF_DIR compile variable to allow linking with
> > libbpf installed into specific directory:
> > 
> >   $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers
> >   $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/
> > 
> > It might be needed to clean build tree first because features
> > framework does not detect the change properly:
> > 
> >   $ make -C tools/build/feature clean
> >   $ make -C tools/bpf/bpftool/ clean
> > 
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/bpf/bpftool/Makefile        | 40 ++++++++++++++++++++++++++++++-
> >  tools/build/feature/test-libbpf.c |  9 +++++++
> >  2 files changed, 48 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > index 39bc6f0f4f0b..2b6ed08cb31e 100644
> > --- a/tools/bpf/bpftool/Makefile
> > +++ b/tools/bpf/bpftool/Makefile
> 
> > @@ -55,7 +64,7 @@ ifneq ($(EXTRA_LDFLAGS),)
> >  LDFLAGS += $(EXTRA_LDFLAGS)
> >  endif
> >  
> > -LIBS = $(LIBBPF) -lelf -lz
> > +LIBS = -lelf -lz
> 
> Hi Jiri,
> 
> This change seems to be breaking the build with the static library for
> me. I know you add back $(LIBBPF) later in the Makefile, see at the end
> of this email...
> 
> >  
> >  INSTALL ?= install
> >  RM ?= rm -f
> > @@ -64,6 +73,23 @@ FEATURE_USER = .bpftool
> >  FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib
> >  FEATURE_DISPLAY = libbfd disassembler-four-args zlib
> >  
> > +ifdef LIBBPF_DYNAMIC
> > +  # Add libbpf check with the flags to ensure bpftool
> > +  # specific version is detected.
> 
> Nit: We do not check for a specific bpftool version, we check for a
> recent enough libbpf version?

hi,
we check for a version that has the latest exported function
that bpftool needs, which is currently libbpf_netlink_open

please check the '#ifdef BPFTOOL' in feature/test-libbpf.c

it's like that because there's currently no support to check
for particular library version in the build/features framework

I'll make that comment more clear

> 
> > +  FEATURE_CHECK_CFLAGS-libbpf := -DBPFTOOL
> > +  FEATURE_TESTS   += libbpf
> > +  FEATURE_DISPLAY += libbpf
> > +
> > +  # for linking with debug library run:
> > +  # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf
> > +  ifdef LIBBPF_DIR
> > +    LIBBPF_CFLAGS  := -I$(LIBBPF_DIR)/include
> > +    LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative)
> > +    FEATURE_CHECK_CFLAGS-libbpf  := $(LIBBPF_CFLAGS)
> > +    FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS)
> > +  endif
> > +endif
> > +
> >  check_feat := 1
> >  NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
> >  ifdef MAKECMDGOALS
> > @@ -88,6 +114,18 @@ ifeq ($(feature-reallocarray), 0)
> >  CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
> >  endif
> >  
> > +ifdef LIBBPF_DYNAMIC
> > +  ifeq ($(feature-libbpf), 1)
> > +    LIBS    += -lbpf
> > +    CFLAGS  += $(LIBBPF_CFLAGS)
> > +    LDFLAGS += $(LIBBPF_LDFLAGS)
> > +  else
> > +    dummy := $(error Error: No libbpf devel library found, please install libbpf-devel)
> 
> libbpf-devel sounds like a RH/Fedora package name, but other
> distributions might have different names (Debian/Ubuntu would go by
> libbpf-dev I suppose, although I don't believe such package exists at
> the moment). Maybe use a more generic message?

sure, actually in perf we use both package names like:

  Error: No libbpf devel library found, please install libbpf-devel or libbpf-dev.

or we can go with generic message:

  Error: No libbpf devel library found, please install.

> 
> > +  endif
> > +else
> > +  LIBS += $(LIBBPF)
> 
> ... I believe the order of the libraries is relevant, and it seems the
> static libbpf should be passed before the dynamic libs. Here I could fix
> the build with the static library on my setup by prepending the library
> path instead, like this:
> 
> 	LIBS := $(LIBBPF) $(LIBS)

could you please paste the build error? I don't see any on Fedora,
anyway I can make the change you're proposing

> 
> On the plus side, all build attempts from
> tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
> my setup with dynamic linking from your branch.

cool, had no idea there was such test ;-)

thanks,
jirka
Arnaldo Nov. 27, 2019, 2:24 p.m. UTC | #3
Em Wed, Nov 27, 2019 at 03:15:20PM +0100, Jiri Olsa escreveu:
> On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
> > 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
> > On the plus side, all build attempts from
> > tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
> > my setup with dynamic linking from your branch.
> 
> cool, had no idea there was such test ;-)

Should be the the equivalent to 'make -C tools/perf build-test' :-)

Perhaps we should make tools/testing/selftests/perf/ link to that?

- Arnaldo
Quentin Monnet Nov. 27, 2019, 2:29 p.m. UTC | #4
2019-11-27 15:15 UTC+0100 ~ Jiri Olsa <jolsa@redhat.com>
> On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
>> 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
>>> Currently we support only static linking with kernel's libbpf
>>> (tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable
>>> that triggers libbpf detection and bpf dynamic linking:
>>>
>>>   $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1
>>>
>>> If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with:
>>>
>>>   $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1
>>>     Auto-detecting system features:
>>>     ...                        libbfd: [ on  ]
>>>     ...        disassembler-four-args: [ on  ]
>>>     ...                          zlib: [ on  ]
>>>     ...                        libbpf: [ OFF ]
>>>
>>>   Makefile:102: *** Error: libbpf-devel is missing, please install it.  Stop.
>>>
>>> Adding specific bpftool's libbpf check for libbpf_netlink_open (LIBBPF_0.0.6)
>>> which is the latest we need for bpftool at the moment.
>>>
>>> Adding LIBBPF_DIR compile variable to allow linking with
>>> libbpf installed into specific directory:
>>>
>>>   $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers
>>>   $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/
>>>
>>> It might be needed to clean build tree first because features
>>> framework does not detect the change properly:
>>>
>>>   $ make -C tools/build/feature clean
>>>   $ make -C tools/bpf/bpftool/ clean
>>>
>>> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>>> ---
>>>  tools/bpf/bpftool/Makefile        | 40 ++++++++++++++++++++++++++++++-
>>>  tools/build/feature/test-libbpf.c |  9 +++++++
>>>  2 files changed, 48 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
>>> index 39bc6f0f4f0b..2b6ed08cb31e 100644
>>> --- a/tools/bpf/bpftool/Makefile
>>> +++ b/tools/bpf/bpftool/Makefile
>>
>>> @@ -55,7 +64,7 @@ ifneq ($(EXTRA_LDFLAGS),)
>>>  LDFLAGS += $(EXTRA_LDFLAGS)
>>>  endif
>>>  
>>> -LIBS = $(LIBBPF) -lelf -lz
>>> +LIBS = -lelf -lz
>>
>> Hi Jiri,
>>
>> This change seems to be breaking the build with the static library for
>> me. I know you add back $(LIBBPF) later in the Makefile, see at the end
>> of this email...
>>
>>>  
>>>  INSTALL ?= install
>>>  RM ?= rm -f
>>> @@ -64,6 +73,23 @@ FEATURE_USER = .bpftool
>>>  FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib
>>>  FEATURE_DISPLAY = libbfd disassembler-four-args zlib
>>>  
>>> +ifdef LIBBPF_DYNAMIC
>>> +  # Add libbpf check with the flags to ensure bpftool
>>> +  # specific version is detected.
>>
>> Nit: We do not check for a specific bpftool version, we check for a
>> recent enough libbpf version?
> 
> hi,
> we check for a version that has the latest exported function
> that bpftool needs, which is currently libbpf_netlink_open
> 
> please check the '#ifdef BPFTOOL' in feature/test-libbpf.c
> 
> it's like that because there's currently no support to check
> for particular library version in the build/features framework
> 
> I'll make that comment more clear

Thanks!
>>> +  FEATURE_CHECK_CFLAGS-libbpf := -DBPFTOOL
>>> +  FEATURE_TESTS   += libbpf
>>> +  FEATURE_DISPLAY += libbpf
>>> +
>>> +  # for linking with debug library run:
>>> +  # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf
>>> +  ifdef LIBBPF_DIR
>>> +    LIBBPF_CFLAGS  := -I$(LIBBPF_DIR)/include
>>> +    LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative)
>>> +    FEATURE_CHECK_CFLAGS-libbpf  := $(LIBBPF_CFLAGS)
>>> +    FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS)
>>> +  endif
>>> +endif
>>> +
>>>  check_feat := 1
>>>  NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
>>>  ifdef MAKECMDGOALS
>>> @@ -88,6 +114,18 @@ ifeq ($(feature-reallocarray), 0)
>>>  CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
>>>  endif
>>>  
>>> +ifdef LIBBPF_DYNAMIC
>>> +  ifeq ($(feature-libbpf), 1)
>>> +    LIBS    += -lbpf
>>> +    CFLAGS  += $(LIBBPF_CFLAGS)
>>> +    LDFLAGS += $(LIBBPF_LDFLAGS)
>>> +  else
>>> +    dummy := $(error Error: No libbpf devel library found, please install libbpf-devel)
>>
>> libbpf-devel sounds like a RH/Fedora package name, but other
>> distributions might have different names (Debian/Ubuntu would go by
>> libbpf-dev I suppose, although I don't believe such package exists at
>> the moment). Maybe use a more generic message?
> 
> sure, actually in perf we use both package names like:
> 
>   Error: No libbpf devel library found, please install libbpf-devel or libbpf-dev.
> 
> or we can go with generic message:
> 
>   Error: No libbpf devel library found, please install.

Either is fine with me, thanks!

>>> +  endif
>>> +else
>>> +  LIBS += $(LIBBPF)
>>
>> ... I believe the order of the libraries is relevant, and it seems the
>> static libbpf should be passed before the dynamic libs. Here I could fix
>> the build with the static library on my setup by prepending the library
>> path instead, like this:
>>
>> 	LIBS := $(LIBBPF) $(LIBS)
> 
> could you please paste the build error? I don't see any on Fedora,

Sure, here it is. On top of your branch (on Ubuntu 18.04):

----------------

$ make -C tools/bpf/bpftool/
make: Entering directory '/root/linux/bpf-next/tools/bpf/bpftool'

Auto-detecting system features:
...                        libbfd: [ on  ]
...        disassembler-four-args: [ on  ]
...                          zlib: [ on  ]

  CC       map_perf_ring.o
  CC       xlated_dumper.o
  CC       btf.o
  CC       tracelog.o
  CC       perf.o
  CC       cfg.o
  CC       btf_dumper.o
  CC       net.o
  CC       netlink_dumper.o
  CC       common.o
  CC       cgroup.o
  CC       main.o
  CC       json_writer.o
  CC       prog.o
  CC       map.o
  CC       feature.o
  CC       jit_disasm.o
  CC       disasm.o
make[1]: Entering directory '/root/linux/bpf-next/tools/lib/bpf'

Auto-detecting system features:
...                        libelf: [ on  ]
...                           bpf: [ on  ]

Parsed description of 117 helper function(s)
  MKDIR    staticobjs/
  CC       staticobjs/libbpf.o
  CC       staticobjs/bpf.o
  CC       staticobjs/nlattr.o
  CC       staticobjs/btf.o
  CC       staticobjs/libbpf_errno.o
  CC       staticobjs/str_error.o
  CC       staticobjs/netlink.o
  CC       staticobjs/bpf_prog_linfo.o
  CC       staticobjs/libbpf_probes.o
  CC       staticobjs/xsk.o
  CC       staticobjs/hashmap.o
  CC       staticobjs/btf_dump.o
  LD       staticobjs/libbpf-in.o
  LINK     libbpf.a
make[1]: Leaving directory '/root/linux/bpf-next/tools/lib/bpf'
  LINK     bpftool
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__init_prog_names':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:466: undefined reference to `gelf_getsym'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:473: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__elf_finish':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:570: undefined reference to `elf_end'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__elf_init':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:600: undefined reference to `elf_memory'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:613: undefined reference to `elf_begin'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:623: undefined reference to `gelf_getehdr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object_search_section_size':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:714: undefined reference to `gelf_getshdr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:720: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:730: undefined reference to `elf_getdata'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:708: undefined reference to `elf_nextscn'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__variable_offset':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:784: undefined reference to `gelf_getsym'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:790: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__init_user_maps':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:937: undefined reference to `elf_getscn'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:939: undefined reference to `elf_getdata'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:957: undefined reference to `gelf_getsym'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:981: undefined reference to `gelf_getsym'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:990: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__init_user_btf_maps':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1359: undefined reference to `elf_getscn'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1361: undefined reference to `elf_getdata'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `section_have_execinstr':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1428: undefined reference to `elf_getscn'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1432: undefined reference to `gelf_getshdr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_object__elf_collect':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1608: undefined reference to `elf_getscn'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1608: undefined reference to `elf_rawdata'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1619: undefined reference to `gelf_getshdr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1625: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1632: undefined reference to `elf_getdata'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1613: undefined reference to `elf_nextscn'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `bpf_program__collect_reloc':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1928: undefined reference to `gelf_getrel'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1932: undefined reference to `gelf_getsym'
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:1941: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `__bpf_object__open':
/root/linux/bpf-next/tools/lib/bpf/libbpf.c:3934: undefined reference to `elf_version'
/root/linux/bpf-next/tools/lib/bpf/libbpf.a(libbpf-in.o): In function `btf__parse_elf':
/root/linux/bpf-next/tools/lib/bpf/btf.c:413: undefined reference to `elf_version'
/root/linux/bpf-next/tools/lib/bpf/btf.c:427: undefined reference to `elf_begin'
/root/linux/bpf-next/tools/lib/bpf/btf.c:432: undefined reference to `gelf_getehdr'
/root/linux/bpf-next/tools/lib/bpf/btf.c:440: undefined reference to `elf_getscn'
/root/linux/bpf-next/tools/lib/bpf/btf.c:440: undefined reference to `elf_rawdata'
/root/linux/bpf-next/tools/lib/bpf/btf.c:450: undefined reference to `gelf_getshdr'
/root/linux/bpf-next/tools/lib/bpf/btf.c:455: undefined reference to `elf_strptr'
/root/linux/bpf-next/tools/lib/bpf/btf.c:462: undefined reference to `elf_getdata'
/root/linux/bpf-next/tools/lib/bpf/btf.c:470: undefined reference to `elf_getdata'
/root/linux/bpf-next/tools/lib/bpf/btf.c:445: undefined reference to `elf_nextscn'
/root/linux/bpf-next/tools/lib/bpf/btf.c:500: undefined reference to `elf_end'
collect2: error: ld returned 1 exit status
Makefile:158: recipe for target 'bpftool' failed
make: *** [bpftool] Error 1
make: Leaving directory '/root/linux/bpf-next/tools/bpf/bpftool'

----------------

Adding the V=1 flag shows the compilation is attempted with the
following command:

gcc -O2 -W -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wbad-function-cast -Wdeclaration-after-statement -Wformat-security -Wformat-y2k -Winit-self -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-system-headers -Wold-style-definition -Wpacked -Wredundant-decls -Wstrict-prototypes -Wswitch-default -Wundef -Wwrite-strings -Wformat -Wstrict-aliasing=3 -Wshadow -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ -I/root/linux/bpf-next/kernel/bpf/ -I/root/linux/bpf-next/tools/include -I/root/linux/bpf-next/tools/include/uapi -I/root/linux/bpf-next/tools/lib/bpf -I/root/linux/bpf-next/tools/perf -DBPFTOOL_VERSION='"5.4.0"' -DDISASM_FOUR_ARGS_SIGNATURE -DHAVE_LIBBFD_SUPPORT  -o bpftool map_perf_ring.o perf.o net.o cgroup.o tracelog.o btf_dumper.o xlated_dumper.o json_writer.o prog.o map.o common.o btf.o cfg.o main.o netlink_dumper.o feature.o jit_disasm.o disasm.o -lelf -lz /root/linux/bpf-next/tools/lib/bpf/libbpf.a -lbfd -ldl -lopcodes

If I move -lelf and -lz after <path>/libbpf.a, then it builds fine.

Hope this helps,
Quentin
Quentin Monnet Nov. 27, 2019, 2:31 p.m. UTC | #5
2019-11-27 11:24 UTC-0300 ~ Arnaldo Carvalho de Melo
<arnaldo.melo@gmail.com>
> Em Wed, Nov 27, 2019 at 03:15:20PM +0100, Jiri Olsa escreveu:
>> On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
>>> 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
>>> On the plus side, all build attempts from
>>> tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
>>> my setup with dynamic linking from your branch.
>>
>> cool, had no idea there was such test ;-)
> 
> Should be the the equivalent to 'make -C tools/perf build-test' :-)
> 
> Perhaps we should make tools/testing/selftests/perf/ link to that?

It is already run as part of the bpf selftests, so probably no need.

Thanks,
Quentin
Arnaldo Nov. 27, 2019, 3:48 p.m. UTC | #6
Em Wed, Nov 27, 2019 at 02:31:31PM +0000, Quentin Monnet escreveu:
> 2019-11-27 11:24 UTC-0300 ~ Arnaldo Carvalho de Melo
> <arnaldo.melo@gmail.com>
> > Em Wed, Nov 27, 2019 at 03:15:20PM +0100, Jiri Olsa escreveu:
> >> On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
> >>> 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
> >>> On the plus side, all build attempts from
> >>> tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
> >>> my setup with dynamic linking from your branch.
> >>
> >> cool, had no idea there was such test ;-)
> > 
> > Should be the the equivalent to 'make -C tools/perf build-test' :-)
> > 
> > Perhaps we should make tools/testing/selftests/perf/ link to that?
> 
> It is already run as part of the bpf selftests, so probably no need.

You mean 'make -C tools/perf build-test' is run from the bpf selftests?
 
> Thanks,
> Quentin
Quentin Monnet Nov. 27, 2019, 3:52 p.m. UTC | #7
2019-11-27 12:48 UTC-0300 ~ Arnaldo Carvalho de Melo
<arnaldo.melo@gmail.com>
> Em Wed, Nov 27, 2019 at 02:31:31PM +0000, Quentin Monnet escreveu:
>> 2019-11-27 11:24 UTC-0300 ~ Arnaldo Carvalho de Melo
>> <arnaldo.melo@gmail.com>
>>> Em Wed, Nov 27, 2019 at 03:15:20PM +0100, Jiri Olsa escreveu:
>>>> On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
>>>>> 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
>>>>> On the plus side, all build attempts from
>>>>> tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
>>>>> my setup with dynamic linking from your branch.
>>>>
>>>> cool, had no idea there was such test ;-)
>>>
>>> Should be the the equivalent to 'make -C tools/perf build-test' :-)
>>>
>>> Perhaps we should make tools/testing/selftests/perf/ link to that?
>>
>> It is already run as part of the bpf selftests, so probably no need.
> 
> You mean 'make -C tools/perf build-test' is run from the bpf selftests?

Ah, no, sorry for the confusion. I meant that test_bpftool_build.sh is
run from the bpf selftests.

I am not familiar with perf build-test, but maybe that's something worth
adding to perf selftests indeed.

Quentin
Arnaldo Nov. 27, 2019, 3:59 p.m. UTC | #8
Em Wed, Nov 27, 2019 at 03:52:06PM +0000, Quentin Monnet escreveu:
> 2019-11-27 12:48 UTC-0300 ~ Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
> > Em Wed, Nov 27, 2019 at 02:31:31PM +0000, Quentin Monnet escreveu:
> >> 2019-11-27 11:24 UTC-0300 ~ Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
> >>> Em Wed, Nov 27, 2019 at 03:15:20PM +0100, Jiri Olsa escreveu:
> >>>> On Wed, Nov 27, 2019 at 01:38:55PM +0000, Quentin Monnet wrote:
> >>>>> 2019-11-27 10:48 UTC+0100 ~ Jiri Olsa <jolsa@kernel.org>
> >>>>> On the plus side, all build attempts from
> >>>>> tools/testing/selftests/bpf/test_bpftool_build.sh pass successfully on
> >>>>> my setup with dynamic linking from your branch.

> >>>> cool, had no idea there was such test ;-)

> >>> Should be the the equivalent to 'make -C tools/perf build-test' :-)

> >>> Perhaps we should make tools/testing/selftests/perf/ link to that?

> >> It is already run as part of the bpf selftests, so probably no need.

> > You mean 'make -C tools/perf build-test' is run from the bpf selftests?

> Ah, no, sorry for the confusion. I meant that test_bpftool_build.sh is
> run from the bpf selftests.

> I am not familiar with perf build-test, but maybe that's something worth
> adding to perf selftests indeed.

Yeah, I think is worth considering plugging perf's build-test to
selftests, if only to expose it to the people that are used with
selftests and may start testing perf builds more regularly.

- Arnaldo
Alexei Starovoitov Nov. 27, 2019, 4:41 p.m. UTC | #9
On Wed, Nov 27, 2019 at 1:49 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> diff --git a/tools/build/feature/test-libbpf.c b/tools/build/feature/test-libbpf.c
> index a508756cf4cc..93566d105a64 100644
> --- a/tools/build/feature/test-libbpf.c
> +++ b/tools/build/feature/test-libbpf.c
> @@ -3,5 +3,14 @@
>
>  int main(void)
>  {
> +#ifdef BPFTOOL
> +       /*
> +        * libbpf_netlink_open (LIBBPF_0.0.6) is the latest
> +        * we need for bpftool at the moment
> +        */
> +       libbpf_netlink_open(NULL);
> +       return 0;
> +#else
>         return bpf_object__open("test") ? 0 : -1;
> +#endif

Such hack should be a clear sign that it's not appropriate for libbpf to
be public netlink api library. Few functions that it already has are for
libbpf and bpftool internal usage only.
diff mbox series

Patch

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 39bc6f0f4f0b..2b6ed08cb31e 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -1,6 +1,15 @@ 
 # SPDX-License-Identifier: GPL-2.0-only
+# LIBBPF_DYNAMIC to enable libbpf dynamic linking.
+
 include ../../scripts/Makefile.include
 include ../../scripts/utilities.mak
+include ../../scripts/Makefile.arch
+
+ifeq ($(LP64), 1)
+  libdir_relative = lib64
+else
+  libdir_relative = lib
+endif
 
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
@@ -55,7 +64,7 @@  ifneq ($(EXTRA_LDFLAGS),)
 LDFLAGS += $(EXTRA_LDFLAGS)
 endif
 
-LIBS = $(LIBBPF) -lelf -lz
+LIBS = -lelf -lz
 
 INSTALL ?= install
 RM ?= rm -f
@@ -64,6 +73,23 @@  FEATURE_USER = .bpftool
 FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib
 FEATURE_DISPLAY = libbfd disassembler-four-args zlib
 
+ifdef LIBBPF_DYNAMIC
+  # Add libbpf check with the flags to ensure bpftool
+  # specific version is detected.
+  FEATURE_CHECK_CFLAGS-libbpf := -DBPFTOOL
+  FEATURE_TESTS   += libbpf
+  FEATURE_DISPLAY += libbpf
+
+  # for linking with debug library run:
+  # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf
+  ifdef LIBBPF_DIR
+    LIBBPF_CFLAGS  := -I$(LIBBPF_DIR)/include
+    LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative)
+    FEATURE_CHECK_CFLAGS-libbpf  := $(LIBBPF_CFLAGS)
+    FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS)
+  endif
+endif
+
 check_feat := 1
 NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
 ifdef MAKECMDGOALS
@@ -88,6 +114,18 @@  ifeq ($(feature-reallocarray), 0)
 CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
 endif
 
+ifdef LIBBPF_DYNAMIC
+  ifeq ($(feature-libbpf), 1)
+    LIBS    += -lbpf
+    CFLAGS  += $(LIBBPF_CFLAGS)
+    LDFLAGS += $(LIBBPF_LDFLAGS)
+  else
+    dummy := $(error Error: No libbpf devel library found, please install libbpf-devel)
+  endif
+else
+  LIBS += $(LIBBPF)
+endif
+
 include $(wildcard $(OUTPUT)*.d)
 
 all: $(OUTPUT)bpftool
diff --git a/tools/build/feature/test-libbpf.c b/tools/build/feature/test-libbpf.c
index a508756cf4cc..93566d105a64 100644
--- a/tools/build/feature/test-libbpf.c
+++ b/tools/build/feature/test-libbpf.c
@@ -3,5 +3,14 @@ 
 
 int main(void)
 {
+#ifdef BPFTOOL
+	/*
+	 * libbpf_netlink_open (LIBBPF_0.0.6) is the latest
+	 * we need for bpftool at the moment
+	 */
+	libbpf_netlink_open(NULL);
+	return 0;
+#else
 	return bpf_object__open("test") ? 0 : -1;
+#endif
 }