| Message ID | 20220629143951.74851-1-quentin@isovalent.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] bpftool: Allow disabling features at compile time | expand |
On 6/29/22 4:39 PM, Quentin Monnet wrote: > Some dependencies for bpftool are optional, and the associated features > may be left aside at compilation time depending on the available > components on the system (libraries, BTF, clang version, etc.). > Sometimes, it is useful to explicitly leave some of those features aside > when compiling, even though the system would support them. For example, > this can be useful: > > - for testing bpftool's behaviour when the feature is not present, > - for copmiling for a different system, where some libraries are > missing, > - for producing a lighter binary, > - for disabling features that do not compile correctly on older > systems - although this is not supposed to happen, this is > currently the case for skeletons support on Linux < 5.15, where > struct bpf_perf_link is not defined in kernel BTF. > > For such cases, we introduce, in the Makefile, some environment > variables that can be used to disable those features: namely, > BPFTOOL_FEATURE_NO_LIBBFD, BPFTOOL_FEATURE_NO_LIBCAP, and > BPFTOOL_FEATURE_NO_SKELETONS. > > Signed-off-by: Quentin Monnet <quentin@isovalent.com> > --- > tools/bpf/bpftool/Makefile | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > index c19e0e4c41bd..b3dd6a1482f6 100644 > --- a/tools/bpf/bpftool/Makefile > +++ b/tools/bpf/bpftool/Makefile > @@ -93,8 +93,24 @@ INSTALL ?= install > RM ?= rm -f > > FEATURE_USER = .bpftool > -FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \ > - clang-bpf-co-re > +FEATURE_TESTS := disassembler-four-args zlib > + > +# Disable libbfd (for disassembling JIT-compiled programs) by setting > +# BPFTOOL_FEATURE_NO_LIBBFD > +ifeq ($(BPFTOOL_FEATURE_NO_LIBBFD),) > + FEATURE_TESTS += libbfd > +endif > +# Disable libcap (for probing features available to unprivileged users) by > +# setting BPFTOOL_FEATURE_NO_LIBCAP > +ifeq ($(BPFTOOL_FEATURE_NO_LIBCAP),) > + FEATURE_TESTS += libcap > +endif The libcap one I think is not really crucial, so that lgtm. The other ones I would keep as requirement so we don't encourage distros to strip away needed functionality for odd reasons. At min, I think the libbfd is a must, imho. > +# Disable skeletons (e.g. for profiling programs or showing PIDs of processes > +# associated to BPF objects) by setting BPFTOOL_FEATURE_NO_SKELETONS > +ifeq ($(BPFTOOL_FEATURE_NO_SKELETONS),) > + FEATURE_TESTS += clang-bpf-co-re > +endif > + > FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \ > clang-bpf-co-re > >
On 30/06/2022 16:16, Daniel Borkmann wrote: > On 6/29/22 4:39 PM, Quentin Monnet wrote: >> Some dependencies for bpftool are optional, and the associated features >> may be left aside at compilation time depending on the available >> components on the system (libraries, BTF, clang version, etc.). >> Sometimes, it is useful to explicitly leave some of those features aside >> when compiling, even though the system would support them. For example, >> this can be useful: >> >> - for testing bpftool's behaviour when the feature is not present, >> - for copmiling for a different system, where some libraries are >> missing, >> - for producing a lighter binary, >> - for disabling features that do not compile correctly on older >> systems - although this is not supposed to happen, this is >> currently the case for skeletons support on Linux < 5.15, where >> struct bpf_perf_link is not defined in kernel BTF. >> >> For such cases, we introduce, in the Makefile, some environment >> variables that can be used to disable those features: namely, >> BPFTOOL_FEATURE_NO_LIBBFD, BPFTOOL_FEATURE_NO_LIBCAP, and >> BPFTOOL_FEATURE_NO_SKELETONS. >> >> Signed-off-by: Quentin Monnet <quentin@isovalent.com> >> --- >> tools/bpf/bpftool/Makefile | 20 ++++++++++++++++++-- >> 1 file changed, 18 insertions(+), 2 deletions(-) >> >> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile >> index c19e0e4c41bd..b3dd6a1482f6 100644 >> --- a/tools/bpf/bpftool/Makefile >> +++ b/tools/bpf/bpftool/Makefile >> @@ -93,8 +93,24 @@ INSTALL ?= install >> RM ?= rm -f >> FEATURE_USER = .bpftool >> -FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \ >> - clang-bpf-co-re >> +FEATURE_TESTS := disassembler-four-args zlib >> + >> +# Disable libbfd (for disassembling JIT-compiled programs) by setting >> +# BPFTOOL_FEATURE_NO_LIBBFD >> +ifeq ($(BPFTOOL_FEATURE_NO_LIBBFD),) >> + FEATURE_TESTS += libbfd >> +endif >> +# Disable libcap (for probing features available to unprivileged >> users) by >> +# setting BPFTOOL_FEATURE_NO_LIBCAP >> +ifeq ($(BPFTOOL_FEATURE_NO_LIBCAP),) >> + FEATURE_TESTS += libcap >> +endif > > The libcap one I think is not really crucial, so that lgtm. The other > ones I would > keep as requirement so we don't encourage distros to strip away needed > functionality > for odd reasons. At min, I think the libbfd is a must, imho. Thanks Daniel, that's a legitimate concern. Probably best to avoid offering an easy option to disable the features in that case - I can live with Makefile edits if I need to test a different feature set. Please drop this patch. Thanks, Quentin
On Wed, Jun 29, 2022 at 7:40 AM Quentin Monnet <quentin@isovalent.com> wrote: > > Some dependencies for bpftool are optional, and the associated features > may be left aside at compilation time depending on the available > components on the system (libraries, BTF, clang version, etc.). > Sometimes, it is useful to explicitly leave some of those features aside > when compiling, even though the system would support them. For example, > this can be useful: > > - for testing bpftool's behaviour when the feature is not present, > - for copmiling for a different system, where some libraries are > missing, > - for producing a lighter binary, > - for disabling features that do not compile correctly on older > systems - although this is not supposed to happen, this is > currently the case for skeletons support on Linux < 5.15, where > struct bpf_perf_link is not defined in kernel BTF. > > For such cases, we introduce, in the Makefile, some environment > variables that can be used to disable those features: namely, > BPFTOOL_FEATURE_NO_LIBBFD, BPFTOOL_FEATURE_NO_LIBCAP, and > BPFTOOL_FEATURE_NO_SKELETONS. > > Signed-off-by: Quentin Monnet <quentin@isovalent.com> > --- > tools/bpf/bpftool/Makefile | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > index c19e0e4c41bd..b3dd6a1482f6 100644 > --- a/tools/bpf/bpftool/Makefile > +++ b/tools/bpf/bpftool/Makefile > @@ -93,8 +93,24 @@ INSTALL ?= install > RM ?= rm -f > > FEATURE_USER = .bpftool > -FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \ > - clang-bpf-co-re > +FEATURE_TESTS := disassembler-four-args zlib as an aside, zlib is not really optional, libbpf depends on it and bpftool depends on libbpf, so... what's the point of a feature test? > + > +# Disable libbfd (for disassembling JIT-compiled programs) by setting > +# BPFTOOL_FEATURE_NO_LIBBFD > +ifeq ($(BPFTOOL_FEATURE_NO_LIBBFD),) > + FEATURE_TESTS += libbfd > +endif > +# Disable libcap (for probing features available to unprivileged users) by > +# setting BPFTOOL_FEATURE_NO_LIBCAP > +ifeq ($(BPFTOOL_FEATURE_NO_LIBCAP),) > + FEATURE_TESTS += libcap > +endif > +# Disable skeletons (e.g. for profiling programs or showing PIDs of processes > +# associated to BPF objects) by setting BPFTOOL_FEATURE_NO_SKELETONS > +ifeq ($(BPFTOOL_FEATURE_NO_SKELETONS),) > + FEATURE_TESTS += clang-bpf-co-re > +endif > + > FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \ > clang-bpf-co-re > > -- > 2.34.1 >
On Thu, 30 Jun 2022 at 20:25, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote: > > On Wed, Jun 29, 2022 at 7:40 AM Quentin Monnet <quentin@isovalent.com> wrote: > > > > Some dependencies for bpftool are optional, and the associated features > > may be left aside at compilation time depending on the available > > components on the system (libraries, BTF, clang version, etc.). > > Sometimes, it is useful to explicitly leave some of those features aside > > when compiling, even though the system would support them. For example, > > this can be useful: > > > > - for testing bpftool's behaviour when the feature is not present, > > - for copmiling for a different system, where some libraries are > > missing, > > - for producing a lighter binary, > > - for disabling features that do not compile correctly on older > > systems - although this is not supposed to happen, this is > > currently the case for skeletons support on Linux < 5.15, where > > struct bpf_perf_link is not defined in kernel BTF. > > > > For such cases, we introduce, in the Makefile, some environment > > variables that can be used to disable those features: namely, > > BPFTOOL_FEATURE_NO_LIBBFD, BPFTOOL_FEATURE_NO_LIBCAP, and > > BPFTOOL_FEATURE_NO_SKELETONS. > > > > Signed-off-by: Quentin Monnet <quentin@isovalent.com> > > --- > > tools/bpf/bpftool/Makefile | 20 ++++++++++++++++++-- > > 1 file changed, 18 insertions(+), 2 deletions(-) > > > > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile > > index c19e0e4c41bd..b3dd6a1482f6 100644 > > --- a/tools/bpf/bpftool/Makefile > > +++ b/tools/bpf/bpftool/Makefile > > @@ -93,8 +93,24 @@ INSTALL ?= install > > RM ?= rm -f > > > > FEATURE_USER = .bpftool > > -FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \ > > - clang-bpf-co-re > > +FEATURE_TESTS := disassembler-four-args zlib > > as an aside, zlib is not really optional, libbpf depends on it and > bpftool depends on libbpf, so... what's the point of a feature test? I'm not sure either, it looks like it's mostly a way to print that the lib is missing (when it's the case) before attempting to compile [0]. Probably something we can look into removing, I agree the feature test doesn't bring much here. We'll soon need a new test for the latest libbfd changes though [1]. [0] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=d66fa3c70e598746a907e5db5ed024035e01817a [1] https://lore.kernel.org/bpf/20220622181918.ykrs5rsnmx3og4sv@alap3.anarazel.de/
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile index c19e0e4c41bd..b3dd6a1482f6 100644 --- a/tools/bpf/bpftool/Makefile +++ b/tools/bpf/bpftool/Makefile @@ -93,8 +93,24 @@ INSTALL ?= install RM ?= rm -f FEATURE_USER = .bpftool -FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \ - clang-bpf-co-re +FEATURE_TESTS := disassembler-four-args zlib + +# Disable libbfd (for disassembling JIT-compiled programs) by setting +# BPFTOOL_FEATURE_NO_LIBBFD +ifeq ($(BPFTOOL_FEATURE_NO_LIBBFD),) + FEATURE_TESTS += libbfd +endif +# Disable libcap (for probing features available to unprivileged users) by +# setting BPFTOOL_FEATURE_NO_LIBCAP +ifeq ($(BPFTOOL_FEATURE_NO_LIBCAP),) + FEATURE_TESTS += libcap +endif +# Disable skeletons (e.g. for profiling programs or showing PIDs of processes +# associated to BPF objects) by setting BPFTOOL_FEATURE_NO_SKELETONS +ifeq ($(BPFTOOL_FEATURE_NO_SKELETONS),) + FEATURE_TESTS += clang-bpf-co-re +endif + FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \ clang-bpf-co-re
Some dependencies for bpftool are optional, and the associated features may be left aside at compilation time depending on the available components on the system (libraries, BTF, clang version, etc.). Sometimes, it is useful to explicitly leave some of those features aside when compiling, even though the system would support them. For example, this can be useful: - for testing bpftool's behaviour when the feature is not present, - for copmiling for a different system, where some libraries are missing, - for producing a lighter binary, - for disabling features that do not compile correctly on older systems - although this is not supposed to happen, this is currently the case for skeletons support on Linux < 5.15, where struct bpf_perf_link is not defined in kernel BTF. For such cases, we introduce, in the Makefile, some environment variables that can be used to disable those features: namely, BPFTOOL_FEATURE_NO_LIBBFD, BPFTOOL_FEATURE_NO_LIBCAP, and BPFTOOL_FEATURE_NO_SKELETONS. Signed-off-by: Quentin Monnet <quentin@isovalent.com> --- tools/bpf/bpftool/Makefile | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)