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@xxxxxxxxxxxxx>
---
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
