On 1/30/25 2:33 PM, Daniel Xu wrote:
Since 67ab80a01886 ("selftests/bpf: Prefer static linking for LLVM
libraries"), only statically linking test_progs is supported. However,
some distros only provide a dynamically linkable LLVM.
This commit adds a fallback for dynamically linking LLVM if static
linking is not available. If both options are available, static linking
is chosen.
Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 6722080b2107..da514030a153 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -184,9 +184,14 @@ ifeq ($(feature-llvm),1)
LLVM_CONFIG_LIB_COMPONENTS := mcdisassembler all-targets
# both llvm-config and lib.mk add -D_GNU_SOURCE, which ends up as conflict
LLVM_CFLAGS += $(filter-out -D_GNU_SOURCE,$(shell $(LLVM_CONFIG) --cflags))
- LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --link-static --libs $(LLVM_CONFIG_LIB_COMPONENTS))
- LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --link-static --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
- LLVM_LDLIBS += -lstdc++
+ # Prefer linking statically if it's available, otherwise fallback to shared
+ ifeq ($(shell $(LLVM_CONFIG) --link-static --libs &> /dev/null && echo static),static)
+ LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --link-static --libs $(LLVM_CONFIG_LIB_COMPONENTS))
+ LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --link-static --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
+ LLVM_LDLIBS += -lstdc++
+ else
+ LLVM_LDLIBS += $(shell $(LLVM_CONFIG) --link-shared --libs $(LLVM_CONFIG_LIB_COMPONENTS))
+ endif
LLVM_LDFLAGS += $(shell $(LLVM_CONFIG) --ldflags)
endif
Although your change looks good, but maybe you can look at bpftool Makefile?
# If LLVM is available, use it for JIT disassembly
CFLAGS += -DHAVE_LLVM_SUPPORT
LLVM_CONFIG_LIB_COMPONENTS := mcdisassembler all-targets
# llvm-config always adds -D_GNU_SOURCE, however, it may already be in CFLAGS
# (e.g. when bpftool build is called from selftests build as selftests
# Makefile includes lib.mk which sets -D_GNU_SOURCE) which would cause
# compilation error due to redefinition. Let's filter it out here.
CFLAGS += $(filter-out -D_GNU_SOURCE,$(shell $(LLVM_CONFIG) --cflags))
LIBS += $(shell $(LLVM_CONFIG) --libs $(LLVM_CONFIG_LIB_COMPONENTS))
ifeq ($(shell $(LLVM_CONFIG) --shared-mode),static)
LIBS += $(shell $(LLVM_CONFIG) --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
LIBS += -lstdc++
endif
LDFLAGS += $(shell $(LLVM_CONFIG) --ldflags)
It would be great if the selftests shared library handling to be the same as bpftool's.
