[PATCH bpf-next v2] bpftool: Allow explicitly skip llvm dependency

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

From: Mykyta Yatsenko <yatsenko@meta.com>

BPF selftests depend on the bpftool. In some environments we may link
bpftool to llvm dynamically and then try to run somewhere where llvm
library is not available.
It's simpler to avoid llvm linking altogether in those cases, this
change allows to do it.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
 tools/bpf/bpftool/Makefile           | 12 +++++++++++-
 tools/testing/selftests/bpf/Makefile |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 5442073a2e42..f2448e247c5d 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -97,6 +97,11 @@ RM ?= rm -f
 
 FEATURE_USER = .bpftool
 
+# Set SKIP_LLVM=1 to build bpftool without LLVM dependency. When set,
+# bpftool will fall back to libbfd for JIT disassembly (if available),
+# or build without disassembly support.
+SKIP_LLVM ?=
+
 FEATURE_TESTS := clang-bpf-co-re
 FEATURE_TESTS += llvm
 FEATURE_TESTS += libcap
@@ -150,7 +155,12 @@ all: $(OUTPUT)bpftool
 SRCS := $(wildcard *.c)
 
 ifeq ($(feature-llvm),1)
-  # If LLVM is available, use it for JIT disassembly
+ifneq ($(SKIP_LLVM),1)
+HAS_LLVM := 1
+endif
+endif
+
+ifeq ($(HAS_LLVM),1)
   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
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c6bf4dfb1495..4dfff1cfacb6 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -331,6 +331,7 @@ $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
 		    OUTPUT=$(HOST_BUILD_DIR)/bpftool/			       \
 		    LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/		       \
 		    LIBBPF_DESTDIR=$(HOST_SCRATCH_DIR)/			       \
+		    SKIP_LLVM=$(SKIP_LLVM)				       \
 		    prefix= DESTDIR=$(HOST_SCRATCH_DIR)/ install-bin
 
 ifneq ($(CROSS_COMPILE),)
@@ -343,6 +344,7 @@ $(CROSS_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)	\
 		    OUTPUT=$(BUILD_DIR)/bpftool/				\
 		    LIBBPF_OUTPUT=$(BUILD_DIR)/libbpf/				\
 		    LIBBPF_DESTDIR=$(SCRATCH_DIR)/				\
+		    SKIP_LLVM=$(SKIP_LLVM)					\
 		    prefix= DESTDIR=$(SCRATCH_DIR)/ install-bin
 endif
 
-- 
2.52.0