[PATCH bpf-next 2/3] bpftool: Add libbpf's version number to "bpftool version" output

[Quentin Monnet <quentin@xxxxxxxxxxxxx>]

To help users check what version of libbpf has been used to compile
bpftool, embed the version number and print it along with bpftool's own
version number.

Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
---
 tools/bpf/bpftool/Documentation/common_options.rst | 3 ++-
 tools/bpf/bpftool/Makefile                         | 2 ++
 tools/bpf/bpftool/main.c                           | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/Documentation/common_options.rst b/tools/bpf/bpftool/Documentation/common_options.rst
index 908487b9c2ad..24166733d3ae 100644
--- a/tools/bpf/bpftool/Documentation/common_options.rst
+++ b/tools/bpf/bpftool/Documentation/common_options.rst
@@ -4,7 +4,8 @@
 	  Print short help message (similar to **bpftool help**).
 
 -V, --version
-	  Print version number (similar to **bpftool version**), and optional
+	  Print bpftool's version number (similar to **bpftool version**), the
+	  version of libbpf that was used to compile the binary, and optional
 	  features that were included when bpftool was compiled. Optional
 	  features include linking against libbfd to provide the disassembler
 	  for JIT-ted programs (**bpftool prog dump jited**) and usage of BPF
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 83369f55df61..bd5a8cafac49 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -42,6 +42,7 @@ LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hash
 ifeq ($(BPFTOOL_VERSION),)
 BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
 endif
+LIBBPF_VERSION := $(shell make -r --no-print-directory -sC $(BPF_DIR) libbpfversion)
 
 $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR):
 	$(QUIET_MKDIR)mkdir -p $@
@@ -84,6 +85,7 @@ CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
 	-I$(srctree)/tools/include \
 	-I$(srctree)/tools/include/uapi
 CFLAGS += -DBPFTOOL_VERSION='"$(BPFTOOL_VERSION)"'
+CFLAGS += -DLIBBPF_VERSION='"$(LIBBPF_VERSION)"'
 ifneq ($(EXTRA_CFLAGS),)
 CFLAGS += $(EXTRA_CFLAGS)
 endif
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 9d01fa9de033..4bda73057980 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -89,6 +89,8 @@ static int do_version(int argc, char **argv)
 
 		jsonw_name(json_wtr, "version");
 		jsonw_printf(json_wtr, "\"%s\"", BPFTOOL_VERSION);
+		jsonw_name(json_wtr, "libbpf_version");
+		jsonw_printf(json_wtr, "\"%s\"", LIBBPF_VERSION);
 
 		jsonw_name(json_wtr, "features");
 		jsonw_start_object(json_wtr);	/* features */
@@ -102,6 +104,7 @@ static int do_version(int argc, char **argv)
 		unsigned int nb_features = 0;
 
 		printf("%s v%s\n", bin_name, BPFTOOL_VERSION);
+		printf("using libbpf v%s\n", LIBBPF_VERSION);
 		printf("features:");
 		if (has_libbfd) {
 			printf(" libbfd");
-- 
2.32.0