[PATCH v2 1/7] tools build: Add feature check for elfutils libasm

[Ian Rogers <irogers@google.com>]

This commit introduces a build-time feature test for the elfutils libasm
library in the shared tools/build system. It adds the test program and
updates the Makefiles to attempt building it to detect support.

Note on static linking: pkg-config for libdw/libelf on modern systems
does not list -lebl as a dependency. Older versions of elfutils that
require explicitly linking -lebl statically are unsupported by this
feature check.
---
 tools/build/Makefile.feature      |  2 ++
 tools/build/feature/Makefile      |  9 +++++++++
 tools/build/feature/test-libasm.c | 19 +++++++++++++++++++
 3 files changed, 30 insertions(+)
 create mode 100644 tools/build/feature/test-libasm.c

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index ed1374af31c1..422329dbc20a 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -118,6 +118,7 @@ FEATURE_TESTS_EXTRA :=                  \
          hello                          \
          babeltrace2-ctf-writer         \
          libcapstone                    \
+         libasm                         \
          libcheck                       \
          libbfd-liberty                 \
          libbfd-liberty-z               \
@@ -150,6 +151,7 @@ FEATURE_DISPLAY ?=              \
          numa_num_possible_cpus \
          libpython              \
          libcapstone            \
+         libasm                 \
          llvm-perf              \
          zlib                   \
          lzma                   \
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 62909a9c799d..f0f39a2ab203 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -47,6 +47,7 @@ FILES=                                          \
          test-timerfd.bin                       \
          test-babeltrace2-ctf-writer.bin        \
          test-libcapstone.bin			\
+         test-libasm.bin			\
          test-libcheck.bin			\
          test-compile-32.bin                    \
          test-compile-x32.bin                   \
@@ -184,6 +185,11 @@ ifeq ($(findstring -static,${LDFLAGS}),-static)
   DWARFLIBS += -ldl
 endif
 
+ASMLIBS := -lasm -ldw -lelf
+ifeq ($(findstring -static,${LDFLAGS}),-static)
+  ASMLIBS += -lz -llzma -lbz2 -lzstd
+endif
+
 $(OUTPUT)test-libdw.bin:
 	$(BUILD) $(DWLIBS)
 
@@ -311,6 +317,9 @@ $(OUTPUT)test-babeltrace2-ctf-writer.bin:
 $(OUTPUT)test-libcapstone.bin:
 	$(BUILD) # -lcapstone provided by $(FEATURE_CHECK_LDFLAGS-libcapstone)
 
+$(OUTPUT)test-libasm.bin:
+	$(BUILD) $(ASMLIBS)
+
 $(OUTPUT)test-libcheck.bin:
 	$(BUILD) # -lcheck is provided by $(FEATURE_CHECK_LDFLAGS-libcheck)
 
diff --git a/tools/build/feature/test-libasm.c b/tools/build/feature/test-libasm.c
new file mode 100644
index 000000000000..f3598ad1cc9e
--- /dev/null
+++ b/tools/build/feature/test-libasm.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stddef.h>
+#include <elfutils/libasm.h>
+#include <gelf.h>
+
+typedef struct ebl Ebl;
+extern Ebl *ebl_openbackend (Elf *elf);
+extern void ebl_closebackend (Ebl *ebl);
+
+int main(void)
+{
+	Elf *elf = elf_begin(0, ELF_C_READ, NULL);
+	Ebl *ebl = ebl_openbackend(elf);
+	DisasmCtx_t *ctx = disasm_begin(ebl, elf, NULL);
+	disasm_end(ctx);
+	ebl_closebackend(ebl);
+	elf_end(elf);
+	return 0;
+}
-- 
2.54.0.1064.gd145956f57-goog