perf build: Add feature detection for libelf's elf_getshdrstrndx()

That appeared after 0.140, and will be used in the SDT code, so, to
avoid bisection break on older systems, add a feature detection and
provide a stub with a pr_debug() to keep it building.

Cc: Ananth N Mavinakayanahalli <[e-mail]>
Cc: Brendan Gregg <[e-mail]>
Cc: Hemant Kumar <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/Makefile.feature

···
 	libbfd				\
 	libelf				\
 	libelf-getphdrnum		\
+	libelf-getshdrstrndx		\
 	libelf-mmap			\
 	libnuma				\
 	numa_num_possible_cpus		\

tools/build/feature/Makefile

···
 	test-cplus-demangle.bin		\
 	test-libelf.bin			\
 	test-libelf-getphdrnum.bin	\
+	test-libelf-getshdrstrndx.bin	\
 	test-libelf-mmap.bin		\
 	test-libnuma.bin		\
 	test-numa_num_possible_cpus.bin	\
···
 	$(BUILD) -lelf
 
 $(OUTPUT)test-libelf-getphdrnum.bin:
+	$(BUILD) -lelf
+
+$(OUTPUT)test-libelf-getshdrstrndx.bin:
 	$(BUILD) -lelf
 
 $(OUTPUT)test-libnuma.bin:

tools/build/feature/test-all.c

···
 # include "test-libelf-getphdrnum.c"
 #undef main
 
+#define main main_test_libelf_getshdrstrndx
+# include "test-libelf-getshdrstrndx.c"
+#undef main
+
 #define main main_test_libunwind
 # include "test-libunwind.c"
 #undef main
···
 	main_test_dwarf();
 	main_test_dwarf_getlocations();
 	main_test_libelf_getphdrnum();
+	main_test_libelf_getshdrstrndx();
 	main_test_libunwind();
 	main_test_libaudit();
 	main_test_libslang();

tools/build/feature/test-libelf-getshdrstrndx.c

···
+#include <libelf.h>
+
+int main(void)
+{
+	size_t dst;
+
+	return elf_getshdrstrndx(0, &dst);
+}

tools/perf/config/Makefile

···
     CFLAGS += -DHAVE_ELF_GETPHDRNUM_SUPPORT
   endif
 
+  ifeq ($(feature-libelf-getshdrstrndx), 1)
+    CFLAGS += -DHAVE_ELF_GETSHDRSTRNDX_SUPPORT
+  endif
+
   ifndef NO_DWARF
     ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
       msg := $(warning DWARF register mappings have not been defined for architecture $(ARCH), DWARF support disabled);

tools/perf/util/symbol-elf.c

···
 }
 #endif
 
+#ifndef HAVE_ELF_GETSHDRSTRNDX_SUPPORT
+static int elf_getshdrstrndx(Elf *elf __maybe_unused, size_t *dst __maybe_unused)
+{
+	pr_err("%s: update your libelf to > 0.140, this one lacks elf_getshdrstrndx().\n", __func__);
+	return -1;
+}
+#endif
+
 #ifndef NT_GNU_BUILD_ID
 #define NT_GNU_BUILD_ID 3
 #endif