[common] Conditionalize RTLD_DI_ORIGIN

RTLD_DI_ORIGIN is used to get absolute path of plugin. It is used only
for logging useful info and not strictly needed, so use it only when it
is defined (only musl is known to author of the patch)

Signed-off-by: Jan Friesse <jfriesse@redhat.com>

configure.ac

@@ -205,6 +205,10 @@ AC_SEARCH_LIBS([dlopen], [dl dld], , [AC_MSG_ERROR([dlopen not found])])
 AC_SUBST([dl_LIBS], [$LIBS])
 LIBS="$saved_LIBS"
 
+# Check RTLD_DI_ORIGIN (not decalred by musl. glibc has it as an enum so cannot use ifdef)
+AC_CHECK_DECL([RTLD_DI_ORIGIN], [AC_DEFINE([HAVE_RTLD_DI_ORIGIN], 1,
+    [define when RTLD_DI_ORIGIN is declared])], ,[[#include <dlfcn.h>]])
+
 # OS detection
 
 AC_MSG_CHECKING([for os in ${host_os}])

libknet/common.c

@@ -12,6 +12,8 @@
 #include <fcntl.h>
 #include <dlfcn.h>
 #include <errno.h>
+#include <libgen.h>
+#include <link.h>
 #include <string.h>
 #include <sys/param.h>
 #include <sys/types.h>
@@ -54,6 +56,30 @@ int _fdset_nonblock(int fd)
 	return 0;
 }
 
+static int get_lib_dir(void *lib_handle, char dir[MAXPATHLEN])
+{
+	int res;
+#ifndef HAVE_RTLD_DI_ORIGIN
+	struct link_map *lm;
+	char l_name[MAXPATHLEN];
+#endif
+
+#ifdef HAVE_RTLD_DI_ORIGIN
+	res = dlinfo(lib_handle, RTLD_DI_ORIGIN, dir);
+#else
+	/*
+	 * musl libc doesn't support RTLD_DI_ORIGIN
+	 */
+	res = dlinfo(lib_handle, RTLD_DI_LINKMAP, &lm);
+	if (res == 0) {
+		snprintf(l_name, sizeof(l_name), "%s", lm->l_name);
+		snprintf(dir, MAXPATHLEN, "%s", dirname(l_name));
+	}
+#endif
+
+	return res;
+}
+
 static void *open_lib(knet_handle_t knet_h, const char *libname, int extra_flags)
 {
 	void *ret = NULL;
@@ -81,7 +107,7 @@ static void *open_lib(knet_handle_t knet_h, const char *libname, int extra_flags
 	memset(dir, 0, sizeof(dir));
 	memset(link, 0, sizeof(link));
 	memset(path, 0, sizeof(path));
-	if (dlinfo(ret, RTLD_DI_ORIGIN, &dir) < 0) {
+	if (get_lib_dir(ret, dir) < 0) {
 		/*
 		 * should we dlclose and return error?
 		 */