perf disassemble: Extract logic to find file to pass to objdump to a separate function

Disentangling this a bit further, more to come.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-7bjv2xazuyzs0xw01mlwosn5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/annotate.c

@@ -1162,29 +1162,19 @@ int symbol__strerror_disassemble(struct symbol *sym __maybe_unused, struct map *
 	return 0;
 }
 
-int symbol__disassemble(struct symbol *sym, struct map *map, size_t privsize)
+static int dso__disassemble_filename(struct dso *dso, char *filename, size_t filename_size)
 {
-	struct dso *dso = map->dso;
-	char *filename;
-	char command[PATH_MAX * 2];
-	FILE *file;
-	char symfs_filename[PATH_MAX];
-	struct kcore_extract kce;
-	bool delete_extract = false;
-	int stdout_fd[2];
-	int lineno = 0;
-	int nline;
-	pid_t pid;
-	int err = SYMBOL_ANNOTATE_ERRNO__NO_VMLINUX;
+	char linkname[PATH_MAX];
+	char *build_id_filename;
 
 	if (dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
 	    !dso__is_kcore(dso))
-		goto out;
+		return SYMBOL_ANNOTATE_ERRNO__NO_VMLINUX;
 
-	filename = dso__build_id_filename(dso, NULL, 0);
-	if (filename) {
-		symbol__join_symfs(symfs_filename, filename);
-		free(filename);
+	build_id_filename = dso__build_id_filename(dso, NULL, 0);
+	if (build_id_filename) {
+		__symbol__join_symfs(filename, filename_size, build_id_filename);
+		free(build_id_filename);
 	} else {
 		if (dso->has_build_id)
 			return ENOMEM;
@@ -1192,18 +1182,38 @@ int symbol__disassemble(struct symbol *sym, struct map *map, size_t privsize)
 	}
 
 	if (dso__is_kcore(dso) ||
-	    readlink(symfs_filename, command, sizeof(command)) < 0 ||
-	    strstr(command, DSO__NAME_KALLSYMS) ||
-	    access(symfs_filename, R_OK)) {
+	    readlink(filename, linkname, sizeof(linkname)) < 0 ||
+	    strstr(linkname, DSO__NAME_KALLSYMS) ||
+	    access(filename, R_OK)) {
 fallback:
 		/*
 		 * If we don't have build-ids or the build-id file isn't in the
 		 * cache, or is just a kallsyms file, well, lets hope that this
 		 * DSO is the same as when 'perf record' ran.
 		 */
-		symbol__join_symfs(symfs_filename, dso->long_name);
+		__symbol__join_symfs(filename, filename_size, dso->long_name);
 	}
 
+	return 0;
+}
+
+int symbol__disassemble(struct symbol *sym, struct map *map, size_t privsize)
+{
+	struct dso *dso = map->dso;
+	char command[PATH_MAX * 2];
+	FILE *file;
+	char symfs_filename[PATH_MAX];
+	struct kcore_extract kce;
+	bool delete_extract = false;
+	int stdout_fd[2];
+	int lineno = 0;
+	int nline;
+	pid_t pid;
+	int err = dso__disassemble_filename(dso, symfs_filename, sizeof(symfs_filename));
+
+	if (err)
+		return err;
+
 	pr_debug("%s: filename=%s, sym=%s, start=%#" PRIx64 ", end=%#" PRIx64 "\n", __func__,
 		 symfs_filename, sym->name, map->unmap_ip(map, sym->start),
 		 map->unmap_ip(map, sym->end));