perf buildid-cache: Consolidate .build-id cache path generators

Consolidate .build-id cache path generating routines to
build_id__filename() function. Other functions must use it to get the
buildid cache path (link path) from build-id. This can reduce the risk
of partial-update.

Signed-off-by: Masami Hiramatsu <[e-mail]>
Acked-by: Namhyung Kim <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Hemant Kumar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/build-id.c

···
 	return raw - build_id;
 }
 
+/* asnprintf consolidates asprintf and snprintf */
+static int asnprintf(char **strp, size_t size, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	if (!strp)
+		return -EINVAL;
+
+	va_start(ap, fmt);
+	if (*strp)
+		ret = vsnprintf(*strp, size, fmt, ap);
+	else
+		ret = vasprintf(strp, fmt, ap);
+	va_end(ap);
+
+	return ret;
+}
+
+static char *build_id__filename(const char *sbuild_id, char *bf, size_t size)
+{
+	char *tmp = bf;
+	int ret = asnprintf(&bf, size, "%s/.build-id/%.2s/%s", buildid_dir,
+			    sbuild_id, sbuild_id + 2);
+	if (ret < 0 || (tmp && size < (unsigned int)ret))
+		return NULL;
+	return bf;
+}
+
 char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size)
 {
 	char build_id_hex[BUILD_ID_SIZE * 2 + 1];
···
 		return NULL;
 
 	build_id__sprintf(dso->build_id, sizeof(dso->build_id), build_id_hex);
-	if (bf == NULL) {
-		if (asprintf(&bf, "%s/.build-id/%.2s/%s", buildid_dir,
-			     build_id_hex, build_id_hex + 2) < 0)
-			return NULL;
-	} else
-		snprintf(bf, size, "%s/.build-id/%.2s/%s", buildid_dir,
-			 build_id_hex, build_id_hex + 2);
-	return bf;
+	return build_id__filename(build_id_hex, bf, size);
 }
 
 #define dsos__for_each_with_build_id(pos, head)	\
···
 {
 	const size_t size = PATH_MAX;
 	char *realname, *filename = zalloc(size),
-	     *linkname = zalloc(size), *targetname;
+	     *linkname = zalloc(size), *targetname, *tmp;
 	int len, err = -1;
 	bool slash = is_kallsyms || is_vdso;
 
···
 			goto out_free;
 	}
 
-	len = scnprintf(linkname, size, "%s/.build-id/%.2s",
-			buildid_dir, sbuild_id);
+	if (!build_id__filename(sbuild_id, linkname, size))
+		goto out_free;
+	tmp = strrchr(linkname, '/');
+	*tmp = '\0';
 
 	if (access(linkname, X_OK) && mkdir_p(linkname, 0755))
 		goto out_free;
 
-	snprintf(linkname + len, size - len, "/%s", sbuild_id + 2);
+	*tmp = '/';
 	targetname = filename + strlen(buildid_dir) - 5;
 	memcpy(targetname, "../..", 5);
 
···
 {
 	const size_t size = PATH_MAX;
 	char *filename = zalloc(size),
-	     *linkname = zalloc(size);
+	     *linkname = zalloc(size), *tmp;
 	int err = -1;
 
 	if (filename == NULL || linkname == NULL)
 		goto out_free;
 
-	snprintf(linkname, size, "%s/.build-id/%.2s/%s",
-		 buildid_dir, sbuild_id, sbuild_id + 2);
+	if (!build_id__filename(sbuild_id, linkname, size))
+		goto out_free;
 
 	if (access(linkname, F_OK))
 		goto out_free;
···
 	/*
 	 * Since the link is relative, we must make it absolute:
 	 */
-	snprintf(linkname, size, "%s/.build-id/%.2s/%s",
-		 buildid_dir, sbuild_id, filename);
+	tmp = strrchr(linkname, '/') + 1;
+	snprintf(tmp, size - (tmp - linkname), "%s", filename);
 
 	if (unlink(linkname))
 		goto out_free;