util: Helper for reading a string from image

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -394,8 +394,6 @@ int collect_reg_files(void)
 		return -1;
 
 	while (1) {
-		int len;
-
 		rfi = xmalloc(sizeof(*rfi));
 		ret = -1;
 		if (rfi == NULL)
@@ -406,18 +404,11 @@ int collect_reg_files(void)
 		if (ret <= 0)
 			break;
 
-		len = rfi->rfe.len;
-		rfi->path = xmalloc(len + 1);
-		ret = -1;
-		if (rfi->path == NULL)
-			break;
-
-		ret = read_img_buf(fd, rfi->path, len);
+		ret = read_img_str(fd, &rfi->path, rfi->rfe.len);
 		if (ret < 0)
 			break;
 
 		rfi->remap_path = NULL;
-		rfi->path[len] = '\0';
 
 		pr_info("Collected [%s] ID %#x\n", rfi->path, rfi->rfe.id);
 		file_desc_add(&rfi->d, rfi->rfe.id, &reg_desc_ops);

include/util.h

@@ -235,6 +235,8 @@ int do_open_proc(pid_t pid, int flags, const char *fmt, ...);
 		___p;							\
 	})
 
+#include <stdlib.h>
+
 #define xstrdup(str)		__xalloc(strdup, strlen(str) + 1, str)
 #define xmalloc(size)		__xalloc(malloc, size, size)
 #define xzalloc(size)		__xalloc(calloc, size, 1, size)
@@ -287,4 +289,29 @@ int is_anon_link_type(int lfd, char *type);
 	 ((c) >= 'a' && (c) <= 'f')	||	\
 	 ((c) >= 'A' && (c) <= 'F'))
 
+/*
+ * read_img_str -- same as read_img_buf, but allocates memory for
+ * the buffer and puts the '\0' at the end
+ */
+
+static inline int read_img_str(int fd, char **pstr, int size)
+{
+	int ret;
+	char *str;
+
+	str = xmalloc(size + 1);
+	if (!str)
+		return -1;
+
+	ret = read_img_buf(fd, str, size);
+	if (ret < 0) {
+		xfree(str);
+		return -1;
+	}
+
+	str[size] = '\0';
+	*pstr = str;
+	return 0;
+}
+
 #endif /* UTIL_H_ */