tools/xenstored: add helpers for filename handling

Add some helpers for handling filenames which might need different
implementations between stubdom and daemon environments:

- expansion of relative filenames (those are not really defined today,
  just expand them to be relative to /var/lib/xen/xenstore)
- expansion of xenstore_daemon_rundir() (used e.g. for saving the state
  file in case of live update - needs to be unchanged in the daemon
  case, but should result in /var/lib/xen/xenstore for stubdom)

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

tools/xenstored/core.c

@@ -63,7 +63,7 @@ char **orig_argv;
 LIST_HEAD(connections);
 int tracefd = -1;
 bool keep_orphans = false;
-char *tracefile = NULL;
+const char *tracefile = NULL;
 static struct hashtable *nodes;
 unsigned int trace_flags = TRACE_OBJ | TRACE_IO;
 
@@ -137,6 +137,17 @@ void trace_destroy(const void *data, const char *type)
 		trace("obj: DESTROY %s %p\n", type, data);
 }
 
+/*
+ * Return an absolute filename.
+ * In case of a relative filename given as input, prepend XENSTORE_LIB_DIR.
+ */
+const char *absolute_filename(const void *ctx, const char *filename)
+{
+	if (filename[0] != '/')
+		return talloc_asprintf(ctx, XENSTORE_LIB_DIR "/%s", filename);
+	return talloc_strdup(ctx, filename);
+}
+
 void close_log(void)
 {
 	if (tracefd >= 0)
@@ -2759,7 +2770,7 @@ int main(int argc, char *argv[])
 #endif
 
 	if (tracefile)
-		tracefile = talloc_strdup(NULL, tracefile);
+		tracefile = absolute_filename(NULL, tracefile);
 
 #ifndef NO_LIVE_UPDATE
 	/* Read state in case of live update. */

tools/xenstored/core.h

@@ -341,7 +341,7 @@ void close_log(void);
 extern int orig_argc;
 extern char **orig_argv;
 
-extern char *tracefile;
+extern const char *tracefile;
 extern int tracefd;
 
 /* Trace flag values must be kept in sync with trace_switches[] contents. */
@@ -405,6 +405,9 @@ void set_socket_fd(int fd);
 void mount_9pfs(void);
 #endif
 
+const char *xenstore_rundir(void);
+const char *absolute_filename(const void *ctx, const char *filename);
+
 /* Close stdin/stdout/stderr to complete daemonize */
 void finish_daemonize(void);
 

tools/xenstored/lu_daemon.c

@@ -24,7 +24,7 @@ void lu_get_dump_state(struct lu_dump_state *state)
 	state->size = 0;
 
 	state->filename = talloc_asprintf(NULL, "%s/state_dump",
-					  xenstore_daemon_rundir());
+					  xenstore_rundir());
 	if (!state->filename)
 		barf("Allocation failure");
 
@@ -65,7 +65,7 @@ FILE *lu_dump_open(const void *ctx)
 	int fd;
 
 	filename = talloc_asprintf(ctx, "%s/state_dump",
-				   xenstore_daemon_rundir());
+				   xenstore_rundir());
 	if (!filename)
 		return NULL;
 

tools/xenstored/minios.c

@@ -128,3 +128,8 @@ void mount_9pfs(void)
 {
 	create_thread("mount-9pfs", mount_thread, NULL);
 }
+
+const char *xenstore_rundir(void)
+{
+	return XENSTORE_LIB_DIR;
+}

tools/xenstored/posix.c

@@ -326,9 +326,10 @@ void early_init(bool live_update, bool dofork, const char *pidfile)
 {
 	reopen_log();
 
-	/* Make sure xenstored directory exists. */
+	/* Make sure xenstored directories exist. */
 	/* Errors ignored here, will be reported when we open files */
 	mkdir(xenstore_daemon_rundir(), 0755);
+	mkdir(XENSTORE_LIB_DIR, 0755);
 
 	if (dofork) {
 		openlog("xenstored", 0, LOG_DAEMON);
@@ -406,3 +407,8 @@ void set_socket_fd(int fd)
 {
 	sock = fd;
 }
+
+const char *xenstore_rundir(void)
+{
+	return xenstore_daemon_rundir();
+}