xenstored: add --priv-domid parameter

This parameter identifies an alternative service domain which has
superuser access to the xenstore database, which is currently required
to set up a new domain's xenstore entries.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>

tools/xenstore/xenstored_core.c

@@ -1752,6 +1752,7 @@ static struct option options[] = {
 	{ "event", 1, NULL, 'e' },
 	{ "help", 0, NULL, 'H' },
 	{ "no-fork", 0, NULL, 'N' },
+	{ "priv-domid", 1, NULL, 'p' },
 	{ "output-pid", 0, NULL, 'P' },
 	{ "entry-size", 1, NULL, 'S' },
 	{ "trace-file", 1, NULL, 'T' },
@@ -1765,6 +1766,7 @@ static struct option options[] = {
 
 extern void dump_conn(struct connection *conn); 
 int dom0_event = 0;
+int priv_domid = 0;
 
 int main(int argc, char *argv[])
 {
@@ -1825,6 +1827,9 @@ int main(int argc, char *argv[])
 		case 'e':
 			dom0_event = strtol(optarg, NULL, 10);
 			break;
+		case 'p':
+			priv_domid = strtol(optarg, NULL, 10);
+			break;
 		}
 	}
 	if (optind != argc)

tools/xenstore/xenstored_core.h

@@ -169,6 +169,7 @@ void dtrace_io(const struct connection *conn, const struct buffered_data *data,
 
 extern int event_fd;
 extern int dom0_event;
+extern int priv_domid;
 
 /* Map the kernel's xenstore page. */
 void *xenbus_map(void);

tools/xenstore/xenstored_domain.c

@@ -259,7 +259,7 @@ bool domain_can_read(struct connection *conn)
 
 bool domain_is_unprivileged(struct connection *conn)
 {
-	return (conn && conn->domain && conn->domain->domid != 0);
+	return (conn && conn->domain && conn->domain->domid != 0 && conn->domain->domid != priv_domid);
 }
 
 bool domain_can_write(struct connection *conn)