parser: Support stacking in exec and change_profile rules

Allow for a leading '&' character to be present in the named transition
target strings to indicate that the transition should stack the current
profile with the specified profile.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: John Johansen <john.johansen@canonical.com>

parser/parser.h

@@ -386,7 +386,7 @@ extern char *process_var(const char *var);
 extern int parse_mode(const char *mode);
 extern int parse_X_mode(const char *X, int valid, const char *str_mode, int *mode, int fail);
 bool label_contains_ns(const char *label);
-void parse_label(char **ns, char **name, const char *label);
+void parse_label(bool *stack, char **ns, char **name, const char *label);
 extern struct cod_entry *new_entry(char *id, int mode, char *link_id);
 
 /* returns -1 if value != true or false, otherwise 0 == false, 1 == true */

parser/parser_lex.l

@@ -192,6 +192,7 @@ OPEN_BRACE 	\{
 CLOSE_BRACE 	\}
 SLASH		\/
 COLON		:
+AMPERSAND	&
 END_OF_RULE	[,]
 RANGE		-
 MODE_CHARS 	([RrWwaLlMmkXx])|(([Pp]|[Cc])[Xx])|(([Pp]|[Cc])?([IiUu])[Xx])
@@ -225,8 +226,8 @@ SET_VAR_PREFIX  @
 SET_VARIABLE	{SET_VAR_PREFIX}(\{{VARIABLE_NAME}\}|{VARIABLE_NAME})
 BOOL_VARIABLE	$(\{{VARIABLE_NAME}\}|{VARIABLE_NAME})
 
-LABEL		(\/|{SET_VARIABLE}{POST_VAR_ID}|{COLON}){ID}*
-QUOTED_LABEL	\"(\/|{SET_VAR_PREFIX}|{COLON})([^\0"]|\\\")*\"
+LABEL		(\/|{SET_VARIABLE}{POST_VAR_ID}|{COLON}|{AMPERSAND}){ID}*
+QUOTED_LABEL	\"(\/|{SET_VAR_PREFIX}|{COLON}|{AMPERSAND})([^\0"]|\\\")*\"
 
 OPEN_PAREN 	\(
 CLOSE_PAREN	\)

parser/parser_misc.c

@@ -571,6 +571,7 @@ int parse_X_mode(const char *X, int valid, const char *str_mode, int *mode, int
 
 /**
  * parse_label - break a label down to the namespace and profile name
+ * @stack: Will be true if the first char in @label is '&' to indicate stacking
  * @ns: Will point to the first char in the namespace upon return or NULL
  *      if no namespace is present
  * @ns_len: Number of chars in the namespace string or 0 if no namespace
@@ -589,7 +590,8 @@ int parse_X_mode(const char *X, int valid, const char *str_mode, int *mode, int
  * 2) Namespace is empty meaning @label starts with "::"
  * 3) Profile name is empty
  */
-static int _parse_label(char **ns, size_t *ns_len,
+static int _parse_label(bool *stack,
+			char **ns, size_t *ns_len,
 			char **name, size_t *name_len,
 			const char *label)
 {
@@ -597,6 +599,17 @@ static int _parse_label(char **ns, size_t *ns_len,
 	const char *ns_start = NULL;
 	const char *ns_end = NULL;
 
+	if (label[0] == '&') {
+		/**
+		 * Leading ampersand means that the current profile should
+		 * be stacked with the rest of the label
+		 */
+		*stack = true;
+		label++;
+	} else {
+		*stack = false;
+	}
+
 	if (label[0] != ':') {
 		/* There is no namespace specified in the label */
 		name_start = label;
@@ -639,15 +652,16 @@ static int _parse_label(char **ns, size_t *ns_len,
 
 bool label_contains_ns(const char *label)
 {
+	bool stack = false;
 	char *ns = NULL;
 	char *name = NULL;
 	size_t ns_len = 0;
 	size_t name_len = 0;
 
-	return _parse_label(&ns, &ns_len, &name, &name_len, label) == 0 && ns;
+	return _parse_label(&stack, &ns, &ns_len, &name, &name_len, label) == 0 && ns;
 }
 
-void parse_label(char **_ns, char **_name, const char *label)
+void parse_label(bool *_stack, char **_ns, char **_name, const char *label)
 {
 	char *ns = NULL;
 	char *name = NULL;
@@ -655,7 +669,7 @@ void parse_label(char **_ns, char **_name, const char *label)
 	size_t name_len = 0;
 	int res;
 
-	res = _parse_label(&ns, &ns_len, &name, &name_len, label);
+	res = _parse_label(_stack, &ns, &ns_len, &name, &name_len, label);
 	if (res == 1) {
 		yyerror(_("Namespace not terminated: %s\n"), label);
 	} else if (res == 2) {

parser/parser_yacc.y

@@ -305,14 +305,19 @@ opt_id_or_var: { /* nothing */ $$ = NULL; }
 profile_base: TOK_ID opt_id_or_var flags TOK_OPEN rules TOK_CLOSE
 	{
 		Profile *prof = $5;
+		bool self_stack = false;
 
 		if (!prof) {
 			yyerror(_("Memory allocation error."));
 		}
 
-		parse_label(&prof->ns, &prof->name, $1);
+		parse_label(&self_stack, &prof->ns, &prof->name, $1);
 		free($1);
 
+		if (self_stack) {
+			yyerror(_("Profile names must begin with a '/' or a namespace"));
+		}
+
 		/* Honor the --namespace-string command line option */
 		if (profile_ns) {
 			/**

parser/tst/simple_tests/change_profile/stacking_ok_1.sd

@@ -0,0 +1,7 @@
+#
+#=DESCRIPTION change_profile w/ stacking
+#=EXRESULT PASS
+#
+/usr/bin/foo {
+   change_profile -> &/bin/foo,
+}

parser/tst/simple_tests/change_profile/stacking_ok_2.sd

@@ -0,0 +1,7 @@
+#
+#=DESCRIPTION change_profile w/ stacking
+#=EXRESULT PASS
+#
+/usr/bin/foo {
+   change_profile -> &bar,
+}

parser/tst/simple_tests/change_profile/stacking_ok_3.sd

@@ -0,0 +1,7 @@
+#
+#=DESCRIPTION change_profile w/ stacking
+#=EXRESULT PASS
+#
+/usr/bin/foo {
+   change_profile /bin/foo -> &bar,
+}

parser/tst/simple_tests/file/stacking_ok_1.sd

@@ -0,0 +1,7 @@
+#
+#=Description basic file exec rule with stacking target
+#=EXRESULT PASS
+#
+/usr/bin/foo {
+  /bin/bar px -> &baz,
+}