[apparmor] [PATCH 06/13] Enable the parser to pass the next token to be returned to the lexer

[Kees Cook]

Hi John,

On Tue, Feb 14, 2012 at 09:32:28AM -0800, John Johansen wrote:
> Currently the parser can not directly influence the lexer output.  This
> limits the grammar and also how the parser can be invoked.  Allow the
> parser to pass the next TOKEN that the lexer will return.
> 
> This is has two uses:  It allows us to trick the bison parser into having
> multiple start symbols, allowing us to say invoke the parser on an
> individual network or file rule.  It also allows the semantic analysis of
> the parser to change the language recognized.  This can be leveraged to
> overcome some of the limitation of bison's LALR parse generator.
> 
> Signed-off-by: John Johansen <john.johansen at canonical.com>
> ---
>  parser/parser.h      |    5 +++++
>  parser/parser_lex.l  |    9 +++++++++
>  parser/parser_yacc.y |    3 +++
>  3 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/parser/parser.h b/parser/parser.h
> index 346620a..7d71fd8 100644
> --- a/parser/parser.h
> +++ b/parser/parser.h
> @@ -25,6 +25,11 @@
>  #include "libapparmor_re/apparmor_re.h"
>  #include "libapparmor_re/aare_rules.h"
>  
> +/* Global variable to pass token to lexer.  Will be replaced by parameter
> + * when lexer and parser are made reentrant
> + */
> +extern int parser_token;
> +
>  typedef enum pattern_t pattern_t;
>  
>  struct flagval {
> diff --git a/parser/parser_lex.l b/parser/parser_lex.l
> index e4f8f66..87ede55 100644
> --- a/parser/parser_lex.l
> +++ b/parser/parser_lex.l
> @@ -222,6 +222,15 @@ LT_EQUAL	<=
>  
>  %%
>  
> +%{
> +/* Copied directly into yylex function */
> +	if (parser_token) {
> +		int t = parser_token;
> +		parser_token = 0;
> +		return t;
> +	}
> +%}
> +
>  <INCLUDE>{
>  	{WS}+	{ /* Eat whitespace */ }
>  	\<([^\> \t\n]+)\>	{	/* <filename> */
> diff --git a/parser/parser_yacc.y b/parser/parser_yacc.y
> index af56a20..2a4fa5d 100644
> --- a/parser/parser_yacc.y
> +++ b/parser/parser_yacc.y
> @@ -69,6 +69,8 @@ struct value_list {
>  	struct value_list *next;
>  };
>  
> +int parser_token = 0;
> +
>  void free_value_list(struct value_list *list);
>  struct cod_entry *do_file_rule(char *namespace, char *id, int mode,
>  			       char *link_id, char *nt);
> @@ -77,6 +79,7 @@ void add_local_entry(struct codomain *cod);
>  
>  %}
>  
> +
>  %token TOK_ID
>  %token TOK_CONDID
>  %token TOK_CARET

Needless whitespace addition in this chunk. Otherwise, looks fine to me.

-Kees

-- 
Kees Cook