kconfig: support user-defined function and recursively expanded variable

Now, we got a basic ability to test compiler capability in Kconfig.

config CC_HAS_STACKPROTECTOR
        def_bool $(shell,($(CC) -Werror -fstack-protector -E -x c /dev/null -o /dev/null 2>/dev/null) && echo y || echo n)

This works, but it is ugly to repeat this long boilerplate.

We want to describe like this:

config CC_HAS_STACKPROTECTOR
        bool
        default $(cc-option,-fstack-protector)

It is straight-forward to add a new function, but I do not like to
hard-code specialized functions like that.  Hence, here is another
feature, user-defined function.  This works as a textual shorthand
with parameterization.

A user-defined function is defined by using the = operator, and can
be referenced in the same way as built-in functions.  A user-defined
function in Make is referenced like $(call my-func,arg1,arg2), but I
omitted the 'call' to make the syntax shorter.

The definition of a user-defined function contains $(1), $(2), etc.
in its body to reference the parameters.  It is grammatically valid
to pass more or fewer arguments when calling it.  We already exploit
this feature in our makefiles; scripts/Kbuild.include defines cc-option
which takes two arguments at most, but most of the callers pass only
one argument.

By the way, a variable is supported as a subset of this feature since
a variable is "a user-defined function with zero argument".  In this
context, I mean "variable" as recursively expanded variable.  I will
add a different flavored variable in the next commit.

The code above can be written as follows:

[Example Code]

  success = $(shell,($(1)) >/dev/null 2>&1 && echo y || echo n)
  cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)

  config CC_HAS_STACKPROTECTOR
          def_bool $(cc-option,-fstack-protector)

[Result]
  $ make -s alldefconfig && tail -n 1 .config
  CONFIG_CC_HAS_STACKPROTECTOR=y

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

4 files changed, 120 insertions, 4 deletions

diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
index c46929fab7d9..2b16d6e1b2db 100644
--- a/scripts/kconfig/lkc_proto.h
+++ b/scripts/kconfig/lkc_proto.h
@@ -50,6 +50,8 @@ const char * prop_get_type_name(enum prop_type type);
 
 /* preprocess.c */
 void env_write_dep(FILE *f, const char *auto_conf_name);
+void variable_add(const char *name, const char *value);
+void variable_all_del(void);
 char *expand_string(const char *in);
 char *expand_dollar(const char **str);
 char *expand_one_token(const char **str);
diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index 528be594e1d0..46487fe6b36c 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -178,6 +178,72 @@ static char *function_expand(const char *name, int argc, char *argv[])
 }
 
 /*
+ * Variables (and user-defined functions)
+ */
+static LIST_HEAD(variable_list);
+
+struct variable {
+        char *name;
+        char *value;
+        struct list_head node;
+};
+
+static struct variable *variable_lookup(const char *name)
+{
+        struct variable *v;
+
+        list_for_each_entry(v, &variable_list, node) {
+                if (!strcmp(name, v->name))
+                        return v;
+        }
+
+        return NULL;
+}
+
+static char *variable_expand(const char *name, int argc, char *argv[])
+{
+        struct variable *v;
+
+        v = variable_lookup(name);
+        if (!v)
+                return NULL;
+
+        return expand_string_with_args(v->value, argc, argv);
+}
+
+void variable_add(const char *name, const char *value)
+{
+        struct variable *v;
+
+        v = variable_lookup(name);
+        if (v) {
+                free(v->value);
+        } else {
+                v = xmalloc(sizeof(*v));
+                v->name = xstrdup(name);
+                list_add_tail(&v->node, &variable_list);
+        }
+
+        v->value = xstrdup(value);
+}
+
+static void variable_del(struct variable *v)
+{
+        list_del(&v->node);
+        free(v->name);
+        free(v->value);
+        free(v);
+}
+
+void variable_all_del(void)
+{
+        struct variable *v, *tmp;
+
+        list_for_each_entry_safe(v, tmp, &variable_list, node)
+                variable_del(v);
+}
+
+/*
  * Evaluate a clause with arguments.  argc/argv are arguments from the upper
  * function call.
  *
@@ -185,14 +251,26 @@ static char *function_expand(const char *name, int argc, char *argv[])
  */
 static char *eval_clause(const char *str, size_t len, int argc, char *argv[])
 {
-        char *tmp, *name, *res, *prev, *p;
+        char *tmp, *name, *res, *endptr, *prev, *p;
         int new_argc = 0;
         char *new_argv[FUNCTION_MAX_ARGS];
         int nest = 0;
         int i;
+        unsigned long n;
 
         tmp = xstrndup(str, len);
 
+        /*
+         * If variable name is '1', '2', etc.  It is generally an argument
+         * from a user-function call (i.e. local-scope variable).  If not
+         * available, then look-up global-scope variables.
+         */
+        n = strtoul(tmp, &endptr, 10);
+        if (!*endptr && n > 0 && n <= argc) {
+                res = xstrdup(argv[n - 1]);
+                goto free_tmp;
+        }
+
         prev = p = tmp;
 
         /*
@@ -238,6 +316,11 @@ static char *eval_clause(const char *str, size_t len, int argc, char *argv[])
                 new_argv[i] = expand_string_with_args(new_argv[i + 1],
                                                       argc, argv);
 
+        /* Search for variables */
+        res = variable_expand(name, new_argc, new_argv);
+        if (res)
+                goto free;
+
         /* Look for built-in functions */
         res = function_expand(name, new_argc, new_argv);
         if (res)
@@ -255,6 +338,7 @@ free:
         for (i = 0; i < new_argc; i++)
                 free(new_argv[i]);
         free(name);
+free_tmp:
         free(tmp);
 
         return res;
diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
index 9a147977dc3f..dd08f7a38ccd 100644
--- a/scripts/kconfig/zconf.l
+++ b/scripts/kconfig/zconf.l
@@ -1,12 +1,13 @@
 %option nostdinit noyywrap never-interactive full ecs
 %option 8bit nodefault yylineno
-%x COMMAND HELP STRING PARAM
+%x COMMAND HELP STRING PARAM ASSIGN_VAL
 %{
 /*
  * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
  * Released under the terms of the GNU GPL v2.0.
  */
 
+#include <assert.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -111,8 +112,10 @@ n	[A-Za-z0-9_-]
                 }
                 alloc_string(yytext, yyleng);
                 yylval.string = text;
-                return T_WORD;
+                return T_VARIABLE;
         }
+        "="     { BEGIN(ASSIGN_VAL); return T_ASSIGN; }
+        [[:blank:]]+
         .       warn_ignored_character(*yytext);
         \n      {
                 BEGIN(INITIAL);
@@ -120,6 +123,16 @@ n	[A-Za-z0-9_-]
         }
 }
 
+<ASSIGN_VAL>{
+        [^[:blank:]\n]+.*       {
+                alloc_string(yytext, yyleng);
+                yylval.string = text;
+                return T_ASSIGN_VAL;
+        }
+        \n      { BEGIN(INITIAL); return T_EOL; }
+        .
+}
+
 <PARAM>{
         "&&"    return T_AND;
         "||"    return T_OR;
diff --git a/scripts/kconfig/zconf.y b/scripts/kconfig/zconf.y
index 8a82aaf27581..e15e8c7063e0 100644
--- a/scripts/kconfig/zconf.y
+++ b/scripts/kconfig/zconf.y
@@ -77,6 +77,9 @@ static struct menu *current_menu, *current_entry;
 %token T_CLOSE_PAREN
 %token T_OPEN_PAREN
 %token T_EOL
+%token <string> T_VARIABLE
+%token T_ASSIGN
+%token <string> T_ASSIGN_VAL
 
 %left T_OR
 %left T_AND
@@ -92,7 +95,7 @@ static struct menu *current_menu, *current_entry;
 %type <id> end
 %type <id> option_name
 %type <menu> if_entry menu_entry choice_entry
-%type <string> symbol_option_arg word_opt
+%type <string> symbol_option_arg word_opt assign_val
 
 %destructor {
         fprintf(stderr, "%s:%d: missing end statement for this entry\n",
@@ -143,6 +146,7 @@ common_stmt:
         | config_stmt
         | menuconfig_stmt
         | source_stmt
+        | assignment_stmt
 ;
 
 option_error:
@@ -511,6 +515,15 @@ symbol:	  nonconst_symbol
 word_opt: /* empty */                   { $$ = NULL; }
         | T_WORD
 
+/* assignment statement */
+
+assignment_stmt:  T_VARIABLE T_ASSIGN assign_val T_EOL  { variable_add($1, $3); free($1); free($3); }
+
+assign_val:
+        /* empty */             { $$ = xstrdup(""); };
+        | T_ASSIGN_VAL
+;
+
 %%
 
 void conf_parse(const char *name)
@@ -525,6 +538,10 @@ void conf_parse(const char *name)
         if (getenv("ZCONF_DEBUG"))
                 yydebug = 1;
         yyparse();
+
+        /* Variables are expanded in the parse phase. We can free them here. */
+        variable_all_del();
+
         if (yynerrs)
                 exit(1);
         if (!modules_sym)