kconfig: Clean up modules handling and fix crash

Kconfig currently doesn't handle 'm' appearing in a Kconfig file before
the modules symbol is defined (the symbol with 'option modules'). The
problem is the following code, which runs during parsing:

	/* change 'm' into 'm' && MODULES */
	if (e->left.sym == &symbol_mod)
		return expr_alloc_and(e, expr_alloc_symbol(modules_sym));

If the modules symbol has not yet been defined, modules_sym is NULL,
giving an invalid expression.

Here is a test file where both BEFORE_1 and BEFORE_2 trigger a segfault.
If the modules symbol is removed, all symbols trigger segfaults.

	config BEFORE_1
		def_tristate y if m

	if m
	config BEFORE_2
		def_tristate y
	endif

	config MODULES
		def_bool y
		option modules

	config AFTER_1
		def_tristate y if m

	if m
	config AFTER_2
		def_tristate y
	endif

Fix the issue by rewriting 'm' in menu_finalize() instead. This function
runs after parsing and is the proper place to do it. The following
existing code in conf_parse() in zconf.y ensures that the modules symbol
exists at that point:

	if (!modules_sym)
		modules_sym = sym_find( "n" );

	...

	menu_finalize(&rootmenu);

The following tests were done to ensure no functional changes for
configurations that don't reference 'm' before the modules symbol:

	- zconfdump(stdout) was run with ARCH=x86 and ARCH=arm before
	  and after the change and verified to produce identical output.
	  This function prints all symbols, choices, and menus together
	  with their properties and their dependency expressions. A
	  rewritten 'm' appears as 'm && MODULES'.

	  A small annoyance is that the assert(len != 0) in xfwrite()
	  needs to be disabled in order to use zconfdump(), because it
	  chokes on e.g. 'default ""'.

	- The Kconfiglib test suite was run to indirectly verify that
	  alldefconfig, allyesconfig, allnoconfig, and all defconfigs in
	  the kernel still generate the same final .config.

	- Valgrind was used to check for memory errors and (new) memory
	  leaks.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

diff --git a/config/menu.c b/config/menu.c
index c8cec26c25354658c0879abe56df322e5087b626..2baebe346de9528d3adc3f89fc1d7bddde0377a4 100644 (file)
--- a/config/menu.c
+++ b/config/menu.c
@@ -110,7 +110,7 @@ static struct expr *rewrite_m(struct expr *e)
 
 void menu_add_dep(struct expr *dep)
 {
-       current_entry->dep = expr_alloc_and(current_entry->dep, rewrite_m(dep));
+       current_entry->dep = expr_alloc_and(current_entry->dep, dep);
 }
 
 void menu_set_type(int type)
@@ -135,7 +135,7 @@ static struct property *menu_add_prop(enum prop_type type, char *prompt, struct
 
        prop->menu = current_entry;
        prop->expr = expr;
-       prop->visible.expr = rewrite_m(dep);
+       prop->visible.expr = dep;
 
        if (prompt) {
                if (isspace(*prompt)) {
@@ -340,7 +340,8 @@ void menu_finalize(struct menu *parent)
                         * Propagate parent dependencies to the child menu
                         * node, also rewriting and simplifying expressions
                         */
-                       basedep = expr_transform(menu->dep);
+                       basedep = rewrite_m(menu->dep);
+                       basedep = expr_transform(basedep);
                        basedep = expr_alloc_and(expr_copy(parentdep), basedep);
                        basedep = expr_eliminate_dups(basedep);
                        menu->dep = basedep;
@@ -383,7 +384,8 @@ void menu_finalize(struct menu *parent)
                                 * property's condition, rewriting and
                                 * simplifying expressions at the same time
                                 */
-                               dep = expr_transform(prop->visible.expr);
+                               dep = rewrite_m(prop->visible.expr);
+                               dep = expr_transform(dep);
                                dep = expr_alloc_and(expr_copy(basedep), dep);
                                dep = expr_eliminate_dups(dep);
                                if (menu->sym && menu->sym->type != S_TRISTATE)