[PATCH AUTOSEL 6.1 28/29] kconfig: remove wrong expr_trans_bool()

Sasha Levin
2024-06-17T13:25:55Z

From: Masahiro Yamada <masahiroy@kernel.org>

[ Upstream commit 77a92660d8fe8d29503fae768d9f5eb529c88b36 ]

expr_trans_bool() performs an incorrect transformation.

[Test Code]

config MODULES
def_bool y
modules

config A
def_bool y
select C if B != n

config B
def_tristate m

config C
tristate

[Result]

CONFIG_MODULES=y
CONFIG_A=y
CONFIG_B=m
CONFIG_C=m

This output is incorrect because CONFIG_C=y is expected.

Documentation/kbuild/kconfig-language.rst clearly explains the function
of the '!=' operator:

If the values of both symbols are equal, it returns 'n',
otherwise 'y'.

Therefore, the statement:

select C if B != n

should be equivalent to:

select C if y

Or, more simply:

select C

Hence, the symbol C should be selected by the value of A, which is 'y'.

However, expr_trans_bool() wrongly transforms it to:

select C if B

Therefore, the symbol C is selected by (A && B), which is 'm'.

The comment block of expr_trans_bool() correctly explains its intention:

* bool FOO!=n => FOO
^^^^

If FOO is bool, FOO!=n can be simplified into FOO. This is correct.

However, the actual code performs this transformation when FOO is
tristate:

if (e->left.sym->type == S_TRISTATE) {
^^^^^^^^^^

While it can be fixed to S_BOOLEAN, there is no point in doing so
because expr_tranform() already transforms FOO!=n to FOO when FOO is
bool. (see the "case E_UNEQUAL" part)

expr_trans_bool() is wrong and unnecessary.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
scripts/kconfig/expr.c | 29 -----------------------------
scripts/kconfig/expr.h | 1 -
scripts/kconfig/menu.c | 2 --
3 files changed, 32 deletions(-)

diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
index 81ebf8108ca74..81dfdf4470f75 100644
--- a/scripts/kconfig/expr.c
+++ b/scripts/kconfig/expr.c
@@ -396,35 +396,6 @@ static struct expr *expr_eliminate_yn(struct expr *e)
return e;
}

-/*
- * bool FOO!=n => FOO
- */
-struct expr *expr_trans_bool(struct expr *e)
-{
- if (!e)
- return NULL;
- switch (e->type) {
- case E_AND:
- case E_OR:
- case E_NOT:
- e->left.expr = expr_trans_bool(e->left.expr);
- e->right.expr = expr_trans_bool(e->right.expr);
- break;
- case E_UNEQUAL:
- // FOO!=n -> FOO
- if (e->left.sym->type == S_TRISTATE) {
- if (e->right.sym == &symbol_no) {
- e->type = E_SYMBOL;
- e->right.sym = NULL;
- }
- }
- break;
- default:
- ;
- }
- return e;
-}
-
/*
* e1 || e2 -> ?
*/
diff --git a/scripts/kconfig/expr.h b/scripts/kconfig/expr.h
index 9c9caca5bd5f2..c91060e19e477 100644
--- a/scripts/kconfig/expr.h
+++ b/scripts/kconfig/expr.h
@@ -296,7 +296,6 @@ void expr_free(struct expr *e);
void expr_eliminate_eq(struct expr **ep1, struct expr **ep2);
int expr_eq(struct expr *e1, struct expr *e2);
tristate expr_calc_value(struct expr *e);
-struct expr *expr_trans_bool(struct expr *e);
struct expr *expr_eliminate_dups(struct expr *e);
struct expr *expr_transform(struct expr *e);
int expr_contains_symbol(struct expr *dep, struct symbol *sym);
diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index 109325f31bef3..9d4c3f366a061 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -380,8 +380,6 @@ void menu_finalize(struct menu *parent)
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)
- dep = expr_trans_bool(dep);
prop->visible.expr = dep;

/*
--
2.43.0