4.19-stable review patch. If anyone has any objections, please let me know.
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From: Masahiro Yamada masahiroy@kernel.org
[ Upstream commit aabdc960a283ba78086b0bf66ee74326f49e218e ]
Currently, comparisons to 'm' or 'n' result in incorrect output.
[Test Code]
config MODULES def_bool y modules
config A def_tristate m
config B def_bool A > n
CONFIG_B is unset, while CONFIG_B=y is expected.
The reason for the issue is because Kconfig compares the tristate values as strings.
Currently, the .type fields in the constant symbol definitions, symbol_{yes,mod,no} are unspecified, i.e., S_UNKNOWN.
When expr_calc_value() evaluates 'A > n', it checks the types of 'A' and 'n' to determine how to compare them.
The left-hand side, 'A', is a tristate symbol with a value of 'm', which corresponds to a numeric value of 1. (Internally, 'y', 'm', and 'n' are represented as 2, 1, and 0, respectively.)
The right-hand side, 'n', has an unknown type, so it is treated as the string "n" during the comparison.
expr_calc_value() compares two values numerically only when both can have numeric values. Otherwise, they are compared as strings.
symbol numeric value ASCII code ------------------------------------- y 2 0x79 m 1 0x6d n 0 0x6e
'm' is greater than 'n' if compared numerically (since 1 is greater than 0), but smaller than 'n' if compared as strings (since the ASCII code 0x6d is smaller than 0x6e).
Specifying .type=S_TRISTATE for symbol_{yes,mod,no} fixes the above test code.
Doing so, however, would cause a regression to the following test code.
[Test Code 2]
config MODULES def_bool n modules
config A def_tristate n
config B def_bool A = m
You would get CONFIG_B=y, while CONFIG_B should not be set.
The reason is because sym_get_string_value() turns 'm' into 'n' when the module feature is disabled. Consequently, expr_calc_value() evaluates 'A = n' instead of 'A = m'. This oddity has been hidden because the type of 'm' was previously S_UNKNOWN instead of S_TRISTATE.
sym_get_string_value() should not tweak the string because the tristate value has already been correctly calculated. There is no reason to return the string "n" where its tristate value is mod.
Fixes: 31847b67bec0 ("kconfig: allow use of relations other than (in)equality") Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- scripts/kconfig/symbol.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c index 5adb60b7e12f3..a28f4af4da2f3 100644 --- a/scripts/kconfig/symbol.c +++ b/scripts/kconfig/symbol.c @@ -13,14 +13,17 @@
struct symbol symbol_yes = { .name = "y", + .type = S_TRISTATE, .curr = { "y", yes }, .flags = SYMBOL_CONST|SYMBOL_VALID, }, symbol_mod = { .name = "m", + .type = S_TRISTATE, .curr = { "m", mod }, .flags = SYMBOL_CONST|SYMBOL_VALID, }, symbol_no = { .name = "n", + .type = S_TRISTATE, .curr = { "n", no }, .flags = SYMBOL_CONST|SYMBOL_VALID, }, symbol_empty = { @@ -774,8 +777,7 @@ const char *sym_get_string_value(struct symbol *sym) case no: return "n"; case mod: - sym_calc_value(modules_sym); - return (modules_sym->curr.tri == no) ? "n" : "m"; + return "m"; case yes: return "y"; }