This is a note to let you know that I've just added the patch titled
kconfig: fix comparison to constant symbols, 'm', 'n'
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kconfig-fix-comparison-to-constant-symbols-m-n.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit a159568f6310724b0d9662677252ea11908938a1
Author: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Date: Sun May 19 18:22:27 2024 +0900
kconfig: fix comparison to constant symbols, 'm', 'n'
[ 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@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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";
}
