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Message-Id: <20240126133010.78999-1-masahiroy@kernel.org>
Date: Fri, 26 Jan 2024 22:30:10 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert+renesas@...der.be>,
Yoann Congal <yoann.congal@...le.fr>,
Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH] kconfig: initialize sym->curr.tri to no for all symbol types again
In C programming, a non-zero value is interpreted as true, and a zero
value as false.
Kconfig has never worked like that; only 'bool' and 'tristate' symbols
are properly handled in conditionals. The other types ('int', 'hex',
'string') are always interpreted as false if used in boolean contexts.
Until commit 4e244c10eab3 ("kconfig: remove unneeded symbol_empty
variable") accidentally changed the behavior, the default of
CONFIG_LOG_CPU_MAX_BUF_SHIFT was unconditionally 12, because the 'int'
symbol 'BASE_SMALL' was evaluated as false, hence 'if !BASE_SMALL' was
always true.
You can confirm it as follows:
$ git checkout 4e244c10eab3^
$ make -s ARCH=x86_64 defconfig
$ grep -e LOG_CPU_MAX_BUF_SHIFT -e BASE_SMALL -e BASE_FULL .config
CONFIG_LOG_CPU_MAX_BUF_SHIFT=12
CONFIG_BASE_FULL=y
CONFIG_BASE_SMALL=0
$ make -s ARCH=arm keystone_defconfig
$ grep -e LOG_CPU_MAX_BUF_SHIFT -e BASE_SMALL -e BASE_FULL .config
CONFIG_LOG_CPU_MAX_BUF_SHIFT=12
# CONFIG_BASE_FULL is not set
CONFIG_BASE_SMALL=1
CONFIG_LOG_CPU_MAX_BUF_SHIFT defaults to 12 irrespective of the value
of CONFIG_BASE_SMALL.
Since commit 4e244c10eab3, this is an undefined behavior because
sym_calc_value() stopped setting the sym->curr.tri field for 'int',
'hex', and 'string' symbols.
Commit 23b2899f7f19 ("printk: allow increasing the ring buffer depending
on the number of CPUs") presumably intended the following:
config LOG_CPU_MAX_BUF_SHIFT
int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
[snip]
default 12 if BASE_SMALL == 0
default 0
But, the correct fixes would potentially impact multiple defconfigs,
hence they should be reviewed in each dedicated subsystem.
Restore the original behavior for now.
Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")
Reported-by: Geert Uytterhoeven <geert+renesas@...der.be>
Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---
scripts/kconfig/symbol.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index f615e2c1e85d..1290c6d2f8c2 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -346,6 +346,8 @@ void sym_calc_value(struct symbol *sym)
oldval = sym->curr;
+ newval.tri = no;
+
switch (sym->type) {
case S_INT:
newval.val = "0";
@@ -358,7 +360,7 @@ void sym_calc_value(struct symbol *sym)
break;
case S_BOOLEAN:
case S_TRISTATE:
- newval = symbol_no.curr;
+ newval.val = "n";
break;
default:
sym->curr.val = sym->name;
--
2.40.1
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