[PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Julian Braha]

The Kconfig interpreter currently allows defaults that are outside of the
range bounds.

In these cases, the 'sym_validate_range' function will adjust the default
value to the nearest range bound. For example, see this example:

  config A
    int
    range 1 2
    default 16

Here, since the default value of 16 is greater than the bounds, the
effective default value gets adjusted down to the upper bound, 2.

However, 'savedefconfig' writes non-default values, and without being
aware of the automatic adjustment to the range bound, it would write: A=2

This limitation is also documented in a comment: "The following fails to
handle the situation where a default value is further limited by the valid
range."

To resolve this, let's factor out the default-range adjustment logic from
the existing 'sym_validate_range' function into its own
'sym_get_near_range_bound' function for 'savedefconfig' to use too, so
that it compares against the effective value.

Adds tests, accordingly.

Fixes: 7cf3d73b4360 ("kconfig: add savedefconfig")
Assisted-by: Codex:gpt-5.6-sol
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Closes: https://lore.kernel.org/lkml/CAMuHMdVyUAA3L4mUkSjmnuE3cvj-+N8z-Bhxsh1wa-FQWc=fjw@mail.gmail.com/
Signed-off-by: Julian Braha <julianbraha@gmail.com>
---
 scripts/kconfig/symbol.c                      | 39 ++++++++----
 .../kconfig/tests/savedefconfig_range/Kconfig | 60 +++++++++++++++++++
 .../tests/savedefconfig_range/__init__.py     |  8 +++
 .../kconfig/tests/savedefconfig_range/config  |  7 +++
 .../savedefconfig_range/expected_defconfig    |  0
 5 files changed, 102 insertions(+), 12 deletions(-)
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/Kconfig
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/__init__.py
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/config
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/expected_defconfig

diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 2d1c021fa395..72aaae9da4b1 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -158,7 +158,12 @@ static long long sym_get_range_val(struct symbol *sym, int base)
 	return strtoll(sym->curr.val, NULL, base);
 }
 
-static void sym_validate_range(struct symbol *sym)
+/*
+ * Return the nearest range bound for an out-of-range default value.
+ * Return NULL if the value is valid or the symbol has no active range.
+ */
+static struct symbol *sym_get_near_range_bound(struct symbol *sym,
+					  const char *value)
 {
 	struct property *prop;
 	struct symbol *range_sym;
@@ -173,21 +178,31 @@ static void sym_validate_range(struct symbol *sym)
 		base = 16;
 		break;
 	default:
-		return;
+		return NULL;
 	}
 	prop = sym_get_range_prop(sym);
 	if (!prop)
-		return;
-	val = strtoll(sym->curr.val, NULL, base);
+		return NULL;
+	val = strtoll(value, NULL, base);
 	range_sym = prop->expr->left.sym;
 	val2 = sym_get_range_val(range_sym, base);
 	if (val >= val2) {
 		range_sym = prop->expr->right.sym;
 		val2 = sym_get_range_val(range_sym, base);
 		if (val <= val2)
-			return;
+			return NULL;
 	}
-	sym->curr.val = range_sym->curr.val;
+
+	return range_sym;
+}
+
+static void sym_validate_range(struct symbol *sym)
+{
+	struct symbol *range_sym;
+
+	range_sym = sym_get_near_range_bound(sym, sym->curr.val);
+	if (range_sym)
+		sym->curr.val = range_sym->curr.val;
 }
 
 static void sym_set_changed(struct symbol *sym)
@@ -832,7 +847,7 @@ bool sym_set_string_value(struct symbol *sym, const char *newval)
 const char *sym_get_string_default(struct symbol *sym)
 {
 	struct property *prop;
-	struct symbol *ds;
+	struct symbol *ds, *range_sym;
 	const char *str = "";
 	tristate val;
 
@@ -850,11 +865,6 @@ const char *sym_get_string_default(struct symbol *sym)
 			val = EXPR_AND(expr_calc_value(prop->expr), prop->visible.tri);
 			break;
 		default:
-			/*
-			 * The following fails to handle the situation
-			 * where a default value is further limited by
-			 * the valid range.
-			 */
 			ds = prop_get_symbol(prop);
 			if (ds != NULL) {
 				sym_calc_value(ds);
@@ -898,6 +908,11 @@ const char *sym_get_string_default(struct symbol *sym)
 	default:
 		break;
 	}
+
+	range_sym = sym_get_near_range_bound(sym, str);
+	if (range_sym)
+		str = range_sym->curr.val;
+
 	return str;
 }
 
diff --git a/scripts/kconfig/tests/savedefconfig_range/Kconfig b/scripts/kconfig/tests/savedefconfig_range/Kconfig
new file mode 100644
index 000000000000..fd59d9082ed5
--- /dev/null
+++ b/scripts/kconfig/tests/savedefconfig_range/Kconfig
@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Static default and range values
+
+config INT_DEFAULT_ABOVE_RANGE
+	int
+	range 1 1
+	default 16
+
+config INT_DEFAULT_BELOW_RANGE
+	int
+	range 4 8
+	default 2
+
+# Default and range values determined by other options
+
+config RANGE_UPPER_BOUND
+	int
+	default 3
+
+config INT_DYNAMIC_RANGE
+	int
+	range 0 RANGE_UPPER_BOUND
+	default 4
+
+# Hex
+
+config HEX_DEFAULT_ABOVE_RANGE
+	hex
+	range 0x10 0x20
+	default 0x40
+
+# Implicit default value of 0
+
+config INT_IMPLICIT_DEFAULT_ZERO
+	int
+	range 1 4
+
+# Conditional range
+
+config USE_FIRST_RANGE
+	bool
+	default y
+
+config INT_CONDITIONAL_RANGE
+	int
+	range 1 2 if USE_FIRST_RANGE
+	range 3 4 if !USE_FIRST_RANGE
+	default 3
+
+# Conditional default
+
+config USE_DEFAULT
+	bool
+	default y
+
+config INT_CONDITIONAL_DEFAULT
+	int
+	range 1 2
+	default 3 if USE_DEFAULT
diff --git a/scripts/kconfig/tests/savedefconfig_range/__init__.py b/scripts/kconfig/tests/savedefconfig_range/__init__.py
new file mode 100644
index 000000000000..961454be732c
--- /dev/null
+++ b/scripts/kconfig/tests/savedefconfig_range/__init__.py
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+"""Test savedefconfig with numerical defaults outside of ranges."""
+
+
+def test(conf):
+    assert conf._run_conf('--savedefconfig=defconfig', dot_config='config',
+                          out_file='defconfig') == 0
+    assert conf.config_matches('expected_defconfig')
diff --git a/scripts/kconfig/tests/savedefconfig_range/config b/scripts/kconfig/tests/savedefconfig_range/config
new file mode 100644
index 000000000000..d939cfe5fd34
--- /dev/null
+++ b/scripts/kconfig/tests/savedefconfig_range/config
@@ -0,0 +1,7 @@
+CONFIG_INT_DEFAULT_ABOVE_RANGE=1
+CONFIG_INT_DEFAULT_BELOW_RANGE=4
+CONFIG_INT_DYNAMIC_RANGE=3
+CONFIG_HEX_DEFAULT_ABOVE_RANGE=0x20
+CONFIG_INT_IMPLICIT_DEFAULT_ZERO=1
+CONFIG_INT_CONDITIONAL_RANGE=2
+CONFIG_INT_CONDITIONAL_DEFAULT=2
diff --git a/scripts/kconfig/tests/savedefconfig_range/expected_defconfig b/scripts/kconfig/tests/savedefconfig_range/expected_defconfig
new file mode 100644
index 000000000000..e69de29bb2d1
-- 
2.55.0

Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Geert Uytterhoeven]

Hi Julian,

Thanks for your patch!

On Mon, 31 Aug 2026 at 00:12, Julian Braha <julianbraha@gmail.com> wrote:
> The Kconfig interpreter currently allows defaults that are outside of the
> range bounds.
>
> In these cases, the 'sym_validate_range' function will adjust the default
> value to the nearest range bound. For example, see this example:
>
>   config A
>     int
>     range 1 2
>     default 16
>
> Here, since the default value of 16 is greater than the bounds, the
> effective default value gets adjusted down to the upper bound, 2.
>
> However, 'savedefconfig' writes non-default values, and without being

s/non-default/non-adjusted/?

> aware of the automatic adjustment to the range bound, it would write: A=2
>
> This limitation is also documented in a comment: "The following fails to
> handle the situation where a default value is further limited by the valid
> range."
>
> To resolve this, let's factor out the default-range adjustment logic from
> the existing 'sym_validate_range' function into its own
> 'sym_get_near_range_bound' function for 'savedefconfig' to use too, so
> that it compares against the effective value.
>
> Adds tests, accordingly.
>
> Fixes: 7cf3d73b4360 ("kconfig: add savedefconfig")
> Assisted-by: Codex:gpt-5.6-sol
> Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Closes: https://lore.kernel.org/lkml/CAMuHMdVyUAA3L4mUkSjmnuE3cvj-+N8z-Bhxsh1wa-FQWc=fjw@mail.gmail.com/
> Signed-off-by: Julian Braha <julianbraha@gmail.com>

Thanks, this fixes the issue, and would let us revert commit
ab74edaeb1ae7c71 ("erofs: Fix EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS
default logic") in v7.3-rc1.

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Geert Uytterhoeven]

On Mon, 31 Aug 2026 at 14:36, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Mon, 31 Aug 2026 at 00:12, Julian Braha <julianbraha@gmail.com> wrote:
> > The Kconfig interpreter currently allows defaults that are outside of the
> > range bounds.
> >
> > In these cases, the 'sym_validate_range' function will adjust the default
> > value to the nearest range bound. For example, see this example:
> >
> >   config A
> >     int
> >     range 1 2
> >     default 16
> >
> > Here, since the default value of 16 is greater than the bounds, the
> > effective default value gets adjusted down to the upper bound, 2.
> >
> > However, 'savedefconfig' writes non-default values, and without being
>
> s/non-default/non-adjusted/?
>
> > aware of the automatic adjustment to the range bound, it would write: A=2
> >
> > This limitation is also documented in a comment: "The following fails to
> > handle the situation where a default value is further limited by the valid
> > range."
> >
> > To resolve this, let's factor out the default-range adjustment logic from
> > the existing 'sym_validate_range' function into its own
> > 'sym_get_near_range_bound' function for 'savedefconfig' to use too, so
> > that it compares against the effective value.
> >
> > Adds tests, accordingly.
> >
> > Fixes: 7cf3d73b4360 ("kconfig: add savedefconfig")
> > Assisted-by: Codex:gpt-5.6-sol
> > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > Closes: https://lore.kernel.org/lkml/CAMuHMdVyUAA3L4mUkSjmnuE3cvj-+N8z-Bhxsh1wa-FQWc=fjw@mail.gmail.com/
> > Signed-off-by: Julian Braha <julianbraha@gmail.com>
>
> Thanks, this fixes the issue, and would let us revert commit
> ab74edaeb1ae7c71 ("erofs: Fix EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS
> default logic") in v7.3-rc1.
>
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

FTR, this will impact all defconfigs that restrict SERIAL_8250_NR_UARTS
to a value lower than 4:

    config SERIAL_8250_NR_UARTS
            int "Maximum number of 8250/16550 serial ports"
            depends on SERIAL_8250
            default "4"

    config SERIAL_8250_RUNTIME_UARTS
            int "Number of 8250/16550 serial ports to register at runtime"
            depends on SERIAL_8250
            range 0 SERIAL_8250_NR_UARTS
            default "4"

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Julian Braha]

CC: Arnd, Christophe

On 9/1/26 11:17, Geert Uytterhoeven wrote:

> FTR, this will impact all defconfigs that restrict SERIAL_8250_NR_UARTS
> to a value lower than 4:
> 
>     config SERIAL_8250_NR_UARTS
>             int "Maximum number of 8250/16550 serial ports"
>             depends on SERIAL_8250
>             default "4"
> 
>     config SERIAL_8250_RUNTIME_UARTS
>             int "Number of 8250/16550 serial ports to register at runtime"
>             depends on SERIAL_8250
>             range 0 SERIAL_8250_NR_UARTS
>             default "4"

I suspected that there could be some cases where these out-of-range
defaults were actually accidents and causing bugs, so I added a check
with my SMT solver [1], which also detected these two (powerpc-only):


  config DATA_SHIFT
    int "Data shift" if DATA_SHIFT_BOOL
    default 24 if STRICT_KERNEL_RWX && PPC64
    range 17 28 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) &&
PPC_BOOK3S_32
    range 14 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) &&
PPC_8xx
    range 20 24 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) &&
PPC_85xx
    default 22 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
    default 18 if (DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32
    default 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) &&
PPC_8xx && \
      (PIN_TLB_DATA || PIN_TLB_TEXT)
    default 19 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) &&
PPC_8xx
    default 24 if STRICT_KERNEL_RWX && PPC_85xx
    default PAGE_SHIFT

  config MODULES_SIZE
    int "Size of modules/execmem area (In Mbytes)" if MODULES_SIZE_BOOL
    range 1 256 if EXECMEM
    default 64 if EXECMEM && PPC_BOOK3S_32
    default 32 if EXECMEM && PPC_8xx
    default 0


The DATA_SHIFT case may be bug, where it should be 12, but incorrectly
adjusts to 20 when:
  PPC_85xx=y

  DEBUG_PAGEALLOC=y

  STRICT_KERNEL_RWX=n

  PAGE_SHIFT=12

The MODULES_SIZE case seems harmless since the only systems using that
option are PPC_BOOK3S_32 and PPC_8xx.

Anyway, this change to savedefconfig would also affect those 2.

[1] https://github.com/julianbraha/kconfirm/tree/smt

- Julian Braha

Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Nathan Chancellor]

> The Kconfig interpreter currently allows defaults that are outside of the
> range bounds.
> 
> In these cases, the 'sym_validate_range' function will adjust the default
> value to the nearest range bound. For example, see this example:
> 
>   config A
>     int
>     range 1 2
>     default 16
> 
> Here, since the default value of 16 is greater than the bounds, the
> effective default value gets adjusted down to the upper bound, 2.
> 
> However, 'savedefconfig' writes non-default values, and without being
> aware of the automatic adjustment to the range bound, it would write: A=2

Should that 'A=2' be 'A=16'?

> This limitation is also documented in a comment: "The following fails to
> handle the situation where a default value is further limited by the valid
> range."
> 
> To resolve this, let's factor out the default-range adjustment logic from
> the existing 'sym_validate_range' function into its own
> 'sym_get_near_range_bound' function for 'savedefconfig' to use too, so
> that it compares against the effective value.
> 
> Adds tests, accordingly.
> 
> Fixes: 7cf3d73b4360 ("kconfig: add savedefconfig")
> Assisted-by: Codex:gpt-5.6-sol
> Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Closes: https://lore.kernel.org/lkml/CAMuHMdVyUAA3L4mUkSjmnuE3cvj-+N8z-Bhxsh1wa-FQWc=fjw@mail.gmail.com/
> Signed-off-by: Julian Braha <julianbraha@gmail.com>

Thanks for the patch!

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

Given this is a long standing issue, it should probably go via
kbuild-next for 7.4, especially in case this results in problems like
noted downthread. I would revert commit ab74edaeb1ae ("erofs: Fix
EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS default logic") on top of that.

I will wait a little bit for the folks CC'd downthread to reply to those
instances impacted by this change before applying this.

-- 
Cheers,
Nathan

Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Julian Braha]

On 9/3/26 23:28, Nathan Chancellor wrote:
>> The Kconfig interpreter currently allows defaults that are outside of the
>> range bounds.
>>
>> In these cases, the 'sym_validate_range' function will adjust the default
>> value to the nearest range bound. For example, see this example:
>>
>>   config A
>>     int
>>     range 1 2
>>     default 16
>>
>> Here, since the default value of 16 is greater than the bounds, the
>> effective default value gets adjusted down to the upper bound, 2.
>>
>> However, 'savedefconfig' writes non-default values, and without being
>> aware of the automatic adjustment to the range bound, it would write: A=2
> 
> Should that 'A=2' be 'A=16'?

No typo, this example is adapted from the original report where it
needlessly writes the adjusted default. In the original it was 1, here
it's 2. [1]

> 
>> This limitation is also documented in a comment: "The following fails to
>> handle the situation where a default value is further limited by the valid
>> range."
>>
>> To resolve this, let's factor out the default-range adjustment logic from
>> the existing 'sym_validate_range' function into its own
>> 'sym_get_near_range_bound' function for 'savedefconfig' to use too, so
>> that it compares against the effective value.
>>
>> Adds tests, accordingly.
>>
>> Fixes: 7cf3d73b4360 ("kconfig: add savedefconfig")
>> Assisted-by: Codex:gpt-5.6-sol
>> Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
>> Closes: https://lore.kernel.org/lkml/CAMuHMdVyUAA3L4mUkSjmnuE3cvj-+N8z-Bhxsh1wa-FQWc=fjw@mail.gmail.com/
>> Signed-off-by: Julian Braha <julianbraha@gmail.com>
> 
> Thanks for the patch!
> 
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> 
> Given this is a long standing issue, it should probably go via
> kbuild-next for 7.4, especially in case this results in problems like
> noted downthread. I would revert commit ab74edaeb1ae ("erofs: Fix
> EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS default logic") on top of that.
> 
> I will wait a little bit for the folks CC'd downthread to reply to those
> instances impacted by this change before applying this.
> 

Makes sense to me, and thanks for reviewing!

[1]
https://lore.kernel.org/lkml/c480ed6b8bf38822263e2c5b7cf32b28600f212d.1787219898.git.geert+renesas@glider.be/

- Julian Braha

Re: [PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Nathan Chancellor]

On Fri, Sep 04, 2026 at 12:19:40AM +0100, Julian Braha wrote:
> No typo, this example is adapted from the original report where it
> needlessly writes the adjusted default. In the original it was 1, here
> it's 2. [1]

Oh, right, this is about savedefconfig, I am not sure what I was
thinking when I wrote that.

-- 
Cheers,
Nathan