Extend the "depends on" syntax to support conditional dependencies
using "depends on X if Y". While functionally equivalent to "depends
on X || (Y == n)", "depends on X if Y" is much more readable and
makes the kconfig language uniform in supporting the "if <expr>"
suffix.
This also improves readability for "optional" dependencies, which
are the subset of conditional dependencies where X is Y.
Previously such optional dependencies had to be expressed as
the counterintuitive "depends on X || !X", now this can be
represented as "depends on X if X".
The change is implemented by converting the "X if Y" syntax into the
"X || (Y == n)" syntax during "depends on" token processing.
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
[Graham Roff: Rewrote commit message, updated patch, added tests]
Signed-off-by: Graham Roff <grahamr@qti.qualcomm.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20251215-kconfig_conditional_deps-v3-1-59519af0a5df@qti.qualcomm.com
[nathan: Minor adjustments to spacing]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
The "transitional" symbol keyword, while working with the "olddefconfig"
target, was prompting during "oldconfig". This occurred because these
symbols were not being marked as user-defined when they received values
from transitional symbols that had user values. The "olddefconfig" target
explicitly doesn't prompt for anything, so this deficiency wasn't noticed.
The issue manifested when a symbol's value came from a transitional
symbol's user value but the receiving symbol wasn't marked with
SYMBOL_DEF_USER. Thus the "oldconfig" logic would then prompt for these
symbols unnecessarily.
Check after value calculation whether a symbol without a user value
gets its value from a single transitional symbol that does have a user
value. In such cases, mark the receiving symbol as user-defined to
prevent prompting.
Update regression tests to verify that symbols with transitional defaults
are not prompted in "oldconfig", except when conditional defaults evaluate
to 'no' and should legitimately be prompted.
Build tested with "make testconfig".
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/lkml/CAHk-=wgZjUk4Cy2XgNkTrQoO8XCmNUHrTe5D519Fij1POK+3qw@mail.gmail.com/
Fixes: f9afce4f32 ("kconfig: Add transitional symbol attribute for migration support")
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Link: https://lore.kernel.org/r/20250930154514.it.623-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
During kernel option migrations (e.g. CONFIG_CFI_CLANG to CONFIG_CFI),
existing .config files need to maintain backward compatibility while
preventing deprecated options from appearing in newly generated
configurations. This is challenging with existing Kconfig mechanisms
because:
1. Simply removing old options breaks existing .config files.
2. Manually listing an option as "deprecated" leaves it needlessly
visible and still writes them to new .config files.
3. Using any method to remove visibility (.e.g no 'prompt', 'if n',
etc) prevents the option from being processed at all.
Add a "transitional" attribute that creates symbols which are:
- Processed during configuration (can influence other symbols' defaults)
- Hidden from user menus (no prompts appear)
- Omitted from newly written .config files (gets migrated)
- Restricted to only having help sections (no defaults, selects, etc)
making it truly just a "prior value pass-through" option.
The transitional syntax requires a type argument and prevents type
redefinition:
config NEW_OPTION
bool "New option"
default OLD_OPTION
config OLD_OPTION
bool
transitional
help
Transitional config for OLD_OPTION migration.
This allows seamless migration: olddefconfig processes existing
CONFIG_OLD_OPTION=y settings to enable CONFIG_NEW_OPTION=y, while
CONFIG_OLD_OPTION is omitted from newly generated .config files.
Added positive and negative testing via "testconfig" make target.
Co-developed-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250923213422.1105654-2-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
The kconfig test harness ("make testconfig") was generating BrokenPipeError
warnings when running interactive tests like oldaskconfig and oldconfig:
/usr/lib/python3/dist-packages/_pytest/unraisableexception.py:85: PytestUnraisableExceptionWarning: Exception ignored in: <_io.BufferedWriter name=12>
Traceback (most recent call last):
File "/srv/code/scripts/kconfig/tests/conftest.py", line 127, in oldaskconfig
return self._run_conf('--oldaskconfig', dot_config=dot_config,
~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
interactive=True, in_keys=in_keys)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
BrokenPipeError: [Errno 32] Broken pipe
The issue occurred when the test framework attempted to write to stdin
after the conf subprocess had already exited.
Wrap stdin write operations in try/except to catch BrokenPipeError and
stop sending more input. Add explicit flush() after writes so we can see
delivery errors immediately. Ignore BrokenPipeError when closing stdin.
Explicitly call wait() to validate subprocess termination.
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250923213422.1105654-1-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
This prevents segfault when getting filename and lineno in recursive
checks.
If the following snippet is found in Kconfig:
[Test code 1]
config FOO
bool
depends on BAR
select BAR
... without BAR defined; then there is a segfault.
Kconfig:34:error: recursive dependency detected!
Kconfig:34: symbol FOO depends on BAR
make[4]: *** [scripts/kconfig/Makefile:85: allnoconfig] Segmentation fault
This is because of the following. BAR is a fake entry created by
sym_lookup() with prop being NULL. In the recursive check, there is a
NULL check for prop to fall back to stack->sym->prop if stack->prop is
NULL. However, in this case, stack->sym points to the fake BAR entry
created by sym_lookup(), so prop is still NULL. prop was then referenced
without additional NULL checks, causing segfault.
As the previous email thread suggests, the file and lineno for select is
also wrong:
[Test code 2]
config FOO
bool
config BAR
bool
config FOO
bool "FOO"
depends on BAR
select BAR
$ make defconfig
*** Default configuration is based on 'x86_64_defconfig'
Kconfig:1:error: recursive dependency detected!
Kconfig:1: symbol FOO depends on BAR
Kconfig:4: symbol BAR is selected by FOO
[...]
Kconfig:4 should be Kconfig:10.
This patch deletes the wrong and segfault-prone filename/lineno
inference completely. With this patch, Test code 1 yields:
error: recursive dependency detected!
symbol FOO depends on BAR
symbol BAR is selected by FOO
Signed-off-by: HONG Yifan <elsk@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
I previously submitted a fix for a bug in the choice feature [1], where
I mentioned, "Another (much cleaner) approach would be to remove the
tristate choice support entirely".
There are more issues in the tristate choice feature. For example, you
can observe a couple of bugs in the following test code.
[Test Code]
config MODULES
def_bool y
modules
choice
prompt "tristate choice"
default A
config A
tristate "A"
config B
tristate "B"
endchoice
Bug 1: the 'default' property is not correctly processed
'make alldefconfig' produces:
CONFIG_MODULES=y
# CONFIG_A is not set
# CONFIG_B is not set
However, the correct output should be:
CONFIG_MODULES=y
CONFIG_A=y
# CONFIG_B is not set
The unit test file, scripts/kconfig/tests/choice/alldef_expected_config,
is wrong as well.
Bug 2: choice members never get 'y' with randconfig
For the test code above, the following combinations are possible:
A B
(1) y n
(2) n y
(3) m m
(4) m n
(5) n m
(6) n n
'make randconfig' never produces (1) or (2).
These bugs are fixable, but a more critical problem is the lack of a
sensible syntax to specify the default for the tristate choice.
The default for the choice must be one of the choice members, which
cannot specify any of the patterns (3) through (6) above.
In addition, I have never seen it being used in a useful way.
The following commits removed unnecessary use of tristate choices:
- df8df5e4bc ("usb: get rid of 'choice' for legacy gadget drivers")
- bfb57ef054 ("rapidio: remove choice for enumeration")
This commit removes the tristate choice support entirely, which allows
me to delete a lot of code, making further refactoring easier.
Note:
This includes the revert of commit fa64e5f6a3 ("kconfig/symbol.c:
handle choice_values that depend on 'm' symbols"). It was suspicious
because it did not address the root cause but introduced inconsistency
in visibility between choice members and other symbols.
[1]: https://lore.kernel.org/linux-kbuild/20240427104231.2728905-1-masahiroy@kernel.org/T/#m0a1bb6992581462ceca861b409bb33cb8fd7dbae
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
The 'choice' statement is primarily used to exclusively select one
option, but the 'optional' property allows all entries to be disabled.
In the following example, both A and B can be disabled simultaneously:
choice
prompt "choose A, B, or nothing"
optional
config A
bool "A"
config B
bool "B"
endchoice
You can achieve the equivalent outcome by other means.
A common solution is to add another option to guard the choice block.
In the following example, you can set ENABLE_A_B_CHOICE=n to disable
the entire choice block:
choice
prompt "choose A or B"
depends on ENABLE_A_B_CHOICE
config A
bool "A"
config B
bool "B"
endchoice
Another approach is to insert one more entry:
choice
prompt "choose A, B, or disable both"
config A
bool "A"
config B
bool "B"
config DISABLE_A_AND_B
bool "choose this to disable both A and B"
endchoice
Some real examples are DEBUG_INFO_NONE, INITRAMFS_COMPRESSION_NONE,
LTO_NONE, etc.
The 'optional' property is even more unnecessary for a tristate choice.
Without the 'optional' property, you can disable A and B; you can set
'm' in the choice prompt, and disable A and B individually:
choice
prompt "choose one built-in or make them modular"
config A
tristate "A"
config B
tristate "B"
endchoice
In conclusion, the 'optional' property was unneeded.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Commit c8fb7d7e48 ("kconfig: fix broken dependency in randconfig-
generated .config") fixed the issue, but I did not add a test case.
This commit adds a test case that emulates the reported situation.
The test would fail without c8fb7d7e48.
To handle the choice "choose X", FOO must be calculated beforehand.
FOO depends on A, which is a member of another choice "choose A or B".
Kconfig _temporarily_ assumes the value of A to proceed. The choice
"choose A or B" will be shuffled later, but the result may or may not
meet "FOO depends on A". Kconfig should invalidate the symbol values
and recompute them.
In the real example for ARCH=arm64, the choice "Instrumentation type"
needs the value of CPU_BIG_ENDIAN. The choice "Endianness" will be
shuffled later.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Since commit 3b9a19e089 ("kconfig: loop as long as we changed some
symbols in randconfig"), conf_set_all_new_symbols() is repeated until
there is no more choice left to be shuffled. The motivation was to
shuffle a choice nested in another choice.
Although commit 09d5873e4d ("kconfig: allow only 'config', 'comment',
and 'if' inside 'choice'") disallowed the nested choice structure,
we must still keep 3b9a19e089 because there are still cases where
conf_set_all_new_symbols() must iterate.
scripts/kconfig/tests/choice_randomize/Kconfig is the test case.
The second choice depends on 'B', which is the member of the first
choice.
With 3b9a19e089 reverted, we would never get the pattern specified by
scripts/kconfig/tests/choice_randomize/expected_config2.
A real example can be found in lib/Kconfig.debug. Without 3b9a19e089,
the randconfig would not shuffle the "Compressed Debug information"
choice, which depends on DEBUG_INFO, which is derived from another
choice "Debug information".
My goal is to refactor Kconfig so that randconfig will work more
simply, without using the loop.
For now, let's add a test case to ensure all dependent choices are
shuffled, as it is a somewhat tricky case for the current Kconfig.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
for_all_symbols() iterates in the symbol hash table. The order of
iteration depends on the hash table implementation.
If you use it for printing errors, they are shown in random order.
For example, the order of following test input and the corresponding
error do not match:
- scripts/kconfig/tests/err_recursive_dep/Kconfig
- scripts/kconfig/tests/err_recursive_dep/expected_stderr
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Now "modules" is the only member of the "option" property.
Remove "option", and move "modules" to the top level property.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
"defconfig_list" is a weird option that defines a static symbol that
declares the list of base config files in case the .config does not
exist yet.
This is quite different from other normal symbols; we just abused the
"string" type and the "default" properties to list out the input files.
They must be fixed values since these are searched for and loaded in
the parse stage.
It is an ugly hack, and should not exist in the first place. Providing
this feature as an environment variable is a saner approach.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Nesting choice statements does not make any sense.
Commit df8df5e4bc ("usb: get rid of 'choice' for legacy gadget
drivers") got rid of the only usecase.
I will turn it into a syntax error. Remove the test in advance.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
The kbuild documentation clearly shows that the documents
there are written at different times: some use markdown,
some use their own peculiar logic to split sections.
Convert everything to ReST without affecting too much
the author's style and avoiding adding uneeded markups.
The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Adding SPDX license identifier is pretty safe; however, here is one
exception.
Since commit ec8f24b7fa ("treewide: Add SPDX license identifier -
Makefile/Kconfig"), "make testconfig" would not pass.
When Kconfig detects a circular file inclusion, it displays error
messages with a file name and a line number prefixed to each line.
The unit test checks if Kconfig emits the error messages correctly
(this also checks the line number correctness).
Now that the test input has the SPDX license identifier at the very top,
the line numbers in the expected stderr should be incremented by 1.
Fixes: ec8f24b7fa ("treewide: Add SPDX license identifier - Makefile/Kconfig")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
All files in lxdialog/ are licensed under GPL-2.0+, and the rest are
under GPL-2.0. I added GPL-2.0 tags to test scripts in tests/.
Documentation/process/license-rules.rst does not suggest anything
about the flex/bison files. Because flex does not accept the C++
comment style at the very top of a file, I used the C style for
zconf.l, and so for zconf.y for consistency.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit improves the messages of the recursive dependency.
Currently, sym->dir_dep.expr is not checked. Hence, any dependency
in property visibility is regarded as the dependency of the symbol.
[Test Code 1]
config A
bool "a"
depends on B
config B
bool "b"
depends on A
[Test Code 2]
config A
bool "a" if B
config B
bool "b"
depends on A
For both cases above, the same message is displayed:
symbol B depends on A
symbol A depends on B
This commit changes the message for the latter, like this:
symbol B depends on A
symbol A prompt is visible depending on B
Also, 'select' and 'imply' are distinguished.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Dirk Gouders <dirk@gouders.net>
Currently, Kconfig does not complain about the recursive dependency
where 'imply' keywords are involved.
[Test Code]
config A
bool "a"
config B
bool "b"
imply A
depends on A
In the code above, Kconfig cannot calculate the symbol values correctly
due to the circular dependency. For example, allyesconfig followed by
syncconfig results in an odd behavior because CONFIG_B becomes visible
in syncconfig.
$ make allyesconfig
scripts/kconfig/conf --allyesconfig Kconfig
#
# configuration written to .config
#
$ cat .config
#
# Automatically generated file; DO NOT EDIT.
# Main menu
#
CONFIG_A=y
$ make syncconfig
scripts/kconfig/conf --syncconfig Kconfig
*
* Restart config...
*
*
* Main menu
*
a (A) [Y/n/?] y
b (B) [N/y/?] (NEW)
To detect this correctly, sym_check_expr_deps() should recurse to
not only sym->rev_dep.expr but also sym->implied.expr .
At this moment, sym_check_print_recursive() cannot distinguish
'select' and 'imply' since it does not know the precise context
where the recursive dependency has been hit. This will be solved
by the next commit.
In fact, even the document and the unit-test are confused. Using
'imply' does not solve recursive dependency since 'imply' addresses
the unmet direct dependency, which 'select' could cause.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Dirk Gouders <dirk@gouders.net>
Originally, recursive dependency was a fatal error for Kconfig
because Kconfig cannot compute symbol values in such a situation.
Commit d595cea624 ("kconfig: print more info when we see a recursive
dependency") changed it to a warning, which I guess was not intentional.
Get it back to an error again.
Also, rename the unit test directory "warn_recursive_dep" to
"err_recursive_dep" so that it matches to the behavior.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Dirk Gouders <dirk@gouders.net>
If "mainmenu" is not specified, "Linux Kernel Configuration" is used
as a default prompt.
Given that Kconfig is used in other projects than Linux, let's use
a more generic prompt, "Main menu".
Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
As in the unit test, the error message for the recursive inclusion
looks like this:
Kconfig.inc1:4: recursive inclusion detected. Inclusion path:
current file : 'Kconfig.inc1'
included from: 'Kconfig.inc3:1'
included from: 'Kconfig.inc2:3'
included from: 'Kconfig.inc1:4'
The 'Kconfig.inc1:4' is duplicated in the first and last lines.
Also, the single quotes do not help readability.
Change the message like follows:
Recursive inclusion detected.
Inclusion path:
current file : Kconfig.inc1
included from: Kconfig.inc3:1
included from: Kconfig.inc2:3
included from: Kconfig.inc1:4
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Nicolas Schier
Nicolas PitreandNathan Chancellor
Kees Cook
HONG YifanandMasahiro Yamada
Mauro Carvalho ChehabandJonathan Corbet
Masahiro Yamada
Thomas GleixnerandGreg Kroah-Hartman