kernel/linux.git/scripts/kconfig/conf.c, branch v7.3-rc1

kconfig: abort rather than loop for ever on EOF

2026-08-05T12:46:48+00:00

When a non-interactive 'make oldconfig' or 'syncconfig' meets a new int or hex symbol whose default cannot be applied, conf_string() reads a value from stdin. At end of file fgets() returns NULL, no value is set and the loop asks again. The result is an endless loop which fills the output until it exhausts memory, rather than a clean failure. Detect this in conf_string(): if the value cannot be set and stdin is at end of file, stop with an error that names the symbol. Note that a symbol with no default doesn't trigger this, since sym_calc_value() falls back to 0, which is accepted at end of file. The loop is triggered by a broken Kconfig file, with a default whose text fails sym_string_valid(). Such mistakes do creep in from time to time and are hard to debug, since the build fills the log with repeated prompts instead of pointing at the offending symbol. Some bad defaults draw a parse-time warning, but menu_validate_number() accepts a reference to any int or hex symbol, so a cross-type reference loops with no warning at all. For example, "0xff" is not a valid int value: config HEXSYM hex default 0xff config VAL int "Value" default HEXSYM Interactive use is unaffected, since feof() only becomes true once a read actually hits end of file: an invalid answer at a terminal still re-prompts, while Ctrl-D at such a prompt exits with the error instead of looping. bool and tristate symbols and choices already accept the default on an empty line, so they still take their defaults in a non-interactive build. Tested with int and hex symbols carrying such defaults: with empty stdin, the code without this change produces around 190MB of repeated prompts within two seconds, while with the change it exits 1 naming the symbol. Piped and interactive (pty) sessions still re-prompt on an invalid answer and then accept a valid one. A new string symbol with no default still takes the empty string at end of file, since any text is valid for a string. Signed-off-by: Simon Glass Link: https://patch.msgid.link/20260714133545.3294648-1-sjg@chromium.org Signed-off-by: Nicolas Schier

kconfig: fix potential NULL pointer dereference in conf_askvalue

2026-04-30T01:05:44+00:00

In conf_askvalue(), the 'def' argument (retrieved via sym_get_string_value) can be NULL. While current call sites ensure that 'def' is valid, calling printf("%s\n", def) is technically undefined behavior and could lead to a segmentation fault on certain libc implementations if the function were called with a NULL pointer in the future. Improve the robustness of conf_askvalue() by providing an empty string as a fallback. Additionally, remove the redundant re-initialization of the 'line' buffer inside the !sym_is_changeable(sym) block, as it is already properly initialized at the function entry. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Xingjing Deng Reviewed-by: Nathan Chancellor Link: https://patch.msgid.link/20260306021709.27068-1-micro6947@gmail.com Signed-off-by: Nathan Chancellor

kconfig: rename menu_get_parent_menu() to menu_get_menu_or_parent_menu()

2025-06-30T03:52:58+00:00

The current menu_get_parent_menu() does not always return the parent menu; if the given argument is itself a menu, it returns that menu. Rename this function to better reflect this behavior. Signed-off-by: Masahiro Yamada Acked-by: Randy Dunlap Tested-by: Randy Dunlap

kconfig: document the positional argument in the help message

2024-11-05T23:46:35+00:00

The positional argument specifies the top-level Kconfig. Include this information in the help message. Signed-off-by: Masahiro Yamada

kconfig: remove sym_get_choice_value()

2024-07-15T16:08:37+00:00

sym_get_choice_value(menu->sym) is equivalent to sym_calc_choice(menu). Convert all call sites of sym_get_choice_value() and then remove it. Signed-off-by: Masahiro Yamada

kconfig: refactor choice value calculation

2024-07-15T16:08:37+00:00

Handling choices has always been in a PITA in Kconfig. For example, fixes and reverts were repeated for randconfig with KCONFIG_ALLCONFIG: - 422c809f03f0 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG") - 23a5dfdad22a ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"") - 8357b48549e1 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG") - 490f16171119 ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"") As these commits pointed out, randconfig does not randomize choices when KCONFIG_ALLCONFIG is used. This issue still remains. [Test Case] choice prompt "choose" config A bool "A" config B bool "B" endchoice $ echo > all.config $ make KCONFIG_ALLCONFIG=1 randconfig The output is always as follows: CONFIG_A=y # CONFIG_B is not set Not only randconfig, but other all*config variants are also broken with KCONFIG_ALLCONFIG. With the same Kconfig, $ echo '# CONFIG_A is not set' > all.config $ make KCONFIG_ALLCONFIG=1 allyesconfig You will get this: CONFIG_A=y # CONFIG_B is not set This is incorrect because it does not respect all.config. The correct output should be: # CONFIG_A is not set CONFIG_B=y To handle user inputs more accurately, this commit refactors the code based on the following principles: - When a user value is given, Kconfig must set it immediately. Do not defer it by setting SYMBOL_NEED_SET_CHOICE_VALUES. - The SYMBOL_DEF_USER flag must not be cleared, unless a new config file is loaded. Kconfig must not forget user inputs. In addition, user values for choices must be managed with priority. If user inputs conflict within a choice block, the newest value wins. The values given by randconfig have lower priority than explicit user inputs. This commit implements it by using a linked list. Every time a choice block gets a new input, it is moved to the top of the list. Let me explain how it works. Let's say, we have a choice block that consists of five symbols: A, B, C, D, and E. Initially, the linked list looks like this: A(=?) --> B(=?) --> C(=?) --> D(=?) --> E(=?) Suppose randconfig is executed with the following KCONFIG_ALLCONFIG: CONFIG_C=y # CONFIG_A is not set CONFIG_D=y First, CONFIG_C=y is read. C is set to 'y' and moved to the top. C(=y) --> A(=?) --> B(=?) --> D(=?) --> E(=?) Next, '# CONFIG_A is not set' is read. A is set to 'n' and moved to the top. A(=n) --> C(=y) --> B(=?) --> D(=?) --> E(=?) Then, 'CONFIG_D=y' is read. D is set to 'y' and moved to the top. D(=y) --> A(=n) --> C(=y) --> B(=?) --> E(=?) Lastly, randconfig shuffles the order of the remaining symbols, resulting in: D(=y) --> A(=n) --> C(=y) --> B(=y) --> E(=y) or D(=y) --> A(=n) --> C(=y) --> E(=y) --> B(=y) When calculating the output, the linked list is traversed and the first visible symbol with 'y' is taken. In this case, it is D if visible. If D is hidden by 'depends on', the next node, A, is examined. Since it is already specified as 'n', it is skipped. Next, C is checked, and selected if it is visible. If C is also invisible, either B or E is chosen as a result of the randomization. If B and E are also invisible, the linked list is traversed in the reverse order, and the least prioritized 'n' symbol is chosen. It is A in this case. Now, Kconfig remembers all user values. This is a big difference from the previous implementation, where Kconfig would forget CONFIG_C=y when CONFIG_D=y appeared in the same input file. The new appaorch respects user-specified values as much as possible. Signed-off-by: Masahiro Yamada

kconfig: introduce choice_set_value() helper

2024-07-15T16:08:36+00:00

Currently, sym_set_tristate_value() is used to set 'y' to a choice member, which is confusing because it not only sets 'y' to the given symbol but also tweaks flags of other symbols as a side effect. Add a dedicated function for setting the value of the given choice. Signed-off-by: Masahiro Yamada

kconfig: refactor conf_set_all_new_symbols() to reduce indentation level

2024-07-15T16:08:36+00:00

The outer switch statement can be avoided by continue'ing earlier the loop when the symbol type is neither S_BOOLEAN nor S_TRISTATE. Remove it to reduce the indentation level by one. In addition, avoid the repetition of sym->def[S_DEF_USER].tri. No functional change intended. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

kconfig: remove tristate choice support

2024-07-15T16:08:36+00:00

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: - df8df5e4bc37 ("usb: get rid of 'choice' for legacy gadget drivers") - bfb57ef0544a ("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 fa64e5f6a35e ("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 Reviewed-by: Nicolas Schier

kconfig: turn conf_choice() into void function

2024-05-09T19:34:53+00:00

The return value of conf_choice() is not used. Signed-off-by: Masahiro Yamada