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>
In gconf, choice entries display the selected symbol in the 'Value'
column, but it is not updated when the selected symbol is changed.
Set the MENU_CHANGED flag, so it is updated.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
The string allocated in sym_warn_unmet_dep() is never freed, leading
to a memory leak when an unmet dependency is detected.
Fixes: f8f69dc0b4 ("kconfig: make unmet dependency warnings readable")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Split out the code that retrieves the menu entry with a prompt, so it
can be reused in other functions.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This function was originally added by commit 8af27e1dc4 ("fixdep: use
hash table instead of a single array").
Move it to scripts/include/ so that other host programs can use it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
P_SYMBOL is a pseudo property that was previously used for data linking
purposes.
It is no longer used except for debug prints. Remove it.
Signed-off-by: Masahiro Yamada <masahiroy@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>
Improve the error messages and clean up redundant code.
[1] remove redundant next_sym->name checks
If 'next_sym' is a choice, the first 'if' block is executed. In the
subsequent 'else if' blocks, 'next_sym" is not a choice, hence
next_sym->name is not NULL.
[2] remove redundant sym->name checks
A choice is never selected or implied by anyone because it has no name
(it is syntactically impossible). If it is, sym->name is not NULL.
[3] Show the location of choice instead of "<choice>"
"part of choice <choice>" does not convey useful information. Since a
choice has no name, it is more informative to display the file name and
line number.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Kconfig detects recursive dependencies in a choice block, but the error
message is unclear.
[Test Code]
choice
prompt "choose"
depends on A
config A
bool "A"
config B
bool "B"
endchoice
[Result]
Kconfig:1:error: recursive dependency detected!
Kconfig:1: choice <choice> contains symbol A
Kconfig:5: symbol A is part of choice <choice>
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"
The phrase "contains symbol A" does not accurately describe the problem.
The issue is that the choice depends on A, which is a member of itself.
The first if-block does not print a sensible message. Remove it.
This commit improves the error message to:
Kconfig:1:error: recursive dependency detected!
Kconfig:1: symbol <choice> symbol is visible depending on A
Kconfig:5: symbol A is part of choice <choice>
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
A choice member must not depend on another member within the same choice
block.
Kconfig detects this, but the error message is not sensible.
[Test Code]
choice
prompt "choose"
config A
bool "A"
depends on B
config B
bool "B"
endchoice
[Result]
Kconfig:1:error: recursive dependency detected!
Kconfig:1: choice <choice> contains symbol A
Kconfig:4: symbol A is part of choice B
Kconfig:8: symbol B is part of choice <choice>
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"
The phrase "part of choice B" is weird because B is not a choice block,
but a choice member.
To determine whether the current symbol is a part of a choice block,
sym_is_choice(next_sym) must be checked.
This commit improves the error message to:
Kconfig:1:error: recursive dependency detected!
Kconfig:1: choice <choice> contains symbol A
Kconfig:4: symbol A symbol is visible depending on B
Kconfig:8: symbol B is part of choice <choice>
For a resolution refer to Documentation/kbuild/kconfig-language.rst
subsection "Kconfig recursive dependency limitations"
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
When a prompt is followed by "if <expr>", the symbol is configurable
when the if-conditional evaluates to true.
A typical usage is as follows:
menuconfig BLOCK
bool "Enable the block layer" if EXPERT
default y
When EXPERT=n, the prompt is hidden, but this config entry is still
active, and BLOCK is set to its default value 'y'. When EXPERT=y, the
prompt is shown, making BLOCK a user-configurable option.
This usage is common throughout the kernel tree, but it has never worked
within a choice block.
[Test Code]
config EXPERT
bool "Allow expert users to modify more options"
choice
prompt "Choose" if EXPERT
config A
bool "A"
config B
bool "B"
endchoice
[Result]
# CONFIG_EXPERT is not set
When the prompt is hidden, the choice block should produce the default
without asking for the user's preference. Hence, the output should be:
# CONFIG_EXPERT is not set
CONFIG_A=y
# CONFIG_B is not set
Removing unnecessary hacks fixes the issue.
This commit also changes the behavior of 'select' by choice members.
[Test Code 2]
config MODULES
def_bool y
modules
config DEP
def_tristate m
if DEP
choice
prompt "choose"
config A
bool "A"
select C
endchoice
config B
def_bool y
select D
endif
config C
tristate
config D
tristate
The current output is as follows:
CONFIG_MODULES=y
CONFIG_DEP=m
CONFIG_A=y
CONFIG_B=y
CONFIG_C=y
CONFIG_D=m
With this commit, the output will be changed as follows:
CONFIG_MODULES=y
CONFIG_DEP=m
CONFIG_A=y
CONFIG_B=y
CONFIG_C=m
CONFIG_D=m
CONFIG_C will be changed to 'm' because 'select C' will inherit the
dependency on DEP, which is 'm'.
This change is aligned with the behavior of 'select' outside a choice
block; 'select D' depends on DEP, therefore D is selected by (B && DEP).
Note:
With this commit, allmodconfig will set CONFIG_USB_ROLE_SWITCH to 'm'
instead of 'y'. I did not see any build regression with this change.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
E_LIST was preveously used to form an expression tree consisting of
choice members.
It is no longer used.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
P_CHOICE is a pseudo property used to link a choice with its members.
There is no more code relying on this, except for some debug code.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Choices and their members are associated via the P_CHOICE property.
Currently, prop_get_symbol(sym_get_choice_prop()) is used to obtain
the choice of the given choice member.
Replace it with sym_get_choice_menu(), which retrieves the choice
without relying on P_CHOICE.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Choices and their members are associated via the P_CHOICE property.
Currently, prop_get_symbol(sym_get_choice_prop()) is used to obtain
the choice of the given choice member.
Replace it with sym_get_choice_menu(), which retrieves the choice
without relying on P_CHOICE.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Choices and their members are associated via the P_CHOICE property.
Currently, prop_get_symbol(sym_get_choice_prop()) is used to obtain
the choice of the given choice member.
Replace it with sym_get_choice_menu(), which retrieves the choice
without relying on P_CHOICE.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Choices and their members are associated via the P_CHOICE property.
Currently, sym_get_choice_prop() and expr_list_for_each_sym() are
used to iterate on choice members.
Replace them with menu_for_each_sub_entry(), which achieves the same
without relying on P_CHOICE.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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 <masahiroy@kernel.org>
Kees Cook
Masahiro Yamada
HONG YifanandMasahiro Yamada