When using a recursively expanded variable, it is a common mistake
to make circular reference.
For example, Make terminates the following code:
X = $(X)
Y := $(X)
Let's detect the circular expansion in Kconfig, too.
On the other hand, a function that recurses itself is a commonly-used
programming technique. So, Make does not check recursion in the
reference with 'call'. For example, the following code continues
running eternally:
X = $(call X)
Y := $(X)
Kconfig allows circular expansion if one or more arguments are given,
but terminates when the same function is recursively invoked 1000 times,
assuming it is a programming mistake.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The special variables, $(filename) and $(lineno), are expanded to a
file name and its line number being parsed, respectively.
Suggested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Syntax:
$(info,<text>)
$(warning-if,<condition>,<text>)
$(error-if,<condition>,<text)
The 'info' function prints a message to stdout as in Make.
The 'warning-if' and 'error-if' are similar to 'warning' and 'error'
in Make, but take the condition parameter. They are effective only
when the <condition> part is y.
Kconfig does not implement the lazy expansion as used in the 'if'
'and, 'or' functions in Make. In other words, Kconfig does not
support conditional expansion. The unconditional 'error' function
would always terminate the parsing, hence would be useless in Kconfig.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Support += operator. This appends a space and the text on the
righthand side to a variable.
The timing of the evaluation of the righthand side depends on the
flavor of the variable. If the lefthand side was originally defined
as a simple variable, the righthand side is expanded immediately.
Otherwise, the expansion is deferred. Appending something to an
undefined variable results in a recursive variable.
To implement this, we need to remember the flavor of variables.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The previous commit added variable and user-defined function. They
work similarly in the sense that the evaluation is deferred until
they are used.
This commit adds another type of variable, simply expanded variable,
as we see in Make.
The := operator defines a simply expanded variable, expanding the
righthand side immediately. This works like traditional programming
language variables.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Now, we got a basic ability to test compiler capability in Kconfig.
config CC_HAS_STACKPROTECTOR
def_bool $(shell,($(CC) -Werror -fstack-protector -E -x c /dev/null -o /dev/null 2>/dev/null) && echo y || echo n)
This works, but it is ugly to repeat this long boilerplate.
We want to describe like this:
config CC_HAS_STACKPROTECTOR
bool
default $(cc-option,-fstack-protector)
It is straight-forward to add a new function, but I do not like to
hard-code specialized functions like that. Hence, here is another
feature, user-defined function. This works as a textual shorthand
with parameterization.
A user-defined function is defined by using the = operator, and can
be referenced in the same way as built-in functions. A user-defined
function in Make is referenced like $(call my-func,arg1,arg2), but I
omitted the 'call' to make the syntax shorter.
The definition of a user-defined function contains $(1), $(2), etc.
in its body to reference the parameters. It is grammatically valid
to pass more or fewer arguments when calling it. We already exploit
this feature in our makefiles; scripts/Kbuild.include defines cc-option
which takes two arguments at most, but most of the callers pass only
one argument.
By the way, a variable is supported as a subset of this feature since
a variable is "a user-defined function with zero argument". In this
context, I mean "variable" as recursively expanded variable. I will
add a different flavored variable in the next commit.
The code above can be written as follows:
[Example Code]
success = $(shell,($(1)) >/dev/null 2>&1 && echo y || echo n)
cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)
config CC_HAS_STACKPROTECTOR
def_bool $(cc-option,-fstack-protector)
[Result]
$ make -s alldefconfig && tail -n 1 .config
CONFIG_CC_HAS_STACKPROTECTOR=y
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This accepts a single command to execute. It returns the standard
output from it.
[Example code]
config HELLO
string
default "$(shell,echo hello world)"
config Y
def_bool $(shell,echo y)
[Result]
$ make -s alldefconfig && tail -n 2 .config
CONFIG_HELLO="hello world"
CONFIG_Y=y
Caveat:
Like environments, functions are expanded in the lexer. You cannot
pass symbols to function arguments. This is a limitation to simplify
the implementation. I want to avoid the dynamic function evaluation,
which would introduce much more complexity.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit adds a new concept 'function' to do more text processing
in Kconfig.
A function call looks like this:
$(function,arg1,arg2,arg3,...)
This commit adds the basic infrastructure to expand functions.
Change the text expansion helpers to take arguments.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
To get access to environment variables, Kconfig needs to define a
symbol using "option env=" syntax. It is tedious to add a symbol entry
for each environment variable given that we need to define much more
such as 'CC', 'AS', 'srctree' etc. to evaluate the compiler capability
in Kconfig.
Adding '$' for symbol references is grammatically inconsistent.
Looking at the code, the symbols prefixed with 'S' are expanded by:
- conf_expand_value()
This is used to expand 'arch/$ARCH/defconfig' and 'defconfig_list'
- sym_expand_string_value()
This is used to expand strings in 'source' and 'mainmenu'
All of them are fixed values independent of user configuration. So,
they can be changed into the direct expansion instead of symbols.
This change makes the code much cleaner. The bounce symbols 'SRCARCH',
'ARCH', 'SUBARCH', 'KERNELVERSION' are gone.
sym_init() hard-coding 'UNAME_RELEASE' is also gone. 'UNAME_RELEASE'
should be replaced with an environment variable.
ARCH_DEFCONFIG is a normal symbol, so it should be simply referenced
without '$' prefix.
The new syntax is addicted by Make. The variable reference needs
parentheses, like $(FOO), but you can omit them for single-letter
variables, like $F. Yet, in Makefiles, people tend to use the
parenthetical form for consistency / clarification.
At this moment, only the environment variable is supported, but I will
extend the concept of 'variable' later on.
The variables are expanded in the lexer so we can simplify the token
handling on the parser side.
For example, the following code works.
[Example code]
config MY_TOOLCHAIN_LIST
string
default "My tools: CC=$(CC), AS=$(AS), CPP=$(CPP)"
[Result]
$ make -s alldefconfig && tail -n 1 .config
CONFIG_MY_TOOLCHAIN_LIST="My tools: CC=gcc, AS=as, CPP=gcc -E"
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Masahiro Yamada