Re: [PATCH 07/23] kconfig: add function support and implement 'shell' function
From: Masahiro Yamada
Date: Mon Feb 19 2018 - 10:58:08 EST
2018-02-18 1:16 GMT+09:00 Ulf Magnusson <ulfalizer@xxxxxxxxx>:
> On Sat, Feb 17, 2018 at 03:38:35AM +0900, Masahiro Yamada wrote:
>> This commit adds a new concept 'function' to Kconfig. A function call
>> resembles a variable reference with arguments, and looks like this:
>>
>> $(function arg1, arg2, arg3, ...)
>>
>> (Actually, this syntax was inspired by Makefile.)
>>
>> Real examples will look like this:
>>
>> $(shell true)
>> $(cc-option -fstackprotector)
>>
>> This commit adds the basic infrastructure to add, delete, evaluate
>> functions.
>>
>> Also, add the first built-in function $(shell ...). This evaluates
>> to 'y' if the given command exits with 0, 'n' otherwise.
>>
>> I am also planning to support user-defined functions (a.k.a 'macro')
>> for cases where hard-coding is not preferred.
>>
>> If you want to try this feature, the hello-world code is someting below.
>>
>> Example code:
>>
>> config CC_IS_GCC
>> bool
>> default $(shell $CC --version | grep -q gcc)
>>
>> config CC_IS_CLANG
>> bool
>> default $(shell $CC --version | grep -q clang)
>>
>> config CC_HAS_OZ
>> bool
>> default $(shell $CC -Werror -Oz -c -x c /dev/null -o /dev/null)
>>
>> Result:
>>
>> $ make -s alldefconfig && tail -n 3 .config
>> CONFIG_CC_IS_GCC=y
>> # CONFIG_CC_IS_CLANG is not set
>> # CONFIG_CC_HAS_OZ is not set
>>
>> $ make CC=clang -s alldefconfig && tail -n 3 .config
>> # CONFIG_CC_IS_GCC is not set
>> CONFIG_CC_IS_CLANG=y
>> CONFIG_CC_HAS_OZ=y
>>
>> A function call can appear anywhere a symbol reference can appear.
>> So, the following code is possible.
>>
>> Example code:
>>
>> config CC_NAME
>> string
>> default "gcc" if $(shell $CC --version | grep -q gcc)
>> default "clang" if $(shell $CC --version | grep -q clang)
>> default "unknown compiler"
>>
>> Result:
>>
>> $ make -s alldefconfig && tail -n 1 .config
>> CONFIG_CC_NAME="gcc"
>>
>> $ make CC=clang -s alldefconfig && tail -n 1 .config
>> CONFIG_CC_NAME="clang"
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
>> ---
>>
>> Reminder for myself:
>> Update Documentation/kbuild/kconfig-language.txt
>>
>>
>> scripts/kconfig/function.c | 149 ++++++++++++++++++++++++++++++++++++++++++++
>> scripts/kconfig/lkc_proto.h | 5 ++
>> scripts/kconfig/util.c | 46 +++++++++++---
>> scripts/kconfig/zconf.l | 38 ++++++++++-
>> scripts/kconfig/zconf.y | 9 +++
>> 5 files changed, 238 insertions(+), 9 deletions(-)
>> create mode 100644 scripts/kconfig/function.c
>>
>> diff --git a/scripts/kconfig/function.c b/scripts/kconfig/function.c
>> new file mode 100644
>> index 0000000..60e59be
>> --- /dev/null
>> +++ b/scripts/kconfig/function.c
>> @@ -0,0 +1,149 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +//
>> +// Copyright (C) 2018 Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
>> +
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +
>> +#include "list.h"
>> +
>> +#define FUNCTION_MAX_ARGS 10
>> +
>> +static LIST_HEAD(function_list);
>> +
>> +struct function {
>> + const char *name;
>> + char *(*func)(int argc, char *argv[]);
>> + struct list_head node;
>> +};
>> +
>> +static struct function *func_lookup(const char *name)
>> +{
>> + struct function *f;
>> +
>> + list_for_each_entry(f, &function_list, node) {
>> + if (!strcmp(name, f->name))
>> + return f;
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +static void func_add(const char *name, char *(*func)(int argc, char *argv[]))
>> +{
>> + struct function *f;
>> +
>> + f = func_lookup(name);
>> + if (f) {
>> + fprintf(stderr, "%s: function already exists. ignored.\n", name);
>> + return;
>> + }
>> +
>> + f = xmalloc(sizeof(*f));
>> + f->name = name;
>> + f->func = func;
>> +
>> + list_add_tail(&f->node, &function_list);
>> +}
>> +
>> +static void func_del(struct function *f)
>> +{
>> + list_del(&f->node);
>> + free(f);
>> +}
>> +
>> +static char *func_call(int argc, char *argv[])
>> +{
>> + struct function *f;
>> +
>> + f = func_lookup(argv[0]);
>> + if (!f) {
>> + fprintf(stderr, "%s: function not found\n", argv[0]);
>> + return NULL;
>> + }
>> +
>> + return f->func(argc, argv);
>> +}
>> +
>> +static char *func_eval(const char *func)
>> +{
>> + char *expanded, *saveptr, *str, *token, *res;
>> + const char *delim;
>> + int argc = 0;
>> + char *argv[FUNCTION_MAX_ARGS];
>> +
>> + expanded = expand_string_value(func);
>> +
>> + str = expanded;
>> + delim = " ";
>> +
>> + while ((token = strtok_r(str, delim, &saveptr))) {
>> + argv[argc++] = token;
>> + str = NULL;
>> + delim = ",";
>> + }
>> +
>> + res = func_call(argc, argv);
>> +
>> + free(expanded);
>> +
>> + return res ?: xstrdup("");
>> +}
>> +
>> +char *func_eval_n(const char *func, size_t n)
>> +{
>> + char *tmp, *res;
>> +
>> + tmp = xmalloc(n + 1);
>> + memcpy(tmp, func, n);
>> + *(tmp + n) = '\0';
>> +
>> + res = func_eval(tmp);
>> +
>> + free(tmp);
>> +
>> + return res;
>> +}
>> +
>> +/* built-in functions */
>> +static char *do_shell(int argc, char *argv[])
>> +{
>> + static const char *pre = "(";
>> + static const char *post = ") >/dev/null 2>&1";
>> + char *cmd;
>> + int ret;
>> +
>> + if (argc != 2)
>> + return NULL;
>> +
>> + /*
>> + * Surround the command with ( ) in case it is piped commands.
>> + * Also, redirect stdout and stderr to /dev/null.
>> + */
>> + cmd = xmalloc(strlen(pre) + strlen(argv[1]) + strlen(post) + 1);
>> + strcpy(cmd, pre);
>> + strcat(cmd, argv[1]);
>> + strcat(cmd, post);
>> +
>> + ret = system(cmd);
>> +
>> + free(cmd);
>> +
>> + return xstrdup(ret == 0 ? "y" : "n");
>> +}
>> +
>> +void func_init(void)
>> +{
>> + /* register built-in functions */
>> + func_add("shell", do_shell);
>> +}
>> +
>> +void func_exit(void)
>> +{
>> + struct function *f, *tmp;
>> +
>> + /* unregister all functions */
>> + list_for_each_entry_safe(f, tmp, &function_list, node)
>> + func_del(f);
>> +}
>> diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
>> index 9884adc..09a4f53 100644
>> --- a/scripts/kconfig/lkc_proto.h
>> +++ b/scripts/kconfig/lkc_proto.h
>> @@ -48,5 +48,10 @@ const char * sym_get_string_value(struct symbol *sym);
>>
>> const char * prop_get_type_name(enum prop_type type);
>>
>> +/* function.c */
>> +char *func_eval_n(const char *func, size_t n);
>> +void func_init(void);
>> +void func_exit(void);
>> +
>> /* expr.c */
>> void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken);
>> diff --git a/scripts/kconfig/util.c b/scripts/kconfig/util.c
>> index dddf85b..ed89fb9 100644
>> --- a/scripts/kconfig/util.c
>> +++ b/scripts/kconfig/util.c
>> @@ -93,9 +93,10 @@ static char *env_expand_n(const char *name, size_t n)
>> }
>>
>> /*
>> - * Expand environments embedded in the string given in argument. Environments
>> - * to be expanded shall be prefixed by a '$'. Unknown environment expands to
>> - * the empty string.
>> + * Expand environments and functions embedded in the string given in argument.
>> + * Environments to be expanded shall be prefixed by a '$'. Functions to be
>> + * evaluated shall be surrounded by $(). Unknown environment/function expands
>> + * to the empty string.
>> */
>> char *expand_string_value(const char *in)
>> {
>> @@ -113,11 +114,40 @@ char *expand_string_value(const char *in)
>> while ((p = strchr(in, '$'))) {
>> char *new;
>>
>> - q = p + 1;
>> - while (isalnum(*q) || *q == '_')
>> - q++;
>> -
>> - new = env_expand_n(p + 1, q - p - 1);
>> + /*
>> + * If the next character is '(', it is a function.
>> + * Otherwise, environment.
>> + */
>> + if (*(p + 1) == '(') {
>> + int nest = 0;
>> +
>> + q = p + 2;
>> + while (1) {
>> + if (*q == '\0') {
>> + fprintf(stderr,
>> + "unterminated function: %s\n",
>> + p);
>> + new = xstrdup("");
>> + break;
>> + } else if (*q == '(') {
>> + nest++;
>> + } else if (*q == ')') {
>> + if (nest-- == 0) {
>> + new = func_eval_n(p + 2,
>> + q - p - 2);
>> + q++;
>> + break;
>> + }
>> + }
>> + q++;
>> + }
>> + } else {
>> + q = p + 1;
>> + while (isalnum(*q) || *q == '_')
>> + q++;
>> +
>> + new = env_expand_n(p + 1, q - p - 1);
>> + }
>>
>> reslen = strlen(res) + (p - in) + strlen(new) + 1;
>> res = xrealloc(res, reslen);
>> diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
>> index 0d89ea6..f433ab0 100644
>> --- a/scripts/kconfig/zconf.l
>> +++ b/scripts/kconfig/zconf.l
>> @@ -1,7 +1,7 @@
>> %option nostdinit noyywrap never-interactive full ecs
>> %option 8bit nodefault perf-report perf-report
>> %option noinput
>> -%x COMMAND HELP STRING PARAM
>> +%x COMMAND HELP STRING PARAM FUNCTION
>> %{
>> /*
>> * Copyright (C) 2002 Roman Zippel <zippel@xxxxxxxxxxxxxx>
>> @@ -25,6 +25,7 @@ static struct {
>>
>> static char *text;
>> static int text_size, text_asize;
>> +static int function_nest;
>>
>> struct buffer {
>> struct buffer *parent;
>> @@ -138,6 +139,12 @@ n [$A-Za-z0-9_-]
>> new_string();
>> BEGIN(STRING);
>> }
>> + "$(" {
>> + new_string();
>> + append_string(yytext, yyleng);
>> + function_nest = 0;
>> + BEGIN(FUNCTION);
>> + }
>> \n BEGIN(INITIAL); current_file->lineno++; return T_EOL;
>> ({n}|[/.])+ {
>> const struct kconf_id *id = kconf_id_lookup(yytext, yyleng);
>> @@ -196,6 +203,35 @@ n [$A-Za-z0-9_-]
>> }
>> }
>>
>> +<FUNCTION>{
>> + [^()\n]* {
>> + append_string(yytext, yyleng);
>> + }
>> + "(" {
>> + append_string(yytext, yyleng);
>> + function_nest++;
>> + }
>> + ")" {
>> + append_string(yytext, yyleng);
>> + if (function_nest-- == 0) {
>> + BEGIN(PARAM);
>> + yylval.string = text;
>> + return T_WORD;
>
> T_WORD_QUOTE (which would turn into a constant symbol in most contexts)
> would be better here, IMO. That would turn $(foo) into just an alias for
> "$(foo)".
>
> See below.
>
>> + }
>> + }
>> + \n {
>> + fprintf(stderr,
>> + "%s:%d:warning: multi-line function not supported\n",
>> + zconf_curname(), zconf_lineno());
>> + current_file->lineno++;
>> + BEGIN(INITIAL);
>> + return T_EOL;
>> + }
>> + <<EOF>> {
>> + BEGIN(INITIAL);
>> + }
>> +}
>> +
>> <HELP>{
>> [ \t]+ {
>> ts = 0;
>> diff --git a/scripts/kconfig/zconf.y b/scripts/kconfig/zconf.y
>> index 784083d..d9977de 100644
>> --- a/scripts/kconfig/zconf.y
>> +++ b/scripts/kconfig/zconf.y
>> @@ -534,11 +534,19 @@ void conf_parse(const char *name)
>>
>> zconf_initscan(name);
>>
>> + func_init();
>> _menu_init();
>>
>> if (getenv("ZCONF_DEBUG"))
>> yydebug = 1;
>> yyparse();
>> +
>> + /*
>> + * Currently, functions are evaluated only when Kconfig files are
>> + * parsed. We can free functions here.
>> + */
>> + func_exit();
>> +
>> if (yynerrs)
>> exit(1);
>> if (!modules_sym)
>> @@ -778,4 +786,5 @@ void zconfdump(FILE *out)
>> #include "confdata.c"
>> #include "expr.c"
>> #include "symbol.c"
>> +#include "function.c"
>> #include "menu.c"
>> --
>> 2.7.4
>>
>
> Here's a simplification idea I'm throwing out there:
>
> What about only allowing $ENV and $() within quotes, and just having
> them always do simple text substitution (so that they'd indirectly
> always generate T_WORD_QUOTE tokens)?
I ended up with a new state <FUNCTION>,
but the real problem is the lexer is too ugly.
So, maybe, the solution is not to make it into a string,
but to re-write the lexer.
<STRING> and <FUNCTION> are almost the same in the sense
that whitespaces do not split tokens.
The difference is the characters to start/end with.
' ... '
" ... "
( ... )
If we encounter with the 3 special characters, ' , '', (,
then we enter into <STRING> state,
then it ends with ', ", ), respectively.
(but we need to take care of nesting, escaping)
Double-surrounding like "$(cc-option -Oz)"
looks ugly to me.
> Pros:
>
> - Zero new syntax outside of strings (until the macro stuff).
>
> - Makes the behavior and limitations of the syntax obvious: You can't
> have $(foo) expand to a full expression, only to (possibly part of) a
> value. This is a good limitation, IMO, and it's already there.
>
> - Super simple and straightforward Kconfig implementation. All the new
> magic would happen in expand_string_value().
>
> Neutral:
>
> - Just as general where it matters. Take something like
>
> default "$(foo)"
>
> If $(foo) happens to expand to "y", then that will do its usual thing
> for a bool/tristate symbol. Same for string symbols, etc. It'd just
> be a thin preprocessing step on constant symbol values.
>
> - The only loss in generality would be that you can no longer have
> a function expand to the name of non-constant symbol. For example,
> take the following:
>
> default $(foo)
>
> If $(foo) expands to MY_SYMBOL, then that would work as
>
> default MY_SYMBOL
Probably, this is a "do not do this".
If the symbol is 'int' type,
and $MY_NUMBER is expanded to 1,
it is our intention.
> (I.e., it would default to the value of the symbol MY_SYMBOL.)
>
> With the quotes, it would instead work as
>
> default "MY_SYMBOL"
>
> IMO, the second version is less confusing, and deliberately using the
> first version seems like a bad idea (there's likely to be cleaner ways
> to do the indirection in plain Kconfig).
>
> This is also why I think T_WORD_QUOTE is better in the code above. It
> would make $(foo) work more like a shorthand for "$(foo)".
>
>
> Cons:
>
> - Bit more typing to add the quotes
>
> - Maybe it isn't widely known that "n", "m", "y" work just like n, m, y
> for bool and tristate symbols (the latter automatically get converted
> to the former), though you see them quite a lot in Kconfig files.
Not only bool/tristate, but also int/hex.
"1" is equivalent to 1.
Kconfig is screwed up in handling of literals.
> ("n", "foo bar", etc., are all just constant symbols. Kconfig keeps
> track of them separately from non-constant symbols. The constant
> symbols "n", "m", and "y" are predefined.)
>
> If we go with obligatory quotes, I volunteer to explain things in
> kconfig-language.txt at least, to make it clear why you'd see quotes
> in bool/tristate symbols using $(shell). I suspect it wouldn't be
> that tricky to figure out anyway.
I think the right thing to do is
to fix the code instead of advertising it.
> What do you think?
>
> Cheers,
> Ulf
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--
Best Regards
Masahiro Yamada