Re: [PATCH 07/23] kconfig: add function support and implement 'shell' function
From: Ulf Magnusson
Date: Sat Feb 17 2018 - 11:17:06 EST
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)?
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
(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.
("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.
What do you think?
Cheers,
Ulf