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Date: Fri, 13 Apr 2018 14:37:22 +0900
From: Masahiro Yamada <yamada.masahiro@...ionext.com>
To: Ulf Magnusson <ulfalizer@...il.com>
Cc: Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
Sam Ravnborg <sam@...nborg.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>,
Kees Cook <keescook@...omium.org>,
Thomas Gleixner <tglx@...utronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Luis R . Rodriguez" <mcgrof@...nel.org>,
Nicolas Pitre <nico@...aro.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 07/21] kconfig: add function support and implement
'shell' function
2018-04-01 13:19 GMT+09:00 Ulf Magnusson <ulfalizer@...il.com>:
> On Tue, Mar 27, 2018 at 7:29 AM, Masahiro Yamada
> <yamada.masahiro@...ionext.com> wrote:
>> This commit adds a new concept 'function' to do more text processing
>> in Kconfig.
>>
>> A function call looks like this:
>>
>> $(function arg1, arg2, arg3, ...)
>>
>> (Actually, this syntax was inspired by make.)
>>
>> Real examples will look like this:
>>
>> $(shell echo hello world)
>> $(cc-option -fstackprotector)
>>
>> This commit adds the basic infrastructure to add, delete, evaluate
>> functions, and also the first built-in function $(shell ...). This
>> accepts a single command to execute. It returns the standard output
>> from it.
>>
>> [Example code]
>>
>> config HELLO
>> string
>> default "$(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@...ionext.com>
>> ---
>>
>> Reminder for myself:
>> Update Documentation/kbuild/kconfig-language.txt
>>
>>
>> Changes in v2:
>> - Use 'shell' for getting stdout from the comment.
>> It was 'shell-stdout' in the previous version.
>> - Symplify the implementation since the expansion has been moved to
>> lexer.
>>
>> scripts/kconfig/function.c | 170 ++++++++++++++++++++++++++++++++++++++++++++
>> scripts/kconfig/lkc_proto.h | 5 ++
>> scripts/kconfig/util.c | 46 +++++++++---
>> scripts/kconfig/zconf.y | 9 +++
>> 4 files changed, 222 insertions(+), 8 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..913685f
>> --- /dev/null
>> +++ b/scripts/kconfig/function.c
>> @@ -0,0 +1,170 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +//
>> +// Copyright (C) 2018 Masahiro Yamada <yamada.masahiro@...ionext.com>
>> +
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +
>> +#include "list.h"
>> +
>> +#define FUNCTION_MAX_ARGS 10
>> +
>> +static LIST_HEAD(function_list);
>> +
>> +struct function {
>> + char *name;
>> + char *(*func)(struct function *f, 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)(struct function *f, 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 = xstrdup(name);
>> + f->func = func;
>> +
>> + list_add_tail(&f->node, &function_list);
>> +}
>> +
>> +static void func_del(struct function *f)
>> +{
>> + list_del(&f->node);
>> + free(f->name);
>> + 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(f, 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;
>
> Would be nice to error out if the array is overstepped.
In V3, I made this a feature.
>> + str = NULL;
>> + delim = ",";
>> + }
>> +
>> + res = func_call(argc, argv);
>> +
>> + free(expanded);
>> +
>> + return res ?: xstrdup("");
>> +}
>
> Since only 'macro' will take multiple parameters, I wonder if it might
> be better to implement the argument parsing there, and simply pass the
> string (minus the function name) as-is to functions.
I may add more built-in functions in the future.
For example, I want to add 'if' function, which takes two or three arguments.
> You would then be able to have ',' in shell commands, which might be
> required -- think gcc -Wl,option and the like.
I fixed 'shell' function in v3.
>> +
>> +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(struct function *f, int argc, char *argv[])
>> +{
>> + static const char *pre = "(";
>> + static const char *post = ") 2>/dev/null";
>
> Arrays seem neater, since the pointers aren't needed.
>
>> + FILE *p;
>> + char buf[256];
>> + char *cmd;
>> + int ret;
>
> Could get rid of 'ret' and just do
>
> if (pclose(p) == -1)
> perror(cmd);
Done.
>> +
>> + if (argc != 2)
>> + return NULL;
>> +
>> + /*
>> + * Surround the command with ( ) in case it is piped commands.
>> + * Also, redirect stderr to /dev/null.
>> + */
>> + cmd = xmalloc(strlen(pre) + strlen(argv[1]) + strlen(post) + 1);
>> + strcpy(cmd, pre);
>> + strcat(cmd, argv[1]);
>> + strcat(cmd, post);
>> +
>> + p = popen(cmd, "r");
>> + if (!p) {
>> + perror(cmd);
>> + goto free;
>> + }
>> + if (fgets(buf, sizeof(buf), p)) {
>> + size_t len = strlen(buf);
>> +
>> + if (buf[len - 1] == '\n')
>> + buf[len - 1] = '\0';
>> + } else {
>> + buf[0] = '\0';
>> + }
>> +
>> + ret = pclose(p);
>> + if (ret == -1)
>> + perror(cmd);
>> +
>> +free:
>> + free(cmd);
>> +
>> + return xstrdup(buf);
>> +}
>> +
>> +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 3d27c49..218b051 100644
>> --- a/scripts/kconfig/util.c
>> +++ b/scripts/kconfig/util.c
>> @@ -13,9 +13,10 @@
>> #include "lkc.h"
>>
>> /*
>> - * 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 $(). Unknown environment/function expands
>> + * to the empty string.
>> */
>> char *expand_string_value(const char *in)
>> {
>> @@ -33,11 +34,40 @@ char *expand_string_value(const char *in)
>> while ((p = strchr(in, '$'))) {
>> 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++;
>> + }
>
> A loop like this might work too:
>
> q = p + 1;
> do {
> if (*q == '\0') {
> *error*
> val = ...
> goto error;
> }
>
> if (*q == '(')
> nest++;
> if (*q == ')')
> nest--;
> q++;
> } while (nest > 0);
>
> val = func_eval_n(...)
> error:
>
>> + } 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.y b/scripts/kconfig/zconf.y
>> index d8120c7..feaea18 100644
>> --- a/scripts/kconfig/zconf.y
>> +++ b/scripts/kconfig/zconf.y
>> @@ -520,11 +520,19 @@ 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)
>> @@ -765,4 +773,5 @@ void zconfdump(FILE *out)
>> #include "confdata.c"
>> #include "expr.c"
>> #include "symbol.c"
>> +#include "function.c"
>> #include "menu.c"
>> --
>> 2.7.4
>>
>
> Cheers,
> Ulf
> --
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--
Best Regards
Masahiro Yamada
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