minikconfig: add parser skeleton

This implements a scanner and recursive descent parser for Kconfig-like
configuration files.  The only "action" of the parser is for now to
detect undefined variables and process include files.

The main differences between Kconfig and this are:

* only the "bool" type is supported

* variables can only be defined once

* choices are not supported (but they could be added as syntactic
sugar for multiple Boolean values)

* menus and other graphical concepts (prompts, help text) are not
supported

* assignments ("CONFIG_FOO=y", "CONFIG_FOO=n") are parsed as part
of the Kconfig language, not as a separate file.

The idea was originally by Ákos Kovács, but I could not find his
implementation so I had to redo it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20190123065618.3520-23-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 441 insertions, 0 deletions

diff --git a/scripts/minikconf.py b/scripts/minikconf.py
new file mode 100644
index 0000000..fd75d96
--- /dev/null
+++ b/scripts/minikconf.py
@@ -0,0 +1,441 @@
+#
+# Mini-Kconfig parser
+#
+# Copyright (c) 2015 Red Hat Inc.
+#
+# Authors:
+#  Paolo Bonzini <pbonzini@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2
+# or, at your option, any later version.  See the COPYING file in
+# the top-level directory.
+
+from __future__ import print_function
+import os
+import sys
+
+__all__ = [ 'KconfigParserError', 'KconfigData', 'KconfigParser' ]
+
+def debug_print(*args):
+    #print('# ' + (' '.join(str(x) for x in args)))
+    pass
+
+# -------------------------------------------
+# KconfigData implements the Kconfig semantics.  For now it can only
+# detect undefined symbols, i.e. symbols that were referenced in
+# assignments or dependencies but were not declared with "config FOO".
+#
+# Semantic actions are represented by methods called do_*.  The do_var
+# method return the semantic value of a variable (which right now is
+# just its name).
+# -------------------------------------------
+
+class KconfigData:
+    def __init__(self):
+        self.previously_included = []
+        self.incl_info = None
+        self.defined_vars = set()
+        self.referenced_vars = set()
+
+    # semantic analysis -------------
+
+    def check_undefined(self):
+        undef = False
+        for i in self.referenced_vars:
+            if not (i in self.defined_vars):
+                print("undefined symbol %s" % (i), file=sys.stderr)
+                undef = True
+        return undef
+
+    # semantic actions -------------
+
+    def do_declaration(self, var):
+        if (var in self.defined_vars):
+            raise Exception('variable "' + var + '" defined twice')
+
+        self.defined_vars.add(var)
+
+    # var is a string with the variable's name.
+    #
+    # For now this just returns the variable's name itself.
+    def do_var(self, var):
+        self.referenced_vars.add(var)
+        return var
+
+    def do_assignment(self, var, val):
+        pass
+
+    def do_default(self, var, val, cond=None):
+        pass
+
+    def do_depends_on(self, var, expr):
+        pass
+
+    def do_select(self, var, symbol, cond=None):
+        pass
+
+    def do_imply(self, var, symbol, cond=None):
+        pass
+
+# -------------------------------------------
+# KconfigParser implements a recursive descent parser for (simplified)
+# Kconfig syntax.
+# -------------------------------------------
+
+# tokens table
+TOKENS = {}
+TOK_NONE = -1
+TOK_LPAREN = 0;   TOKENS[TOK_LPAREN] = '"("';
+TOK_RPAREN = 1;   TOKENS[TOK_RPAREN] = '")"';
+TOK_EQUAL = 2;    TOKENS[TOK_EQUAL] = '"="';
+TOK_AND = 3;      TOKENS[TOK_AND] = '"&&"';
+TOK_OR = 4;       TOKENS[TOK_OR] = '"||"';
+TOK_NOT = 5;      TOKENS[TOK_NOT] = '"!"';
+TOK_DEPENDS = 6;  TOKENS[TOK_DEPENDS] = '"depends"';
+TOK_ON = 7;       TOKENS[TOK_ON] = '"on"';
+TOK_SELECT = 8;   TOKENS[TOK_SELECT] = '"select"';
+TOK_IMPLY = 9;    TOKENS[TOK_IMPLY] = '"imply"';
+TOK_CONFIG = 10;  TOKENS[TOK_CONFIG] = '"config"';
+TOK_DEFAULT = 11; TOKENS[TOK_DEFAULT] = '"default"';
+TOK_Y = 12;       TOKENS[TOK_Y] = '"y"';
+TOK_N = 13;       TOKENS[TOK_N] = '"n"';
+TOK_SOURCE = 14;  TOKENS[TOK_SOURCE] = '"source"';
+TOK_BOOL = 15;    TOKENS[TOK_BOOL] = '"bool"';
+TOK_IF = 16;      TOKENS[TOK_IF] = '"if"';
+TOK_ID = 17;      TOKENS[TOK_ID] = 'identifier';
+TOK_EOF = 18;     TOKENS[TOK_EOF] = 'end of file';
+
+class KconfigParserError(Exception):
+    def __init__(self, parser, msg, tok=None):
+        self.loc = parser.location()
+        tok = tok or parser.tok
+        if tok != TOK_NONE:
+            location = TOKENS.get(tok, None) or ('"%s"' % tok)
+            msg = '%s before %s' % (msg, location)
+        self.msg = msg
+
+    def __str__(self):
+        return "%s: %s" % (self.loc, self.msg)
+
+class KconfigParser:
+    @classmethod
+    def parse(self, fp):
+        data = KconfigData()
+        parser = KconfigParser(data)
+        parser.parse_file(fp)
+        if data.check_undefined():
+            raise KconfigParserError(parser, "there were undefined symbols")
+
+        return data
+
+    def __init__(self, data):
+        self.data = data
+
+    def parse_file(self, fp):
+        self.abs_fname = os.path.abspath(fp.name)
+        self.fname = fp.name
+        self.data.previously_included.append(self.abs_fname)
+        self.src = fp.read()
+        if self.src == '' or self.src[-1] != '\n':
+            self.src += '\n'
+        self.cursor = 0
+        self.line = 1
+        self.line_pos = 0
+        self.get_token()
+        self.parse_config()
+
+    # file management -----
+
+    def error_path(self):
+        inf = self.data.incl_info
+        res = ""
+        while inf:
+            res = ("In file included from %s:%d:\n" % (inf['file'],
+                                                       inf['line'])) + res
+            inf = inf['parent']
+        return res
+
+    def location(self):
+        col = 1
+        for ch in self.src[self.line_pos:self.pos]:
+            if ch == '\t':
+                col += 8 - ((col - 1) % 8)
+            else:
+                col += 1
+        return '%s%s:%d:%d' %(self.error_path(), self.fname, self.line, col)
+
+    def do_include(self, include):
+        incl_abs_fname = os.path.join(os.path.dirname(self.abs_fname),
+                                      include)
+        # catch inclusion cycle
+        inf = self.data.incl_info
+        while inf:
+            if incl_abs_fname == os.path.abspath(inf['file']):
+                raise KconfigParserError(self, "Inclusion loop for %s"
+                                    % include)
+            inf = inf['parent']
+
+        # skip multiple include of the same file
+        if incl_abs_fname in self.data.previously_included:
+            return
+        try:
+            fp = open(incl_abs_fname, 'r')
+        except IOError as e:
+            raise KconfigParserError(self,
+                                '%s: %s' % (e.strerror, include))
+
+        inf = self.data.incl_info
+        self.data.incl_info = { 'file': self.fname, 'line': self.line,
+                'parent': inf }
+        KconfigParser(self.data).parse_file(fp)
+        self.data.incl_info = inf
+
+    # recursive descent parser -----
+
+    # y_or_n: Y | N
+    def parse_y_or_n(self):
+        if self.tok == TOK_Y:
+            self.get_token()
+            return True
+        if self.tok == TOK_N:
+            self.get_token()
+            return False
+        raise KconfigParserError(self, 'Expected "y" or "n"')
+
+    # var: ID
+    def parse_var(self):
+        if self.tok == TOK_ID:
+            val = self.val
+            self.get_token()
+            return self.data.do_var(val)
+        else:
+            raise KconfigParserError(self, 'Expected identifier')
+
+    # assignment_var: ID (starting with "CONFIG_")
+    def parse_assignment_var(self):
+        if self.tok == TOK_ID:
+            val = self.val
+            if not val.startswith("CONFIG_"):
+                raise KconfigParserError(self,
+                           'Expected identifier starting with "CONFIG_"', TOK_NONE)
+            self.get_token()
+            return self.data.do_var(val[7:])
+        else:
+            raise KconfigParserError(self, 'Expected identifier')
+
+    # assignment: var EQUAL y_or_n
+    def parse_assignment(self):
+        var = self.parse_assignment_var()
+        if self.tok != TOK_EQUAL:
+            raise KconfigParserError(self, 'Expected "="')
+        self.get_token()
+        self.data.do_assignment(var, self.parse_y_or_n())
+
+    # primary: NOT primary
+    #       | LPAREN expr RPAREN
+    #       | var
+    def parse_primary(self):
+        if self.tok == TOK_NOT:
+            self.get_token()
+            self.parse_primary()
+        elif self.tok == TOK_LPAREN:
+            self.get_token()
+            self.parse_expr()
+            if self.tok != TOK_RPAREN:
+                raise KconfigParserError(self, 'Expected ")"')
+            self.get_token()
+        elif self.tok == TOK_ID:
+            self.parse_var()
+        else:
+            raise KconfigParserError(self, 'Expected "!" or "(" or identifier')
+
+    # disj: primary (OR primary)*
+    def parse_disj(self):
+        self.parse_primary()
+        while self.tok == TOK_OR:
+            self.get_token()
+            self.parse_primary()
+
+    # expr: disj (AND disj)*
+    def parse_expr(self):
+        self.parse_disj()
+        while self.tok == TOK_AND:
+            self.get_token()
+            self.parse_disj()
+
+    # condition: IF expr
+    #       | empty
+    def parse_condition(self):
+        if self.tok == TOK_IF:
+            self.get_token()
+            return self.parse_expr()
+        else:
+            return None
+
+    # property: DEFAULT y_or_n condition
+    #       | DEPENDS ON expr
+    #       | SELECT var condition
+    #       | BOOL
+    def parse_property(self, var):
+        if self.tok == TOK_DEFAULT:
+            self.get_token()
+            val = self.parse_y_or_n()
+            cond = self.parse_condition()
+            self.data.do_default(var, val, cond)
+        elif self.tok == TOK_DEPENDS:
+            self.get_token()
+            if self.tok != TOK_ON:
+                raise KconfigParserError(self, 'Expected "on"')
+            self.get_token()
+            self.data.do_depends_on(var, self.parse_expr())
+        elif self.tok == TOK_SELECT:
+            self.get_token()
+            symbol = self.parse_var()
+            cond = self.parse_condition()
+            self.data.do_select(var, symbol, cond)
+        elif self.tok == TOK_IMPLY:
+            self.get_token()
+            symbol = self.parse_var()
+            cond = self.parse_condition()
+            self.data.do_imply(var, symbol, cond)
+        elif self.tok == TOK_BOOL:
+            self.get_token()
+        else:
+            raise KconfigParserError(self, 'Error in recursive descent?')
+
+    # properties: properties property
+    #       | /* empty */
+    def parse_properties(self, var):
+        had_default = False
+        while self.tok == TOK_DEFAULT or self.tok == TOK_DEPENDS or \
+              self.tok == TOK_SELECT or self.tok == TOK_BOOL or \
+              self.tok == TOK_IMPLY:
+            self.parse_property(var)
+        self.data.do_default(var, False)
+
+        # for nicer error message
+        if self.tok != TOK_SOURCE and self.tok != TOK_CONFIG and \
+           self.tok != TOK_ID and self.tok != TOK_EOF:
+            raise KconfigParserError(self, 'expected "source", "config", identifier, '
+                    + '"default", "depends on", "imply" or "select"')
+
+    # declaration: config var properties
+    def parse_declaration(self):
+        if self.tok == TOK_CONFIG:
+            self.get_token()
+            var = self.parse_var()
+            self.data.do_declaration(var)
+            self.parse_properties(var)
+        else:
+            raise KconfigParserError(self, 'Error in recursive descent?')
+
+    # clause: SOURCE
+    #       | declaration
+    #       | assignment
+    def parse_clause(self):
+        if self.tok == TOK_SOURCE:
+            val = self.val
+            self.get_token()
+            self.do_include(val)
+        elif self.tok == TOK_CONFIG:
+            self.parse_declaration()
+        elif self.tok == TOK_ID:
+            self.parse_assignment()
+        else:
+            raise KconfigParserError(self, 'expected "source", "config" or identifier')
+
+    # config: clause+ EOF
+    def parse_config(self):
+        while self.tok != TOK_EOF:
+            self.parse_clause()
+        return self.data
+
+    # scanner -----
+
+    def get_token(self):
+        while True:
+            self.tok = self.src[self.cursor]
+            self.pos = self.cursor
+            self.cursor += 1
+
+            self.val = None
+            self.tok = self.scan_token()
+            if self.tok is not None:
+                return
+
+    def check_keyword(self, rest):
+        if not self.src.startswith(rest, self.cursor):
+            return False
+        length = len(rest)
+        if self.src[self.cursor + length].isalnum() or self.src[self.cursor + length] == '|':
+            return False
+        self.cursor += length
+        return True
+
+    def scan_token(self):
+        if self.tok == '#':
+            self.cursor = self.src.find('\n', self.cursor)
+            return None
+        elif self.tok == '=':
+            return TOK_EQUAL
+        elif self.tok == '(':
+            return TOK_LPAREN
+        elif self.tok == ')':
+            return TOK_RPAREN
+        elif self.tok == '&' and self.src[self.pos+1] == '&':
+            self.cursor += 1
+            return TOK_AND
+        elif self.tok == '|' and self.src[self.pos+1] == '|':
+            self.cursor += 1
+            return TOK_OR
+        elif self.tok == '!':
+            return TOK_NOT
+        elif self.tok == 'd' and self.check_keyword("epends"):
+            return TOK_DEPENDS
+        elif self.tok == 'o' and self.check_keyword("n"):
+            return TOK_ON
+        elif self.tok == 's' and self.check_keyword("elect"):
+            return TOK_SELECT
+        elif self.tok == 'i' and self.check_keyword("mply"):
+            return TOK_IMPLY
+        elif self.tok == 'c' and self.check_keyword("onfig"):
+            return TOK_CONFIG
+        elif self.tok == 'd' and self.check_keyword("efault"):
+            return TOK_DEFAULT
+        elif self.tok == 'b' and self.check_keyword("ool"):
+            return TOK_BOOL
+        elif self.tok == 'i' and self.check_keyword("f"):
+            return TOK_IF
+        elif self.tok == 'y' and self.check_keyword(""):
+            return TOK_Y
+        elif self.tok == 'n' and self.check_keyword(""):
+            return TOK_N
+        elif (self.tok == 's' and self.check_keyword("ource")) or \
+              self.tok == 'i' and self.check_keyword("nclude"):
+            # source FILENAME
+            # include FILENAME
+            while self.src[self.cursor].isspace():
+                self.cursor += 1
+            start = self.cursor
+            self.cursor = self.src.find('\n', self.cursor)
+            self.val = self.src[start:self.cursor]
+            return TOK_SOURCE
+        elif self.tok.isalpha():
+            # identifier
+            while self.src[self.cursor].isalnum() or self.src[self.cursor] == '_':
+                self.cursor += 1
+            self.val = self.src[self.pos:self.cursor]
+            return TOK_ID
+        elif self.tok == '\n':
+            if self.cursor == len(self.src):
+                return TOK_EOF
+            self.line += 1
+            self.line_pos = self.cursor
+        elif not self.tok.isspace():
+            raise KconfigParserError(self, 'invalid input')
+
+        return None
+
+if __name__ == '__main__':
+    fname = len(sys.argv) > 1 and sys.argv[1] or 'Kconfig.test'
+    KconfigParser.parse(open(fname, 'r'))