script/lua/grub_main.c

   1 /*
   2  *  GRUB  --  GRand Unified Bootloader
   3  *  Copyright (C) 2009  Free Software Foundation, Inc.
   4  *
   5  *  GRUB is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  GRUB is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "lua.h"
  20 #include "lauxlib.h"
  21 #include "lualib.h"
  22 #include "grub_lib.h"
  23
  24 #include <grub/dl.h>
  25 #include <grub/parser.h>
  26
  27 static lua_State *state;
  28
  29 /* Call `grub_error' to report a Lua error.  The error message string must be
  30    on the top of the Lua stack (at index -1).  The error message is popped off
  31    the Lua stack before this function returns.  */
  32 static void
  33 handle_lua_error (const char *error_type)
  34 {
  35   const char *error_msg;
  36   error_msg = lua_tostring (state, -1);
  37   if (error_msg == NULL)
  38     error_msg = "(error message not a string)";
  39   grub_error (GRUB_ERR_BAD_ARGUMENT, "%s: %s", error_type, error_msg);
  40   /* Pop the error message.  */
  41   lua_pop (state, 1);
  42 }
  43
  44 static grub_err_t
  45 grub_lua_parse_line (char *line, grub_reader_getline_t getline)
  46 {
  47   int r;
  48   char *old_line = 0;
  49
  50   lua_settop(state, 0);
  51   while (1)
  52     {
  53       r = luaL_loadbuffer (state, line, grub_strlen (line), "=grub");
  54       if (! r)
  55         {
  56           /* No error: Execute the statement.  */
  57           r = lua_pcall (state, 0, 0, 0);
  58           if (r)
  59             {
  60               handle_lua_error ("Lua");
  61               break;
  62             }
  63           else
  64             {
  65               grub_free (old_line);
  66               return grub_errno;
  67             }
  68         }
  69
  70       if (r == LUA_ERRSYNTAX)
  71         {
  72           /* Check whether the syntax error is a result of an incomplete
  73              statement.  If it is, then try to complete the statement by
  74              reading more lines.  */
  75           size_t lmsg;
  76           const char *msg = lua_tolstring (state, -1, &lmsg);
  77           const char *tp = msg + lmsg - (sizeof (LUA_QL ("<eof>")) - 1);
  78           if (grub_strstr (msg, LUA_QL ("<eof>")) == tp)
  79             {
  80               char *n, *t;
  81               int len;
  82
  83               /* Discard the error message.  */
  84               lua_pop (state, 1);
  85               /* Try to read another line to complete the statement.  */
  86               if ((getline (&n, 1)) || (! n))
  87                 {
  88                   grub_error (GRUB_ERR_BAD_ARGUMENT, "incomplete command");
  89                   break;
  90                 }
  91
  92               /* More input was available: Add it to the current statement
  93                  contents.  */
  94               len = grub_strlen (line);
  95               t = grub_malloc (len + grub_strlen (n) + 2);
  96               if (! t)
  97                 break;
  98
  99               grub_strcpy (t, line);
 100               t[len] = '\n';
 101               grub_strcpy (t + len + 1, n);
 102               grub_free (old_line);
 103               line = old_line = t;
 104               /* Try again to execute the statement now that more input has
 105                  been appended.  */
 106               continue;
 107             }
 108           /* The syntax error was not the result of an incomplete line.  */
 109           handle_lua_error ("Lua syntax error");
 110         }
 111       else
 112         {
 113           /* Handle errors other than syntax errors (out of memory, etc.).  */
 114           handle_lua_error ("Lua parser failed");
 115         }
 116
 117       break;
 118     }
 119
 120   grub_free (old_line);
 121   lua_gc (state, LUA_GCCOLLECT, 0);
 122
 123   return grub_errno;
 124 }
 125
 126 static struct grub_parser grub_lua_parser =
 127   {
 128     .name = "lua",
 129     .parse_line = grub_lua_parse_line
 130   };
 131
 132 GRUB_MOD_INIT(lua)
 133 {
 134   (void) mod;
 135
 136   state = lua_open ();
 137   if (state)
 138     {
 139       lua_gc (state, LUA_GCSTOP, 0);
 140       luaL_openlibs (state);
 141       luaL_register (state, "grub", grub_lua_lib);
 142       lua_gc (state, LUA_GCRESTART, 0);
 143       grub_parser_register ("lua", &grub_lua_parser);
 144     }
 145 }
 146
 147 GRUB_MOD_FINI(lua)
 148 {
 149   if (state)
 150     {
 151       grub_parser_unregister (&grub_lua_parser);
 152       lua_close (state);
 153     }
 154 }