linux 0.11 copy_page_tables()º¯Êý

/* Ëûͨ¹ýÖ»¸´ÖÆÄÚ´æÒ³ÃæÀ´¸´ÖÆÒ»¶¨·¶Î§ÄÚµÄÏßÐÔµØÖ·µÄÄÚÈÝ*/
00150int copy_page_tables(unsigned long from,unsigned long to,long size)
00151 {
00152     unsigned long * from_page_table;
00153     unsigned long * to_page_table;
00154     unsigned long this_page;
00155     unsigned long * from_dir, * to_dir;
00156     unsigned long nr;
00157 //ÏÂÃæÊÇÅжÏfrom ºÍto ÊÇ·ñÔÚ£´£ÍµÄ±ß½ç´¦
00158     if ((from&0x3fffff) || (to&0x3fffff))
00159         panic("copy_page_tables called with wrong alignment");
¡¡¡¡¡¡¡¡//¸³給from_dir ҳĿ¼±íµÄԴĿ¼ÆðʼºÅ (from>>20)&oxfffc £½(from>>22)<<2
00160     from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
               //¸³給to_dir ҳĿ¼±íµÄÄ¿µÄĿ¼ÆðʼºÅ (to>>20)&oxfffc £½(to>>22)<<2
00161     to_dir = (unsigned long *) ((to>>20) & 0xffc);
              //¸³給sizeÒª¸´ÖƵÄĿ¼±íÏîµÄ¸öÊý
00162     size = ((unsigned) (size+0x3fffff)) >> 22;
¡¡¡¡¡¡¡¡//ÏÂÃæÁ½¸öforÑ­»·ÊǸ´ÖƵĿªÊ¼¡£Íâ²ãÑ­»·¿ØÖÆĿ¼±íÏîµÄÒƶ¯£¬Äڲ㡡¡¡
               //Ñ­»·¿ØÖƶþ¼¶Ò³±íÏîÒƶ¯£¬¸´ÖƵÄÄÚÈÝÊǸ´ÖÆĿ¼ÏîºÍÒ³±íÏî
00163     for( ; size-->0 ; from_dir++,to_dir++) {
00164         if (1 & *to_dir)
00165             panic("copy_page_tables: already exist");
00166         if (!(1 & *from_dir))
00167        &