cpu/call_far.cc

   1 ////////////////////////////////////////////////////////////////////////
   2 // $Id: call_far.cc,v 1.41 2008/09/06 17:44:02 sshwarts Exp $
   3 /////////////////////////////////////////////////////////////////////////
   4 //
   5 //   Copyright (c) 2005 Stanislav Shwartsman
   6 //          Written by Stanislav Shwartsman [sshwarts at sourceforge net]
   7 //
   8 //  This library is free software; you can redistribute it and/or
   9 //  modify it under the terms of the GNU Lesser General Public
  10 //  License as published by the Free Software Foundation; either
  11 //  version 2 of the License, or (at your option) any later version.
  12 //
  13 //  This library is distributed in the hope that it will be useful,
  14 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 //  Lesser General Public License for more details.
  17 //
  18 //  You should have received a copy of the GNU Lesser General Public
  19 //  License along with this library; if not, write to the Free Software
  20 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  21 //
  22 /////////////////////////////////////////////////////////////////////////
  23
  24 #define NEED_CPU_REG_SHORTCUTS 1
  25 #include "bochs.h"
  26 #include "cpu.h"
  27 #define LOG_THIS BX_CPU_THIS_PTR
  28
  29 #if BX_SUPPORT_X86_64==0
  30 // Make life easier merging cpu64 & cpu code.
  31 #define RIP EIP
  32 #endif
  33
  34   void BX_CPP_AttrRegparmN(3)
  35 BX_CPU_C::call_protected(bxInstruction_c *i, Bit16u cs_raw, bx_address disp)
  36 {
  37   bx_selector_t cs_selector;
  38   Bit32u dword1, dword2;
  39   bx_descriptor_t cs_descriptor;
  40   Bit32u temp_RSP;
  41
  42   /* new cs selector must not be null, else #GP(0) */
  43   if ((cs_raw & 0xfffc) == 0) {
  44     BX_ERROR(("call_protected: CS selector null"));
  45     exception(BX_GP_EXCEPTION, 0, 0);
  46   }
  47
  48   parse_selector(cs_raw, &cs_selector);
  49   // check new CS selector index within its descriptor limits,
  50   // else #GP(new CS selector)
  51   fetch_raw_descriptor(&cs_selector, &dword1, &dword2, BX_GP_EXCEPTION);
  52   parse_descriptor(dword1, dword2, &cs_descriptor);
  53
  54   // examine AR byte of selected descriptor for various legal values
  55   if (cs_descriptor.valid==0) {
  56     BX_ERROR(("call_protected: invalid CS descriptor"));
  57     exception(BX_GP_EXCEPTION, cs_raw & 0xfffc, 0);
  58   }
  59
  60   if (cs_descriptor.segment)   // normal segment
  61   {
  62     check_cs(&cs_descriptor, cs_raw, BX_SELECTOR_RPL(cs_raw), CPL);
  63
  64 #if BX_SUPPORT_X86_64
  65     if (cs_descriptor.u.segment.l) {
  66       // moving to long mode, push return address onto 64-bit stack
  67       if (i->os64L()) {
  68         write_new_stack_qword_64(RSP -  8, cs_descriptor.dpl,
  69              BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
  70         write_new_stack_qword_64(RSP - 16, cs_descriptor.dpl, RIP);
  71         RSP -= 16;
  72       }
  73       else if (i->os32L()) {
  74         write_new_stack_dword_64(RSP - 4, cs_descriptor.dpl,
  75              BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
  76         write_new_stack_dword_64(RSP - 8, cs_descriptor.dpl, EIP);
  77         RSP -= 8;
  78       }
  79       else {
  80         write_new_stack_word_64(RSP - 2, cs_descriptor.dpl,
  81              BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
  82         write_new_stack_word_64(RSP - 4, cs_descriptor.dpl, IP);
  83         RSP -= 4;
  84       }
  85     }
  86     else
  87 #endif
  88     {
  89       // moving to legacy mode, push return address onto 32-bit stack
  90       if (BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].cache.u.segment.d_b)
  91         temp_RSP = ESP;
  92       else
  93         temp_RSP = SP;
  94
  95 #if BX_SUPPORT_X86_64
  96       if (i->os64L()) {
  97         write_new_stack_qword_32(&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS],
  98              temp_RSP -  8, cs_descriptor.dpl,
  99              BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
 100         write_new_stack_qword_32(&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS],
 101              temp_RSP - 16, cs_descriptor.dpl, RIP);
 102         temp_RSP -= 16;
 103       }
 104       else
 105 #endif
 106       if (i->os32L()) {
 107         write_new_stack_dword_32(&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS],
 108              temp_RSP - 4, cs_descriptor.dpl,
 109              BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
 110         write_new_stack_dword_32(&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS],
 111              temp_RSP - 8, cs_descriptor.dpl, EIP);
 112         temp_RSP -= 8;
 113       }
 114       else {
 115         write_new_stack_word_32(&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS],
 116              temp_RSP - 2, cs_descriptor.dpl,
 117              BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
 118         write_new_stack_word_32(&BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS],
 119              temp_RSP - 4, cs_descriptor.dpl, IP);
 120         temp_RSP -= 4;
 121       }
 122
 123       if (BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].cache.u.segment.d_b)
 124         ESP = (Bit32u) temp_RSP;
 125       else
 126          SP = (Bit16u) temp_RSP;
 127     }
 128
 129     // load code segment descriptor into CS cache
 130     // load CS with new code segment selector
 131     // set RPL of CS to CPL
 132     branch_far64(&cs_selector, &cs_descriptor, disp, CPL);
 133
 134     return;
 135   }
 136   else { // gate & special segment
 137     bx_descriptor_t  gate_descriptor = cs_descriptor;
 138     bx_selector_t    gate_selector = cs_selector;
 139     Bit32u new_EIP;
 140     Bit16u dest_selector;
 141     Bit16u          raw_tss_selector;
 142     bx_selector_t   tss_selector;
 143     bx_descriptor_t tss_descriptor;
 144     Bit32u temp_eIP;
 145
 146     // descriptor DPL must be >= CPL else #GP(gate selector)
 147     if (gate_descriptor.dpl < CPL) {
 148       BX_ERROR(("call_protected: descriptor.dpl < CPL"));
 149       exception(BX_GP_EXCEPTION, cs_raw & 0xfffc, 0);
 150     }
 151
 152     // descriptor DPL must be >= gate selector RPL else #GP(gate selector)
 153     if (gate_descriptor.dpl < gate_selector.rpl) {
 154       BX_ERROR(("call_protected: descriptor.dpl < selector.rpl"));
 155       exception(BX_GP_EXCEPTION, cs_raw & 0xfffc, 0);
 156     }
 157
 158 #if BX_SUPPORT_X86_64
 159     if (long_mode()) {
 160       // call gate type is higher priority than non-present bit check
 161       if (gate_descriptor.type != BX_386_CALL_GATE) {
 162         BX_ERROR(("call_protected: gate type %u unsupported in long mode", (unsigned) gate_descriptor.type));
 163         exception(BX_GP_EXCEPTION, cs_raw & 0xfffc, 0);
 164       }
 165     }
 166     else
 167 #endif
 168     {
 169       switch (gate_descriptor.type) {
 170         case BX_SYS_SEGMENT_AVAIL_286_TSS:
 171         case BX_SYS_SEGMENT_AVAIL_386_TSS:
 172         case BX_TASK_GATE:
 173         case BX_286_CALL_GATE:
 174         case BX_386_CALL_GATE:
 175           break;
 176         default:
 177           BX_ERROR(("call_protected(): gate.type(%u) unsupported", (unsigned) gate_descriptor.type));
 178           exception(BX_GP_EXCEPTION, cs_raw & 0xfffc, 0);
 179       }
 180     }
 181
 182     // gate descriptor must be present else #NP(gate selector)
 183     if (! IS_PRESENT(gate_descriptor)) {
 184       BX_ERROR(("call_protected: gate not present"));
 185       exception(BX_NP_EXCEPTION, cs_raw & 0xfffc, 0);
 186     }
 187
 188 #if BX_SUPPORT_X86_64
 189     if (long_mode()) {
 190       call_gate64(&gate_selector);
 191       return;
 192     }
 193 #endif
 194
 195     switch (gate_descriptor.type) {
 196       case BX_SYS_SEGMENT_AVAIL_286_TSS:
 197       case BX_SYS_SEGMENT_AVAIL_386_TSS:
 198
 199         if (gate_descriptor.type==BX_SYS_SEGMENT_AVAIL_286_TSS)
 200           BX_DEBUG(("call_protected: 16bit available TSS"));
 201         else
 202           BX_DEBUG(("call_protected: 32bit available TSS"));
 203
 204         // SWITCH_TASKS _without_ nesting to TSS
 205         task_switch(&gate_selector, &gate_descriptor,
 206           BX_TASK_FROM_CALL_OR_INT, dword1, dword2);
 207
 208         // EIP must be in code seg limit, else #GP(0)
 209         if (EIP > BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].cache.u.segment.limit_scaled) {
 210           BX_ERROR(("call_protected: EIP not within CS limits"));
 211           exception(BX_GP_EXCEPTION, 0, 0);
 212         }
 213         return;
 214
 215       case BX_TASK_GATE:
 216         // examine selector to TSS, given in Task Gate descriptor
 217         // must specify global in the local/global bit else #TS(TSS selector)
 218         raw_tss_selector = gate_descriptor.u.taskgate.tss_selector;
 219         parse_selector(raw_tss_selector, &tss_selector);
 220
 221         if (tss_selector.ti) {
 222           BX_ERROR(("call_protected: tss_selector.ti=1"));
 223           exception(BX_GP_EXCEPTION, raw_tss_selector & 0xfffc, 0);
 224         }
 225
 226         // index must be within GDT limits else #TS(TSS selector)
 227         fetch_raw_descriptor(&tss_selector, &dword1, &dword2, BX_GP_EXCEPTION);
 228
 229         parse_descriptor(dword1, dword2, &tss_descriptor);
 230
 231         // descriptor AR byte must specify available TSS
 232         //   else #GP(TSS selector)
 233         if (tss_descriptor.valid==0 || tss_descriptor.segment) {
 234           BX_ERROR(("call_protected: TSS selector points to bad TSS"));
 235           exception(BX_GP_EXCEPTION, raw_tss_selector & 0xfffc, 0);
 236         }
 237         if (tss_descriptor.type!=BX_SYS_SEGMENT_AVAIL_286_TSS &&
 238             tss_descriptor.type!=BX_SYS_SEGMENT_AVAIL_386_TSS)
 239         {
 240           BX_ERROR(("call_protected: TSS selector points to bad TSS"));
 241           exception(BX_GP_EXCEPTION, raw_tss_selector & 0xfffc, 0);
 242         }
 243
 244         // task state segment must be present, else #NP(tss selector)
 245         if (! IS_PRESENT(tss_descriptor)) {
 246           BX_ERROR(("call_protected: task descriptor.p == 0"));
 247           exception(BX_NP_EXCEPTION, raw_tss_selector & 0xfffc, 0);
 248         }
 249
 250         // SWITCH_TASKS without nesting to TSS
 251         task_switch(&tss_selector, &tss_descriptor,
 252                     BX_TASK_FROM_CALL_OR_INT, dword1, dword2);
 253
 254         // EIP must be within code segment limit, else #TS(0)
 255         if (BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].cache.u.segment.d_b)
 256           temp_eIP = EIP;
 257         else
 258           temp_eIP =  IP;
 259
 260         if (temp_eIP > BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].cache.u.segment.limit_scaled)
 261         {
 262           BX_ERROR(("call_protected: EIP > CS.limit"));
 263           exception(BX_GP_EXCEPTION, 0, 0);
 264         }
 265         return;
 266
 267       case BX_286_CALL_GATE:
 268       case BX_386_CALL_GATE:
 269         // examine code segment selector in call gate descriptor
 270         BX_DEBUG(("call_protected: call gate"));
 271         dest_selector = gate_descriptor.u.gate.dest_selector;
 272         new_EIP       = gate_descriptor.u.gate.dest_offset;
 273
 274         // selector must not be null else #GP(0)
 275         if ((dest_selector & 0xfffc) == 0) {
 276           BX_ERROR(("call_protected: selector in gate null"));
 277           exception(BX_GP_EXCEPTION, 0, 0);
 278         }
 279
 280         parse_selector(dest_selector, &cs_selector);
 281         // selector must be within its descriptor table limits,
 282         //   else #GP(code segment selector)
 283         fetch_raw_descriptor(&cs_selector, &dword1, &dword2, BX_GP_EXCEPTION);
 284         parse_descriptor(dword1, dword2, &cs_descriptor);
 285
 286         // AR byte of selected descriptor must indicate code segment,
 287         //   else #GP(code segment selector)
 288         // DPL of selected descriptor must be <= CPL,
 289         // else #GP(code segment selector)
 290         if (cs_descriptor.valid==0 || cs_descriptor.segment==0 ||
 291             IS_DATA_SEGMENT(cs_descriptor.type) ||
 292             cs_descriptor.dpl > CPL)
 293         {
 294           BX_ERROR(("call_protected: selected descriptor is not code"));
 295           exception(BX_GP_EXCEPTION, dest_selector & 0xfffc, 0);
 296         }
 297
 298         // code segment must be present else #NP(selector)
 299         if (! IS_PRESENT(cs_descriptor)) {
 300           BX_ERROR(("call_protected: code segment not present !"));
 301           exception(BX_NP_EXCEPTION, dest_selector & 0xfffc, 0);
 302         }
 303
 304         // CALL GATE TO MORE PRIVILEGE
 305         // if non-conforming code segment and DPL < CPL then
 306         if (IS_CODE_SEGMENT_NON_CONFORMING(cs_descriptor.type) && (cs_descriptor.dpl < CPL))
 307         {
 308           Bit16u SS_for_cpl_x;
 309           Bit32u ESP_for_cpl_x;
 310           bx_selector_t   ss_selector;
 311           bx_descriptor_t ss_descriptor;
 312           Bit16u   return_SS, return_CS;
 313           Bit32u   return_ESP, return_EIP;
 314           Bit16u   parameter_word[32];
 315           Bit32u   parameter_dword[32];
 316
 317           BX_DEBUG(("CALL GATE TO MORE PRIVILEGE LEVEL"));
 318
 319           // get new SS selector for new privilege level from TSS
 320           get_SS_ESP_from_TSS(cs_descriptor.dpl, &SS_for_cpl_x, &ESP_for_cpl_x);
 321
 322           // check selector & descriptor for new SS:
 323           // selector must not be null, else #TS(0)
 324           if ((SS_for_cpl_x & 0xfffc) == 0) {
 325             BX_ERROR(("call_protected: new SS null"));
 326             exception(BX_TS_EXCEPTION, 0, 0);
 327           }
 328
 329           // selector index must be within its descriptor table limits,
 330           //   else #TS(SS selector)
 331           parse_selector(SS_for_cpl_x, &ss_selector);
 332           fetch_raw_descriptor(&ss_selector, &dword1, &dword2, BX_TS_EXCEPTION);
 333           parse_descriptor(dword1, dword2, &ss_descriptor);
 334
 335           // selector's RPL must equal DPL of code segment,
 336           //   else #TS(SS selector)
 337           if (ss_selector.rpl != cs_descriptor.dpl) {
 338             BX_ERROR(("call_protected: SS selector.rpl != CS descr.dpl"));
 339             exception(BX_TS_EXCEPTION, SS_for_cpl_x & 0xfffc, 0);
 340           }
 341
 342           // stack segment DPL must equal DPL of code segment,
 343           //   else #TS(SS selector)
 344           if (ss_descriptor.dpl != cs_descriptor.dpl) {
 345             BX_ERROR(("call_protected: SS descr.rpl != CS descr.dpl"));
 346             exception(BX_TS_EXCEPTION, SS_for_cpl_x & 0xfffc, 0);
 347           }
 348
 349           // descriptor must indicate writable data segment,
 350           //   else #TS(SS selector)
 351           if (ss_descriptor.valid==0 || ss_descriptor.segment==0 ||
 352                IS_CODE_SEGMENT(ss_descriptor.type) ||
 353               !IS_DATA_SEGMENT_WRITEABLE(ss_descriptor.type))
 354           {
 355             BX_ERROR(("call_protected: ss descriptor is not writable data seg"));
 356             exception(BX_TS_EXCEPTION, SS_for_cpl_x & 0xfffc, 0);
 357           }
 358
 359           // segment must be present, else #SS(SS selector)
 360           if (! IS_PRESENT(ss_descriptor)) {
 361             BX_ERROR(("call_protected: ss descriptor not present"));
 362             exception(BX_SS_EXCEPTION, SS_for_cpl_x & 0xfffc, 0);
 363           }
 364
 365           // get word count from call gate, mask to 5 bits
 366           unsigned param_count = gate_descriptor.u.gate.param_count & 0x1f;
 367
 368           // save return SS:eSP to be pushed on new stack
 369           return_SS = BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].selector.value;
 370           if (BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].cache.u.segment.d_b)
 371             return_ESP = ESP;
 372           else
 373             return_ESP =  SP;
 374
 375           // save return CS:eIP to be pushed on new stack
 376           return_CS = BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value;
 377           if (cs_descriptor.u.segment.d_b)
 378             return_EIP = EIP;
 379           else
 380             return_EIP = IP;
 381
 382           if (gate_descriptor.type==BX_286_CALL_GATE) {
 383             for (unsigned n=0; n<param_count; n++) {
 384               parameter_word[n] = read_virtual_word_32(BX_SEG_REG_SS, return_ESP + n*2);
 385             }
 386           }
 387           else {
 388             for (unsigned n=0; n<param_count; n++) {
 389               parameter_dword[n] = read_virtual_dword_32(BX_SEG_REG_SS, return_ESP + n*4);
 390             }
 391           }
 392
 393           // Prepare new stack segment
 394           bx_segment_reg_t new_stack;
 395           new_stack.selector = ss_selector;
 396           new_stack.cache = ss_descriptor;
 397           new_stack.selector.rpl = cs_descriptor.dpl;
 398           // add cpl to the selector value
 399           new_stack.selector.value = (0xfffc & new_stack.selector.value) |
 400             new_stack.selector.rpl;
 401
 402           /* load new SS:SP value from TSS */
 403           if (ss_descriptor.u.segment.d_b) {
 404             Bit32u temp_ESP = ESP_for_cpl_x;
 405
 406             // push pointer of old stack onto new stack
 407             if (gate_descriptor.type==BX_386_CALL_GATE) {
 408               write_new_stack_dword_32(&new_stack, temp_ESP-4, cs_descriptor.dpl, return_SS);
 409               write_new_stack_dword_32(&new_stack, temp_ESP-8, cs_descriptor.dpl, return_ESP);
 410               temp_ESP -= 8;
 411
 412               for (unsigned n=param_count; n>0; n--) {
 413                 temp_ESP -= 4;
 414                 write_new_stack_dword_32(&new_stack, temp_ESP, cs_descriptor.dpl, parameter_dword[n-1]);
 415               }
 416               // push return address onto new stack
 417               write_new_stack_dword_32(&new_stack, temp_ESP-4, cs_descriptor.dpl, return_CS);
 418               write_new_stack_dword_32(&new_stack, temp_ESP-8, cs_descriptor.dpl, return_EIP);
 419               temp_ESP -= 8;
 420             }
 421             else {
 422               write_new_stack_word_32(&new_stack, temp_ESP-2, cs_descriptor.dpl, return_SS);
 423               write_new_stack_word_32(&new_stack, temp_ESP-4, cs_descriptor.dpl, (Bit16u) return_ESP);
 424               temp_ESP -= 4;
 425
 426               for (unsigned n=param_count; n>0; n--) {
 427                 temp_ESP -= 2;
 428                 write_new_stack_word_32(&new_stack, temp_ESP, cs_descriptor.dpl, parameter_word[n-1]);
 429               }
 430               // push return address onto new stack
 431               write_new_stack_word_32(&new_stack, temp_ESP-2, cs_descriptor.dpl, return_CS);
 432               write_new_stack_word_32(&new_stack, temp_ESP-4, cs_descriptor.dpl, (Bit16u) return_EIP);
 433               temp_ESP -= 4;
 434             }
 435
 436             ESP = temp_ESP;
 437           }
 438           else {
 439             Bit16u temp_SP = (Bit16u) ESP_for_cpl_x;
 440
 441             // push pointer of old stack onto new stack
 442             if (gate_descriptor.type==BX_386_CALL_GATE) {
 443               write_new_stack_dword_32(&new_stack, (Bit16u)(temp_SP-4), cs_descriptor.dpl, return_SS);
 444               write_new_stack_dword_32(&new_stack, (Bit16u)(temp_SP-8), cs_descriptor.dpl, return_ESP);
 445               temp_SP -= 8;
 446
 447               for (unsigned n=param_count; n>0; n--) {
 448                 temp_SP -= 4;
 449                 write_new_stack_dword_32(&new_stack, temp_SP, cs_descriptor.dpl, parameter_dword[n-1]);
 450               }
 451               // push return address onto new stack
 452               write_new_stack_dword_32(&new_stack, (Bit16u)(temp_SP-4), cs_descriptor.dpl, return_CS);
 453               write_new_stack_dword_32(&new_stack, (Bit16u)(temp_SP-8), cs_descriptor.dpl, return_EIP);
 454               temp_SP -= 8;
 455             }
 456             else {
 457               write_new_stack_word_32(&new_stack, (Bit16u)(temp_SP-2), cs_descriptor.dpl, return_SS);
 458               write_new_stack_word_32(&new_stack, (Bit16u)(temp_SP-4), cs_descriptor.dpl, (Bit16u) return_ESP);
 459               temp_SP -= 4;
 460
 461               for (unsigned n=param_count; n>0; n--) {
 462                 temp_SP -= 2;
 463                 write_new_stack_word_32(&new_stack, temp_SP, cs_descriptor.dpl, parameter_word[n-1]);
 464               }
 465               // push return address onto new stack
 466               write_new_stack_word_32(&new_stack, (Bit16u)(temp_SP-2), cs_descriptor.dpl, return_CS);
 467               write_new_stack_word_32(&new_stack, (Bit16u)(temp_SP-4), cs_descriptor.dpl, (Bit16u) return_EIP);
 468               temp_SP -= 4;
 469             }
 470
 471             SP = temp_SP;
 472           }
 473
 474           // new eIP must be in code segment limit else #GP(0)
 475           if (new_EIP > cs_descriptor.u.segment.limit_scaled) {
 476             BX_ERROR(("call_protected: EIP not within CS limits"));
 477             exception(BX_GP_EXCEPTION, 0, 0);
 478           }
 479
 480           /* load SS descriptor */
 481           load_ss(&ss_selector, &ss_descriptor, cs_descriptor.dpl);
 482
 483           /* load new CS:IP value from gate */
 484           /* load CS descriptor */
 485           /* set CPL to stack segment DPL */
 486           /* set RPL of CS to CPL */
 487           load_cs(&cs_selector, &cs_descriptor, cs_descriptor.dpl);
 488           EIP = new_EIP;
 489         }
 490         else   // CALL GATE TO SAME PRIVILEGE
 491         {
 492           BX_DEBUG(("CALL GATE TO SAME PRIVILEGE"));
 493
 494           if (gate_descriptor.type == BX_386_CALL_GATE) {
 495             // call gate 32bit, push return address onto stack
 496             push_32(BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
 497             push_32(EIP);
 498           }
 499           else {
 500             // call gate 16bit, push return address onto stack
 501             push_16(BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value);
 502             push_16(IP);
 503           }
 504
 505           // load CS:EIP from gate
 506           // load code segment descriptor into CS register
 507           // set RPL of CS to CPL
 508           branch_far32(&cs_selector, &cs_descriptor, new_EIP, CPL);
 509         }
 510         return;
 511
 512       default: // can't get here
 513         BX_PANIC(("call_protected: gate type %u unsupported", (unsigned) cs_descriptor.type));
 514         exception(BX_GP_EXCEPTION, cs_raw & 0xfffc, 0);
 515     }
 516   }
 517 }
 518
 519 #if BX_SUPPORT_X86_64
 520   void BX_CPP_AttrRegparmN(3)
 521 BX_CPU_C::call_gate64(bx_selector_t *gate_selector)
 522 {
 523   bx_selector_t cs_selector;
 524   Bit32u dword1, dword2, dword3;
 525   bx_descriptor_t cs_descriptor;
 526   bx_descriptor_t gate_descriptor;
 527
 528   // examine code segment selector in call gate descriptor
 529   BX_DEBUG(("call_gate64: CALL 64bit call gate"));
 530
 531   fetch_raw_descriptor_64(gate_selector, &dword1, &dword2, &dword3, BX_GP_EXCEPTION);
 532   parse_descriptor(dword1, dword2, &gate_descriptor);
 533
 534   Bit16u dest_selector = gate_descriptor.u.gate.dest_selector;
 535   // selector must not be null else #GP(0)
 536   if ((dest_selector & 0xfffc) == 0) {
 537     BX_ERROR(("call_gate64: selector in gate null"));
 538     exception(BX_GP_EXCEPTION, 0, 0);
 539   }
 540
 541   parse_selector(dest_selector, &cs_selector);
 542   // selector must be within its descriptor table limits,
 543   //   else #GP(code segment selector)
 544   fetch_raw_descriptor(&cs_selector, &dword1, &dword2, BX_GP_EXCEPTION);
 545   parse_descriptor(dword1, dword2, &cs_descriptor);
 546
 547   // find the RIP in the gate_descriptor
 548   Bit64u new_RIP = gate_descriptor.u.gate.dest_offset;
 549   new_RIP |= ((Bit64u)dword3 << 32);
 550
 551   // AR byte of selected descriptor must indicate code segment,
 552   //   else #GP(code segment selector)
 553   // DPL of selected descriptor must be <= CPL,
 554   // else #GP(code segment selector)
 555   if (cs_descriptor.valid==0 || cs_descriptor.segment==0 ||
 556       IS_DATA_SEGMENT(cs_descriptor.type) ||
 557       cs_descriptor.dpl > CPL)
 558   {
 559     BX_ERROR(("call_gate64: selected descriptor is not code"));
 560     exception(BX_GP_EXCEPTION, dest_selector & 0xfffc, 0);
 561   }
 562
 563   // In long mode, only 64-bit call gates are allowed, and they must point
 564   // to 64-bit code segments, else #GP(selector)
 565   if (! IS_LONG64_SEGMENT(cs_descriptor) || cs_descriptor.u.segment.d_b)
 566   {
 567     BX_ERROR(("call_gate64: not 64-bit code segment in call gate 64"));
 568     exception(BX_GP_EXCEPTION, dest_selector & 0xfffc, 0);
 569   }
 570
 571   // code segment must be present else #NP(selector)
 572   if (! IS_PRESENT(cs_descriptor)) {
 573     BX_ERROR(("call_gate64: code segment not present !"));
 574     exception(BX_NP_EXCEPTION, dest_selector & 0xfffc, 0);
 575   }
 576
 577   Bit64u old_CS  = BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value;
 578   Bit64u old_RIP = RIP;
 579
 580   // CALL GATE TO MORE PRIVILEGE
 581   // if non-conforming code segment and DPL < CPL then
 582   if (IS_CODE_SEGMENT_NON_CONFORMING(cs_descriptor.type) && (cs_descriptor.dpl < CPL))
 583   {
 584     Bit64u RSP_for_cpl_x;
 585
 586     BX_DEBUG(("CALL GATE TO MORE PRIVILEGE LEVEL"));
 587
 588     // get new RSP for new privilege level from TSS
 589     RSP_for_cpl_x  = get_RSP_from_TSS(cs_descriptor.dpl);
 590     Bit64u old_SS  = BX_CPU_THIS_PTR sregs[BX_SEG_REG_SS].selector.value;
 591     Bit64u old_RSP = RSP;
 592
 593     if (! IsCanonical(RSP_for_cpl_x)) {
 594       // #SS(selector) when changing priviledge level
 595       BX_ERROR(("call_gate64: canonical address failure %08x%08x",
 596          GET32H(RSP_for_cpl_x), GET32L(RSP_for_cpl_x)));
 597       exception(BX_SS_EXCEPTION, old_SS & 0xfffc, 0);
 598     }
 599
 600     // push old stack long pointer onto new stack
 601     write_new_stack_qword_64(RSP_for_cpl_x -  8, cs_descriptor.dpl, old_SS);
 602     write_new_stack_qword_64(RSP_for_cpl_x - 16, cs_descriptor.dpl, old_RSP);
 603     // push long pointer to return address onto new stack
 604     write_new_stack_qword_64(RSP_for_cpl_x - 24, cs_descriptor.dpl, old_CS);
 605     write_new_stack_qword_64(RSP_for_cpl_x - 32, cs_descriptor.dpl, old_RIP);
 606     RSP_for_cpl_x -= 32;
 607
 608     // prepare new stack null SS selector
 609     bx_selector_t ss_selector;
 610     bx_descriptor_t ss_descriptor;
 611
 612     // set up a null descriptor
 613     parse_selector(0, &ss_selector);
 614     parse_descriptor(0, 0, &ss_descriptor);
 615
 616     // load CS:RIP (guaranteed to be in 64 bit mode)
 617     branch_far64(&cs_selector, &cs_descriptor, new_RIP, cs_descriptor.dpl);
 618
 619     // set up null SS descriptor
 620     load_ss(&ss_selector, &ss_descriptor, cs_descriptor.dpl);
 621     RSP = RSP_for_cpl_x;
 622   }
 623   else
 624   {
 625     BX_DEBUG(("CALL GATE TO SAME PRIVILEGE"));
 626
 627     // push to 64-bit stack, switch to long64 guaranteed
 628     write_new_stack_qword_64(RSP -  8, CPL, old_CS);
 629     write_new_stack_qword_64(RSP - 16, CPL, old_RIP);
 630     RSP -= 16;
 631
 632     // load CS:RIP (guaranteed to be in 64 bit mode)
 633     branch_far64(&cs_selector, &cs_descriptor, new_RIP, CPL);
 634   }
 635 }
 636 #endif