git.oblomov.eu Git - wine/blob - programs/winedbg/memory.c

   1 /*
   2  * Debugger memory handling
   3  *
   4  * Copyright 1993 Eric Youngdale
   5  * Copyright 1995 Alexandre Julliard
   6  * Copyright 2000-2005 Eric Pouech
   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 2.1 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  21  */
  22
  23 #include "config.h"
  24 #include "wine/port.h"
  25
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <stdio.h>
  29
  30 #include "debugger.h"
  31 #include "wine/debug.h"
  32
  33 WINE_DEFAULT_DEBUG_CHANNEL(winedbg);
  34
  35 void* be_cpu_linearize(HANDLE hThread, const ADDRESS64* addr)
  36 {
  37     assert(addr->Mode == AddrModeFlat);
  38     return (void*)(DWORD_PTR)addr->Offset;
  39 }
  40
  41 unsigned be_cpu_build_addr(HANDLE hThread, const CONTEXT* ctx, ADDRESS64* addr,
  42                            unsigned seg, unsigned long offset)
  43 {
  44     addr->Mode    = AddrModeFlat;
  45     addr->Segment = 0; /* don't need segment */
  46     addr->Offset  = offset;
  47     return TRUE;
  48 }
  49
  50 void* memory_to_linear_addr(const ADDRESS64* addr)
  51 {
  52     return be_cpu->linearize(dbg_curr_thread->handle, addr);
  53 }
  54
  55 BOOL memory_get_current_pc(ADDRESS64* addr)
  56 {
  57     assert(be_cpu->get_addr);
  58     return be_cpu->get_addr(dbg_curr_thread->handle, &dbg_context,
  59                             be_cpu_addr_pc, addr);
  60 }
  61
  62 BOOL memory_get_current_stack(ADDRESS64* addr)
  63 {
  64     assert(be_cpu->get_addr);
  65     return be_cpu->get_addr(dbg_curr_thread->handle, &dbg_context,
  66                             be_cpu_addr_stack, addr);
  67 }
  68
  69 BOOL memory_get_current_frame(ADDRESS64* addr)
  70 {
  71     assert(be_cpu->get_addr);
  72     return be_cpu->get_addr(dbg_curr_thread->handle, &dbg_context,
  73                             be_cpu_addr_frame, addr);
  74 }
  75
  76 static void     memory_report_invalid_addr(const void* addr)
  77 {
  78     ADDRESS64   address;
  79
  80     address.Mode    = AddrModeFlat;
  81     address.Segment = 0;
  82     address.Offset  = (unsigned long)addr;
  83     dbg_printf("*** Invalid address ");
  84     print_address(&address, FALSE);
  85     dbg_printf(" ***\n");
  86 }
  87
  88 /***********************************************************************
  89  *           memory_read_value
  90  *
  91  * Read a memory value.
  92  */
  93 BOOL memory_read_value(const struct dbg_lvalue* lvalue, DWORD size, void* result)
  94 {
  95     BOOL ret = FALSE;
  96
  97     if (lvalue->cookie == DLV_TARGET)
  98     {
  99         void*   linear = memory_to_linear_addr(&lvalue->addr);
 100         if (!(ret = dbg_read_memory(linear, result, size)))
 101             memory_report_invalid_addr(linear);
 102     }
 103     else
 104     {
 105         if (lvalue->addr.Offset)
 106         {
 107             memcpy(result, (void*)(DWORD_PTR)lvalue->addr.Offset, size);
 108             ret = TRUE;
 109         }
 110     }
 111     return ret;
 112 }
 113
 114 /***********************************************************************
 115  *           memory_write_value
 116  *
 117  * Store a value in memory.
 118  */
 119 BOOL memory_write_value(const struct dbg_lvalue* lvalue, DWORD size, void* value)
 120 {
 121     BOOL        ret = TRUE;
 122     DWORD64     os;
 123
 124     os = ~(DWORD64)size;
 125     types_get_info(&lvalue->type, TI_GET_LENGTH, &os);
 126     assert(size == os);
 127
 128     /* FIXME: only works on little endian systems */
 129     if (lvalue->cookie == DLV_TARGET)
 130     {
 131         void*       linear = memory_to_linear_addr(&lvalue->addr);
 132         if (!(ret = dbg_write_memory(linear, value, size)))
 133             memory_report_invalid_addr(linear);
 134     }
 135     else
 136     {
 137         memcpy((void*)(DWORD_PTR)lvalue->addr.Offset, value, size);
 138     }
 139     return ret;
 140 }
 141
 142 /***********************************************************************
 143  *           memory_examine
 144  *
 145  * Implementation of the 'x' command.
 146  */
 147 void memory_examine(const struct dbg_lvalue *lvalue, int count, char format)
 148 {
 149     int                 i;
 150     char                buffer[256];
 151     ADDRESS64           addr;
 152     void               *linear;
 153
 154     types_extract_as_address(lvalue, &addr);
 155     linear = memory_to_linear_addr(&addr);
 156
 157     if (format != 'i' && count > 1)
 158     {
 159         print_address(&addr, FALSE);
 160         dbg_printf(": ");
 161     }
 162
 163     switch (format)
 164     {
 165     case 'u':
 166         if (count == 1) count = 256;
 167         memory_get_string(dbg_curr_process, linear,
 168                           TRUE, TRUE, buffer, min(count, sizeof(buffer)));
 169         dbg_printf("%s\n", buffer);
 170         return;
 171     case 's':
 172         if (count == 1) count = 256;
 173         memory_get_string(dbg_curr_process, linear,
 174                           TRUE, FALSE, buffer, min(count, sizeof(buffer)));
 175         dbg_printf("%s\n", buffer);
 176         return;
 177     case 'i':
 178         while (count-- && memory_disasm_one_insn(&addr));
 179         return;
 180     case 'g':
 181         while (count--)
 182         {
 183             GUID guid;
 184             if (!dbg_read_memory(linear, &guid, sizeof(guid)))
 185             {
 186                 memory_report_invalid_addr(linear);
 187                 break;
 188             }
 189             dbg_printf("{%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x}\n",
 190                        guid.Data1, guid.Data2, guid.Data3,
 191                        guid.Data4[0], guid.Data4[1], guid.Data4[2], guid.Data4[3],
 192                        guid.Data4[4], guid.Data4[5], guid.Data4[6], guid.Data4[7]);
 193             linear = (char*)linear + sizeof(guid);
 194             addr.Offset += sizeof(guid);
 195             if (count)
 196             {
 197                 print_address(&addr, FALSE);
 198                 dbg_printf(": ");
 199             }
 200         }
 201         return;
 202
 203 #define DO_DUMP2(_t,_l,_f,_vv) {                                        \
 204             _t _v;                                                      \
 205             for (i = 0; i < count; i++) {                               \
 206                 if (!dbg_read_memory(linear, &_v, sizeof(_t)))          \
 207                 { memory_report_invalid_addr(linear); break; }          \
 208                 dbg_printf(_f, (_vv));                                  \
 209                 addr.Offset += sizeof(_t);                              \
 210                 linear = (char*)linear + sizeof(_t);                    \
 211                 if ((i % (_l)) == (_l) - 1 && i != count - 1)           \
 212                 {                                                       \
 213                     dbg_printf("\n");                                   \
 214                     print_address(&addr, FALSE);                        \
 215                     dbg_printf(": ");                                   \
 216                 }                                                       \
 217             }                                                           \
 218             dbg_printf("\n");                                           \
 219         }                                                               \
 220         return
 221 #define DO_DUMP(_t,_l,_f) DO_DUMP2(_t,_l,_f,_v)
 222
 223     case 'x': DO_DUMP(int, 4, " %8.8x");
 224     case 'd': DO_DUMP(unsigned int, 4, " %4.4d");
 225     case 'w': DO_DUMP(unsigned short, 8, " %04x");
 226     case 'c': DO_DUMP2(char, 32, " %c", (_v < 0x20) ? ' ' : _v);
 227     case 'b': DO_DUMP2(char, 16, " %02x", (_v) & 0xff);
 228     }
 229 }
 230
 231 BOOL memory_get_string(struct dbg_process* pcs, void* addr, BOOL in_debuggee,
 232                        BOOL unicode, char* buffer, int size)
 233 {
 234     SIZE_T      sz;
 235     WCHAR*      buffW;
 236
 237     buffer[0] = 0;
 238     if (!addr) return FALSE;
 239     if (in_debuggee)
 240     {
 241         BOOL ret;
 242
 243         if (!unicode) ret = pcs->process_io->read(pcs->handle, addr, buffer, size, &sz);
 244         else
 245         {
 246             buffW = HeapAlloc(GetProcessHeap(), 0, size * sizeof(WCHAR));
 247             ret = pcs->process_io->read(pcs->handle, addr, buffW, size * sizeof(WCHAR), &sz);
 248             WideCharToMultiByte(CP_ACP, 0, buffW, sz / sizeof(WCHAR), buffer, size,
 249                                 NULL, NULL);
 250             HeapFree(GetProcessHeap(), 0, buffW);
 251         }
 252         if (size) buffer[size-1] = 0;
 253         return ret;
 254     }
 255     else
 256     {
 257         lstrcpynA(buffer, addr, size);
 258     }
 259     return TRUE;
 260 }
 261
 262 BOOL memory_get_string_indirect(struct dbg_process* pcs, void* addr, BOOL unicode, WCHAR* buffer, int size)
 263 {
 264     void*       ad;
 265     SIZE_T      sz;
 266
 267     buffer[0] = 0;
 268     if (addr &&
 269         pcs->process_io->read(pcs->handle, addr, &ad, sizeof(ad), &sz) && sz == sizeof(ad) && ad)
 270     {
 271         LPSTR buff;
 272         BOOL ret;
 273
 274         if (unicode)
 275             ret = pcs->process_io->read(pcs->handle, ad, buffer, size * sizeof(WCHAR), &sz) && sz != 0;
 276         else
 277         {
 278             if ((buff = HeapAlloc(GetProcessHeap(), 0, size)))
 279             {
 280                 ret = pcs->process_io->read(pcs->handle, ad, buff, size, &sz) && sz != 0;
 281                 MultiByteToWideChar(CP_ACP, 0, buff, sz, buffer, size);
 282                 HeapFree(GetProcessHeap(), 0, buff);
 283             }
 284             else ret = FALSE;
 285         }
 286         if (size) buffer[size-1] = 0;
 287         return ret;
 288     }
 289     return FALSE;
 290 }
 291
 292 /*
 293  * Convert an address offset to hex string. If mode == 32, treat offset as
 294  * 32 bits (discard upper 32 bits), if mode == 64 use all 64 bits, if mode == 0
 295  * treat as either 32 or 64 bits, depending on whether we're running as
 296  * Wine32 or Wine64.
 297  */
 298 char* memory_offset_to_string(char *str, DWORD64 offset, unsigned mode)
 299 {
 300     if (mode != 32 && mode != 64)
 301     {
 302 #ifdef _WIN64
 303         mode = 64;
 304 #else
 305         mode = 32;
 306 #endif
 307     }
 308
 309     if (mode == 32)
 310         sprintf(str, "0x%08x", (unsigned int) offset);
 311     else
 312         sprintf(str, "0x%08x%08x", (unsigned int)(offset >> 32),
 313                 (unsigned int)offset);
 314
 315     return str;
 316 }
 317
 318 static void dbg_print_longlong(LONGLONG sv, BOOL is_signed)
 319 {
 320     char      tmp[24], *ptr = tmp + sizeof(tmp) - 1;
 321     ULONGLONG uv, div;
 322     *ptr = '\0';
 323     if (is_signed && sv < 0)    uv = -sv;
 324     else                        { uv = sv; is_signed = FALSE; }
 325     for (div = 10; uv; div *= 10, uv /= 10)
 326         *--ptr = '0' + (uv % 10);
 327     if (ptr == tmp + sizeof(tmp) - 1) *--ptr = '0';
 328     if (is_signed) *--ptr = '-';
 329     dbg_printf("%s", ptr);
 330 }
 331
 332 static void print_typed_basic(const struct dbg_lvalue* lvalue)
 333 {
 334     LONGLONG            val_int;
 335     void*               val_ptr;
 336     long double         val_real;
 337     DWORD64             size64;
 338     DWORD               tag, size, count, bt;
 339     struct dbg_type     type = lvalue->type;
 340     struct dbg_type     sub_type;
 341
 342     if (!types_get_real_type(&type, &tag)) return;
 343
 344     switch (tag)
 345     {
 346     case SymTagBaseType:
 347         if (!types_get_info(&type, TI_GET_LENGTH, &size64) ||
 348             !types_get_info(&type, TI_GET_BASETYPE, &bt))
 349         {
 350             WINE_ERR("Couldn't get information\n");
 351             RaiseException(DEBUG_STATUS_INTERNAL_ERROR, 0, 0, NULL);
 352         }
 353         size = (DWORD)size64;
 354         switch (bt)
 355         {
 356         case btInt:
 357         case btLong:
 358             if (!be_cpu->fetch_integer(lvalue, size, TRUE, &val_int)) return;
 359             if (size == 1) goto print_char;
 360             dbg_print_longlong(val_int, TRUE);
 361             break;
 362         case btUInt:
 363         case btULong:
 364             if (!be_cpu->fetch_integer(lvalue, size, FALSE, &val_int)) return;
 365             dbg_print_longlong(val_int, FALSE);
 366             break;
 367         case btFloat:
 368             if (!be_cpu->fetch_float(lvalue, size, &val_real)) return;
 369             dbg_printf("%Lf", val_real);
 370             break;
 371         case btChar:
 372             if (!be_cpu->fetch_integer(lvalue, size, TRUE, &val_int)) return;
 373             /* FIXME: should do the same for a Unicode character (size == 2) */
 374         print_char:
 375             if (size == 1 && (val_int < 0x20 || val_int > 0x80))
 376                 dbg_printf("%d", (int)val_int);
 377             else
 378                 dbg_printf("'%c'", (char)val_int);
 379             break;
 380         case btBool:
 381             if (!be_cpu->fetch_integer(lvalue, size, TRUE, &val_int)) return;
 382             dbg_printf("%s", val_int ? "true" : "false");
 383             break;
 384         default:
 385             WINE_FIXME("Unsupported basetype %u\n", bt);
 386             break;
 387         }
 388         break;
 389     case SymTagPointerType:
 390         if (!memory_read_value(lvalue, sizeof(void*), &val_ptr)) return;
 391
 392         sub_type.module = lvalue->type.module;
 393         if (!types_get_info(&type, TI_GET_TYPE, &sub_type.id) ||
 394             sub_type.id == dbg_itype_none)
 395         {
 396             dbg_printf("Internal symbol error: unable to access memory location %p", val_ptr);
 397             break;
 398         }
 399         if (!types_get_real_type(&sub_type, &tag)) return;
 400
 401         if (types_get_info(&sub_type, TI_GET_SYMTAG, &tag) && tag == SymTagBaseType &&
 402             types_get_info(&sub_type, TI_GET_BASETYPE, &bt) && (bt == btChar || bt == btInt) &&
 403             types_get_info(&sub_type, TI_GET_LENGTH, &size64) && size64 == 1)
 404         {
 405             char    buffer[1024];
 406
 407             if (!val_ptr) dbg_printf("0x0");
 408             else if (memory_get_string(dbg_curr_process, val_ptr,
 409                                        lvalue->cookie == DLV_TARGET,
 410                                        size64 == 2, buffer, sizeof(buffer)))
 411                 dbg_printf("\"%s\"", buffer);
 412             else
 413                 dbg_printf("*** invalid address %p ***", val_ptr);
 414         }
 415         else dbg_printf("%p", val_ptr);
 416         break;
 417     case SymTagArrayType:
 418     case SymTagUDT:
 419         if (!memory_read_value(lvalue, sizeof(val_ptr), &val_ptr)) return;
 420         dbg_printf("%p", val_ptr);
 421         break;
 422     case SymTagEnum:
 423         {
 424             BOOL        ok = FALSE;
 425
 426             /* FIXME: it depends on underlying type for enums
 427              * (not supported yet in dbghelp)
 428              * Assuming 4 as for an int
 429              */
 430             if (!be_cpu->fetch_integer(lvalue, 4, TRUE, &val_int)) return;
 431
 432             if (types_get_info(&type, TI_GET_CHILDRENCOUNT, &count))
 433             {
 434                 char                    buffer[sizeof(TI_FINDCHILDREN_PARAMS) + 256 * sizeof(DWORD)];
 435                 TI_FINDCHILDREN_PARAMS* fcp = (TI_FINDCHILDREN_PARAMS*)buffer;
 436                 WCHAR*                  ptr;
 437                 char                    tmp[256];
 438                 VARIANT                 variant;
 439                 int                     i;
 440
 441                 fcp->Start = 0;
 442                 while (count)
 443                 {
 444                     fcp->Count = min(count, 256);
 445                     if (types_get_info(&type, TI_FINDCHILDREN, fcp))
 446                     {
 447                         sub_type.module = type.module;
 448                         for (i = 0; i < min(fcp->Count, count); i++)
 449                         {
 450                             sub_type.id = fcp->ChildId[i];
 451                             if (!types_get_info(&sub_type, TI_GET_VALUE, &variant))
 452                                 continue;
 453                             switch (variant.n1.n2.vt)
 454                             {
 455                             case VT_I4: ok = (val_int == variant.n1.n2.n3.lVal); break;
 456                             default: WINE_FIXME("Unsupported variant type (%u)\n", variant.n1.n2.vt);
 457                             }
 458                             if (ok)
 459                             {
 460                                 ptr = NULL;
 461                                 types_get_info(&sub_type, TI_GET_SYMNAME, &ptr);
 462                                 if (!ptr) continue;
 463                                 WideCharToMultiByte(CP_ACP, 0, ptr, -1, tmp, sizeof(tmp), NULL, NULL);
 464                                 HeapFree(GetProcessHeap(), 0, ptr);
 465                                 dbg_printf("%s", tmp);
 466                                 count = 0; /* so that we'll get away from outter loop */
 467                                 break;
 468                             }
 469                         }
 470                     }
 471                     count -= min(count, 256);
 472                     fcp->Start += 256;
 473                 }
 474             }
 475             if (!ok) dbg_print_longlong(val_int, TRUE);
 476         }
 477         break;
 478     default:
 479         WINE_FIXME("Unsupported tag %u\n", tag);
 480         break;
 481     }
 482 }
 483
 484 /***********************************************************************
 485  *           print_basic
 486  *
 487  * Implementation of the 'print' command.
 488  */
 489 void print_basic(const struct dbg_lvalue* lvalue, char format)
 490 {
 491     if (lvalue->type.id == dbg_itype_none)
 492     {
 493         dbg_printf("Unable to evaluate expression\n");
 494         return;
 495     }
 496
 497     if (format != 0)
 498     {
 499         unsigned size;
 500         LONGLONG res = types_extract_as_longlong(lvalue, &size);
 501         DWORD hi;
 502         WCHAR wch;
 503
 504         /* FIXME: this implies i386 byte ordering */
 505         switch (format)
 506         {
 507         case 'x':
 508             hi = (ULONG64)res >> 32;
 509             if (size == 8 && hi)
 510                 dbg_printf("0x%x%08x", hi, (DWORD)res);
 511             else
 512                 dbg_printf("0x%x", (DWORD)res);
 513             return;
 514
 515         case 'd':
 516             dbg_print_longlong(res, TRUE);
 517             dbg_printf("\n");
 518             return;
 519
 520         case 'c':
 521             dbg_printf("%d = '%c'", (char)(res & 0xff), (char)(res & 0xff));
 522             return;
 523
 524         case 'u':
 525             wch = (WCHAR)(res & 0xFFFF);
 526             dbg_printf("%d = '", wch);
 527             dbg_outputW(&wch, 1);
 528             dbg_printf("'");
 529             return;
 530
 531         case 'i':
 532         case 's':
 533         case 'w':
 534         case 'b':
 535             dbg_printf("Format specifier '%c' is meaningless in 'print' command\n", format);
 536         }
 537     }
 538     if (lvalue->type.id == dbg_itype_segptr)
 539     {
 540         dbg_print_longlong(types_extract_as_longlong(lvalue, NULL), TRUE);
 541         dbg_printf("\n");
 542     }
 543     else print_typed_basic(lvalue);
 544 }
 545
 546 void print_bare_address(const ADDRESS64* addr)
 547 {
 548     char hexbuf[MAX_OFFSET_TO_STR_LEN];
 549
 550     switch (addr->Mode)
 551     {
 552     case AddrModeFlat:
 553         dbg_printf("%s", memory_offset_to_string(hexbuf, addr->Offset, 0));
 554         break;
 555     case AddrModeReal:
 556     case AddrMode1616:
 557         dbg_printf("0x%04x:0x%04x", addr->Segment, (unsigned) addr->Offset);
 558         break;
 559     case AddrMode1632:
 560         dbg_printf("0x%04x:%s", addr->Segment,
 561                    memory_offset_to_string(hexbuf, addr->Offset, 32));
 562         break;
 563     default:
 564         dbg_printf("Unknown mode %x\n", addr->Mode);
 565         break;
 566     }
 567 }
 568
 569 /***********************************************************************
 570  *           print_address
 571  *
 572  * Print an 16- or 32-bit address, with the nearest symbol if any.
 573  */
 574 void print_address(const ADDRESS64* addr, BOOLEAN with_line)
 575 {
 576     char                buffer[sizeof(SYMBOL_INFO) + 256];
 577     SYMBOL_INFO*        si = (SYMBOL_INFO*)buffer;
 578     void*               lin = memory_to_linear_addr(addr);
 579     DWORD64             disp64;
 580     DWORD               disp;
 581
 582     print_bare_address(addr);
 583
 584     si->SizeOfStruct = sizeof(*si);
 585     si->MaxNameLen   = 256;
 586     if (!SymFromAddr(dbg_curr_process->handle, (DWORD_PTR)lin, &disp64, si)) return;
 587     dbg_printf(" %s", si->Name);
 588     if (disp64) dbg_printf("+0x%lx", (DWORD_PTR)disp64);
 589     if (with_line)
 590     {
 591         IMAGEHLP_LINE               il;
 592         IMAGEHLP_MODULE             im;
 593
 594         il.SizeOfStruct = sizeof(il);
 595         if (SymGetLineFromAddr(dbg_curr_process->handle, (DWORD_PTR)lin, &disp, &il))
 596             dbg_printf(" [%s:%u]", il.FileName, il.LineNumber);
 597         im.SizeOfStruct = sizeof(im);
 598         if (SymGetModuleInfo(dbg_curr_process->handle, (DWORD_PTR)lin, &im))
 599             dbg_printf(" in %s", im.ModuleName);
 600     }
 601 }
 602
 603 BOOL memory_disasm_one_insn(ADDRESS64* addr)
 604 {
 605     char        ch;
 606
 607     print_address(addr, TRUE);
 608     dbg_printf(": ");
 609     if (!dbg_read_memory(memory_to_linear_addr(addr), &ch, sizeof(ch)))
 610     {
 611         dbg_printf("-- no code accessible --\n");
 612         return FALSE;
 613     }
 614     be_cpu->disasm_one_insn(addr, TRUE);
 615     dbg_printf("\n");
 616     return TRUE;
 617 }
 618
 619 void memory_disassemble(const struct dbg_lvalue* xstart,
 620                         const struct dbg_lvalue* xend, int instruction_count)
 621 {
 622     static ADDRESS64 last = {0,0,0};
 623     int stop = 0;
 624     int i;
 625
 626     if (!xstart && !xend)
 627     {
 628         if (!last.Segment && !last.Offset) memory_get_current_pc(&last);
 629     }
 630     else
 631     {
 632         if (xstart)
 633             types_extract_as_address(xstart, &last);
 634         if (xend)
 635             stop = types_extract_as_integer(xend);
 636     }
 637     for (i = 0; (instruction_count == 0 || i < instruction_count)  &&
 638                 (stop == 0 || last.Offset <= stop); i++)
 639         memory_disasm_one_insn(&last);
 640 }
 641
 642 BOOL memory_get_register(DWORD regno, DWORD** value, char* buffer, int len)
 643 {
 644     const struct dbg_internal_var*  div;
 645
 646     /* negative register values are wine's dbghelp hacks
 647      * see dlls/dbghelp/dbghelp_internal.h for the details
 648      */
 649     switch (regno)
 650     {
 651     case -1:
 652         if (buffer) snprintf(buffer, len, "<internal error>");
 653         return FALSE;
 654     case -2:
 655         if (buffer) snprintf(buffer, len, "<couldn't compute location>");
 656         return FALSE;
 657     case -3:
 658         if (buffer) snprintf(buffer, len, "<is not available>");
 659         return FALSE;
 660     case -4:
 661         if (buffer) snprintf(buffer, len, "<couldn't read memory>");
 662         return FALSE;
 663     }
 664
 665     for (div = dbg_context_vars; div->name; div++)
 666     {
 667         if (div->val == regno)
 668         {
 669             if (dbg_curr_thread->curr_frame != 0)
 670             {
 671                 if (!stack_get_register_current_frame(regno, value))
 672                 {
 673                     if (buffer) snprintf(buffer, len, "<register %s not in topmost frame>", div->name);
 674                     return FALSE;
 675                 }
 676             }
 677             else
 678                 *value = div->pval;
 679
 680             if (buffer) lstrcpynA(buffer, div->name, len);
 681             return TRUE;
 682         }
 683     }
 684     if (buffer) snprintf(buffer, len, "<unknown register %u>", regno);
 685     return FALSE;
 686 }