win32/except.c

   1 /*
   2  * Win32 exception functions
   3  *
   4  * Copyright (c) 1996 Onno Hovers, (onno@stack.urc.tue.nl)
   5  *
   6  * Notes:
   7  *  What really happens behind the scenes of those new
   8  *  __try{...}__except(..){....}  and
   9  *  __try{...}__finally{...}
  10  *  statements is simply not documented by Microsoft. There could be different
  11  *  reasons for this:
  12  *  One reason could be that they try to hide the fact that exception
  13  *  handling in Win32 looks almost the same as in OS/2 2.x.
  14  *  Another reason could be that Microsoft does not want others to write
  15  *  binary compatible implementations of the Win32 API (like us).
  16  *
  17  *  Whatever the reason, THIS SUCKS!! Ensuring portabilty or future
  18  *  compatability may be valid reasons to keep some things undocumented.
  19  *  But exception handling is so basic to Win32 that it should be
  20  *  documented!
  21  *
  22  * Fixmes:
  23  *  -Most functions need better parameter checking.
  24  *  -I do not know how to handle exceptions within an exception handler.
  25  *   or what is done when ExceptionNestedException is returned from an
  26  *   exception handler
  27  *  -Real exceptions are not yet implemented. only the exception functions
  28  *   are implemented. A real implementation needs some new code in
  29  *   loader/signal.c. There would also be a need for showing debugging
  30  *   information in UnhandledExceptionFilter.
  31  *
  32  */
  33
  34 #include <assert.h>
  35 #include "winuser.h"
  36 #include "winerror.h"
  37 #include "ldt.h"
  38 #include "process.h"
  39 #include "thread.h"
  40 #include "debug.h"
  41 #include "except.h"
  42 #include "stackframe.h"
  43
  44 #define TEB_EXCEPTION_FRAME(pcontext) \
  45     ((PEXCEPTION_FRAME)((TEB *)GET_SEL_BASE((pcontext)->SegFs))->except)
  46
  47 /*******************************************************************
  48  *         RtlUnwind  (KERNEL32.443)
  49  *
  50  *  This function is undocumented. This is the general idea of
  51  *  RtlUnwind, though. Note that error handling is not yet implemented.
  52  *
  53  * The real prototype is:
  54  * void WINAPI EXC_RtlUnwind( PEXCEPTION_FRAME pEndFrame, LPVOID unusedEip,
  55  *                            PEXCEPTION_RECORD pRecord, DWORD returnEax );
  56  */
  57 REGS_ENTRYPOINT(RtlUnwind)
  58 {
  59     EXCEPTION_RECORD record;
  60     DWORD            dispatch;
  61     int              retval;
  62     PEXCEPTION_FRAME pEndFrame;
  63     PEXCEPTION_RECORD pRecord;
  64
  65     /* get the arguments from the stack */
  66
  67     DWORD ret        = STACK32_POP(context);  /* return addr */
  68     pEndFrame        = (PEXCEPTION_FRAME)STACK32_POP(context);
  69     (void)STACK32_POP(context);  /* unused arg */
  70     pRecord          = (PEXCEPTION_RECORD)STACK32_POP(context);
  71     EAX_reg(context) = STACK32_POP(context);
  72     STACK32_PUSH(context,ret);  /* restore return addr */
  73
  74    /* build an exception record, if we do not have one */
  75    if(!pRecord)
  76    {
  77      record.ExceptionCode    = STATUS_INVALID_DISPOSITION;
  78      record.ExceptionFlags   = 0;
  79      record.ExceptionRecord  = NULL;
  80      record.ExceptionAddress = (LPVOID)EIP_reg(context);
  81      record.NumberParameters = 0;
  82      pRecord = &record;
  83    }
  84
  85    if(pEndFrame)
  86      pRecord->ExceptionFlags|=EH_UNWINDING;
  87    else
  88      pRecord->ExceptionFlags|=EH_UNWINDING | EH_EXIT_UNWIND;
  89
  90    /* get chain of exception frames */
  91    while ((TEB_EXCEPTION_FRAME(context) != NULL) &&
  92           (TEB_EXCEPTION_FRAME(context) != ((void *)0xffffffff)) &&
  93           (TEB_EXCEPTION_FRAME(context) != pEndFrame))
  94    {
  95        TRACE(win32, "calling exception handler at 0x%x\n",
  96                       (int)TEB_EXCEPTION_FRAME(context)->Handler );
  97
  98        dispatch=0;
  99        retval = TEB_EXCEPTION_FRAME(context)->Handler( pRecord,
 100                                                 TEB_EXCEPTION_FRAME(context),
 101                                                 context, &dispatch);
 102
 103        TRACE(win32,"exception handler returns 0x%x, dispatch=0x%x\n",
 104                               retval, (int) dispatch);
 105
 106        if (     (retval == ExceptionCollidedUnwind) &&
 107                 (TEB_EXCEPTION_FRAME(context) != (LPVOID)dispatch)
 108        )
 109            TEB_EXCEPTION_FRAME(context) = (LPVOID)dispatch;
 110        else if (        (TEB_EXCEPTION_FRAME(context) != pEndFrame) &&
 111                         (TEB_EXCEPTION_FRAME(context) != TEB_EXCEPTION_FRAME(context)->Prev)
 112        )
 113            TEB_EXCEPTION_FRAME(context) = TEB_EXCEPTION_FRAME(context)->Prev;
 114        else
 115           break;
 116    }
 117 }
 118
 119
 120 /*******************************************************************
 121  *         RaiseException  (KERNEL32.418)
 122  *
 123  * The real prototype is:
 124  * void WINAPI EXC_RaiseException(DWORD dwExceptionCode,
 125  *                                DWORD dwExceptionFlags,
 126  *                                DWORD cArguments,
 127  *                                const LPDWORD lpArguments );
 128  */
 129 REGS_ENTRYPOINT(RaiseException)
 130 {
 131     PEXCEPTION_FRAME    pframe;
 132     EXCEPTION_RECORD    record;
 133     DWORD               dispatch; /* is this used in raising exceptions ?? */
 134     int                 retval;
 135     int                 i;
 136
 137     /* Get the arguments from the stack */
 138
 139     DWORD ret                 = STACK32_POP(context);  /* return addr */
 140     DWORD dwExceptionCode     = STACK32_POP(context);
 141     DWORD dwExceptionFlags    = STACK32_POP(context);
 142     DWORD cArguments          = STACK32_POP(context);
 143     const LPDWORD lpArguments = (LPDWORD)STACK32_POP(context);
 144     STACK32_PUSH(context,ret);  /* Restore the return address */
 145
 146     /* compose an exception record */
 147
 148     record.ExceptionCode       = dwExceptionCode;
 149     record.ExceptionFlags      = dwExceptionFlags;
 150     record.ExceptionRecord     = NULL;
 151     record.NumberParameters    = cArguments;
 152     record.ExceptionAddress    = (LPVOID)EIP_reg(context);
 153
 154     if (lpArguments) for( i = 0; i < cArguments; i++)
 155         record.ExceptionInformation[i] = lpArguments[i];
 156
 157     /* get chain of exception frames */
 158
 159     retval = ExceptionContinueSearch;
 160     pframe = TEB_EXCEPTION_FRAME( context );
 161
 162     while((pframe!=NULL)&&(pframe!=((void *)0xFFFFFFFF)))
 163     {
 164        PEXCEPTION_FRAME    prevframe;
 165        TRACE(win32,"calling exception handler at 0x%x\n",
 166                                                 (int) pframe->Handler);
 167        dispatch=0;
 168        TRACE(relay,"(except=%p,record=%p,frame=%p,context=%p,dispatch=%p)\n",
 169                      pframe->Handler, &record, pframe, context, &dispatch );
 170        prevframe = pframe->Prev;
 171        retval=pframe->Handler(&record,pframe,context,&dispatch);
 172
 173        TRACE(win32,"exception handler returns 0x%x, dispatch=0x%x\n",
 174                               retval, (int) dispatch);
 175
 176        if(retval==ExceptionContinueExecution)
 177           break;
 178        pframe=prevframe;
 179    }
 180
 181    if (retval!=ExceptionContinueExecution)
 182    {
 183        /* FIXME: what should we do here? */
 184        TRACE(win32,"no handler wanted to handle the exception, exiting\n");
 185        ExitProcess(dwExceptionCode); /* what status should be used here ? */
 186    }
 187 }
 188
 189
 190 /*******************************************************************
 191  *         UnhandledExceptionFilter   (KERNEL32.537)
 192  */
 193 DWORD WINAPI UnhandledExceptionFilter(PEXCEPTION_POINTERS epointers)
 194 {
 195     char message[80];
 196     PDB *pdb = PROCESS_Current();
 197
 198     /* FIXME: Should check if the process is being debugged */
 199
 200     if (pdb->top_filter)
 201     {
 202         DWORD ret = pdb->top_filter( epointers );
 203         if (ret != EXCEPTION_CONTINUE_SEARCH) return ret;
 204     }
 205
 206     /* FIXME: Should check the current error mode */
 207
 208     sprintf( message, "Unhandled exception 0x%08lx at address 0x%08lx.",
 209              epointers->ExceptionRecord->ExceptionCode,
 210              (DWORD)epointers->ExceptionRecord->ExceptionAddress );
 211     MessageBoxA( 0, message, "Error", MB_OK | MB_ICONHAND );
 212     return EXCEPTION_EXECUTE_HANDLER;
 213 }
 214
 215
 216 /*************************************************************
 217  *            SetUnhandledExceptionFilter   (KERNEL32.516)
 218  */
 219 LPTOP_LEVEL_EXCEPTION_FILTER WINAPI SetUnhandledExceptionFilter(
 220                                           LPTOP_LEVEL_EXCEPTION_FILTER filter )
 221 {
 222     PDB *pdb = PROCESS_Current();
 223     LPTOP_LEVEL_EXCEPTION_FILTER old = pdb->top_filter;
 224     pdb->top_filter = filter;
 225     return old;
 226 }