--- /dev/null
+#define WIN32_LEAN_AND_MEAN
+#define STRICT
+#include <windows.h>
+
+#include <assert.h>
+#include <setjmp.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <limits.h>
+#include <time.h>
+
+static unsigned int nRandBytes;
+
+static int initrand(void)
+{
+ unsigned int nRandMax;
+ unsigned int nRandMaxBits;
+ time_t tLoc;
+
+ nRandMax = RAND_MAX;
+
+ for(nRandMaxBits = 0; nRandMax != 0; nRandMax >>= 1, ++ nRandMaxBits);
+
+ nRandBytes = nRandMaxBits / CHAR_BIT;
+
+ assert(nRandBytes != 0);
+
+ srand((unsigned)(time(&tLoc) & UINT_MAX));
+
+ return 1;
+}
+
+static void randbytes(void * p, size_t n)
+{
+ unsigned char * b;
+ size_t i;
+ int r;
+
+ b = (unsigned char *)p;
+
+ for(i = 0; i < n; ++ i)
+ {
+ if(i % nRandBytes == 0)
+ r = rand();
+
+ b[i] = (unsigned char)(r & UCHAR_MAX);
+ r >>= CHAR_BIT;
+ }
+}
+
+static ULONG randULONG(void)
+{
+ ULONG n;
+ randbytes(&n, sizeof(n));
+ return n;
+}
+
+#ifdef _M_IX86
+#define ZWC_SEGMENT_BITS (0xFFFF)
+#define ZWC_EFLAGS_BITS (0x3C0CD5)
+#endif
+
+static jmp_buf jmpbuf;
+static CONTEXT continueContext;
+
+extern void continuePoint(void);
+extern void check(CONTEXT *);
+extern LONG NTAPI ZwContinue(IN CONTEXT *, IN BOOLEAN);
+
+void check(CONTEXT * actualContext)
+{
+#ifdef _M_IX86
+ assert(actualContext->ContextFlags == CONTEXT_FULL);
+
+ /* Random data segments */
+ assert
+ (
+ (actualContext->SegGs & ZWC_SEGMENT_BITS) ==
+ (continueContext.SegGs & ZWC_SEGMENT_BITS)
+ );
+
+ assert
+ (
+ (actualContext->SegFs & ZWC_SEGMENT_BITS) ==
+ (continueContext.SegFs & ZWC_SEGMENT_BITS)
+ );
+
+ assert
+ (
+ (actualContext->SegEs & ZWC_SEGMENT_BITS) ==
+ (continueContext.SegEs & ZWC_SEGMENT_BITS)
+ );
+
+ assert
+ (
+ (actualContext->SegDs & ZWC_SEGMENT_BITS) ==
+ (continueContext.SegDs & ZWC_SEGMENT_BITS)
+ );
+
+ /* Integer registers */
+ assert(actualContext->Edi == continueContext.Edi);
+ assert(actualContext->Esi == continueContext.Esi);
+ assert(actualContext->Ebx == continueContext.Ebx);
+ printf("%s %lX : %lX\n", "Edx", actualContext->Edx, continueContext.Edx);
+ //assert(actualContext->Edx == continueContext.Edx);
+ assert(actualContext->Ecx == continueContext.Ecx);
+ assert(actualContext->Eax == continueContext.Eax);
+
+ /* Control registers and segments */
+ assert(actualContext->Ebp == continueContext.Ebp);
+ assert(actualContext->Eip == continueContext.Eip);
+
+ assert
+ (
+ (actualContext->SegCs & ZWC_SEGMENT_BITS) ==
+ (continueContext.SegCs & ZWC_SEGMENT_BITS)
+ );
+
+ assert
+ (
+ (actualContext->EFlags & ZWC_EFLAGS_BITS) ==
+ (continueContext.EFlags & ZWC_EFLAGS_BITS)
+ );
+
+ assert(actualContext->Esp == continueContext.Esp);
+
+ assert
+ (
+ (actualContext->SegSs & ZWC_SEGMENT_BITS) ==
+ (continueContext.SegSs & ZWC_SEGMENT_BITS)
+ );
+#endif
+
+ longjmp(jmpbuf, 1);
+}
+
+int main(void)
+{
+ initrand();
+
+ /* First time */
+ if(setjmp(jmpbuf) == 0)
+ {
+ CONTEXT bogus;
+
+ continueContext.ContextFlags = CONTEXT_FULL;
+ GetThreadContext(GetCurrentThread(), &continueContext);
+
+#ifdef _M_IX86
+ continueContext.ContextFlags = CONTEXT_FULL;
+
+ /* Fill the integer registers with random values */
+ continueContext.Edi = randULONG();
+ continueContext.Esi = randULONG();
+ continueContext.Ebx = randULONG();
+ continueContext.Edx = randULONG();
+ continueContext.Ecx = randULONG();
+ continueContext.Eax = randULONG();
+ continueContext.Ebp = randULONG();
+
+ /* Randomize all the allowed flags (determined experimentally with WinDbg) */
+ continueContext.EFlags = randULONG() & 0x3C0CD5;
+
+ /* Randomize the stack pointer as much as possible */
+ continueContext.Esp =
+ (ULONG)(((ULONG_PTR)&bogus) & 0xFFFFFFFF) +
+ sizeof(bogus) -
+ (randULONG() & 0xF) * 4;
+
+ /* continuePoint() is implemented in assembler */
+ continueContext.Eip = (ULONG)((ULONG_PTR)continuePoint & 0xFFFFFFF);
+
+ /* Can't do a lot about segments */
+#endif
+
+ ZwContinue(&continueContext, FALSE);
+ }
+ /* Second time */
+ else
+ return 0;
+
+ assert(0);
+ return 1;
+}