-//
-// Converts a base thread to a GUI thread
-//
-#ifdef __GNUC__
-FORCEINLINE
-NTSTATUS
-KiConvertToGuiThread(VOID)
-{
- NTSTATUS NTAPI PsConvertToGuiThread(VOID);
- NTSTATUS Result;
- PVOID StackFrame;
-
- /*
- * Converting to a GUI thread safely updates ESP in-place as well as the
- * current Thread->TrapFrame and EBP when KeSwitchKernelStack is called.
- *
- * However, PsConvertToGuiThread "helpfully" restores EBP to the original
- * caller's value, since it is considered a nonvolatile register. As such,
- * as soon as we're back after the conversion and we try to store the result
- * which will probably be in some stack variable (EBP-based), we'll crash as
- * we are touching the de-allocated non-expanded stack.
- *
- * Thus we need a way to update our EBP before EBP is touched, and the only
- * way to guarantee this is to do the call itself in assembly, use the EAX
- * register to store the result, fixup EBP, and then let the C code continue
- * on its merry way.
- *
- */
- __asm__ __volatile__
- (
- "movl %%ebp, %1\n\t"
- "subl %%esp, %1\n\t"
- "call _PsConvertToGuiThread@0\n\t"
- "addl %%esp, %1\n\t"
- "movl %1, %%ebp"
- : "=a"(Result), "=r"(StackFrame)
- : "p"(PsConvertToGuiThread)
- : "%esp", "%ecx", "%edx", "memory"
- );
- return Result;
-}
-#elif defined(_MSC_VER)
-NTSTATUS
-NTAPI
-KiConvertToGuiThread(VOID);
-#else
-#error Unknown Compiler
-#endif
-