[ros-dev] Re: [ros-diffs] [weiden] 17474: added a macro IsKernelPointer() to test whether a pointer value points to the kernel address space. This is needed because on IA-64 the MSB is not necessarily set for pointers to the kernel address space.

[Filip Navara]

weiden at svn.reactos.com wrote:

>added a macro IsKernelPointer() to test whether a pointer value points to the kernel address space. This is needed because on IA-64 the MSB is not necessarily set for pointers to the kernel address space.
>
>Modified: trunk/reactos/ntoskrnl/include/internal/ntoskrnl.h
>Modified: trunk/reactos/ntoskrnl/ob/wait.c
>  
>
> ------------------------------------------------------------------------
> *Modified: trunk/reactos/ntoskrnl/include/internal/ntoskrnl.h*
>
>--- trunk/reactos/ntoskrnl/include/internal/ntoskrnl.h	2005-08-22 10:51:05 UTC (rev 17473)
>+++ trunk/reactos/ntoskrnl/include/internal/ntoskrnl.h	2005-08-22 13:38:30 UTC (rev 17474)
>@@ -147,8 +147,26 @@
>
> #define ProbeForReadLargeInteger(Ptr) ((LARGE_INTEGER)ProbeForReadGenericType(&(Ptr)->QuadPart, LONGLONG, 0))
> #define ProbeForReadUlargeInteger(Ptr) ((ULARGE_INTEGER)ProbeForReadGenericType(&(Ptr)->QuadPart, ULONGLONG, 0))
> 
>  
>
>+/*
>+ * Use IsKernelPointer to test whether a pointer points to the kernel address
>+ * space
>+ */
>+#if defined(_X86_) || defined(_M_AMD64)
>  
>
> 
>  
>
>+/* for x86 and x86-64 the MSB is 1 so we can simply test on that */
>+#define IsKernelPointer(Ptr) ((LONG_PTR)(Ptr) < 0)
>+
>+#elif defined(_IA64_)
>+
>+/* on Itanium if the 24 most significant bits are set, we're not dealing with
>+   user mode pointers. */
>+#define IsKernelPointer(Ptr)  (((ULONG_PTR)(Ptr) & 0xFFFFFF0000000000ULL) != 0)
>+
>+#else
>+#error IsKernelPointer() needs to be defined for this architecture
>  
>
> #endif
>  
>
>+
>+#endif
>  
>
This looks really really wrong ... the macro will incorrectly evaluate 
to TRUE for user mode pointers on 3GB kernels. I don't understand the 
purpose of the code, but why don't you just check for Ptr >= 
MM_SYSTEM_RANGE_START ?

- Filip