[rharabien] 51108: Fix ProbeForRead. It wasn't ever checking if memory can be accessed. Thanks to big-endian it wasn't breaking MmUserProbeAddress as well. Code is now nearly the same as in ProbeFo...

Author: rharabien
Date: Mon Mar 21 14:43:56 2011
New Revision: 51108

URL: http://svn.reactos.org/svn/reactos?rev=51108&view=rev
Log:
Fix ProbeForRead. It wasn't ever checking if memory can be accessed. Thanks to
big-endian it wasn't breaking MmUserProbeAddress as well. Code is now nearly the same
as in ProbeForWrite. It shouldn't break anything. If it does, it's not bug in this
code. :)

Modified:
    trunk/reactos/ntoskrnl/ex/exintrin.c

Modified: trunk/reactos/ntoskrnl/ex/exintrin.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/ex/exintrin.c?rev…
==============================================================================
--- trunk/reactos/ntoskrnl/ex/exintrin.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/ex/exintrin.c [iso-8859-1] Mon Mar 21 14:43:56 2011
@@ -103,6 +103,8 @@
              IN SIZE_T Length,
              IN ULONG Alignment)
 {
+	ULONG_PTR Last, Current = (ULONG_PTR)Address;
+	CHAR Temp;
     PAGED_CODE();
 
     /* Only probe if we have a valid length */
@@ -115,18 +117,31 @@
                (Alignment == 8) ||
                (Alignment == 16));
 
-        /* Check for correct alignment */
-        if (((ULONG_PTR)Address & (Alignment - 1)) != 0)
+        /* Check the alignment */
+        if ((Current & (Alignment - 1)) != 0)
         {
             /* Incorrect alignment */
             ExRaiseDatatypeMisalignment();
         }
-        else if (((ULONG_PTR)Address + Length) < (ULONG_PTR)Address ||
-                 ((ULONG_PTR)Address + Length) > (ULONG_PTR)MmUserProbeAddress)
+        
+        /* Get the end address */
+        Last = Current + Length - 1;
+        if ((Last < Current) || (Last >= (ULONG_PTR)MmUserProbeAddress))
+        {
+            /* Raise an access violation */
+            ExRaiseAccessViolation();
+        }
+
+        /* Round down to the last page */
+        Last = PAGE_ROUND_DOWN(Last) + PAGE_SIZE;
+        do
         {
             /* Attempt a read */
-            *(volatile CHAR* const)MmUserProbeAddress = 0;
-        }
+            Temp = *(volatile CHAR*)Current;
+
+            /* Go to the next address */
+            Current = PAGE_ROUND_DOWN(Current) + PAGE_SIZE;
+        } while (Current != Last);
     }
 }