[ros-dev] [ros-diffs] [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...

[Timo Kreuzer]

Windows doesn't do any access checks in ProbeForRead, it only checks the 
range and alignment. The MmUserProbeAddress access is used to raise an 
exception with the appropriate parameters. So the old version was 
correct (except for the misleading comment maybe)


Am 21.03.2011 15:43, schrieb rharabien at svn.reactos.org:
> 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=51108&r1=51107&r2=51108&view=diff
> ==============================================================================
> --- 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);
>       }
>   }
>
>
>
>