[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...

[Minas Abrahamyan]

> So the old version was correct (except for the misleading comment maybe)
At the same time, with /FIRSTCHANCE key enabled
do we need ROS to popup kdbg at every start?
It's so bothering...
just annoying

On Tue, Mar 22, 2011 at 4:58 AM, Timo Kreuzer <timo.kreuzer at web.de> wrote:
>
> 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);
>>      }
>>  }
>>
>>
>>
>>
>
>
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