Re: [ros-dev] [ros-diffs] [reactos] 02/02: [NTOS:MM] Get rid of unnecessary MmZeroingPageThreadActive.

[M. Ziggyesque]

I agree with Alex's reasoning, plus in a multiprocessor environment such page zeroing
may be done asynchronously to other cores or processors attempting to acquire use of that
page while its state is inconsistent. Removing it counts as a security hole, in other
words, except for single core processors that have interrupts disabled, that I see.

Sent from Outlook Mobile<https://aka.ms/blhgte>

________________________________
From: Ros-dev &lt;ros-dev-bounces(a)reactos.org&gt; on behalf of Alex Ionescu
&lt;ionucu(a)videotron.ca&gt;
Sent: Sunday, May 10, 2020 12:37:09 PM
To: ReactOS Development List &lt;ros-dev(a)reactos.org&gt;rg>; Thomas Faber
&lt;thomas.faber(a)reactos.org&gt;
Cc: Linda Wang &lt;ros-diffs(a)reactos.org&gt;
Subject: Re: [ros-dev] [ros-diffs] [reactos] 02/02: [NTOS:MM] Get rid of unnecessary
MmZeroingPageThreadActive.

I know I probably don't have much weight anymore but, I re-iterate
that one of the goals of the project should be to make things as
similar as possible for debugging/troubleshooting and learning as
Server 2003... which does have this variable. I don't think it's the
end of the world to keep it around. Stuff like this also tends to
break kdexts.dll.

Best regards,
Alex Ionescu

On Mon, Apr 6, 2020 at 5:15 AM Thomas Faber &lt;thomas.faber(a)reactos.org&gt; wrote:
>  
>
> https://git.reactos.org/?p=reactos.git;a=commitdiff;h=25a5aee86f43e9f526d4d…
>
>  commit 25a5aee86f43e9f526d4d360e4e4f35feb9d22b4
>  Author:     Thomas Faber &lt;thomas.faber(a)reactos.org&gt;
>  AuthorDate: Sat Feb 22 12:31:54 2020 +0100
>  Commit:     Thomas Faber &lt;thomas.faber(a)reactos.org&gt;
>  CommitDate: Mon Apr 6 11:13:55 2020 +0200
>
>      [NTOS:MM] Get rid of unnecessary MmZeroingPageThreadActive.
>  ---
>   ntoskrnl/mm/ARM3/miarm.h    | 1 -
>   ntoskrnl/mm/ARM3/mminit.c   | 5 ++---
>   ntoskrnl/mm/ARM3/pfnlist.c  | 3 +--
>   ntoskrnl/mm/ARM3/zeropage.c | 3 +--
>   4 files changed, 4 insertions(+), 8 deletions(-)
>
>  diff --git a/ntoskrnl/mm/ARM3/miarm.h b/ntoskrnl/mm/ARM3/miarm.h
>  index c242b795af6..9d85c42afff 100644
>  --- a/ntoskrnl/mm/ARM3/miarm.h
>  +++ b/ntoskrnl/mm/ARM3/miarm.h
>  @@ -639,7 +639,6 @@ extern PMMPDE MiHighestUserPde;
>   extern PFN_NUMBER MmSystemPageDirectory[PPE_PER_PAGE];
>   extern PMMPTE MmSharedUserDataPte;
>   extern LIST_ENTRY MmProcessList;
>  -extern BOOLEAN MmZeroingPageThreadActive;
>   extern KEVENT MmZeroingPageEvent;
>   extern ULONG MmSystemPageColor;
>   extern ULONG MmProcessColorSeed;
>  diff --git a/ntoskrnl/mm/ARM3/mminit.c b/ntoskrnl/mm/ARM3/mminit.c
>  index 7cd7af10838..d72e7186193 100644
>  --- a/ntoskrnl/mm/ARM3/mminit.c
>  +++ b/ntoskrnl/mm/ARM3/mminit.c
>  @@ -2181,9 +2181,8 @@ MmArmInitSystem(IN ULONG Phase,
>           /* Initialize the Loader Lock */
>           KeInitializeMutant(&MmSystemLoadLock, FALSE);
>
>  -        /* Set the zero page event */
>  -        KeInitializeEvent(&MmZeroingPageEvent, SynchronizationEvent, FALSE);
>  -        MmZeroingPageThreadActive = FALSE;
>  +        /* Set up the zero page event */
>  +        KeInitializeEvent(&MmZeroingPageEvent, NotificationEvent, FALSE);
>
>           /* Initialize the dead stack S-LIST */
>           InitializeSListHead(&MmDeadStackSListHead);
>  diff --git a/ntoskrnl/mm/ARM3/pfnlist.c b/ntoskrnl/mm/ARM3/pfnlist.c
>  index eac3a043418..f175541a500 100644
>  --- a/ntoskrnl/mm/ARM3/pfnlist.c
>  +++ b/ntoskrnl/mm/ARM3/pfnlist.c
>  @@ -701,10 +701,9 @@ MiInsertPageInFreeList(IN PFN_NUMBER PageFrameIndex)
>       ColorTable->Count++;
>
>       /* Notify zero page thread if enough pages are on the free list now */
>  -    if ((ListHead->Total >= 8) && !(MmZeroingPageThreadActive))
>  +    if (ListHead->Total >= 8)
>       {
>           /* Set the event */
>  -        MmZeroingPageThreadActive = TRUE;
>           KeSetEvent(&MmZeroingPageEvent, IO_NO_INCREMENT, FALSE);
>       }
>
>  diff --git a/ntoskrnl/mm/ARM3/zeropage.c b/ntoskrnl/mm/ARM3/zeropage.c
>  index 6d859f6806f..5fe22294199 100644
>  --- a/ntoskrnl/mm/ARM3/zeropage.c
>  +++ b/ntoskrnl/mm/ARM3/zeropage.c
>  @@ -17,7 +17,6 @@
>
>   /* GLOBALS ********************************************************************/
>
>  -BOOLEAN MmZeroingPageThreadActive;
>   KEVENT MmZeroingPageEvent;
>
>   /* PRIVATE FUNCTIONS **********************************************************/
>  @@ -73,7 +72,7 @@ MmZeroPageThread(VOID)
>           {
>               if (!MmFreePageListHead.Total)
>               {
>  -                MmZeroingPageThreadActive = FALSE;
>  +                KeClearEvent(&MmZeroingPageEvent);
>                   MiReleasePfnLock(OldIrql);
>                   break;
>               }
>  
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