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Thank you Richard. I reread the remarks and I see that you are correct.
Quote: However, because a 32-bit application must run the hook code, the system executes the hook in the hooking app's context; specifically, on the thread that called SetWindowsHookEx. This means that the hooking application must continue to pump messages or it might block the normal functioning of the 64-bit processes.
When I install the hook, I must pass a pointer to the hook callback function. However, that's a pointer that's only valid inside the process space of the application installing the hook. How does it use that pointer to call the correct code inside the address space of the application that is a target of the hook? 
The difficult we do right away...
...the impossible takes slightly longer.
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Richard Andrew x64 wrote: a pointer to the hook callback function.
The system keeps that address (which is the target of the hook) and uses it to call back into your application at the appropriate time (i.e when the relevant hook event triggers). But if you close your application, its address space is destroyed and the hook is no longer valid, so the system will no longer call it.
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Thank you for your response.
OK, so if the system calls back into my application at the appropriate time, why must the system load the DLL containing the filter function into each process that is hooked?
IOW, if the hook function is run inside the installing application, why must the hook function DLL be injected into every targeted application?
The difficult we do right away...
...the impossible takes slightly longer.
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Sorry I don't know the answer to that one. There is an implication that injecting the hook into another process can be done of the call-back function is in a dll. If that is the case then the dll must be associated withe the address space of that process. I must admit it is a long time since I used this feature so my recollection of it is not 100%.
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OK Thank you for your contributions thus far.
The difficult we do right away...
...the impossible takes slightly longer.
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You need an instance handle to load the DLL ... guess what happens to the instance handle when the application terminates 
In vino veritas
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Yes, thank you. I progressed to the point where I'm creating the hook and processing it successfully.
But now the problem is that when the hook installer application terminates, it crashes all of the hooked applications *even though* I call UnhookWindowsHookEx() to remove the hook before terminating.
Would you have any hints what I can do about that?
The difficult we do right away...
...the impossible takes slightly longer.
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The unhook is usually just done in WM_DESTROY of the main application.
From memory it must be before you post WM_QUIT which will kill the instance handle.
In vino veritas
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Do you mean that the system waits until the window receives the WM_DESTROY message before it actually unhooks the hook?
Or do you mean that I must call UnhookWindowsHookEx BEFORE the WM_QUIT message is posted?
The difficult we do right away...
...the impossible takes slightly longer.
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Unhook it before you post the WM_QUIT message
In vino veritas
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How is the way to open a HDD drive with _open function in such a way to read even the boot section of this drive ? Here is the code:
int hd_h = _open(device, O_BINARY | O_RDWR | O_EXCL);
device is provided with
"\\\\?\\E:"
This is the code from ntfs library GitHub - vitalif/ntfs-3g: Fork of git://ntfs-3g.git.sourceforge.net/gitroot/ntfs-3g/ntfs-3g with FIEMAP support patch[^]
Why I am asking that ? Even if _open return 3, further more, the reading of boot section has failed.
Function
ntfs_boot_sector_is_ntfs say that my boot device is not NTFS:
if (! ntfs_boot_sector_is_ntfs(bs))
{
errno = EINVAL;
goto error_exit;
}
BOOL ntfs_boot_sector_is_ntfs(NTFS_BOOT_SECTOR* b)
{
u32 i;
BOOL ret = FALSE;
ntfs_log_debug("Beginning bootsector check.\n");
ntfs_log_debug("Checking OEMid, NTFS signature.\n");
if (b->oem_id != const_cpu_to_le64(0x202020205346544eULL))
{
ntfs_log_error("NTFS signature is missing.\n");
goto not_ntfs;
}
....
Of course, this debugging session ran as admin mode.
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I not sure that you can access the boot sector using a drive letter. I think you need to address it as something like Device\Partition0. Google can probably find the correct syntax.
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Good point, I have tried in this way:
"\\\\.\\PHYSICALDRIVE2" ... but with exactly the same result ... strange ...
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I think there is a page somewhere on MSDN that explains how to access low level disks.
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I haven't gotten around to check this out myself yet, but I am studying the "Windows Internals" book by Mark Russinovich (the guy creating the Sysinternals suite). There I found that the object name \Device\HarddiskX\DRX (with 'X' being replaced by a digit from 0 upwards; you can find it using the Sysinternals WinObj utility).
It is not clear to me when to use this name and when to use the \Global??\PhysicalDriveX name. Russinovich writes that "The Windows application layer converts the name to \Global??\PhysicalDriveX berofe handling the name to the Windwows object manager" - it seems like that PhysicalDriveX format is some old legacy format. It is far from clear to me!
So you may try a Global??\ prefix, or you might try \Device\HarddiskX\DRX (appearently with X replaced by 2 in your case). When you find out what works, tell it, and I will use it when I get that far myself!
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As that document say, I have tried "\\\\.\\PhysicalDrive2", with exactly the same result.
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Are you sure that is a valid disk name? If you enter the command Get-PhysicalDisk in a PowerShell window, you will get a list of the known physical disks on your system. See Get-PhysicalDisk[^].
[edit]
Here is a better command:
Get-WmiObject Win32_DiskDrive
[/edit]
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I just tried the following code and it returns a valid handle. Note that this must run with administrator privileges:
HANDLE hFile = CreateFileW(L"\\\\.\\PhysicalDrive0",
GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL
);
cout << "Handle: " << hex << hFile << endl;
CloseHandle(hFile);
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Yes, the name of the drive is correct, that is for sure. And I have tried:
HANDLE hFile = CreateFileW(L"\\\\.\\PhysicalDrive2",
GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL
);
TRACE("Handle: %X %p", hFile, hFile);
CloseHandle(hFile);
and the result was: Handle: 434 00000434. So this prove that I have read it successfully ?
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I was not pointing out the name to be used -- I was pointing out the access that must be used. Since your disk name is correct (assuming that drive 2 exists ), the access mode seems like a good subject for investigation. A quick google indicates this is OS-dependent when using the open function.
Be wary of strong drink. It can make you shoot at tax collectors - and miss.
Lazarus Long, "Time Enough For Love" by Robert A. Heinlein
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There is this structure:
typedef struct _D3DLOCKED_RECT
{
INT Pitch;
void* pBits;
} D3DLOCKED_RECT;
How do I interpret pBits here?
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fearless_ wrote: How do I interpret pBits
Any way you like. What does it point to?
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it`s a pointer back to a texture (surface) data.
(I found people do this:
DWORD* pBits=(DWORD*)lockedrect.pBits; )
I don`t understand how void works though Richard. isn`t a variable a sequence of bytes? long is 8 bytes so the data is split at an 8 size step? which doesn`t make sense since a pixel is made of 3 maybe 4 bytes.
modified 11-Apr-20 5:01am.
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fearless_ wrote: I don`t understand how void works
It's just a way of allowing the compiler to generate the correct code for a pointer, without needing to know what it actually points to. It is often used when the ultimate data may be more than one type. In order to access the actual content you need to use a cast, like you have shown above.
As to the structure of the real data, you will need to look at the documentation.
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