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kernel mode :

<pre>VOID DriverLoop() {

	while (TRUE)
	{
		//DbgPrintEx(0, 0, "First loop is running \n");
		ReadSharedMemory();
		
		
			if (!(PCHAR)SharedSection == NULL && strcmp((PCHAR)SharedSection, "Read") == 0)
			{
				DbgPrintEx(0, 0, "Read looping \n");

				RtlZeroMemory(SharedSection, sizeof(SharedSection));
				break;
			}
			else if (!(PCHAR)SharedSection == NULL && strcmp((PCHAR)SharedSection, "Write") == 0)
			{
				DbgPrintEx(0, 0, "Write looping \n");
				RtlZeroMemory(SharedSection, sizeof(SharedSection));
				break;
			}
		LARGE_INTEGER Timeout;
		Timeout.QuadPart = RELATIVE(SECONDS(1));
		KeDelayExecutionThread(KernelMode, FALSE, &Timeout);
	}
}



user mode :

auto pBufW = (char*)MapViewOfFile(hMapFileW, FILE_MAP_WRITE, 0, 0, 4096);


	RtlCopyMemory(pBufW, "Read", 4);

	printf("message has been sent to kernel! \n");


	UnmapViewOfFile(pBufW);

	Sleep(10);

	auto pBfW = (char*)MapViewOfFile(hMapFileW, FILE_MAP_WRITE, 0, 0, 4096);


	RtlCopyMemory(pBfW, "Write", 5);

	printf("message has been sent to kernel! \n");


	UnmapViewOfFile(pBfW);


i can't figure it out why when i call Read and Write . only Write execute i have tried it multiple times and its always doing this + i have tried to add a sleep(1); in my user mode (thought it was executing real fast).

basically i just need them to execute normally like Read should be executed first then Write .

What I have tried:

i have tried to add a sleep of 1 and 10 seconds and it didn't work idk what i am doing wrong here.
Posted
Updated 17-Mar-19 16:15pm

1 solution

What you are doing wrong is hoping that two processes in different execution rings can coordinate themselves by pure luck.

As I have written to you before, you need to use a signalling mechanism. This can be a simple counter that the processes watch for a change or it could be an event (or two) that is/are signalled when work needs to be done and when it is complete. There are certainly many more possibilities but those are two that are quite simple to implement.
 
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Member 14130865 18-Mar-19 12:06pm    
@Rick York could you link some of them , because i don't know how to share a mutex or an event between kernel and user mode . btw i don't want to use any system threads or DevicIocontrol . :D

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