- Stop code pool corruption in file area drivers#
- Stop code pool corruption in file area driver#
- Stop code pool corruption in file area windows#
You can test the status of a pending asynchronous I/O operation with the Windows HasOverlappedIoCompleted macro. Notice that if a wait is done, which depends on the overlapped flag in the file object, it is done in kernel mode by the NtReadFile function. Figure 8-8 illustrates the flow of control when a read operation is initiated. Whether or not the I/O system returns immediately to the caller depends on whether the handle was opened for synchronous or asynchronous I/O.
Stop code pool corruption in file area driver#
Regardless of the type of I/O request, internally I/O operations issued to a driver on behalf of the application are performed asynchronously that is, once an I/O request has been initiated, the device driver returns to the I/O system. The thread must synchronize its execution with the completion of the I/O request by monitoring a handle of a synchronization object (whether that’s an event object, an I/O completion port, or the file object itself) that will be signaled when the I/O is complete. Of course, after issuing an asynchronous I/O operation, the thread must be careful not to access any data from the I/O operation until the device driver has finished the data operation. To use asynchronous I/O, you must specify the FILE_FLAG_OVERLAPPED flag when you call the Windows CreateFile function. This type of I/O can improve an application’s throughput because it allows the application thread to continue with other work while an I/O operation is in progress. They complete the I/O operation before returning control to the caller.Īsynchronous I/O allows an application to issue multiple I/O requests and continue executing while the device performs the I/O operation. When used in their simplest form, the Windows ReadFile and WriteFile functions are executed synchronously. The program can then continue and access the transferred data immediately. Most I/O operations that applications issue are synchronous (which is the default) that is, the application thread waits while the device performs the data operation and returns a status code when the I/O is complete.
In this section, we’ll explain these options for I/O requests.
Stop code pool corruption in file area drivers#
Furthermore, the I/O manager gives drivers the choice of implementing a shortcut I/O interface that can often mitigate IRP allocation for I/O processing. Types of I/OĪpplications have several options for the I/O requests they issue. Processing varies further depending on whether the caller specified synchronous or asynchronous I/O, so we’ll begin our discussion of I/O types with these two and then move on to others. The stages vary depending on whether the request is destined for a device operated by a single-layered driver or for a device reached through a multilayered driver. I/O requests pass through several predictable stages of processing.
Now that we’ve covered the structure and types of drivers and the data structures that support them, let’s look at how I/O requests flow through the system.
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