Patching system calls in data protection operations
Systems and methods for patching system calls issued on a device. System calls are patched by transforming system calls to provide additional functionality. The system calls can then be rerouted to the updated or custom functions.
1. A method for communicating with a driver configured to track changes to a disk, the method comprising:
initiating a write tracking driver associated with the disk that is being tracked by the write tracking driver;
patching a system call while initializing the write tracking driver;
checking the system call when the system call is issued to the write tracking driver to determine whether the system call is associated with a backup operation or a different application;
selecting a custom functions when the system call is associated with the backup operation, wherein default functions are selected with the system call is associated with the different application; and
performing the custom functions.
2. The method of claim 1 , wherein performing the custom functions includes one or more of tracking the device with a particular backup level, returning a subset of extents for the device, and/or closing a session with the driver.
3. The method of claim 1 , wherein patching the system call includes opening the device.
4. The method of claim 3 , further comprising storing current device functions associated with the system call in a variable and/or backing up current device functions.
5. The method of claim 3 , backing up current function pointers for default functions associated with the system call.
6. The method of claim 5 , further comprising creating a copy of a block device operations structure for patching.
7. The method of claim 6 , further comprising updating the default functions with the custom functions and updating original block device operations with modified structure of function pointers.
8. The method of claim 1 , further comprising unpatching the system call.
9. A method for patching a system call, the method comprising:
opening a block device associated with a system call;
backing up default function pointers for functions of the block device associated with the system call;
creating a copy of a block device operations structure for patching;
overwriting the default functions with custom functions in the block device operations structure, wherein the copy of the block device operations structure includes default functions; and
updating the block device operations with a modified structure of pointer functions.
10. The method of claim 9 , further comprising performing a backup operation that includes issuing the system call.