How to artificially cause a page fault in linux kernel?

How to artificially cause a page fault in Linux kernel?

• I am pretty new to the Linux kernel. I would like to make the kernel fault every time a specified page 'P' is being fetched. One simple conceptual idea is to clear the bit indicating the presence of page 'P' in Page Table Entry (PTE). Can anyone provide more details on how to go about achieving this in x86? Also please point me to where in the source code one needs to make this modification, if possible. Background I have to invoke my custom page handler which is applicable only for handling a set of pages in an user's application. This custom page handler must to be enabled after some prologue is executed in a given application. For testing purposes, I need to induce faults after my prologue is executed. Currently the kernel loads everything well before my prologue is executed, so I need to artificially cause faults to test my handler.

• Answer:

  I have not played with the swapping code since I moved from Minix to Linux, but a swapping algorithm does two things. When there is a shortage of memory, it moves the page from memory to disk, and when a page is needed, it copies it back (probably after moving another page to disk). I would use the full swap out function that you are writing to clear the page present flag. I would probably also use a character device to send the command to the test code to force the swap.