fault_hook.patch

--- ../../../linux-4.19.13/arch/x86/mm/fault.c	2018-12-29 18:07:59.000000000 +0530
+++ fault.c	2019-01-27 09:59:37.398145215 +0530
@@ -1202,6 +1202,12 @@
 	return true;
 }
 
+// Export variables to access from module.
+int page_fault_pid = -1;
+EXPORT_SYMBOL(page_fault_pid);
+int (*rsvd_fault_hook)(struct mm_struct *mm, struct pt_regs *regs, unsigned long error_code, unsigned long address) = NULL;
+EXPORT_SYMBOL(rsvd_fault_hook);
+
 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
@@ -1260,13 +1266,23 @@
 
 		return;
 	}
+   // Log the page fault for the given pid.
+   if (unlikely(tsk->pid == page_fault_pid))
+       printk(KERN_INFO "Page fault occured pid [%d] address [%lx] error_code [%lx]\n", tsk->pid, address, error_code);
 
 	/* kprobes don't want to hook the spurious faults: */
 	if (unlikely(kprobes_fault(regs)))
 		return;
+         
+   if (unlikely(error_code & X86_PF_RSVD)) {
+       if (!rsvd_fault_hook || rsvd_fault_hook(mm, regs, error_code, address))
+           pgtable_bad(regs, error_code, address);
+       return;
+   }
+   /* Comment out original code
 
 	if (unlikely(error_code & X86_PF_RSVD))
-		pgtable_bad(regs, error_code, address);
+		pgtable_bad(regs, error_code, address); */
 
 	if (unlikely(smap_violation(error_code, regs))) {
 		bad_area_nosemaphore(regs, error_code, address, NULL);