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-rw-r--r--arch/x86/mm/fault.c56
1 files changed, 56 insertions, 0 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 8bcb6f40ccb6..42394b353c6a 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -49,6 +49,60 @@
#define PF_RSVD (1<<3)
#define PF_INSTR (1<<4)
+#ifdef CONFIG_PAGE_FAULT_HANDLERS
+static HLIST_HEAD(pf_handlers); /* protected by RCU */
+static DEFINE_SPINLOCK(pf_handlers_writer);
+
+void register_page_fault_handler(struct pf_handler *new_pfh)
+{
+ unsigned long flags;
+ spin_lock_irqsave(&pf_handlers_writer, flags);
+ hlist_add_head_rcu(&new_pfh->hlist, &pf_handlers);
+ spin_unlock_irqrestore(&pf_handlers_writer, flags);
+}
+EXPORT_SYMBOL_GPL(register_page_fault_handler);
+
+/**
+ * unregister_page_fault_handler:
+ * The caller must ensure @old_pfh is not in use anymore before freeing it.
+ * This function does not guarantee it. The list of handlers is protected by
+ * RCU, so you can do this by e.g. calling synchronize_rcu().
+ */
+void unregister_page_fault_handler(struct pf_handler *old_pfh)
+{
+ unsigned long flags;
+ spin_lock_irqsave(&pf_handlers_writer, flags);
+ hlist_del_rcu(&old_pfh->hlist);
+ spin_unlock_irqrestore(&pf_handlers_writer, flags);
+}
+EXPORT_SYMBOL_GPL(unregister_page_fault_handler);
+#endif
+
+/* returns non-zero if do_page_fault() should return */
+static int handle_custom_pf(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
+{
+#ifdef CONFIG_PAGE_FAULT_HANDLERS
+ int ret = 0;
+ struct pf_handler *cur;
+ struct hlist_node *ncur;
+
+ if (hlist_empty(&pf_handlers))
+ return 0;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(cur, ncur, &pf_handlers, hlist) {
+ ret = cur->handler(regs, error_code, address);
+ if (ret)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+#else
+ return 0;
+#endif
+}
+
static inline int notify_page_fault(struct pt_regs *regs)
{
#ifdef CONFIG_KPROBES
@@ -606,6 +660,8 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
if (notify_page_fault(regs))
return;
+ if (handle_custom_pf(regs, error_code, address))
+ return;
/*
* We fault-in kernel-space virtual memory on-demand. The