x86: explicit call to mmiotrace in do_page_fault()

The custom page fault handler list is replaced with a single function
pointer. All related functions and variables are renamed for
mmiotrace.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: pq@iki.fi
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 34 insertions, 32 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 343f5c1aacc8..e9a086a1a9ff 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -49,53 +49,55 @@
 #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);
+#ifdef CONFIG_MMIOTRACE_HOOKS
+static pf_handler_func mmiotrace_pf_handler; /* protected by RCU */
+static DEFINE_SPINLOCK(mmiotrace_handler_lock);
 
-void register_page_fault_handler(struct pf_handler *new_pfh)
+int mmiotrace_register_pf(pf_handler_func new_pfh)
 {
+        int ret = 0;
         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);
+        spin_lock_irqsave(&mmiotrace_handler_lock, flags);
+        if (mmiotrace_pf_handler)
+                ret = -EBUSY;
+        else
+                mmiotrace_pf_handler = new_pfh;
+        spin_unlock_irqrestore(&mmiotrace_handler_lock, flags);
+        return ret;
 }
-EXPORT_SYMBOL_GPL(register_page_fault_handler);
+EXPORT_SYMBOL_GPL(mmiotrace_register_pf);
 
 /**
- * unregister_page_fault_handler:
+ * mmiotrace_unregister_pf:
  * 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().
+ * This function does not guarantee it. The handler function pointer 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)
+int mmiotrace_unregister_pf(pf_handler_func old_pfh)
 {
+        int ret = 0;
         unsigned long flags;
-        spin_lock_irqsave(&pf_handlers_writer, flags);
-        hlist_del_rcu(&old_pfh->hlist);
-        spin_unlock_irqrestore(&pf_handlers_writer, flags);
+        spin_lock_irqsave(&mmiotrace_handler_lock, flags);
+        if (mmiotrace_pf_handler != old_pfh)
+                ret = -EPERM;
+        else
+                mmiotrace_pf_handler = NULL;
+        spin_unlock_irqrestore(&mmiotrace_handler_lock, flags);
+        return ret;
 }
-EXPORT_SYMBOL_GPL(unregister_page_fault_handler);
-#endif
+EXPORT_SYMBOL_GPL(mmiotrace_unregister_pf);
+#endif /* CONFIG_MMIOTRACE_HOOKS */
 
 /* 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)
+static inline int call_mmiotrace(struct pt_regs *regs,
+                                        unsigned long error_code,
+                                        unsigned long address)
 {
-#ifdef CONFIG_PAGE_FAULT_HANDLERS
+#ifdef CONFIG_MMIOTRACE_HOOKS
         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;
-        }
+        if (mmiotrace_pf_handler)
+                ret = mmiotrace_pf_handler(regs, error_code, address);
         rcu_read_unlock();
         return ret;
 #else
@@ -655,7 +657,7 @@ 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))
+        if (call_mmiotrace(regs, error_code, address))
                 return;
 
         /*