arm64: Return early when break handler is found on linked-list

The search for breakpoint handlers iterate through the entire
linked list. Given that all registered hook has a valid fn field, and no
registered hooks share the same mask and imm. This commit optimize the
efficiency slightly by returning early as a matching handler is found.

Signed-off-by: Liao Chang <[email protected]>
Acked-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

Author: Liao Chang

arch/arm64/kernel/debug-monitors.c

@@ -303,7 +303,6 @@ static int call_break_hook(struct pt_regs *regs, unsigned long esr)
 {
 	struct break_hook *hook;
 	struct list_head *list;
-	int (*fn)(struct pt_regs *regs, unsigned long esr) = NULL;
 
 	list = user_mode(regs) ? &user_break_hook : &kernel_break_hook;
 
@@ -313,10 +312,10 @@ static int call_break_hook(struct pt_regs *regs, unsigned long esr)
 	 */
 	list_for_each_entry_rcu(hook, list, node) {
 		if ((esr_brk_comment(esr) & ~hook->mask) == hook->imm)
-			fn = hook->fn;
+			return hook->fn(regs, esr);
 	}
 
-	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
+	return DBG_HOOK_ERROR;
 }
 NOKPROBE_SYMBOL(call_break_hook);