x86/int3: Inline bsearch()

Avoid calling out to bsearch() by inlining it, for normal kernel configs
this was the last external call and poke_int3_handler() is now fully self
sufficient -- no calls to external code.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135313.731774429@linutronix.de

arch/x86/kernel/alternative.c

@@ -1033,7 +1033,7 @@ static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
 	return _stext + tp->rel_addr;
 }
 
-static int noinstr patch_cmp(const void *key, const void *elt)
+static __always_inline int patch_cmp(const void *key, const void *elt)
 {
 	struct text_poke_loc *tp = (struct text_poke_loc *) elt;
 
@@ -1077,9 +1077,9 @@ int noinstr poke_int3_handler(struct pt_regs *regs)
 	 * Skip the binary search if there is a single member in the vector.
 	 */
 	if (unlikely(desc->nr_entries > 1)) {
-		tp = bsearch(ip, desc->vec, desc->nr_entries,
-			     sizeof(struct text_poke_loc),
-			     patch_cmp);
+		tp = __inline_bsearch(ip, desc->vec, desc->nr_entries,
+				      sizeof(struct text_poke_loc),
+				      patch_cmp);
 		if (!tp)
 			goto out_put;
 	} else {

arch/x86/kernel/traps.c

@@ -570,6 +570,11 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
 
 dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
 {
+	/*
+	 * poke_int3_handler() is completely self contained code; it does (and
+	 * must) *NOT* call out to anything, lest it hits upon yet another
+	 * INT3.
+	 */
 	if (poke_int3_handler(regs))
 		return;