linux-kernel - [PATCH 05/18] locking/lockdep: Improve noinstr vs errors

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Message-ID: <20210621120120.784404944@infradead.org>
Date:   Mon, 21 Jun 2021 13:12:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     jpoimboe@...hat.com, tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        joro@...tes.org, boris.ostrovsky@...cle.com, jgross@...e.com,
        x86@...nel.org, mbenes@...e.com
Subject: [PATCH 05/18] locking/lockdep: Improve noinstr vs errors

Better handle the failure paths.

vmlinux.o: warning: objtool: debug_locks_off()+0x23: call to console_verbose() leaves .noinstr.text section
vmlinux.o: warning: objtool: debug_locks_off()+0x19: call to __kasan_check_write() leaves .noinstr.text section

debug_locks_off+0x19/0x40:
instrument_atomic_write at include/linux/instrumented.h:86
(inlined by) __debug_locks_off at include/linux/debug_locks.h:17
(inlined by) debug_locks_off at lib/debug_locks.c:41

Fixes: 6eebad1ad303 ("lockdep: __always_inline more for noinstr")
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h
index 2915f56ad421..edb5c186b0b7 100644
--- a/include/linux/debug_locks.h
+++ b/include/linux/debug_locks.h
@@ -27,8 +27,10 @@ extern int debug_locks_off(void);
 	int __ret = 0;							\
 									\
 	if (!oops_in_progress && unlikely(c)) {				\
+		instrumentation_begin();				\
 		if (debug_locks_off() && !debug_locks_silent)		\
 			WARN(1, "DEBUG_LOCKS_WARN_ON(%s)", #c);		\
+		instrumentation_end();					\
 		__ret = 1;						\
 	}								\
 	__ret;								\
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index cb8af6a3e154..6fc60d363d26 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -843,7 +843,7 @@ static int count_matching_names(struct lock_class *new_class)
 }
 
 /* used from NMI context -- must be lockless */
-static __always_inline struct lock_class *
+static noinstr struct lock_class *
 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 {
 	struct lockdep_subclass_key *key;
@@ -851,12 +851,14 @@ look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 	struct lock_class *class;
 
 	if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
+		instrumentation_begin();
 		debug_locks_off();
 		printk(KERN_ERR
 			"BUG: looking up invalid subclass: %u\n", subclass);
 		printk(KERN_ERR
 			"turning off the locking correctness validator.\n");
 		dump_stack();
+		instrumentation_end();
 		return NULL;
 	}
 
diff --git a/lib/debug_locks.c b/lib/debug_locks.c
index 06d3135bd184..a75ee30b77cb 100644
--- a/lib/debug_locks.c
+++ b/lib/debug_locks.c
@@ -36,7 +36,7 @@ EXPORT_SYMBOL_GPL(debug_locks_silent);
 /*
  * Generic 'turn off all lock debugging' function:
  */
-noinstr int debug_locks_off(void)
+int debug_locks_off(void)
 {
 	if (debug_locks && __debug_locks_off()) {
 		if (!debug_locks_silent) {