4 files changed, 8 insertions, 44 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 17670573dda8..ba2b0c87e65b 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1281,6 +1281,7 @@ config RCU_TORTURE_TEST_SLOW_INIT_DELAY
         int "How much to slow down RCU grace-period initialization"
         range 0 5
         default 3
+        depends on RCU_TORTURE_TEST_SLOW_INIT
         help
           This option specifies the number of jiffies to wait between
           each rcu_node structure initialization.
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 4fecaedc80a2..777eda7d1ab4 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -10,8 +10,11 @@ config KASAN
         help
           Enables kernel address sanitizer - runtime memory debugger,
           designed to find out-of-bounds accesses and use-after-free bugs.
-          This is strictly debugging feature. It consumes about 1/8
-          of available memory and brings about ~x3 performance slowdown.
+          This is strictly a debugging feature and it requires a gcc version
+          of 4.9.2 or later. Detection of out of bounds accesses to stack or
+          global variables requires gcc 5.0 or later.
+          This feature consumes about 1/8 of available memory and brings about
+          ~x3 performance slowdown.
           For better error detection enable CONFIG_STACKTRACE,
           and add slub_debug=U to boot cmdline.
 
@@ -40,6 +43,7 @@ config KASAN_INLINE
           memory accesses. This is faster than outline (in some workloads
           it gives about x2 boost over outline instrumentation), but
           make kernel's .text size much bigger.
+          This requires a gcc version of 5.0 or later.
 
 endchoice
 
diff --git a/lib/find_last_bit.c b/lib/find_last_bit.c
deleted file mode 100644
index 3e3be40c6a6e..000000000000
--- a/lib/find_last_bit.c
+++ /dev/null
@@ -1,41 +0,0 @@
-/* find_last_bit.c: fallback find next bit implementation
- *
- * Copyright (C) 2008 IBM Corporation
- * Written by Rusty Russell <rusty@rustcorp.com.au>
- * (Inspired by David Howell's find_next_bit implementation)
- *
- * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
- * size and improve performance, 2015.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
-
-#include <linux/bitops.h>
-#include <linux/bitmap.h>
-#include <linux/export.h>
-#include <linux/kernel.h>
-
-#ifndef find_last_bit
-
-unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
-{
-        if (size) {
-                unsigned long val = BITMAP_LAST_WORD_MASK(size);
-                unsigned long idx = (size-1) / BITS_PER_LONG;
-
-                do {
-                        val &= addr[idx];
-                        if (val)
-                                return idx * BITS_PER_LONG + __fls(val);
-
-                        val = ~0ul;
-                } while (idx--);
-        }
-        return size;
-}
-EXPORT_SYMBOL(find_last_bit);
-
-#endif
diff --git a/lib/string.c b/lib/string.c
index a5792019193c..bb3d4b6993c4 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -607,7 +607,7 @@ EXPORT_SYMBOL(memset);
 void memzero_explicit(void *s, size_t count)
 {
         memset(s, 0, count);
-        barrier();
+        barrier_data(s);
 }
 EXPORT_SYMBOL(memzero_explicit);