kmemleak: Introduce a default off mode for kmemleak

Introduce a new DEBUG_KMEMLEAK_DEFAULT_OFF config parameter that allows
kmemleak to be disabled by default, but enabled on the command line
via: kmemleak=on. Although a reboot is required to turn it on, its still
useful to not require a re-compile.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>

2 files changed, 20 insertions, 1 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e722e9d62221..95ab402db9c0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -400,6 +400,13 @@ config DEBUG_KMEMLEAK_TEST
 
           If unsure, say N.
 
+config DEBUG_KMEMLEAK_DEFAULT_OFF
+        bool "Default kmemleak to off"
+        depends on DEBUG_KMEMLEAK
+        help
+          Say Y here to disable kmemleak by default. It can then be enabled
+          on the command line via kmemleak=on.
+
 config DEBUG_PREEMPT
         bool "Debug preemptible kernel"
         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index c2c9feb3097f..d33e990e0668 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -211,6 +211,9 @@ static signed long jiffies_scan_wait;
 static int kmemleak_stack_scan = 1;
 /* protects the memory scanning, parameters and debug/kmemleak file access */
 static DEFINE_MUTEX(scan_mutex);
+/* setting kmemleak=on, will set this var, skipping the disable */
+static int kmemleak_skip_disable;
+
 
 /*
  * Early object allocation/freeing logging. Kmemleak is initialized after the
@@ -1604,7 +1607,9 @@ static int kmemleak_boot_config(char *str)
                 return -EINVAL;
         if (strcmp(str, "off") == 0)
                 kmemleak_disable();
-        else if (strcmp(str, "on") != 0)
+        else if (strcmp(str, "on") == 0)
+                kmemleak_skip_disable = 1;
+        else
                 return -EINVAL;
         return 0;
 }
@@ -1618,6 +1623,13 @@ void __init kmemleak_init(void)
         int i;
         unsigned long flags;
 
+#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
+        if (!kmemleak_skip_disable) {
+                kmemleak_disable();
+                return;
+        }
+#endif
+
         jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
         jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);