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Subject[PATCH] introduce a default off mode for kmemleak
Hi,

Kmemleak can be very useful in figuring out where a kernel leak is
suspected, but I've run into issues it which makes it hard to enable
by default - reports false positives, oom kills on low memory systems (512 MB).
Although these can be addressed, there is still the memory footprint,
and runtime overhead, so I think it might make sense to create mode
where it is disabled by default, but can still be enabled on the command
line via: kmemleak=on.

thanks,

-Jason

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>
---
lib/Kconfig.debug | 7 +++++++
mm/kmemleak.c | 26 +++++++++++++++++++++++++-
2 files changed, 32 insertions(+), 1 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e722e9d..95ab402 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 2c0d032..1006267 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -211,6 +211,11 @@ 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);
+#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
+/* setting kmemleak=on, will set this var, skipping the disable */
+static int kmemleak_skip_disable;
+#endif
+

/*
* Early object allocation/freeing logging. Kmemleak is initialized after the
@@ -1600,10 +1605,22 @@ static int kmemleak_boot_config(char *str)
{
if (!str)
return -EINVAL;
+
if (strcmp(str, "off") == 0)
+#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
+ return -EINVAL;
+#else
kmemleak_disable();
- else if (strcmp(str, "on") != 0)
+#endif
+ else if (strcmp(str, "on") == 0)
+#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
+ kmemleak_skip_disable = 1;
+#else
+ return -EINVAL;
+#endif
+ else
return -EINVAL;
+
return 0;
}
early_param("kmemleak", kmemleak_boot_config);
@@ -1616,6 +1633,13 @@ 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);

--
1.7.1


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