linux-kernel - [PATCH 4/4] mm: kfence: Only load kfence

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Date:   Wed, 25 Aug 2021 17:21:16 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Russell King <linux@...linux.org.uk>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: [PATCH 4/4] mm: kfence: Only load kfence_test when kfence is enabled

Provide kfence_is_enabled() helper, only load kfence_test module
when kfence is enabled.

Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
---
 include/linux/kfence.h  | 2 ++
 mm/kfence/core.c        | 8 ++++++++
 mm/kfence/kfence_test.c | 2 ++
 3 files changed, 12 insertions(+)

diff --git a/include/linux/kfence.h b/include/linux/kfence.h
index 3fe6dd8a18c1..f08f24e8a726 100644
--- a/include/linux/kfence.h
+++ b/include/linux/kfence.h
@@ -22,6 +22,8 @@
 #define KFENCE_POOL_SIZE ((CONFIG_KFENCE_NUM_OBJECTS + 1) * 2 * PAGE_SIZE)
 extern char *__kfence_pool;
 
+bool kfence_is_enabled(void);
+
 #ifdef CONFIG_KFENCE_STATIC_KEYS
 #include <linux/static_key.h>
 DECLARE_STATIC_KEY_FALSE(kfence_allocation_key);
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 7a97db8bc8e7..f1aaa7ebdcad 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -51,6 +51,14 @@ static unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE
 #endif
 #define MODULE_PARAM_PREFIX "kfence."
 
+bool kfence_is_enabled(void)
+{
+	if (!kfence_sample_interval || !READ_ONCE(kfence_enabled))
+		return false;
+	return true;
+}
+EXPORT_SYMBOL_GPL(kfence_is_enabled);
+
 static int param_set_sample_interval(const char *val, const struct kernel_param *kp)
 {
 	unsigned long num;
diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
index eb6307c199ea..4087f9f1497e 100644
--- a/mm/kfence/kfence_test.c
+++ b/mm/kfence/kfence_test.c
@@ -847,6 +847,8 @@ static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
  */
 static int __init kfence_test_init(void)
 {
+	if (!kfence_is_enabled())
+		return 0;
 	/*
 	 * Because we want to be able to build the test as a module, we need to
 	 * iterate through all known tracepoints, since the static registration
-- 
2.26.2