[PATCH] mm: kfence: export kfence_enabled as global variables

[Zhenhua Huang]

Export the variable to ease the judgement of whether kfence enabled
at runtime. It should be more precise than through kernel config
"CONFIG_KFENCE".

For example We can disable kfence at runtime using bootargs
"kfence.sample_interval=0" but CONFIG_KFENCE enabled.
It was false positive.

Signed-off-by: Zhenhua Huang <quic_zhenhuah at quicinc.com>
---
 arch/arm64/mm/pageattr.c | 3 ++-
 include/linux/kfence.h   | 2 ++
 mm/kfence/core.c         | 2 +-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 79dd201..208d780 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -7,6 +7,7 @@
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/vmalloc.h>
+#include <linux/kfence.h>
 
 #include <asm/cacheflush.h>
 #include <asm/set_memory.h>
@@ -27,7 +28,7 @@ bool can_set_direct_map(void)
 	 * protect/unprotect single pages.
 	 */
 	return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() ||
-		IS_ENABLED(CONFIG_KFENCE);
+		kfence_enabled;
 }
 
 static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
diff --git a/include/linux/kfence.h b/include/linux/kfence.h
index 726857a..9fac824 100644
--- a/include/linux/kfence.h
+++ b/include/linux/kfence.h
@@ -26,6 +26,7 @@ extern unsigned long kfence_sample_interval;
  */
 #define KFENCE_POOL_SIZE ((CONFIG_KFENCE_NUM_OBJECTS + 1) * 2 * PAGE_SIZE)
 extern char *__kfence_pool;
+extern bool kfence_enabled;
 
 DECLARE_STATIC_KEY_FALSE(kfence_allocation_key);
 extern atomic_t kfence_allocation_gate;
@@ -222,6 +223,7 @@ bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *sla
 
 #else /* CONFIG_KFENCE */
 
+#define kfence_enabled 0
 static inline bool is_kfence_address(const void *addr) { return false; }
 static inline void kfence_alloc_pool(void) { }
 static inline void kfence_init(void) { }
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 5349c37..e5bf93d 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -48,7 +48,7 @@
 
 /* === Data ================================================================= */
 
-static bool kfence_enabled __read_mostly;
+bool kfence_enabled __read_mostly;
 static bool disabled_by_warn __read_mostly;
 
 unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE_INTERVAL;
-- 
2.7.4