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Message-Id: <20250626153147.145312-2-snovitoll@gmail.com>
Date: Thu, 26 Jun 2025 20:31:37 +0500
From: Sabyrzhan Tasbolatov <snovitoll@...il.com>
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Subject: [PATCH v2 01/11] kasan: unify static kasan_flag_enabled across modes
Historically, the runtime static key kasan_flag_enabled existed only for
CONFIG_KASAN_HW_TAGS mode. Generic and SW_TAGS modes either relied on
architecture-specific kasan_arch_is_ready() implementations or evaluated
KASAN checks unconditionally, leading to code duplication.
This patch unifies the approach by:
1. Moving kasan_flag_enabled declaration under CONFIG_KASAN (all modes)
instead of only CONFIG_KASAN_HW_TAGS
2. Moving the static key definition to common.c for shared usage
3. Adding kasan_init_generic() function that enables the static key and
handles initialization for Generic mode
4. Updating SW_TAGS mode to enable the unified static key
5. Removing the duplicate static key definition from HW_TAGS
After this change, all KASAN modes use the same underlying static key
infrastructure. The kasan_enabled() function now provides consistent
runtime enable behavior across Generic, SW_TAGS, and HW_TAGS modes.
This maintains a backward compatibility - existing architecture code
continues to work unchanged, but now benefits from the unified runtime
control mechanism. The architecture-specific kasan_arch_is_ready()
implementations can be gradually replaced with calls to the new
kasan_init_generic() function.
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218315
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@...il.com>
---
include/linux/kasan-enabled.h | 10 ++++++++--
include/linux/kasan.h | 6 ++++++
mm/kasan/common.c | 7 +++++++
mm/kasan/generic.c | 11 +++++++++++
mm/kasan/hw_tags.c | 7 -------
mm/kasan/sw_tags.c | 2 ++
6 files changed, 34 insertions(+), 9 deletions(-)
diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
index 6f612d69ea0..2b1351c30c6 100644
--- a/include/linux/kasan-enabled.h
+++ b/include/linux/kasan-enabled.h
@@ -4,9 +4,15 @@
#include <linux/static_key.h>
-#ifdef CONFIG_KASAN_HW_TAGS
-
+#ifdef CONFIG_KASAN
+/*
+ * Global runtime flag. Starts ‘false’; switched to ‘true’ by
+ * the appropriate kasan_init_*() once KASAN is fully initialized.
+ */
DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
+#endif
+
+#ifdef CONFIG_KASAN_HW_TAGS
static __always_inline bool kasan_enabled(void)
{
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 890011071f2..51a8293d1af 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -543,6 +543,12 @@ void kasan_report_async(void);
#endif /* CONFIG_KASAN_HW_TAGS */
+#ifdef CONFIG_KASAN_GENERIC
+void __init kasan_init_generic(void);
+#else
+static inline void kasan_init_generic(void) { }
+#endif
+
#ifdef CONFIG_KASAN_SW_TAGS
void __init kasan_init_sw_tags(void);
#else
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index ed4873e18c7..525194da25f 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -32,6 +32,13 @@
#include "kasan.h"
#include "../slab.h"
+/*
+ * Definition of the unified static key declared in kasan-enabled.h.
+ * This provides consistent runtime enable/disable across all KASAN modes.
+ */
+DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
+EXPORT_SYMBOL(kasan_flag_enabled);
+
struct slab *kasan_addr_to_slab(const void *addr)
{
if (virt_addr_valid(addr))
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index d54e89f8c3e..32c432df24a 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -36,6 +36,17 @@
#include "kasan.h"
#include "../slab.h"
+/*
+ * Initialize Generic KASAN and enable runtime checks.
+ * This should be called from arch kasan_init() once shadow memory is ready.
+ */
+void __init kasan_init_generic(void)
+{
+ static_branch_enable(&kasan_flag_enabled);
+
+ pr_info("KernelAddressSanitizer initialized (generic)\n");
+}
+
/*
* All functions below always inlined so compiler could
* perform better optimizations in each of __asan_loadX/__assn_storeX
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 9a6927394b5..8e819fc4a26 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -45,13 +45,6 @@ static enum kasan_arg kasan_arg __ro_after_init;
static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
static enum kasan_arg_vmalloc kasan_arg_vmalloc __initdata;
-/*
- * Whether KASAN is enabled at all.
- * The value remains false until KASAN is initialized by kasan_init_hw_tags().
- */
-DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
-EXPORT_SYMBOL(kasan_flag_enabled);
-
/*
* Whether the selected mode is synchronous, asynchronous, or asymmetric.
* Defaults to KASAN_MODE_SYNC.
diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
index b9382b5b6a3..525bc91e2fc 100644
--- a/mm/kasan/sw_tags.c
+++ b/mm/kasan/sw_tags.c
@@ -45,6 +45,8 @@ void __init kasan_init_sw_tags(void)
kasan_init_tags();
+ static_branch_enable(&kasan_flag_enabled);
+
pr_info("KernelAddressSanitizer initialized (sw-tags, stacktrace=%s)\n",
str_on_off(kasan_stack_collection_enabled()));
}
--
2.34.1
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