linux-kernel - [PATCH 2/4] mm/kasan: move kasan= code to common place

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Message-ID: <20250805062333.121553-3-bhe@redhat.com>
Date: Tue,  5 Aug 2025 14:23:31 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-mm@...ck.org
Cc: ryabinin.a.a@...il.com,
	glider@...gle.com,
	andreyknvl@...il.com,
	dvyukov@...gle.com,
	vincenzo.frascino@....com,
	akpm@...ux-foundation.org,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH 2/4] mm/kasan: move kasan= code to common place

This allows generic and sw_tags to be set in kernel cmdline too.

When at it, rename 'kasan_arg' to 'kasan_arg_disabled' as a bool
variable. And expose 'kasan_flag_enabled' to kasan common place
too.

This is prepared for later adding kernel parameter kasan=on|off for
all kasan modes.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 include/linux/kasan-enabled.h |  4 +++-
 mm/kasan/common.c             | 27 +++++++++++++++++++++++++++
 mm/kasan/hw_tags.c            | 35 ++---------------------------------
 3 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
index 6f612d69ea0c..32f2d19f599f 100644
--- a/include/linux/kasan-enabled.h
+++ b/include/linux/kasan-enabled.h
@@ -4,10 +4,12 @@
 
 #include <linux/static_key.h>
 
-#ifdef CONFIG_KASAN_HW_TAGS
+extern bool kasan_arg_disabled;
 
 DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
 
+#ifdef CONFIG_KASAN_HW_TAGS
+
 static __always_inline bool kasan_enabled(void)
 {
 	return static_branch_likely(&kasan_flag_enabled);
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index ed4873e18c75..fe6937654203 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -32,6 +32,33 @@
 #include "kasan.h"
 #include "../slab.h"
 
+/*
+ * Whether KASAN is enabled at all.
+ * The value remains false until KASAN is initialized.
+ */
+DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
+EXPORT_SYMBOL(kasan_flag_enabled);
+
+bool kasan_arg_disabled;
+/* kasan=off/on */
+static int __init early_kasan_flag(char *arg)
+{
+	if (!arg)
+		return -EINVAL;
+
+	if (!strcmp(arg, "off"))
+		kasan_arg_disabled = true;
+	else if (!strcmp(arg, "on"))
+		kasan_arg_disabled = false;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+early_param("kasan", early_kasan_flag);
+
+
+
 struct slab *kasan_addr_to_slab(const void *addr)
 {
 	if (virt_addr_valid(addr))
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 9a6927394b54..377e9c285a74 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -22,12 +22,6 @@
 
 #include "kasan.h"
 
-enum kasan_arg {
-	KASAN_ARG_DEFAULT,
-	KASAN_ARG_OFF,
-	KASAN_ARG_ON,
-};
-
 enum kasan_arg_mode {
 	KASAN_ARG_MODE_DEFAULT,
 	KASAN_ARG_MODE_SYNC,
@@ -41,17 +35,9 @@ enum kasan_arg_vmalloc {
 	KASAN_ARG_VMALLOC_ON,
 };
 
-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.
@@ -85,23 +71,6 @@ unsigned int kasan_page_alloc_sample_order = PAGE_ALLOC_SAMPLE_ORDER_DEFAULT;
 
 DEFINE_PER_CPU(long, kasan_page_alloc_skip);
 
-/* kasan=off/on */
-static int __init early_kasan_flag(char *arg)
-{
-	if (!arg)
-		return -EINVAL;
-
-	if (!strcmp(arg, "off"))
-		kasan_arg = KASAN_ARG_OFF;
-	else if (!strcmp(arg, "on"))
-		kasan_arg = KASAN_ARG_ON;
-	else
-		return -EINVAL;
-
-	return 0;
-}
-early_param("kasan", early_kasan_flag);
-
 /* kasan.mode=sync/async/asymm */
 static int __init early_kasan_mode(char *arg)
 {
@@ -209,7 +178,7 @@ void kasan_init_hw_tags_cpu(void)
 	 * When this function is called, kasan_flag_enabled is not yet
 	 * set by kasan_init_hw_tags(). Thus, check kasan_arg instead.
 	 */
-	if (kasan_arg == KASAN_ARG_OFF)
+	if (kasan_arg_disabled)
 		return;
 
 	/*
@@ -227,7 +196,7 @@ void __init kasan_init_hw_tags(void)
 		return;
 
 	/* If KASAN is disabled via command line, don't initialize it. */
-	if (kasan_arg == KASAN_ARG_OFF)
+	if (kasan_arg_disabled)
 		return;
 
 	switch (kasan_arg_mode) {
-- 
2.41.0