linux-kernel - [PATCH v4 02/12] mm/kasan: move kasan= code to common place

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Message-ID: <20251128033320.1349620-3-bhe@redhat.com>
Date: Fri, 28 Nov 2025 11:33:10 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-mm@...ck.org
Cc: ryabinin.a.a@...il.com,
	andreyknvl@...il.com,
	glider@...gle.com,
	dvyukov@...gle.com,
	vincenzo.frascino@....com,
	akpm@...ux-foundation.org,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	elver@...gle.com,
	sj@...nel.org,
	lorenzo.stoakes@...cle.com,
	snovitoll@...il.com,
	christophe.leroy@...roup.eu,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH v4 02/12] 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 three kasan modes.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 include/linux/kasan-enabled.h |  4 +++-
 mm/kasan/common.c             | 20 ++++++++++++++++++--
 mm/kasan/hw_tags.c            | 28 ++--------------------------
 3 files changed, 23 insertions(+), 29 deletions(-)

diff --git a/include/linux/kasan-enabled.h b/include/linux/kasan-enabled.h
index 9eca967d8526..b05ec6329fbe 100644
--- a/include/linux/kasan-enabled.h
+++ b/include/linux/kasan-enabled.h
@@ -4,13 +4,15 @@
 
 #include <linux/static_key.h>
 
-#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
+extern bool kasan_arg_disabled;
+
 /*
  * Global runtime flag for KASAN modes that need runtime control.
  * Used by ARCH_DEFER_KASAN architectures and HW_TAGS mode.
  */
 DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled);
 
+#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
 /*
  * Runtime control for shadow memory initialization or HW_TAGS mode.
  * Uses static key for architectures that need deferred KASAN or HW_TAGS.
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 1d27f1bd260b..ac14956986ee 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -32,14 +32,30 @@
 #include "kasan.h"
 #include "../slab.h"
 
-#if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
 /*
  * Definition of the unified static key declared in kasan-enabled.h.
  * This provides consistent runtime enable/disable across KASAN modes.
  */
 DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
 EXPORT_SYMBOL_GPL(kasan_flag_enabled);
-#endif
+
+bool kasan_arg_disabled __ro_after_init;
+/* 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)
 {
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 1c373cc4b3fa..709c91abc1b1 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,
@@ -41,7 +35,6 @@ 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;
 
@@ -81,23 +74,6 @@ 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)
 {
@@ -222,7 +198,7 @@ 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;
 
 	/*
@@ -240,7 +216,7 @@ 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