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Message-ID: <20250805062333.121553-4-bhe@redhat.com>
Date: Tue,  5 Aug 2025 14:23:32 +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 3/4] mm/kasan: don't initialize kasan if it's disabled

This is mainly done in all architectures which support kasan, and also
need be done in sw_tags init funciton kasan_init_sw_tags().

And also add code to enable kasan_flag_enabled, this is for later usage.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/arm/mm/kasan_init.c               | 6 ++++++
 arch/arm64/mm/kasan_init.c             | 7 +++++++
 arch/loongarch/mm/kasan_init.c         | 5 +++++
 arch/powerpc/mm/kasan/init_32.c        | 8 +++++++-
 arch/powerpc/mm/kasan/init_book3e_64.c | 6 ++++++
 arch/powerpc/mm/kasan/init_book3s_64.c | 6 ++++++
 arch/riscv/mm/kasan_init.c             | 6 ++++++
 arch/um/kernel/mem.c                   | 6 ++++++
 arch/x86/mm/kasan_init_64.c            | 6 ++++++
 arch/xtensa/mm/kasan_init.c            | 6 ++++++
 mm/kasan/sw_tags.c                     | 6 ++++++
 11 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
index 111d4f703136..c764e1b9c9c5 100644
--- a/arch/arm/mm/kasan_init.c
+++ b/arch/arm/mm/kasan_init.c
@@ -212,6 +212,8 @@ void __init kasan_init(void)
 	phys_addr_t pa_start, pa_end;
 	u64 i;
 
+	if (kasan_arg_disabled)
+		return;
 	/*
 	 * We are going to perform proper setup of shadow memory.
 	 *
@@ -300,6 +302,10 @@ void __init kasan_init(void)
 	local_flush_tlb_all();
 
 	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
+
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	pr_info("Kernel address sanitizer initialized\n");
 	init_task.kasan_depth = 0;
 }
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index d541ce45daeb..0e4ffe3f5d0e 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -384,6 +384,9 @@ void __init kasan_populate_early_vm_area_shadow(void *start, unsigned long size)
 {
 	unsigned long shadow_start, shadow_end;
 
+	if (!kasan_enabled())
+		return;
+
 	if (!is_vmalloc_or_module_addr(start))
 		return;
 
@@ -397,6 +400,9 @@ void __init kasan_populate_early_vm_area_shadow(void *start, unsigned long size)
 
 void __init kasan_init(void)
 {
+	if (kasan_arg_disabled)
+		return;
+
 	kasan_init_shadow();
 	kasan_init_depth();
 #if defined(CONFIG_KASAN_GENERIC)
@@ -405,6 +411,7 @@ void __init kasan_init(void)
 	 * Software and Hardware Tag-Based modes still require
 	 * kasan_init_sw_tags() and kasan_init_hw_tags() correspondingly.
 	 */
+	static_branch_enable(&kasan_flag_enabled);
 	pr_info("KernelAddressSanitizer initialized (generic)\n");
 #endif
 }
diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
index d2681272d8f0..0c32eee6910f 100644
--- a/arch/loongarch/mm/kasan_init.c
+++ b/arch/loongarch/mm/kasan_init.c
@@ -267,6 +267,8 @@ void __init kasan_init(void)
 	u64 i;
 	phys_addr_t pa_start, pa_end;
 
+	if (kasan_arg_disabled)
+		return;
 	/*
 	 * If PGDIR_SIZE is too large for cpu_vabits, KASAN_SHADOW_END will
 	 * overflow UINTPTR_MAX and then looks like a user space address.
@@ -327,6 +329,9 @@ void __init kasan_init(void)
 	csr_write64(__pa_symbol(swapper_pg_dir), LOONGARCH_CSR_PGDH);
 	local_flush_tlb_all();
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KernelAddressSanitizer initialized.\n");
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c
index 03666d790a53..b0c465f3fbf5 100644
--- a/arch/powerpc/mm/kasan/init_32.c
+++ b/arch/powerpc/mm/kasan/init_32.c
@@ -141,6 +141,9 @@ void __init kasan_init(void)
 	u64 i;
 	int ret;
 
+	if (kasan_arg_disabled)
+		return;
+
 	for_each_mem_range(i, &base, &end) {
 		phys_addr_t top = min(end, total_lowmem);
 
@@ -163,6 +166,9 @@ void __init kasan_init(void)
 
 	clear_page(kasan_early_shadow_page);
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KASAN init done\n");
@@ -170,7 +176,7 @@ void __init kasan_init(void)
 
 void __init kasan_late_init(void)
 {
-	if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
+	if (IS_ENABLED(CONFIG_KASAN_VMALLOC) && kasan_enabled())
 		kasan_unmap_early_shadow_vmalloc();
 }
 
diff --git a/arch/powerpc/mm/kasan/init_book3e_64.c b/arch/powerpc/mm/kasan/init_book3e_64.c
index 60c78aac0f63..1e1c10467a2b 100644
--- a/arch/powerpc/mm/kasan/init_book3e_64.c
+++ b/arch/powerpc/mm/kasan/init_book3e_64.c
@@ -111,6 +111,9 @@ void __init kasan_init(void)
 	u64 i;
 	pte_t zero_pte = pfn_pte(virt_to_pfn(kasan_early_shadow_page), PAGE_KERNEL_RO);
 
+	if (kasan_arg_disabled)
+		return;
+
 	for_each_mem_range(i, &start, &end)
 		kasan_init_phys_region(phys_to_virt(start), phys_to_virt(end));
 
@@ -125,6 +128,9 @@ void __init kasan_init(void)
 
 	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	/* Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KASAN init done\n");
diff --git a/arch/powerpc/mm/kasan/init_book3s_64.c b/arch/powerpc/mm/kasan/init_book3s_64.c
index 7d959544c077..9c5cf2354c8b 100644
--- a/arch/powerpc/mm/kasan/init_book3s_64.c
+++ b/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -56,6 +56,9 @@ void __init kasan_init(void)
 	u64 i;
 	pte_t zero_pte = pfn_pte(virt_to_pfn(kasan_early_shadow_page), PAGE_KERNEL);
 
+	if (kasan_arg_disabled)
+		return;
+
 	if (!early_radix_enabled()) {
 		pr_warn("KASAN not enabled as it requires radix!");
 		return;
@@ -94,6 +97,9 @@ void __init kasan_init(void)
 
 	static_branch_inc(&powerpc_kasan_enabled_key);
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	/* Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KASAN init done\n");
diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index 41c635d6aca4..ac3ac227c765 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -485,6 +485,9 @@ void __init kasan_init(void)
 	phys_addr_t p_start, p_end;
 	u64 i;
 
+	if (kasan_arg_disabled)
+		return;
+
 	create_tmp_mapping();
 	csr_write(CSR_SATP, PFN_DOWN(__pa(tmp_pg_dir)) | satp_mode);
 
@@ -531,6 +534,9 @@ void __init kasan_init(void)
 	memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 	init_task.kasan_depth = 0;
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	csr_write(CSR_SATP, PFN_DOWN(__pa(swapper_pg_dir)) | satp_mode);
 	local_flush_tlb_all();
 }
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 76bec7de81b5..6961841daa12 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -26,6 +26,9 @@
 int kasan_um_is_ready;
 void kasan_init(void)
 {
+
+	if (kasan_arg_disabled)
+		return;
 	/*
 	 * kasan_map_memory will map all of the required address space and
 	 * the host machine will allocate physical memory as necessary.
@@ -33,6 +36,9 @@ void kasan_init(void)
 	kasan_map_memory((void *)KASAN_SHADOW_START, KASAN_SHADOW_SIZE);
 	init_task.kasan_depth = 0;
 	kasan_um_is_ready = true;
+
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
 }
 
 static void (*kasan_init_ptr)(void)
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 0539efd0d216..d7e8c59da435 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -343,6 +343,9 @@ void __init kasan_init(void)
 	unsigned long shadow_cea_begin, shadow_cea_per_cpu_begin, shadow_cea_end;
 	int i;
 
+	if (kasan_arg_disabled)
+		return;
+
 	memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt));
 
 	/*
@@ -450,6 +453,9 @@ void __init kasan_init(void)
 	/* Flush TLBs again to be sure that write protection applied. */
 	__flush_tlb_all();
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	init_task.kasan_depth = 0;
 	pr_info("KernelAddressSanitizer initialized\n");
 }
diff --git a/arch/xtensa/mm/kasan_init.c b/arch/xtensa/mm/kasan_init.c
index f39c4d83173a..4a7b77f47225 100644
--- a/arch/xtensa/mm/kasan_init.c
+++ b/arch/xtensa/mm/kasan_init.c
@@ -70,6 +70,9 @@ void __init kasan_init(void)
 {
 	int i;
 
+	if (kasan_arg_disabled)
+		return;
+
 	BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_START -
 		     (KASAN_START_VADDR >> KASAN_SHADOW_SCALE_SHIFT));
 	BUILD_BUG_ON(VMALLOC_START < KASAN_START_VADDR);
@@ -92,6 +95,9 @@ void __init kasan_init(void)
 	local_flush_tlb_all();
 	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	/* At this point kasan is fully initialized. Enable error messages. */
 	current->kasan_depth = 0;
 	pr_info("KernelAddressSanitizer initialized\n");
diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c
index 01f19bc4a326..dd963ba4d143 100644
--- a/mm/kasan/sw_tags.c
+++ b/mm/kasan/sw_tags.c
@@ -40,11 +40,17 @@ void __init kasan_init_sw_tags(void)
 {
 	int cpu;
 
+	if (kasan_arg_disabled)
+		return;
+
 	for_each_possible_cpu(cpu)
 		per_cpu(prng_state, cpu) = (u32)get_cycles();
 
 	kasan_init_tags();
 
+	/* KASAN is now initialized, enable it. */
+	static_branch_enable(&kasan_flag_enabled);
+
 	pr_info("KernelAddressSanitizer initialized (sw-tags, stacktrace=%s)\n",
 		str_on_off(kasan_stack_collection_enabled()));
 }
-- 
2.41.0


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