LoongArch: Add KASAN (Kernel Address Sanitizer) support

1/8 of kernel addresses reserved for shadow memory. But for LoongArch,
There are a lot of holes between different segments and valid address
space (256T available) is insufficient to map all these segments to kasan
shadow memory with the common formula provided by kasan core, saying
(addr >> KASAN_SHADOW_SCALE_SHIFT) + KASAN_SHADOW_OFFSET

So LoongArch has a arch-specific mapping formula, different segments are
mapped individually, and only limited space lengths of these specific
segments are mapped to shadow.

At early boot stage the whole shadow region populated with just one
physical page (kasan_early_shadow_page). Later, this page is reused as
readonly zero shadow for some memory that kasan currently don't track.
After mapping the physical memory, pages for shadow memory are allocated
and mapped.

Functions like memset()/memcpy()/memmove() do a lot of memory accesses.
If bad pointer passed to one of these function it is important to be
caught. Compiler's instrumentation cannot do this since these functions
are written in assembly.

KASan replaces memory functions with manually instrumented variants.
Original functions declared as weak symbols so strong definitions in
mm/kasan/kasan.c could replace them. Original functions have aliases
with '__' prefix in names, so we could call non-instrumented variant
if needed.
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Documentation/dev-tools/kasan.rst

@@ -41,8 +41,8 @@ Support
 Architectures
 ~~~~~~~~~~~~~
 
-Generic KASAN is supported on x86_64, arm, arm64, powerpc, riscv, s390, and
-xtensa, and the tag-based KASAN modes are supported only on arm64.
+Generic KASAN is supported on x86_64, arm, arm64, powerpc, riscv, s390, xtensa,
+and loongarch, and the tag-based KASAN modes are supported only on arm64.
 
 Compilers
 ~~~~~~~~~

Documentation/features/debug/KASAN/arch-support.txt

@@ -13,7 +13,7 @@
     |        csky: | TODO |
     |     hexagon: | TODO |
     |        ia64: | TODO |
-    |   loongarch: | TODO |
+    |   loongarch: |  ok  |
     |        m68k: | TODO |
     |  microblaze: | TODO |
     |        mips: | TODO |

Documentation/translations/zh_CN/dev-tools/kasan.rst

@@ -42,7 +42,7 @@ KASAN有三种模式:
 体系架构
 ~~~~~~~~
 
-在x86_64、arm、arm64、powerpc、riscv、s390和xtensa上支持通用KASAN，
+在x86_64、arm、arm64、powerpc、riscv、s390、xtensa和loongarch上支持通用KASAN，
 而基于标签的KASAN模式只在arm64上支持。
 
 编译器

arch/loongarch/Kconfig

@@ -8,6 +8,7 @@ config LOONGARCH
 	select ACPI_PPTT if ACPI
 	select ACPI_SYSTEM_POWER_STATES_SUPPORT	if ACPI
 	select ARCH_BINFMT_ELF_STATE
+	select ARCH_DISABLE_KASAN_INLINE
 	select ARCH_ENABLE_MEMORY_HOTPLUG
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
 	select ARCH_HAS_ACPI_TABLE_UPGRADE	if ACPI
@@ -92,6 +93,7 @@ config LOONGARCH
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
+	select HAVE_ARCH_KASAN
 	select HAVE_ARCH_KFENCE
 	select HAVE_ARCH_KGDB if PERF_EVENTS
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
@@ -669,6 +671,11 @@ config ARCH_MMAP_RND_BITS_MAX
 config ARCH_SUPPORTS_UPROBES
 	def_bool y
 
+config KASAN_SHADOW_OFFSET
+	hex
+	default 0x0
+	depends on KASAN
+
 menu "Power management options"
 
 config ARCH_SUSPEND_POSSIBLE

arch/loongarch/Makefile

@@ -84,7 +84,10 @@ LDFLAGS_vmlinux			+= -static -pie --no-dynamic-linker -z notext
 endif
 
 cflags-y += $(call cc-option, -mno-check-zero-division)
+
+ifndef CONFIG_KASAN
 cflags-y += -fno-builtin-memcpy -fno-builtin-memmove -fno-builtin-memset
+endif
 
 load-y		= 0x9000000000200000
 bootvars-y	= VMLINUX_LOAD_ADDRESS=$(load-y)

arch/loongarch/include/asm/kasan.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_KASAN_H
+#define __ASM_KASAN_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/linkage.h>
+#include <linux/mmzone.h>
+#include <asm/addrspace.h>
+#include <asm/io.h>
+#include <asm/pgtable.h>
+
+#define __HAVE_ARCH_SHADOW_MAP
+
+#define KASAN_SHADOW_SCALE_SHIFT 3
+#define KASAN_SHADOW_OFFSET	_AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
+
+#define XRANGE_SHIFT (48)
+
+/* Valid address length */
+#define XRANGE_SHADOW_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
+/* Used for taking out the valid address */
+#define XRANGE_SHADOW_MASK	GENMASK_ULL(XRANGE_SHADOW_SHIFT - 1, 0)
+/* One segment whole address space size */
+#define XRANGE_SIZE		(XRANGE_SHADOW_MASK + 1)
+
+/* 64-bit segment value. */
+#define XKPRANGE_UC_SEG		(0x8000)
+#define XKPRANGE_CC_SEG		(0x9000)
+#define XKVRANGE_VC_SEG		(0xffff)
+
+/* Cached */
+#define XKPRANGE_CC_START		CACHE_BASE
+#define XKPRANGE_CC_SIZE		XRANGE_SIZE
+#define XKPRANGE_CC_KASAN_OFFSET	(0)
+#define XKPRANGE_CC_SHADOW_SIZE		(XKPRANGE_CC_SIZE >> KASAN_SHADOW_SCALE_SHIFT)
+#define XKPRANGE_CC_SHADOW_END		(XKPRANGE_CC_KASAN_OFFSET + XKPRANGE_CC_SHADOW_SIZE)
+
+/* UnCached */
+#define XKPRANGE_UC_START		UNCACHE_BASE
+#define XKPRANGE_UC_SIZE		XRANGE_SIZE
+#define XKPRANGE_UC_KASAN_OFFSET	XKPRANGE_CC_SHADOW_END
+#define XKPRANGE_UC_SHADOW_SIZE		(XKPRANGE_UC_SIZE >> KASAN_SHADOW_SCALE_SHIFT)
+#define XKPRANGE_UC_SHADOW_END		(XKPRANGE_UC_KASAN_OFFSET + XKPRANGE_UC_SHADOW_SIZE)
+
+/* VMALLOC (Cached or UnCached)  */
+#define XKVRANGE_VC_START		MODULES_VADDR
+#define XKVRANGE_VC_SIZE		round_up(KFENCE_AREA_END - MODULES_VADDR + 1, PGDIR_SIZE)
+#define XKVRANGE_VC_KASAN_OFFSET	XKPRANGE_UC_SHADOW_END
+#define XKVRANGE_VC_SHADOW_SIZE		(XKVRANGE_VC_SIZE >> KASAN_SHADOW_SCALE_SHIFT)
+#define XKVRANGE_VC_SHADOW_END		(XKVRANGE_VC_KASAN_OFFSET + XKVRANGE_VC_SHADOW_SIZE)
+
+/* KAsan shadow memory start right after vmalloc. */
+#define KASAN_SHADOW_START		round_up(KFENCE_AREA_END, PGDIR_SIZE)
+#define KASAN_SHADOW_SIZE		(XKVRANGE_VC_SHADOW_END - XKPRANGE_CC_KASAN_OFFSET)
+#define KASAN_SHADOW_END		round_up(KASAN_SHADOW_START + KASAN_SHADOW_SIZE, PGDIR_SIZE)
+
+#define XKPRANGE_CC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKPRANGE_CC_KASAN_OFFSET)
+#define XKPRANGE_UC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKPRANGE_UC_KASAN_OFFSET)
+#define XKVRANGE_VC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKVRANGE_VC_KASAN_OFFSET)
+
+extern bool kasan_early_stage;
+extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
+
+#define kasan_arch_is_ready kasan_arch_is_ready
+static __always_inline bool kasan_arch_is_ready(void)
+{
+	return !kasan_early_stage;
+}
+
+static inline void *kasan_mem_to_shadow(const void *addr)
+{
+	if (!kasan_arch_is_ready()) {
+		return (void *)(kasan_early_shadow_page);
+	} else {
+		unsigned long maddr = (unsigned long)addr;
+		unsigned long xrange = (maddr >> XRANGE_SHIFT) & 0xffff;
+		unsigned long offset = 0;
+
+		maddr &= XRANGE_SHADOW_MASK;
+		switch (xrange) {
+		case XKPRANGE_CC_SEG:
+			offset = XKPRANGE_CC_SHADOW_OFFSET;
+			break;
+		case XKPRANGE_UC_SEG:
+			offset = XKPRANGE_UC_SHADOW_OFFSET;
+			break;
+		case XKVRANGE_VC_SEG:
+			offset = XKVRANGE_VC_SHADOW_OFFSET;
+			break;
+		default:
+			WARN_ON(1);
+			return NULL;
+		}
+
+		return (void *)((maddr >> KASAN_SHADOW_SCALE_SHIFT) + offset);
+	}
+}
+
+static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
+{
+	unsigned long addr = (unsigned long)shadow_addr;
+
+	if (unlikely(addr > KASAN_SHADOW_END) ||
+		unlikely(addr < KASAN_SHADOW_START)) {
+		WARN_ON(1);
+		return NULL;
+	}
+
+	if (addr >= XKVRANGE_VC_SHADOW_OFFSET)
+		return (void *)(((addr - XKVRANGE_VC_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT) + XKVRANGE_VC_START);
+	else if (addr >= XKPRANGE_UC_SHADOW_OFFSET)
+		return (void *)(((addr - XKPRANGE_UC_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT) + XKPRANGE_UC_START);
+	else if (addr >= XKPRANGE_CC_SHADOW_OFFSET)
+		return (void *)(((addr - XKPRANGE_CC_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT) + XKPRANGE_CC_START);
+	else {
+		WARN_ON(1);
+		return NULL;
+	}
+}
+
+void kasan_init(void);
+asmlinkage void kasan_early_init(void);
+
+#endif
+#endif

arch/loongarch/include/asm/pgtable.h

@@ -89,9 +89,16 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
 #endif
 
 #define VMALLOC_START	MODULES_END
+
+#ifndef CONFIG_KASAN
 #define VMALLOC_END	\
 	(vm_map_base +	\
 	 min(PTRS_PER_PGD * PTRS_PER_PUD * PTRS_PER_PMD * PTRS_PER_PTE * PAGE_SIZE, (1UL << cpu_vabits)) - PMD_SIZE - VMEMMAP_SIZE - KFENCE_AREA_SIZE)
+#else
+#define VMALLOC_END	\
+	(vm_map_base +	\
+	 min(PTRS_PER_PGD * PTRS_PER_PUD * PTRS_PER_PMD * PTRS_PER_PTE * PAGE_SIZE, (1UL << cpu_vabits) / 2) - PMD_SIZE - VMEMMAP_SIZE - KFENCE_AREA_SIZE)
+#endif
 
 #define vmemmap		((struct page *)((VMALLOC_END + PMD_SIZE) & PMD_MASK))
 #define VMEMMAP_END	((unsigned long)vmemmap + VMEMMAP_SIZE - 1)

arch/loongarch/include/asm/string.h

@@ -7,11 +7,31 @@
 
 #define __HAVE_ARCH_MEMSET
 extern void *memset(void *__s, int __c, size_t __count);
+extern void *__memset(void *__s, int __c, size_t __count);
 
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *__to, __const__ void *__from, size_t __n);
+extern void *__memcpy(void *__to, __const__ void *__from, size_t __n);
 
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *__dest, __const__ void *__src, size_t __n);
+extern void *__memmove(void *__dest, __const__ void *__src, size_t __n);
+
+#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
+
+/*
+ * For files that are not instrumented (e.g. mm/slub.c) we
+ * should use not instrumented version of mem* functions.
+ */
+
+#define memset(s, c, n) __memset(s, c, n)
+#define memcpy(dst, src, len) __memcpy(dst, src, len)
+#define memmove(dst, src, len) __memmove(dst, src, len)
+
+#ifndef __NO_FORTIFY
+#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
+#endif
+
+#endif
 
 #endif /* _ASM_STRING_H */

arch/loongarch/kernel/Makefile

@@ -34,6 +34,12 @@ ifdef CONFIG_FUNCTION_TRACER
   CFLAGS_REMOVE_rethook_trampoline.o = $(CC_FLAGS_FTRACE)
 endif
 
+KASAN_SANITIZE_efi.o := n
+KASAN_SANITIZE_cpu-probe.o := n
+KASAN_SANITIZE_traps.o := n
+KASAN_SANITIZE_smp.o := n
+KASAN_SANITIZE_vdso.o := n
+
 obj-$(CONFIG_MODULES)		+= module.o module-sections.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 

arch/loongarch/kernel/head.S

@@ -104,6 +104,10 @@ SYM_CODE_START(kernel_entry)			# kernel entry point
 
 #endif /* CONFIG_RELOCATABLE */
 
+#ifdef CONFIG_KASAN
+	bl		kasan_early_init
+#endif
+
 	bl		start_kernel
 	ASM_BUG()
 

arch/loongarch/kernel/setup.c

@@ -626,4 +626,8 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 	paging_init();
+
+#ifdef CONFIG_KASAN
+	kasan_init();
+#endif
 }

arch/loongarch/lib/memcpy.S

@@ -10,6 +10,8 @@
 #include <asm/cpu.h>
 #include <asm/regdef.h>
 
+.section .noinstr.text, "ax"
+
 SYM_FUNC_START(memcpy)
 	/*
 	 * Some CPUs support hardware unaligned access
@@ -17,9 +19,13 @@ SYM_FUNC_START(memcpy)
 	ALTERNATIVE	"b __memcpy_generic", \
 			"b __memcpy_fast", CPU_FEATURE_UAL
 SYM_FUNC_END(memcpy)
-_ASM_NOKPROBE(memcpy)
+SYM_FUNC_ALIAS(__memcpy, memcpy)
 
 EXPORT_SYMBOL(memcpy)
+EXPORT_SYMBOL(__memcpy)
+
+_ASM_NOKPROBE(memcpy)
+_ASM_NOKPROBE(__memcpy)
 
 /*
  * void *__memcpy_generic(void *dst, const void *src, size_t n)

arch/loongarch/lib/memmove.S

@@ -10,23 +10,29 @@
 #include <asm/cpu.h>
 #include <asm/regdef.h>
 
+.section .noinstr.text, "ax"
+
 SYM_FUNC_START(memmove)
-	blt	a0, a1, memcpy	/* dst < src, memcpy */
-	blt	a1, a0, rmemcpy	/* src < dst, rmemcpy */
-	jr	ra		/* dst == src, return */
+	blt	a0, a1, __memcpy	/* dst < src, memcpy */
+	blt	a1, a0, __rmemcpy	/* src < dst, rmemcpy */
+	jr	ra			/* dst == src, return */
 SYM_FUNC_END(memmove)
-_ASM_NOKPROBE(memmove)
+SYM_FUNC_ALIAS(__memmove, memmove)
 
 EXPORT_SYMBOL(memmove)
+EXPORT_SYMBOL(__memmove)
+
+_ASM_NOKPROBE(memmove)
+_ASM_NOKPROBE(__memmove)
 
-SYM_FUNC_START(rmemcpy)
+SYM_FUNC_START(__rmemcpy)
 	/*
 	 * Some CPUs support hardware unaligned access
 	 */
 	ALTERNATIVE	"b __rmemcpy_generic", \
 			"b __rmemcpy_fast", CPU_FEATURE_UAL
-SYM_FUNC_END(rmemcpy)
-_ASM_NOKPROBE(rmemcpy)
+SYM_FUNC_END(__rmemcpy)
+_ASM_NOKPROBE(__rmemcpy)
 
 /*
  * void *__rmemcpy_generic(void *dst, const void *src, size_t n)

arch/loongarch/lib/memset.S

@@ -16,6 +16,8 @@
 	bstrins.d \r0, \r0, 63, 32
 .endm
 
+.section .noinstr.text, "ax"
+
 SYM_FUNC_START(memset)
 	/*
 	 * Some CPUs support hardware unaligned access
@@ -23,9 +25,13 @@ SYM_FUNC_START(memset)
 	ALTERNATIVE	"b __memset_generic", \
 			"b __memset_fast", CPU_FEATURE_UAL
 SYM_FUNC_END(memset)
-_ASM_NOKPROBE(memset)
+SYM_FUNC_ALIAS(__memset, memset)
 
 EXPORT_SYMBOL(memset)
+EXPORT_SYMBOL(__memset)
+
+_ASM_NOKPROBE(memset)
+_ASM_NOKPROBE(__memset)
 
 /*
  * void *__memset_generic(void *s, int c, size_t n)

arch/loongarch/mm/Makefile

@@ -7,3 +7,6 @@ obj-y				+= init.o cache.o tlb.o tlbex.o extable.o \
 				   fault.o ioremap.o maccess.o mmap.o pgtable.o page.o
 
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
+obj-$(CONFIG_KASAN)		+= kasan_init.o
+
+KASAN_SANITIZE_kasan_init.o     := n

arch/loongarch/mm/kasan_init.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ */
+#define pr_fmt(fmt) "kasan: " fmt
+#include <linux/kasan.h>
+#include <linux/memblock.h>
+#include <linux/sched/task.h>
+
+#include <asm/tlbflush.h>
+#include <asm/pgalloc.h>
+#include <asm-generic/sections.h>
+
+static pgd_t kasan_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+
+#ifdef __PAGETABLE_PUD_FOLDED
+#define __p4d_none(early, p4d) (0)
+#else
+#define __p4d_none(early, p4d) (early ? (p4d_val(p4d) == 0) : \
+(__pa(p4d_val(p4d)) == (unsigned long)__pa(kasan_early_shadow_pud)))
+#endif
+
+#ifdef __PAGETABLE_PMD_FOLDED
+#define __pud_none(early, pud) (0)
+#else
+#define __pud_none(early, pud) (early ? (pud_val(pud) == 0) : \
+(__pa(pud_val(pud)) == (unsigned long)__pa(kasan_early_shadow_pmd)))
+#endif
+
+#define __pmd_none(early, pmd) (early ? (pmd_val(pmd) == 0) : \
+(__pa(pmd_val(pmd)) == (unsigned long)__pa(kasan_early_shadow_pte)))
+
+#define __pte_none(early, pte) (early ? pte_none(pte) : \
+((pte_val(pte) & _PFN_MASK) == (unsigned long)__pa(kasan_early_shadow_page)))
+
+bool kasan_early_stage = true;
+
+/*
+ * Alloc memory for shadow memory page table.
+ */
+static phys_addr_t __init kasan_alloc_zeroed_page(int node)
+{
+	void *p = memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
+					__pa(MAX_DMA_ADDRESS), MEMBLOCK_ALLOC_ACCESSIBLE, node);
+	if (!p)
+		panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
+			__func__, PAGE_SIZE, PAGE_SIZE, node, __pa(MAX_DMA_ADDRESS));
+
+	return __pa(p);
+}
+
+static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node, bool early)
+{
+	if (__pmd_none(early, READ_ONCE(*pmdp))) {
+		phys_addr_t pte_phys = early ?
+				__pa_symbol(kasan_early_shadow_pte) : kasan_alloc_zeroed_page(node);
+		if (!early)
+			memcpy(__va(pte_phys), kasan_early_shadow_pte, sizeof(kasan_early_shadow_pte));
+		pmd_populate_kernel(NULL, pmdp, (pte_t *)__va(pte_phys));
+	}
+
+	return pte_offset_kernel(pmdp, addr);
+}
+
+static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node, bool early)
+{
+	if (__pud_none(early, READ_ONCE(*pudp))) {
+		phys_addr_t pmd_phys = early ?
+				__pa_symbol(kasan_early_shadow_pmd) : kasan_alloc_zeroed_page(node);
+		if (!early)
+			memcpy(__va(pmd_phys), kasan_early_shadow_pmd, sizeof(kasan_early_shadow_pmd));
+		pud_populate(&init_mm, pudp, (pmd_t *)__va(pmd_phys));
+	}
+
+	return pmd_offset(pudp, addr);
+}
+
+static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node, bool early)
+{
+	if (__p4d_none(early, READ_ONCE(*p4dp))) {
+		phys_addr_t pud_phys = early ?
+			__pa_symbol(kasan_early_shadow_pud) : kasan_alloc_zeroed_page(node);
+		if (!early)
+			memcpy(__va(pud_phys), kasan_early_shadow_pud, sizeof(kasan_early_shadow_pud));
+		p4d_populate(&init_mm, p4dp, (pud_t *)__va(pud_phys));
+	}
+
+	return pud_offset(p4dp, addr);
+}
+
+static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
+				      unsigned long end, int node, bool early)
+{
+	unsigned long next;
+	pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
+
+	do {
+		phys_addr_t page_phys = early ?
+					__pa_symbol(kasan_early_shadow_page)
+					      : kasan_alloc_zeroed_page(node);
+		next = addr + PAGE_SIZE;
+		set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
+	} while (ptep++, addr = next, addr != end && __pte_none(early, READ_ONCE(*ptep)));
+}
+
+static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
+				      unsigned long end, int node, bool early)
+{
+	unsigned long next;
+	pmd_t *pmdp = kasan_pmd_offset(pudp, addr, node, early);
+
+	do {
+		next = pmd_addr_end(addr, end);
+		kasan_pte_populate(pmdp, addr, next, node, early);
+	} while (pmdp++, addr = next, addr != end && __pmd_none(early, READ_ONCE(*pmdp)));
+}
+
+static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
+					    unsigned long end, int node, bool early)
+{
+	unsigned long next;
+	pud_t *pudp = kasan_pud_offset(p4dp, addr, node, early);
+
+	do {
+		next = pud_addr_end(addr, end);
+		kasan_pmd_populate(pudp, addr, next, node, early);
+	} while (pudp++, addr = next, addr != end);
+}
+
+static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
+					    unsigned long end, int node, bool early)
+{
+	unsigned long next;
+	p4d_t *p4dp = p4d_offset(pgdp, addr);
+
+	do {
+		next = p4d_addr_end(addr, end);
+		kasan_pud_populate(p4dp, addr, next, node, early);
+	} while (p4dp++, addr = next, addr != end);
+}
+
+static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
+				      int node, bool early)
+{
+	unsigned long next;
+	pgd_t *pgdp;
+
+	pgdp = pgd_offset_k(addr);
+
+	do {
+		next = pgd_addr_end(addr, end);
+		kasan_p4d_populate(pgdp, addr, next, node, early);
+	} while (pgdp++, addr = next, addr != end);
+
+}
+
+/* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
+static void __init kasan_map_populate(unsigned long start, unsigned long end,
+				      int node)
+{
+	kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
+}
+
+asmlinkage void __init kasan_early_init(void)
+{
+	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
+	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
+}
+
+static inline void kasan_set_pgd(pgd_t *pgdp, pgd_t pgdval)
+{
+	WRITE_ONCE(*pgdp, pgdval);
+}
+
+static void __init clear_pgds(unsigned long start, unsigned long end)
+{
+	/*
+	 * Remove references to kasan page tables from
+	 * swapper_pg_dir. pgd_clear() can't be used
+	 * here because it's nop on 2,3-level pagetable setups
+	 */
+	for (; start < end; start += PGDIR_SIZE)
+		kasan_set_pgd((pgd_t *)pgd_offset_k(start), __pgd(0));
+}
+
+void __init kasan_init(void)
+{
+	u64 i;
+	phys_addr_t pa_start, pa_end;
+
+	/*
+	 * PGD was populated as invalid_pmd_table or invalid_pud_table
+	 * in pagetable_init() which depends on how many levels of page
+	 * table you are using, but we had to clean the gpd of kasan
+	 * shadow memory, as the pgd value is none-zero.
+	 * The assertion pgd_none is going to be false and the formal populate
+	 * afterwards is not going to create any new pgd at all.
+	 */
+	memcpy(kasan_pg_dir, swapper_pg_dir, sizeof(kasan_pg_dir));
+	csr_write64(__pa_symbol(kasan_pg_dir), LOONGARCH_CSR_PGDH);
+	local_flush_tlb_all();
+
+	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
+
+	/* Maps everything to a single page of zeroes */
+	kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE, true);
+
+	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
+					kasan_mem_to_shadow((void *)KFENCE_AREA_END));
+
+	kasan_early_stage = false;
+
+	/* Populate the linear mapping */
+	for_each_mem_range(i, &pa_start, &pa_end) {
+		void *start = (void *)phys_to_virt(pa_start);
+		void *end   = (void *)phys_to_virt(pa_end);
+
+		if (start >= end)
+			break;
+
+		kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
+			(unsigned long)kasan_mem_to_shadow(end), NUMA_NO_NODE);
+	}
+
+	/* Populate modules mapping */
+	kasan_map_populate((unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR),
+		(unsigned long)kasan_mem_to_shadow((void *)MODULES_END), NUMA_NO_NODE);
+	/*
+	 * KAsan may reuse the contents of kasan_early_shadow_pte directly, so we
+	 * should make sure that it maps the zero page read-only.
+	 */
+	for (i = 0; i < PTRS_PER_PTE; i++)
+		set_pte(&kasan_early_shadow_pte[i],
+			pfn_pte(__phys_to_pfn(__pa_symbol(kasan_early_shadow_page)), PAGE_KERNEL_RO));
+
+	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
+	csr_write64(__pa_symbol(swapper_pg_dir), LOONGARCH_CSR_PGDH);
+	local_flush_tlb_all();
+
+	/* At this point kasan is fully initialized. Enable error messages */
+	init_task.kasan_depth = 0;
+	pr_info("KernelAddressSanitizer initialized.\n");
+}

arch/loongarch/vdso/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Objects to go into the VDSO.
 
+KASAN_SANITIZE := n
 KCOV_INSTRUMENT := n
 
 # Include the generic Makefile to check the built vdso.