Re: [PATCH v3 4/4] LoongArch: Add kernel address sanitizer support

From: Huacai Chen
Date: Thu Jun 15 2023 - 08:58:32 EST

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Hi, Qing,

On Fri, May 12, 2023 at 9:58 AM Qing Zhang <zhangqing@xxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxxx>
> ---
> Documentation/dev-tools/kasan.rst | 4 +-
> .../features/debug/KASAN/arch-support.txt | 2 +-
> .../translations/zh_CN/dev-tools/kasan.rst | 2 +-
> arch/loongarch/Kconfig | 7 +
> arch/loongarch/include/asm/kasan.h | 120 +++++++++
> arch/loongarch/include/asm/pgtable.h | 7 +
> arch/loongarch/include/asm/string.h | 20 ++
> arch/loongarch/kernel/Makefile | 6 +
> arch/loongarch/kernel/head.S | 4 +
> arch/loongarch/kernel/setup.c | 4 +
> arch/loongarch/lib/memcpy.S | 4 +-
> arch/loongarch/lib/memmove.S | 16 +-
> arch/loongarch/lib/memset.S | 4 +-
> arch/loongarch/mm/Makefile | 2 +
> arch/loongarch/mm/kasan_init.c | 255 ++++++++++++++++++
> arch/loongarch/vdso/Makefile | 4 +
> 16 files changed, 448 insertions(+), 13 deletions(-)
> create mode 100644 arch/loongarch/include/asm/kasan.h
> create mode 100644 arch/loongarch/mm/kasan_init.c
>
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index e66916a483cd..ee91f2872767 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/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
> ~~~~~~~~~
> diff --git a/Documentation/features/debug/KASAN/arch-support.txt b/Documentation/features/debug/KASAN/arch-support.txt
> index bf0124fae643..c4581c2edb28 100644
> --- a/Documentation/features/debug/KASAN/arch-support.txt
> +++ b/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 |
> diff --git a/Documentation/translations/zh_CN/dev-tools/kasan.rst b/Documentation/translations/zh_CN/dev-tools/kasan.rst
> index 05ef904dbcfb..8fdb20c9665b 100644
> --- a/Documentation/translations/zh_CN/dev-tools/kasan.rst
> +++ b/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
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index ac3d3d9b5716..a9c879fd037e 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -7,6 +7,7 @@ config LOONGARCH
> select ACPI_MCFG 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
> @@ -82,6 +83,7 @@ config LOONGARCH
> select GENERIC_TIME_VSYSCALL
> select GPIOLIB
> select HAVE_ARCH_AUDITSYSCALL
> + select HAVE_ARCH_KASAN
> select HAVE_ARCH_MMAP_RND_BITS if MMU
> select HAVE_ARCH_SECCOMP_FILTER
> select HAVE_ARCH_TRACEHOOK
> @@ -595,6 +597,11 @@ config ARCH_MMAP_RND_BITS_MIN
> config ARCH_MMAP_RND_BITS_MAX
> default 18
>
> +config KASAN_SHADOW_OFFSET
> + hex
> + default 0x0
> + depends on KASAN
> +
> menu "Power management options"
>
> config ARCH_SUSPEND_POSSIBLE
> diff --git a/arch/loongarch/include/asm/kasan.h b/arch/loongarch/include/asm/kasan.h
> new file mode 100644
> index 000000000000..04fb6c210945
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kasan.h
> @@ -0,0 +1,120 @@
> +/* 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)
Use space instead of tab here.

> +
> +/* 64-bit segment value. */
> +#define XKPRANGE_UC_SEG (UNCACHE_BASE >> DMW_PABITS)
> +#define XKPRANGE_CC_SEG (CACHE_BASE >> DMW_PABITS)
> +#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(VMEMMAP_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(VMEMMAP_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];
> +
> +static inline void *kasan_mem_to_shadow(const void *addr)
> +{
> + if (kasan_early_stage) {
> + 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
> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
> index d28fb9dbec59..5cfdf79b287e 100644
> --- a/arch/loongarch/include/asm/pgtable.h
> +++ b/arch/loongarch/include/asm/pgtable.h
> @@ -86,9 +86,16 @@ extern unsigned long zero_page_mask;
> #define MODULES_END (MODULES_VADDR + SZ_256M)
>
> #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)
> +#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)
> +#endif
>
> #define vmemmap ((struct page *)((VMALLOC_END + PMD_SIZE) & PMD_MASK))
> #define VMEMMAP_END ((unsigned long)vmemmap + VMEMMAP_SIZE - 1)
> diff --git a/arch/loongarch/include/asm/string.h b/arch/loongarch/include/asm/string.h
> index 7b29cc9c70aa..5bb5a90d2681 100644
> --- a/arch/loongarch/include/asm/string.h
> +++ b/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 */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 9a72d91cd104..b45c6932a6cf 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -30,6 +30,12 @@ ifdef CONFIG_FUNCTION_TRACER
> CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE)
> endif
>
> +KASAN_SANITIZE_efi.o := n
> +KASAN_SANITIZE_vdso.o := n
> +KASAN_SANITIZE_cpu-probe.o := n
> +KASAN_SANITIZE_traps.o := n
> +KASAN_SANITIZE_smp.o := n
> +
> obj-$(CONFIG_MODULES) += module.o module-sections.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
>
> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> index aace7a300cd3..0d8180153ec0 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/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()
>
> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
> index 4444b13418f0..9e94bf60c900 100644
> --- a/arch/loongarch/kernel/setup.c
> +++ b/arch/loongarch/kernel/setup.c
> @@ -610,4 +610,8 @@ void __init setup_arch(char **cmdline_p)
> #endif
>
> paging_init();
> +
> +#ifdef CONFIG_KASAN
> + kasan_init();
> +#endif
> }
> diff --git a/arch/loongarch/lib/memcpy.S b/arch/loongarch/lib/memcpy.S
> index 39ce6621c704..b9eb89e90550 100644
> --- a/arch/loongarch/lib/memcpy.S
> +++ b/arch/loongarch/lib/memcpy.S
> @@ -10,16 +10,18 @@
> #include <asm/export.h>
> #include <asm/regdef.h>
>
> -SYM_FUNC_START(memcpy)
> +SYM_FUNC_START_WEAK(memcpy)
> /*
> * Some CPUs support hardware unaligned access
> */
> ALTERNATIVE "b __memcpy_generic", \
> "b __memcpy_fast", CPU_FEATURE_UAL
> SYM_FUNC_END(memcpy)
> +SYM_FUNC_ALIAS(__memcpy, memcpy)
> _ASM_NOKPROBE(memcpy)
>
> EXPORT_SYMBOL(memcpy)
> +EXPORT_SYMBOL(__memcpy)
>
> /*
> * void *__memcpy_generic(void *dst, const void *src, size_t n)
> diff --git a/arch/loongarch/lib/memmove.S b/arch/loongarch/lib/memmove.S
> index 45b725ba7867..df521f8b9c9a 100644
> --- a/arch/loongarch/lib/memmove.S
> +++ b/arch/loongarch/lib/memmove.S
> @@ -10,23 +10,25 @@
> #include <asm/export.h>
> #include <asm/regdef.h>
>
> -SYM_FUNC_START(memmove)
> - blt a0, a1, memcpy /* dst < src, memcpy */
> - blt a1, a0, rmemcpy /* src < dst, rmemcpy */
> - jr ra /* dst == src, return */
> +SYM_FUNC_START_WEAK(memmove)
> + blt a0, a1, __memcpy /* dst < src, memcpy */
> + blt a1, a0, __rmemcpy /* src < dst, rmemcpy */
> + jr ra /* dst == src, return */
> SYM_FUNC_END(memmove)
> +SYM_FUNC_ALIAS(__memmove, memmove)
> _ASM_NOKPROBE(memmove)
>
> EXPORT_SYMBOL(memmove)
> +EXPORT_SYMBOL(__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)
> diff --git a/arch/loongarch/lib/memset.S b/arch/loongarch/lib/memset.S
> index b39c6194e3ae..392901aba970 100644
> --- a/arch/loongarch/lib/memset.S
> +++ b/arch/loongarch/lib/memset.S
> @@ -16,16 +16,18 @@
> bstrins.d \r0, \r0, 63, 32
> .endm
>
> -SYM_FUNC_START(memset)
> +SYM_FUNC_START_WEAK(memset)
> /*
> * Some CPUs support hardware unaligned access
> */
> ALTERNATIVE "b __memset_generic", \
> "b __memset_fast", CPU_FEATURE_UAL
> SYM_FUNC_END(memset)
> +SYM_FUNC_ALIAS(__memset, memset)
> _ASM_NOKPROBE(memset)
>
> EXPORT_SYMBOL(memset)
> +EXPORT_SYMBOL(__memset)
>
> /*
> * void *__memset_generic(void *s, int c, size_t n)
> diff --git a/arch/loongarch/mm/Makefile b/arch/loongarch/mm/Makefile
> index 8ffc6383f836..6e50cf6cf733 100644
> --- a/arch/loongarch/mm/Makefile
> +++ b/arch/loongarch/mm/Makefile
> @@ -7,3 +7,5 @@ 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
> diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
> new file mode 100644
> index 000000000000..fb3077f8d508
> --- /dev/null
> +++ b/arch/loongarch/mm/kasan_init.c
> @@ -0,0 +1,255 @@
> +// 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 tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
> +
> +static inline int __p4d_none(int early, p4d_t p4d) {return 0; }
> +
> +#ifndef __PAGETABLE_PUD_FOLDED
> +#define __p4d_none(early, p4d) (early ? (p4d_val(p4d) == 0) : \
> +(__pa(p4d_val(p4d)) == (unsigned long)__pa(kasan_early_shadow_pud)))
> +#endif
__p4d_none() is redefined in some cases here.

> +
> +#define __pud_none(early, pud) (early ? (pud_val(pud) == 0) : \
> +(__pa(pud_val(pud)) == (unsigned long)__pa(kasan_early_shadow_pmd)))
> +
> +#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 *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 inline void kasan_set_pgd(pgd_t *pgdp, pgd_t pgdval)
> +{
> + WRITE_ONCE(*pgdp, pgdval);
> +}
> +
> +static pmd_t *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 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 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);
> +
> +}
> +
> +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));
> +}
> +
> +/* 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);
> +}
> +
> +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(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
tmp_pg_dir can be a local variable, I think.

> + __sync();
I don't know why we need __sync(), keep the memory ordering or flush
the write buffer?

Huacai
> + csr_write64(__pa_symbol(tmp_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 *)MODULES_END),
> + kasan_mem_to_shadow((void *)VMEMMAP_END));
> +
> + if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
> + kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
> + kasan_mem_to_shadow((void *)VMALLOC_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);
> + __sync();
> + 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");
> +}
> diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile
> index d89e2ac75f7b..df328cd92875 100644
> --- a/arch/loongarch/vdso/Makefile
> +++ b/arch/loongarch/vdso/Makefile
> @@ -1,6 +1,10 @@
> # SPDX-License-Identifier: GPL-2.0
> # Objects to go into the VDSO.
>
> +ifdef CONFIG_KASAN
> +KASAN_SANITIZE := n
> +endif
> +
> # Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
> # the inclusion of generic Makefile.
> ARCH_REL_TYPE_ABS := R_LARCH_32|R_LARCH_64|R_LARCH_MARK_LA|R_LARCH_JUMP_SLOT
> --
> 2.36.0
>
>

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