[v3,4/4] LoongArch: Add 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>
---
 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
  

Hi, Qing,

On Fri, May 12, 2023 at 9:58 AM Qing Zhang <zhangqing@loongson.cn> 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@loongson.cn>
> ---
>  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
>
>