Re: [PATCH] LoongArch: Add kernel address sanitizer support

From: Youling Tang
Date: Tue Mar 28 2023 - 07:58:08 EST

Hi, Qing

On 03/28/2023 07:17 PM, Qing Zhang 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
`Loongarch` -> `LoongArch`

are mapped individually, and only limited length of space of that
specific segment is 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/memmove/memcpy do a lot of memory accesses.
If bad pointer passed to one of these function it is important
to catch this. 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 name, 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 +-
arch/loongarch/Kconfig | 7 +
arch/loongarch/include/asm/kasan.h | 120 +++++++++
arch/loongarch/include/asm/pgtable.h | 7 +
arch/loongarch/include/asm/setup.h | 2 +-
arch/loongarch/include/asm/string.h | 20 ++
arch/loongarch/kernel/Makefile | 3 +
arch/loongarch/kernel/head.S | 14 +-
arch/loongarch/kernel/relocate.c | 8 +-
arch/loongarch/kernel/setup.c | 4 +
arch/loongarch/lib/memcpy.S | 4 +-
arch/loongarch/lib/memmove.S | 13 +-
arch/loongarch/lib/memset.S | 4 +-
arch/loongarch/mm/Makefile | 2 +
arch/loongarch/mm/kasan_init.c | 255 ++++++++++++++++++
arch/loongarch/vdso/Makefile | 4 +
include/linux/kasan.h | 2 +
mm/kasan/generic.c | 5 +
mm/kasan/init.c | 10 +-
mm/kasan/kasan.h | 6 +
21 files changed, 470 insertions(+), 26 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/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 72dd00f48b8c..61f883c51045 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
@@ -83,6 +84,7 @@ config LOONGARCH
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_SECCOMP_FILTER
+ select HAVE_ARCH_KASAN if 64BIT
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_ASM_MODVERSIONS
@@ -626,6 +628,11 @@ 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..582bcded311e
--- /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)
+
+/* 64-bit segment value. */
+#define XKPRANGE_UC_SEG (0x8000)
+#define XKPRANGE_CC_SEG (0x9000)
It is not recommended to use a fixed value, it can be as follows,

CACHE_BASE >> DMW_PABITS
UNCACHE_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/setup.h b/arch/loongarch/include/asm/setup.h
index be05c0e706a2..2dca0d1dd90a 100644
--- a/arch/loongarch/include/asm/setup.h
+++ b/arch/loongarch/include/asm/setup.h
@@ -33,7 +33,7 @@ extern long __la_abs_end;
extern long __rela_dyn_begin;
extern long __rela_dyn_end;

-extern void * __init relocate_kernel(void);
+extern unsigned long __init relocate_kernel(void);

#endif

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..0055e7582e15 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -30,6 +30,9 @@ ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE)
endif

+KASAN_SANITIZE_vdso.o := n
+KASAN_SANITIZE_efi.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 aa64b179744f..19d4be5c8381 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -95,13 +95,17 @@ SYM_CODE_START(kernel_entry) # kernel entry point
PTR_LI sp, (_THREAD_SIZE - PT_SIZE)
PTR_ADD sp, sp, tp
set_saved_sp sp, t0, t1
-#endif
-
- /* relocate_kernel() returns the new kernel entry point */
- jr a0
- ASM_BUG()

+ /* Jump to new kernel: new_pc = current_pc + random_offset */
+ pcaddi t0, 0
+ add.d t0, t0, a0
+ jirl zero, t0, 0xc
#endif
+#endif
+
+ #ifdef CONFIG_KASAN
+ bl kasan_early_init
+ #endif
No tab operation is required before `#ifdef`.


bl start_kernel
ASM_BUG()
diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index 01f94d1e3edf..6c3eff9af9fb 100644
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -157,12 +157,11 @@ static inline void __init update_reloc_offset(unsigned long *addr, long random_o
*new_addr = (unsigned long)reloc_offset;
}

-void * __init relocate_kernel(void)
+unsigned long __init relocate_kernel(void)
{
unsigned long kernel_length;
unsigned long random_offset = 0;
void *location_new = _text; /* Default to original kernel start */
- void *kernel_entry = start_kernel; /* Default to original kernel entry point */
char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */

strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);
@@ -190,9 +189,6 @@ void * __init relocate_kernel(void)

reloc_offset += random_offset;

- /* Return the new kernel's entry point */
- kernel_entry = RELOCATED_KASLR(start_kernel);
-
/* The current thread is now within the relocated kernel */
__current_thread_info = RELOCATED_KASLR(__current_thread_info);

@@ -204,7 +200,7 @@ void * __init relocate_kernel(void)

relocate_absolute(random_offset);

- return kernel_entry;
+ return random_offset;
}

/*
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 27f71f9531e1..18453f8cb9e8 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();
+
+#if defined(CONFIG_KASAN)
+ kasan_init();
+#endif
Can be added in arch/loongarch/include/asm/kasan.h,
#else
static inline void kasan_init(void) { }
#endif


Youling.