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Subject[PATCH 00/11] KASan for arm
These patches add arch specific code for kernel address sanitizer
(see Documentation/kasan.txt).

1/8 of kernel addresses reserved for shadow memory. There was no
big enough hole for this, so virtual addresses for shadow were
stolen from user space.

At early boot stage the whole shadow region populated with just
one physical page (kasan_zero_page). Later, this page reused
as readonly zero shadow for some memory that KASan currently
don't track (vmalloc).

After mapping the physical memory, pages for shadow memory are
allocated and mapped.

KASan's stack instrumentation significantly increases stack's
consumption, so CONFIG_KASAN doubles THREAD_SIZE.

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.

Some files built without kasan instrumentation (e.g. mm/slub.c).
Original mem* function replaced (via #define) with prefixed variants
to disable memory access checks for such files.

On arm LPAE architecture, the mapping table of KASan shadow memory(if
PAGE_OFFSET is 0xc0000000, the KASan shadow memory's virtual space is
0xb6e000000~0xbf000000) can't be filled in do_translation_fault function,
because kasan instrumentation maybe cause do_translation_fault function
accessing KASan shadow memory. The accessing of KASan shadow memory in
do_translation_fault function maybe cause dead circle. So the mapping table
of KASan shadow memory need be copyed in pgd_alloc function.

Most of the code comes from:

These patches are tested on vexpress-ca15, vexpress-ca9

Cc: Andrey Ryabinin <>
Tested-by: Abbott Liu <>
Signed-off-by: Abbott Liu <>

Abbott Liu (6):
Define the virtual space of KASan's shadow region
change memory_is_poisoned_16 for aligned error
Add support arm LPAE
Don't need to map the shadow of KASan's shadow memory
Change mapping of kasan_zero_page int readonly
Add KASan layout

Andrey Ryabinin (5):
Initialize the mapping of KASan shadow memory
replace memory function
arm: Kconfig: enable KASan
Disable kasan's instrumentation
Avoid cleaning the KASan shadow area's mapping table

arch/arm/Kconfig | 1 +
arch/arm/boot/compressed/Makefile | 1 +
arch/arm/include/asm/kasan.h | 20 +++
arch/arm/include/asm/kasan_def.h | 51 +++++++
arch/arm/include/asm/memory.h | 5 +
arch/arm/include/asm/pgalloc.h | 5 +-
arch/arm/include/asm/pgtable.h | 1 +
arch/arm/include/asm/proc-fns.h | 33 +++++
arch/arm/include/asm/string.h | 18 ++-
arch/arm/include/asm/thread_info.h | 4 +
arch/arm/kernel/entry-armv.S | 7 +-
arch/arm/kernel/head-common.S | 4 +
arch/arm/kernel/setup.c | 2 +
arch/arm/kernel/unwind.c | 3 +-
arch/arm/lib/memcpy.S | 3 +
arch/arm/lib/memmove.S | 5 +-
arch/arm/lib/memset.S | 3 +
arch/arm/mm/Makefile | 5 +
arch/arm/mm/init.c | 6 +
arch/arm/mm/kasan_init.c | 265 +++++++++++++++++++++++++++++++++++++
arch/arm/mm/mmu.c | 7 +-
arch/arm/mm/pgd.c | 12 ++
arch/arm/vdso/Makefile | 2 +
mm/kasan/kasan.c | 22 ++-
24 files changed, 478 insertions(+), 7 deletions(-)
create mode 100644 arch/arm/include/asm/kasan.h
create mode 100644 arch/arm/include/asm/kasan_def.h
create mode 100644 arch/arm/mm/kasan_init.c


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