[PATCH v3 0/5] arm64: kasan: support CONFIG_KASAN_VMALLOC

[Lecopzer Chen]

Linux supports KAsan for VMALLOC since commit 3c5c3cfb9ef4da9
("kasan: support backing vmalloc space with real shadow memory")

Acroding to how x86 ported it [1], they early allocated p4d and pgd,
but in arm64 I just simulate how KAsan supports MODULES_VADDR in arm64
by not to populate the vmalloc area except for kimg address.

  -----------  vmalloc_shadow_start
 |           |
 |           | 
 |           | <= non-mapping
 |           |
 |           |
 |-----------|
 |///////////|<- kimage shadow with page table mapping.
 |-----------|
 |           |
 |           | <= non-mapping
 |           |
 ------------- vmalloc_shadow_end
 |00000000000|
 |00000000000| <= Zero shadow
 |00000000000|
 ------------- KASAN_SHADOW_END


Test environment:
    4G and 8G Qemu virt, 
    39-bit VA + 4k PAGE_SIZE with 3-level page table,
    test by lib/test_kasan.ko and lib/test_kasan_module.ko

It works in Kaslr with CONFIG_RANDOMIZE_MODULE_REGION_FULL
and randomize module region inside vmalloc area.

Also work with VMAP_STACK, thanks Ard for testing it.


[1]: commit 0609ae011deb41c ("x86/kasan: support KASAN_VMALLOC")


Signed-off-by: Lecopzer Chen <lecopzer.chen at mediatek.com>
Acked-by: Andrey Konovalov <andreyknvl at google.com>
Tested-by: Andrey Konovalov <andreyknvl at google.com>
Tested-by: Ard Biesheuvel <ardb at kernel.org>

---
Thanks Will Deacon, Ard Biesheuvel and Andrey Konovalov
for reviewing and suggestion.

v3 -> v2
rebase on 5.11-rc6
	1. remove always true condition in kasan_init() and remove unsed
	   vmalloc_shadow_start.
	2. select KASAN_VMALLOC if KANSAN_GENERIC is enabled
	   for VMAP_STACK.
	3. tweak commit message

v2 -> v1
	1. kasan_init.c tweak indent
	2. change Kconfig depends only on HAVE_ARCH_KASAN
	3. support randomized module region.


v2:
https://lkml.org/lkml/2021/1/9/49
v1:
https://lore.kernel.org/lkml/20210103171137.153834-1-lecopzer@gmail.com/
---
Lecopzer Chen (5):
  arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC
  arm64: kasan: abstract _text and _end to KERNEL_START/END
  arm64: Kconfig: support CONFIG_KASAN_VMALLOC
  arm64: kaslr: support randomized module area with KASAN_VMALLOC
  arm64: Kconfig: select KASAN_VMALLOC if KANSAN_GENERIC is enabled

 arch/arm64/Kconfig         |  2 ++
 arch/arm64/kernel/kaslr.c  | 18 ++++++++++--------
 arch/arm64/kernel/module.c | 16 +++++++++-------
 arch/arm64/mm/kasan_init.c | 24 ++++++++++++++++--------
 4 files changed, 37 insertions(+), 23 deletions(-)

-- 
2.25.1