This patch series addresses the fragmentation in KASAN initialization
across architectures by introducing a unified approach that eliminates
duplicate static keys and arch-specific kasan_arch_is_ready()
implementations.
The core issue is that different architectures have inconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions
or always-on behavior
Changes in v5:
- Unified patches where arch (powerpc, UML, loongarch) selects
ARCH_DEFER_KASAN in the first patch not to break
bisectability. So in v5 we have 2 patches now in the series instead of 9.
- Removed kasan_arch_is_ready completely as there is no user
- Removed __wrappers in v4, left only those where it's necessary
due to different implementations
Tested on:
- powerpc - selects ARCH_DEFER_KASAN
Built ppc64_defconfig (PPC_BOOK3S_64) - OK
Booted via qemu-system-ppc64 - OK
I have not tested in v4 powerpc without KASAN enabled.
In v4 arch/powerpc/Kconfig it was:
select ARCH_DEFER_KASAN if PPC_RADIX_MMU
and compiling with ppc64_defconfig caused:
lib/stackdepot.o:(__jump_table+0x8): undefined reference to
`kasan_flag_enabled'
I have fixed it in v5 via adding KASAN condition:
select ARCH_DEFER_KASAN if KASAN && PPC_RADIX_MMU
- um - selects ARCH_DEFER_KASAN
KASAN_GENERIC && KASAN_INLINE && STATIC_LINK
Before:
In file included from mm/kasan/common.c:32:
mm/kasan/kasan.h:550:2: error: #error kasan_arch_is_ready only
works in KASAN generic outline mode!
550 | #error kasan_arch_is_ready only works in KASAN generic
outline mode
After (with auto-selected ARCH_DEFER_KASAN):
./arch/um/include/asm/kasan.h:29:2: error: #error UML does not
work in KASAN_INLINE mode with STATIC_LINK enabled!
29 | #error UML does not work in KASAN_INLINE mode with
STATIC_LINK enabled!
KASAN_GENERIC && KASAN_OUTLINE && STATIC_LINK &&
Before:
./linux boots.
After (with auto-selected ARCH_DEFER_KASAN):
./linux boots.
KASAN_GENERIC && KASAN_OUTLINE && !STATIC_LINK
Before:
./linux boots
After (with auto-disabled !ARCH_DEFER_KASAN):
./linux boots
- loongarch - selects ARCH_DEFER_KASAN
Built defconfig with KASAN_GENERIC - OK
Haven't tested the boot. Asking Loongarch developers to verify - N/A
But should be good, since Loongarch does not have specific "kasan_init()"
call like UML does. It selects ARCH_DEFER_KASAN and calls kasan_init()
in the end of setup_arch() after jump_label_init().
Previous v4 thread:
https://lore.kernel.org/all/20250805142622.560992-1-snovit...@gmail.com/
Previous v3 thread:
https://lore.kernel.org/all/20250717142732.292822-1-snovit...@gmail.com/
Previous v2 thread:
https://lore.kernel.org/all/20250626153147.145312-1-snovit...@gmail.com/
Sabyrzhan Tasbolatov (2):
kasan: introduce ARCH_DEFER_KASAN and unify static key across modes
kasan: call kasan_init_generic in kasan_init
arch/arm/mm/kasan_init.c | 2 +-
arch/arm64/mm/kasan_init.c | 4 +---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/kasan.h | 7 ------
arch/loongarch/mm/kasan_init.c | 8 +++----
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/kasan.h | 12 ----------
arch/powerpc/mm/kasan/init_32.c | 2 +-
arch/powerpc/mm/kasan/init_book3e_64.c | 2 +-
arch/powerpc/mm/kasan/init_book3s_64.c | 6 +----
arch/riscv/mm/kasan_init.c | 1 +
arch/s390/kernel/early.c | 3 ++-
arch/um/Kconfig | 1 +
arch/um/include/asm/kasan.h | 5 ++--
arch/um/kernel/mem.c | 10 ++++++--
arch/x86/mm/kasan_init_64.c | 2 +-
arch/xtensa/mm/kasan_init.c | 2 +-
include/linux/kasan-enabled.h | 32 ++++++++++++++++++--------
include/linux/kasan.h | 6 +++++
lib/Kconfig.kasan | 8 +++++++
mm/kasan/common.c | 17 ++++++++++----
mm/kasan/generic.c | 19 +++++++++++----
mm/kasan/hw_tags.c | 9 +-------
mm/kasan/kasan.h | 8 ++++++-
mm/kasan/shadow.c | 12 +++++-----
mm/kasan/sw_tags.c | 1 +
mm/kasan/tags.c | 2 +-
27 files changed, 107 insertions(+), 76 deletions(-)
--
2.34.1
