Message-Id: <20250626153147.145312-1-snovitoll@gmail.com>
Date: Thu, 26 Jun 2025 20:31:36 +0500
From: Sabyrzhan Tasbolatov <snovitoll@...il.com>
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Subject: [PATCH v2 00/11] kasan: unify kasan_arch_is_ready with kasan_enabled

This patch series unifies the kasan_arch_is_ready() and kasan_enabled()
interfaces by extending the existing kasan_enabled() infrastructure to
work consistently across all KASAN modes (Generic, SW_TAGS, HW_TAGS).

Currently, kasan_enabled() only works for HW_TAGS mode using a static key,
while other modes either return IS_ENABLED(CONFIG_KASAN) (compile-time
constant) or rely on architecture-specific kasan_arch_is_ready()
implementations with custom static keys and global variables.

This leads to:
- Code duplication across architectures  
- Inconsistent runtime behavior between KASAN modes
- Architecture-specific readiness tracking

After this series:
- All KASAN modes use the same kasan_flag_enabled static key
- Consistent runtime enable/disable behavior across modes
- Simplified architecture code with unified kasan_init_generic() calls
- Elimination of arch specific kasan_arch_is_ready() implementations
- Unified vmalloc integration using kasan_enabled() checks

This addresses the bugzilla issue [1] about making
kasan_flag_enabled and kasan_enabled() work for Generic mode,
and extends it to provide true unification across all modes.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=217049

=== Current mainline KUnit status

To see if there is any regression, I've tested first on the following
commit 739a6c93cc75 ("Merge tag 'nfsd-6.16-1' of
git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux").

Tested via compiling a kernel with CONFIG_KASAN_KUNIT_TEST and running
QEMU VM. There are failing tests in SW_TAGS and GENERIC modes in arm64:

arm64 CONFIG_KASAN_HW_TAGS:
	# kasan: pass:62 fail:0 skip:13 total:75
	# Totals: pass:62 fail:0 skip:13 total:75
	ok 1 kasan

arm64 CONFIG_KASAN_SW_TAGS=y:
	# kasan: pass:65 fail:1 skip:9 total:75
	# Totals: pass:65 fail:1 skip:9 total:75
	not ok 1 kasan
	# kasan_strings: EXPECTATION FAILED at mm/kasan/kasan_test_c.c:1598
	KASAN failure expected in "strscpy(ptr, src + KASAN_GRANULE_SIZE, KASAN_GRANULE_SIZE)", but none occurred

arm64 CONFIG_KASAN_GENERIC=y, CONFIG_KASAN_OUTLINE=y:
	# kasan: pass:61 fail:1 skip:13 total:75
	# Totals: pass:61 fail:1 skip:13 total:75
	not ok 1 kasan
	# same failure as above

x86_64 CONFIG_KASAN_GENERIC=y:
	# kasan: pass:58 fail:0 skip:17 total:75
	# Totals: pass:58 fail:0 skip:17 total:75
	ok 1 kasan

=== Testing with patches

Testing in v2:

- Compiled every affected arch with no errors:

$ make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \
	OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \
	HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld \
	ARCH=$ARCH

$ clang --version
ClangBuiltLinux clang version 19.1.4
Target: x86_64-unknown-linux-gnu
Thread model: posix

- make ARCH=um produces the warning during compiling:
	MODPOST Module.symvers
	WARNING: modpost: vmlinux: section mismatch in reference: \
		kasan_init+0x43 (section: .ltext) -> \
		kasan_init_generic (section: .init.text)

AFAIU, it's due to the code in arch/um/kernel/mem.c, where kasan_init()
is placed in own section ".kasan_init", which calls kasan_init_generic()
which is marked with "__init".

- Booting via qemu-system- and running KUnit tests:

* arm64  (GENERIC, HW_TAGS, SW_TAGS): no regression, same above results.
* x86_64 (GENERIC): no regression, no errors

=== NB

I haven't tested the kernel boot on the following arch. due to the absence
of qemu-system- support on those arch on my machine, so I defer this to
relevant arch people to test KASAN initialization:
- loongarch
- s390
- um
- xtensa
- powerpc
- riscv

Code changes in v2:
- Replace the order of patches. Move "kasan: replace kasan_arch_is_ready
	with kasan_enabled" at the end to keep the compatibility.
- arch/arm, arch/riscv: add 2 arch. missed in v1
- arch/powerpc: add kasan_init_generic() in other kasan_init() calls:
	arch/powerpc/mm/kasan/init_32.c
	arch/powerpc/mm/kasan/init_book3e_64.c
- arch/um: add the proper header `#include <linux/kasan.h>`. Tested
	via compiling with no errors. In the v1 arch/um changes were acked-by
	Johannes Berg, though I don't include it due to the changed code in v2.
- arch/powerpc: add back `#ifdef CONFIG_KASAN` deleted in v1 and tested
	the compilation.
- arch/loongarch: update git commit message about non-standard flow of
	calling kasan_init_generic()

Sabyrzhan Tasbolatov (11):
  kasan: unify static kasan_flag_enabled across modes
  kasan/arm64: call kasan_init_generic in kasan_init
  kasan/arm: call kasan_init_generic in kasan_init
  kasan/xtensa: call kasan_init_generic in kasan_init
  kasan/loongarch: call kasan_init_generic in kasan_init
  kasan/um: call kasan_init_generic in kasan_init
  kasan/x86: call kasan_init_generic in kasan_init
  kasan/s390: call kasan_init_generic in kasan_init
  kasan/powerpc: call kasan_init_generic in kasan_init
  kasan/riscv: call kasan_init_generic in kasan_init
  kasan: replace kasan_arch_is_ready with kasan_enabled

 arch/arm/mm/kasan_init.c               |  2 +-
 arch/arm64/mm/kasan_init.c             |  4 +---
 arch/loongarch/include/asm/kasan.h     |  7 -------
 arch/loongarch/mm/kasan_init.c         |  7 ++-----
 arch/powerpc/include/asm/kasan.h       | 13 -------------
 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/include/asm/kasan.h            |  5 -----
 arch/um/kernel/mem.c                   |  4 ++--
 arch/x86/mm/kasan_init_64.c            |  2 +-
 arch/xtensa/mm/kasan_init.c            |  2 +-
 include/linux/kasan-enabled.h          | 22 ++++++++++++++++------
 include/linux/kasan.h                  |  6 ++++++
 mm/kasan/common.c                      | 15 +++++++++++----
 mm/kasan/generic.c                     | 17 ++++++++++++++---
 mm/kasan/hw_tags.c                     |  7 -------
 mm/kasan/kasan.h                       |  6 ------
 mm/kasan/shadow.c                      | 15 +++------------
 mm/kasan/sw_tags.c                     |  2 ++
 22 files changed, 66 insertions(+), 84 deletions(-)

-- 
2.34.1

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