From: Kees Cook <kees@kernel.org>
To: linux-arch@vger.kernel.org
Cc: Kees Cook <kees@kernel.org>,
linux-kernel@vger.kernel.org, x86@kernel.org,
linux-alpha@vger.kernel.org, linux-csky@vger.kernel.org,
linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org,
linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
llvm@lists.linux.dev, linux-hardening@vger.kernel.org
Subject: [PATCH 00/17] Add __attribute_const__ to ffs()-family implementations
Date: Mon, 4 Aug 2025 09:43:56 -0700 [thread overview]
Message-ID: <20250804163910.work.929-kees@kernel.org> (raw)
Hi,
While tracking down a problem where constant expressions used by
BUILD_BUG_ON() suddenly stopped working[1], we found that an added static
initializer was convincing the compiler that it couldn't track the state
of the prior statically initialized value. Tracing this down found that
ffs() was used in the initializer macro, but since it wasn't marked with
__attribute_const__, the compiler had to assume the function might
change variable states as a side-effect (which is not true for ffs(),
which provides deterministic math results).
Add KUnit tests for the family of functions and then add __attribute_const__
to all architecture implementations and wrappers.
-Kees
[1] https://github.com/KSPP/linux/issues/364
Kees Cook (17):
KUnit: Introduce ffs()-family tests
bitops: Add __attribute_const__ to generic ffs()-family
implementations
csky: Add __attribute_const__ to ffs()-family implementations
x86: Add __attribute_const__ to ffs()-family implementations
powerpc: Add __attribute_const__ to ffs()-family implementations
sh: Add __attribute_const__ to ffs()-family implementations
alpha: Add __attribute_const__ to ffs()-family implementations
hexagon: Add __attribute_const__ to ffs()-family implementations
riscv: Add __attribute_const__ to ffs()-family implementations
openrisc: Add __attribute_const__ to ffs()-family implementations
m68k: Add __attribute_const__ to ffs()-family implementations
mips: Add __attribute_const__ to ffs()-family implementations
parisc: Add __attribute_const__ to ffs()-family implementations
s390: Add __attribute_const__ to ffs()-family implementations
xtensa: Add __attribute_const__ to ffs()-family implementations
sparc: Add __attribute_const__ to ffs()-family implementations
KUnit: ffs: Validate all the __attribute_const__ annotations
lib/Kconfig.debug | 14 +
lib/tests/Makefile | 1 +
arch/alpha/include/asm/bitops.h | 14 +-
arch/csky/include/asm/bitops.h | 8 +-
arch/hexagon/include/asm/bitops.h | 10 +-
arch/m68k/include/asm/bitops.h | 14 +-
arch/mips/include/asm/bitops.h | 8 +-
arch/openrisc/include/asm/bitops/__ffs.h | 2 +-
arch/openrisc/include/asm/bitops/__fls.h | 2 +-
arch/openrisc/include/asm/bitops/ffs.h | 2 +-
arch/openrisc/include/asm/bitops/fls.h | 2 +-
arch/parisc/include/asm/bitops.h | 6 +-
arch/powerpc/include/asm/bitops.h | 4 +-
arch/riscv/include/asm/bitops.h | 6 +-
arch/s390/include/asm/bitops.h | 10 +-
arch/sh/include/asm/bitops.h | 4 +-
arch/sparc/include/asm/bitops_64.h | 8 +-
arch/x86/include/asm/bitops.h | 12 +-
arch/xtensa/include/asm/bitops.h | 10 +-
include/asm-generic/bitops/__ffs.h | 2 +-
include/asm-generic/bitops/__fls.h | 2 +-
include/asm-generic/bitops/builtin-__ffs.h | 2 +-
include/asm-generic/bitops/builtin-__fls.h | 2 +-
include/asm-generic/bitops/builtin-fls.h | 2 +-
include/asm-generic/bitops/ffs.h | 2 +-
include/asm-generic/bitops/fls.h | 2 +-
include/asm-generic/bitops/fls64.h | 4 +-
include/linux/bitops.h | 2 +-
lib/clz_ctz.c | 8 +-
lib/tests/ffs_kunit.c | 566 +++++++++++++++++++++
30 files changed, 656 insertions(+), 75 deletions(-)
create mode 100644 lib/tests/ffs_kunit.c
--
2.34.1
next reply other threads:[~2025-08-04 16:44 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-04 16:43 Kees Cook [this message]
2025-08-04 16:43 ` [PATCH 01/17] KUnit: Introduce ffs()-family tests Kees Cook
2025-08-04 16:43 ` [PATCH 02/17] bitops: Add __attribute_const__ to generic ffs()-family implementations Kees Cook
2025-08-04 16:43 ` [PATCH 03/17] csky: Add __attribute_const__ to " Kees Cook
2025-08-04 16:44 ` [PATCH 04/17] x86: " Kees Cook
2025-08-04 16:44 ` [PATCH 05/17] powerpc: " Kees Cook
2025-08-07 9:46 ` Madhavan Srinivasan
2025-08-15 16:34 ` Segher Boessenkool
2025-08-15 16:41 ` Segher Boessenkool
2025-08-04 16:44 ` [PATCH 06/17] sh: " Kees Cook
2025-08-04 16:44 ` [PATCH 07/17] alpha: " Kees Cook
2025-08-04 16:44 ` [PATCH 08/17] hexagon: " Kees Cook
2025-08-04 16:44 ` [PATCH 09/17] riscv: " Kees Cook
2025-08-07 14:43 ` Alexandre Ghiti
2025-08-04 16:44 ` [PATCH 10/17] openrisc: " Kees Cook
2025-08-04 17:15 ` Stafford Horne
2025-08-04 16:44 ` [PATCH 11/17] m68k: " Kees Cook
2025-08-05 8:12 ` Geert Uytterhoeven
2025-08-04 16:44 ` [PATCH 12/17] mips: " Kees Cook
2025-08-04 16:44 ` [PATCH 13/17] parisc: " Kees Cook
2025-08-08 9:01 ` Helge Deller
2025-08-04 16:44 ` [PATCH 14/17] s390: " Kees Cook
2025-08-06 10:33 ` Heiko Carstens
2025-08-04 16:44 ` [PATCH 15/17] xtensa: " Kees Cook
2025-08-04 16:44 ` [PATCH 16/17] sparc: " Kees Cook
2025-08-04 16:44 ` [PATCH 17/17] KUnit: ffs: Validate all the __attribute_const__ annotations Kees Cook
2025-08-15 14:16 ` [PATCH 00/17] Add __attribute_const__ to ffs()-family implementations Peter Zijlstra
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