+ atomic-add-alignment-check-to-instrumented-atomic-operations.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: atomic: add alignment check to instrumented atomic operations
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     atomic-add-alignment-check-to-instrumented-atomic-operations.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/atomic-add-alignment-check-to-instrumented-atomic-operations.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Peter Zijlstra <peterz@infradead.org>
Subject: atomic: add alignment check to instrumented atomic operations
Date: Wed, 31 Dec 2025 19:25:42 +1100

Add a Kconfig option for debug builds which logs a warning when an
instrumented atomic operation takes place that's misaligned.  Some
platforms don't trap for this.

[fthain@linux-m68k.org: added __DISABLE_BUG_TABLE macro]
Link: https://lkml.kernel.org/r/f8cfe0d121be0849f5175495e73eafeeb85e1ad3.1767169542.git.fthain@linux-m68k.org
Link: https://lore.kernel.org/lkml/20250901093600.GF4067720@noisy.programming.kicks-ass.net/
Link: https://lore.kernel.org/linux-next/df9fbd22-a648-ada4-fee0-68fe4325ff82@linux-m68k.org/
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Daniel Borkman <daniel@iogearbox.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Rich Felker <dalias@libc.org>
Cc: Song Liu <song@kernel.org>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Will Deacon <will@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/boot/compressed/Makefile     |    1 +
 drivers/firmware/efi/libstub/Makefile |    1 +
 include/linux/instrumented.h          |   10 ++++++++++
 lib/Kconfig.debug                     |   10 ++++++++++
 4 files changed, 22 insertions(+)

--- a/arch/x86/boot/compressed/Makefile~atomic-add-alignment-check-to-instrumented-atomic-operations
+++ a/arch/x86/boot/compressed/Makefile
@@ -42,6 +42,7 @@ KBUILD_CFLAGS += -Wno-microsoft-anon-tag
 endif
 KBUILD_CFLAGS += -Wno-pointer-sign
 KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
+KBUILD_CFLAGS += -D__DISABLE_BUG_TABLE
 KBUILD_CFLAGS += -D__DISABLE_EXPORTS
 # Disable relocation relaxation in case the link is not PIE.
 KBUILD_CFLAGS += $(call cc-option,-Wa$(comma)-mrelax-relocations=no)
--- a/drivers/firmware/efi/libstub/Makefile~atomic-add-alignment-check-to-instrumented-atomic-operations
+++ a/drivers/firmware/efi/libstub/Makefile
@@ -42,6 +42,7 @@ KBUILD_CFLAGS			:= $(subst $(CC_FLAGS_FT
 				   -ffreestanding \
 				   -fno-stack-protector \
 				   $(call cc-option,-fno-addrsig) \
+				   -D__DISABLE_BUG_TABLE \
 				   -D__DISABLE_EXPORTS
 
 #
--- a/include/linux/instrumented.h~atomic-add-alignment-check-to-instrumented-atomic-operations
+++ a/include/linux/instrumented.h
@@ -7,6 +7,7 @@
 #ifndef _LINUX_INSTRUMENTED_H
 #define _LINUX_INSTRUMENTED_H
 
+#include <linux/bug.h>
 #include <linux/compiler.h>
 #include <linux/kasan-checks.h>
 #include <linux/kcsan-checks.h>
@@ -67,6 +68,9 @@ static __always_inline void instrument_a
 {
 	kasan_check_read(v, size);
 	kcsan_check_atomic_read(v, size);
+#ifndef __DISABLE_BUG_TABLE
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_DEBUG_ATOMIC) && ((unsigned long)v & (size - 1)));
+#endif
 }
 
 /**
@@ -81,6 +85,9 @@ static __always_inline void instrument_a
 {
 	kasan_check_write(v, size);
 	kcsan_check_atomic_write(v, size);
+#ifndef __DISABLE_BUG_TABLE
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_DEBUG_ATOMIC) && ((unsigned long)v & (size - 1)));
+#endif
 }
 
 /**
@@ -95,6 +102,9 @@ static __always_inline void instrument_a
 {
 	kasan_check_write(v, size);
 	kcsan_check_atomic_read_write(v, size);
+#ifndef __DISABLE_BUG_TABLE
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_DEBUG_ATOMIC) && ((unsigned long)v & (size - 1)));
+#endif
 }
 
 /**
--- a/lib/Kconfig.debug~atomic-add-alignment-check-to-instrumented-atomic-operations
+++ a/lib/Kconfig.debug
@@ -1360,6 +1360,16 @@ config DEBUG_PREEMPT
 	  depending on workload as it triggers debugging routines for each
 	  this_cpu operation. It should only be used for debugging purposes.
 
+config DEBUG_ATOMIC
+	bool "Debug atomic variables"
+	depends on DEBUG_KERNEL
+	help
+	  If you say Y here then the kernel will add a runtime alignment check
+	  to atomic accesses. Useful for architectures that do not have trap on
+	  mis-aligned access.
+
+	  This option has potentially significant overhead.
+
 menu "Lock Debugging (spinlocks, mutexes, etc...)"
 
 config LOCK_DEBUGGING_SUPPORT
_

Patches currently in -mm which might be from peterz@infradead.org are

atomic-add-alignment-check-to-instrumented-atomic-operations.patch