Enable strict percpu address space checks [LWN.net]

From:		Uros Bizjak <ubizjak-AT-gmail.com>
To:		x86-AT-kernel.org, linux-sparse-AT-vger.kernel.org, linux-mm-AT-kvack.org, linux-kernel-AT-vger.kernel.org, linux-bcachefs-AT-vger.kernel.org, linux-arch-AT-vger.kernel.org, netdev-AT-vger.kernel.org
Subject:		[PATCH 0/6] Enable strict percpu address space checks
Date:		Tue, 26 Nov 2024 18:21:17 +0100
Message-ID:		<20241126172332.112212-1-ubizjak@gmail.com>
Cc:		Uros Bizjak <ubizjak-AT-gmail.com>, Thomas Gleixner <tglx-AT-linutronix.de>, Dennis Zhou <dennis-AT-kernel.org>, Tejun Heo <tj-AT-kernel.org>, Christoph Lameter <cl-AT-linux.com>, Linus Torvalds <torvalds-AT-linux-foundation.org>, Andy Lutomirski <luto-AT-kernel.org>, Ingo Molnar <mingo-AT-kernel.org>, Luc Van Oostenryck <luc.vanoostenryck-AT-gmail.com>, Nadav Amit <nadav.amit-AT-gmail.com>, Brian Gerst <brgerst-AT-gmail.com>, "H . Peter Anvin" <hpa-AT-zytor.com>, Peter Zijlstra <peterz-AT-infradead.org>
Archive-link:		Article

This patchset enables strict percpu address space checks via x86 named 
address space qualifiers. Percpu variables are declared in
__seg_gs/__seg_fs named AS and kept named AS qualified until they
are dereferenced via percpu accessor. This approach enables various
compiler checks for cross-namespace variable assignments.

Please note that current version of sparse doesn't know anything about
__typeof_unqual__() operator. Avoid the usage of __typeof_unqual__()
when sparse checking is active to prevent sparse errors with unknowing
keyword.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>

Uros Bizjak (6):
  x86/kgdb: Use IS_ERR_PCPU() macro
  compiler.h: Introduce TYPEOF_UNQUAL() macro
  percpu: Use TYPEOF_UNQUAL() in variable declarations
  percpu: Use TYPEOF_UNQUAL() in *_cpu_ptr() accessors
  percpu: Repurpose __percpu tag as a named address space qualifier
  percpu/x86: Enable strict percpu checks via named AS qualifiers

 arch/x86/include/asm/percpu.h  | 34 +++++++++++++++++++---------
 arch/x86/kernel/kgdb.c         |  2 +-
 fs/bcachefs/util.h             |  2 +-
 include/asm-generic/percpu.h   | 41 +++++++++++++++++++++++-----------
 include/linux/compiler.h       | 13 +++++++++++
 include/linux/compiler_types.h |  2 +-
 include/linux/part_stat.h      |  2 +-
 include/linux/percpu-defs.h    |  6 ++---
 include/net/snmp.h             |  5 ++---
 init/Kconfig                   |  3 +++
 kernel/locking/percpu-rwsem.c  |  2 +-
 net/mpls/internal.h            |  4 ++--
 12 files changed, 80 insertions(+), 36 deletions(-)

-- 
2.42.0