[PATCH v3 0/6] Enable strict percpu address space checks

Uros Bizjak
2024-12-08T20:47:23Z

Enable 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. The proposed patch by Dan Carpenter to implement
__typeof_unqual__() handling in sparse is located at:

https://lore.kernel.org/lkml/5b8d0dee-8fb6-45af-ba6c-7f74aff9a4b8@stanley.mountain/

v2: - Add comment to remove test for __CHECKER__ once sparse learns
about __typeof_unqual__.
- Add Acked-by: tags.
v3: - Rename __per_cpu_qual to __percpu_qual.
- Add more Acked-by: tags.

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: Nadav Amit <nadav.amit@gmail.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
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 | 38 ++++++++++++++++++++++++---------
arch/x86/kernel/kgdb.c | 2 +-
fs/bcachefs/util.h | 2 +-
include/asm-generic/percpu.h | 39 ++++++++++++++++++++++------------
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, 82 insertions(+), 36 deletions(-)

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2.42.0