On Thu, Dec 14, 2023 at 12:24:47AM +0100, Ilya Leoshkevich wrote:
> KMSAN generates the following false positives on s390x:
>
> [ 6.063666] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
> [ ...]
> [ 6.577050] Call Trace:
> [ 6.619637] [<000000000690d2de>] check_flags+0x1fe/0x210
> [ 6.665411] ([<000000000690d2da>] check_flags+0x1fa/0x210)
> [ 6.707478] [<00000000006cec1a>] lock_acquire+0x2ca/0xce0
> [ 6.749959] [<00000000069820ea>] _raw_spin_lock_irqsave+0xea/0x190
> [ 6.794912] [<00000000041fc988>] __stack_depot_save+0x218/0x5b0
> [ 6.838420] [<000000000197affe>] __msan_poison_alloca+0xfe/0x1a0
> [ 6.882985] [<0000000007c5827c>] start_kernel+0x70c/0xd50
> [ 6.927454] [<0000000000100036>] startup_continue+0x36/0x40
>
> Between trace_hardirqs_on() and `stosm __mask, 3` lockdep thinks that
> interrupts are on, but on the CPU they are still off. KMSAN
> instrumentation takes spinlocks, giving lockdep a chance to see and
> complain about this discrepancy.
>
> KMSAN instrumentation is inserted in order to poison the __mask
> variable. Disable instrumentation in the respective functions. They are
> very small and it's easy to see that no important metadata updates are
> lost because of this.
>
> Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
> ---
> arch/s390/include/asm/irqflags.h | 18 +++++++++++++++---
> drivers/s390/char/sclp.c | 2 +-
> 2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/include/asm/irqflags.h
> b/arch/s390/include/asm/irqflags.h
> index 02427b205c11..7353a88b2ae2 100644
> --- a/arch/s390/include/asm/irqflags.h
> +++ b/arch/s390/include/asm/irqflags.h
> @@ -37,12 +37,19 @@ static __always_inline void __arch_local_irq_ssm(unsigned
> long flags)
> asm volatile("ssm %0" : : "Q" (flags) : "memory");
> }
>
> -static __always_inline unsigned long arch_local_save_flags(void)
> +#ifdef CONFIG_KMSAN
> +#define ARCH_LOCAL_IRQ_ATTRIBUTES \
> + noinline notrace __no_sanitize_memory __maybe_unused
> +#else
> +#define ARCH_LOCAL_IRQ_ATTRIBUTES __always_inline
> +#endif
> +
> +static ARCH_LOCAL_IRQ_ATTRIBUTES unsigned long arch_local_save_flags(void)
> {
Please change this to lower case and long single lines, so it matches the
more common patterns:
#ifdef CONFIG_KMSAN
#define __arch_local_irq_attributes noinline notrace __no_sanitize_memory
__maybe_unused
#else
#define __arch_local_irq_attributes __always_inline
#endif
static __arch_local_irq_attributes unsigned long arch_local_save_flags(void)
...
