[RFT PATCH] ARM: vfp: Fix broken softirq handling with instrumentation enabled

[Frederic Weisbecker]

Le Tue, Mar 14, 2023 at 01:57:43PM +0100, Ard Biesheuvel a écrit :
> diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S
> index 9a89264cdcc0b46e..9555c0a1c46fd47b 100644
> --- a/arch/arm/vfp/entry.S
> +++ b/arch/arm/vfp/entry.S
> @@ -22,7 +22,23 @@
>  @  IRQs enabled.
>  @
>  ENTRY(do_vfp)
> -	local_bh_disable r10, r4
> +#if defined(CONFIG_PREEMPT_RT) || defined(CONFIG_TRACE_IRQFLAGS)
> +	mov	r4, r0			@ stash r0, r2, lr
> +	mov	r5, r2
> +	mov	r6, lr
> +
> +	adr	r0, .
> +	mov	r1, #SOFTIRQ_DISABLE_OFFSET
> +	bl	__local_bh_disable_ip
> +
> +	mov	r0, r4			@ restore r0, r2, lr
> +	mov	r2, r5
> +	mov	lr, r6
> +#else
> +	ldr	r4, [r10, #TI_PREEMPT]
> +	add	r4, r4, #SOFTIRQ_DISABLE_OFFSET
> +	str	r4, [r10, #TI_PREEMPT]
> +#endi

I suggest you avoid taking any risk and unconditionally call
__local_bh_disable_ip(). You never know what will be added to softirq
APIs in the future.

For example you're missing the CONFIG_DEBUG_PREEMPT part.

Thanks.
>