[PATCH 5/6] arm64: Advertise CPUs capable of running 32-bit applcations in sysfs

[Catalin Marinas]

On Tue, Oct 27, 2020 at 09:51:17PM +0000, Will Deacon wrote:
> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
> index b555df825447..19893fb8e870 100644
> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> @@ -472,6 +472,14 @@ Description:	AArch64 CPU registers
>  		'identification' directory exposes the CPU ID registers for
>  		 identifying model and revision of the CPU.
>  
> +What:		/sys/devices/system/cpu/aarch32_el0

Nitpick: should we call this aarch32_el0_present? It's not exactly
present as we populate it as CPUs come online but it's closer to this
mask than to the online one.

> +Date:		October 2020
> +Contact:	Linux ARM Kernel Mailing list <linux-arm-kernel at lists.infradead.org>
> +Description:	Identifies the subset of CPUs in the system that can execute
> +		AArch32 (32-bit ARM) applications. If absent, then all or none
> +		of the CPUs can execute AArch32 applications and execve() will
> +		behave accordingly.

What does "accordingly" mean? Normally, we'd get ENOEXEC but here the
execve() "succeeds" followed by a SIGKILL if it ends up on the wrong
CPU.

-- 
Catalin