[PATCH 5/6] arm64: Advertise CPUs capable of running 32-bit applcations in sysfs
Will Deacon
will at kernel.org
Wed Oct 28 08:27:59 EDT 2020
On Wed, Oct 28, 2020 at 12:15:07PM +0000, Catalin Marinas wrote:
> 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.
I don't think so, because a CPU could be set in this mask but not in the
present mask, which is hugely confusing it it has "present" in the name!
> > +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.
No; if the file is absent then execve() behaves as it always has.
Will
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