Re: [Y2038] [PATCH v2 2/2] ppdev: add support for compat ioctl

From: Sudip Mukherjee
Date: Mon Jan 04 2016 - 08:15:10 EST


On Sat, Jan 02, 2016 at 11:40:51PM +0100, Arnd Bergmann wrote:
> On Saturday 02 January 2016 11:59:29 Sudip Mukherjee wrote:
> > >
> > > Just to be sure we are talking about the same thing: you mean running a 64-bit
> > > kernel in a kvm guest with a 32-bit file system, right? Running a 32-bit
> > > kvm guest on a 64-bit host would not be interesting of course.
> >
> > The kvm (actually qemu, started from virt-manager with -enable-kvm) that
> > I just configured shows the following:
> >
> > lscpu shows:
> >
> > Architecture: i686
> > CPU op-mode(s): 32-bit, 64-bit
> > Byte Order: Little Endian
> > CPU(s): 1
> > On-line CPU(s) list: 0
> > Thread(s) per core: 1
> > Core(s) per socket: 1
> > Socket(s): 1
> > Vendor ID: GenuineIntel
> > CPU family: 6
> > Model: 6
> > Stepping: 3
> > CPU MHz: 2993.200
> > BogoMIPS: 5986.40
> > Virtualization: VT-x
> > Hypervisor vendor: KVM
> > Virtualization type: full
> > L1d cache: 32K
> > L1i cache: 32K
> > L2 cache: 4096K
> >
> > uname -i shows:
> > i686
> >
> >
> > Will it be ok to test in this one?
>
>
> If 'uname -i' reports i686, that usually means you have configured the
> kernel for 32-bit. Try rebuilding the kernel with 'CONFIG_64BIT' and
> 'CONFIG_IA32_EMULATION' enabled to test that the 32-bit user space now
> also works under a 64-bit kernel.

done... tested with CONFIG_64BIT and CONFIG_IA32_EMULATION. The original
ppdev code failed with my userspace test code. After applying patch 1/2
of v3 it still failed, but after applying 2/2 of v3 it worked.
will you take v3 through your y2038 tree? or I can keep them for,
ummmmm, 4.6 merge window.

>
> That reminds me, we should now remove the code from fs/compat_ioctl.c
> that was handling emulating the other ioctl commands, the new .compat_ioctl
> callback in ppdev takes care of that along with the PPGETTIME/PPSETTIME
> calls, see below

Bamvor, care to send a patch for these also...

regards
sudip
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