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

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Message-ID: <5335761.T8zu0iijAy@wuerfel>
Date:	Sat, 02 Jan 2016 23:40:51 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	y2038@...ts.linaro.org
Cc:	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	gregkh@...uxfoundation.org, broonie@...nel.org,
	Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [Y2038] [PATCH v2 2/2] ppdev: add support for compat ioctl

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.

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

	Arnd


diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index dcf26537c935..e65e7d932566 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -1019,28 +1019,6 @@ COMPATIBLE_IOCTL(PPPIOCGL2TPSTATS)
 /* PPPOX */
 COMPATIBLE_IOCTL(PPPOEIOCSFWD)
 COMPATIBLE_IOCTL(PPPOEIOCDFWD)
-/* ppdev */
-COMPATIBLE_IOCTL(PPSETMODE)
-COMPATIBLE_IOCTL(PPRSTATUS)
-COMPATIBLE_IOCTL(PPRCONTROL)
-COMPATIBLE_IOCTL(PPWCONTROL)
-COMPATIBLE_IOCTL(PPFCONTROL)
-COMPATIBLE_IOCTL(PPRDATA)
-COMPATIBLE_IOCTL(PPWDATA)
-COMPATIBLE_IOCTL(PPCLAIM)
-COMPATIBLE_IOCTL(PPRELEASE)
-COMPATIBLE_IOCTL(PPYIELD)
-COMPATIBLE_IOCTL(PPEXCL)
-COMPATIBLE_IOCTL(PPDATADIR)
-COMPATIBLE_IOCTL(PPNEGOT)
-COMPATIBLE_IOCTL(PPWCTLONIRQ)
-COMPATIBLE_IOCTL(PPCLRIRQ)
-COMPATIBLE_IOCTL(PPSETPHASE)
-COMPATIBLE_IOCTL(PPGETMODES)
-COMPATIBLE_IOCTL(PPGETMODE)
-COMPATIBLE_IOCTL(PPGETPHASE)
-COMPATIBLE_IOCTL(PPGETFLAGS)
-COMPATIBLE_IOCTL(PPSETFLAGS)
 /* Big A */
 /* sparc only */
 /* Big Q for sound/OSS */

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