Re: ioctl structs differ from x86_64?

Re: ioctl structs differ from x86_64?

[Harshal Patil]

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Re: ioctl structs differ from x86_64?

[Harshal Patil]

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ioctl structs differ from x86_64?

[Harshal Patil]

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Re: ioctl structs differ from x86_64?

[Arnd Bergmann]

On Tue, Mar 14, 2017 at 11:37 AM, Harshal Patil
<harshal.patil@in.ibm.com> wrote:
> Hello,
>
> I am looking into a bug,
> https://bugzilla.linux.ibm.com/show_bug.cgi?id=152493 ( external mirror is
> at, https://github.com/opencontainers/runc/issues/1364)
>
> Recently in runc code, they added this code
> https://github.com/opencontainers/runc/commit/eea28f480db435dbef4a275de9776b9934818b8c#diff-5f5c07d0cab3ce2086437d3d43c0d25fR155.
> As you can see they set -onlcr to get rid of \r (line no. 164). Golang, in
> which runc is written, doesn't have any bindings for ioctls.  This means you
> have to invoke C code directly (that's what they are doing there).
>
> Our guess is the ioctls in ppc64le differ than x86_64, and thats why the
> code which is clearing onclr bit
> (https://github.com/opencontainers/runc/commit/eea28f480db435dbef4a275de9776b9934818b8c#diff-5f5c07d0cab3ce2086437d3d43c0d25fR164)
> is failing on ppc64le but works fine on x86_64.
>
> Any pointers on the possible solution would be really helpful.

There are a couple of reasons for ioctl numbers to differ:

- like this one, the command number may be defined in asm/ioctls.h.
Most architectures
  in the kernel are the same, some (arm, blackfin, frv, m68k, and
s390) only differ
  in FIOQSIZE, others (alpha, mips, parisc, powerpc, sh, sparc, and
xtensa) redefine
  all the traditional file (FIO*) and tty (TC*, TIO*) commands

- command numbers that are defined in terms of structure sizes depend on the
  architectures type definitions (e.g. long, off_t, uid_t, ...) that
can differ in both
  size and alignment

- alpha, mips, powerpc and sparc use _IOC_SIZEBITS==13, everything else uses
  _IOC_SIZEBITS==14, and that in turn means that the majority of ioctl commands
  are different between those four and the rest.

      Arnd

Re: ioctl structs differ from x86_64?

[Reza Arbab]

On Tue, Mar 14, 2017 at 10:37:44AM +0000, Harshal Patil wrote:
>Our guess is the ioctls in ppc64le differ than x86_64, and thats why 
>the code which is clearing onclr bit 
>([4]https://github.com/opencontainers/runc/commit/eea28f480db435dbef4a275de9776b9934818b8c#diff-5f5c07d0cab3ce2086437d3d43c0d25fR164)
>is failing on ppc64le but works fine on x86_64. 
> 
>Any pointers on the possible solution would be really helpful. 

This looks like a bug in Go.

The syscall.TCGETS and syscall.TCSETS constants have the wrong values. 
They were generated using the glibc termios struct instead of the kernel 
termios struct. It's the issue described here:

https://groups.google.com/forum/#!topic/golang-nuts/K5NoG8slez0

Things work if you replace syscall.TCGETS with 0x402c7413 and 
syscall.TCSETS with 0x802c7414, the correct values on ppc64le.

-- 
Reza Arbab

Re: ioctl structs differ from x86_64?

[Reza Arbab]

On Wed, Mar 15, 2017 at 01:11:19PM -0500, Reza Arbab wrote:
>https://groups.google.com/forum/#!topic/golang-nuts/K5NoG8slez0

Oops.

https://groups.google.com/d/msg/golang-nuts/K5NoG8slez0/mixUse17iaMJ

-- 
Reza Arbab

Re: ioctl structs differ from x86_64?

[Michael Ellerman]

Harshal Patil <harshal.patil@in.ibm.com> writes:

> Hello,
> I am looking into a bug, https://bugzilla.linux.ibm.com/show_bug.cgi?id=152493
> ( external mirror is at, https://github.com/opencontainers/runc/issues/1364) 
> Recently in runc code, they added this code
> https://github.com/opencontainers/runc/commit/eea28f480db435dbef4a275de9776b9934818b8c#diff-5f5c07d0cab3ce2086437d3d43c0d25fR155.
> As you can see they set -onlcr to get rid of \r (line no. 164). Golang, in which
> runc is written, doesn't have any bindings for ioctls. This means you have to
> invoke C code directly (that's what they are doing there).
> Our guess is the ioctls in ppc64le differ than x86_64, and thats why the code
> which is clearing onclr bit
> (https://github.com/opencontainers/runc/commit/eea28f480db435dbef4a275de9776b9934818b8c#diff-5f5c07d0cab3ce2086437d3d43c0d25fR164)
> is failing on ppc64le but works fine on x86_64. 

I think you've probably got enough replies, but the short answer is
"yes", IOCTL numbers do differ across architectures - including
potentially between 32-bit and 64-bit.

cheers