ioctl ABI considerations for 64b ARM?

Arnd Bergmann arnd at arndb.de
Mon Sep 19 17:44:28 UTC 2011


On Monday 19 September 2011 19:36:27 Arnd Bergmann wrote:
> > 
> > Hmm, so then since you can build the kernel w/ OABI compatibility, it
> > seems like structs should always have padding fields to force them to
> > be a multiple of 32bits...
> 
> It depends on whether you want those structures to be compatible with
> any other structure. To give a different example, qemu-user supports
> converting ioctl data structures to the host data structure for
> any commands it knows. When you want to run an arm-oabi binary for
> instance on an x86-32 host, you need to conver the data structures
> that have this layout, but not when running the same program built
> for arm-eabi.
> 
> In either case however, you will have to convert the data structures
> that contain pointers running qemu-user on x86-64.

Sorry, I misunderstood your question. Yes, as Nicolas explained,
the oabi-compat code in an arm-eabi kernel is broken indeed but
works most of the time in practice.

	Arnd



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