[vbox-dev] [RFC] VGDrvCommonIoCtl: Add f32bit flag argument

Knut St. Osmundsen knut.osmundsen at oracle.com
Mon Aug 14 11:43:44 UTC 2017

Hi Hans,

the other platforms also have KPIs or similar constructs for figuring
out whether the client process issuing the I/O controls is a 32-bit or
64-bit one.  However, using the VBOXGUEST_IOCTL_FLAG set to 0 or 0x80 if
32-bit or 64-bit was a less complex (+faster(+safer)) way of deal with
this.  The host driver does this as well.  I would like the structure of
the two to be as similar as possible.

I'm not very keen to adding linux specific clutter (f32Bit + #ifndef
RT_OS_LINUX) to the common code just because you can do it differently
only Linux.  Sorry.  Want minimal platform specific cruft in common
code.  Hope you understand.


PS. I noticed in the Linux kernel RFC email thread that we've agreed to
freeze the I/O control ABI.  We cannot guarantee that's it's 100% frozen
at this point, since the generic status code fix (getting rid of that
ioctl non-zero return value) hasn't been done yet.  I will see if I can
squeeze it in later this week.

On 2017-08-14 9:30 AM, Hans de Goede wrote:
> On 14-08-17 09:27, Hans de Goede wrote:
>> Note to linux-kernel readers: This Cc-ed to linux-kernel because it is
>> relevant for the "[RFC 0/2] Add Virtual Box vboxguest and vboxsf guest
>> drivers to the mainline kernel" thread.
>> Hi Michael, Knut,
>> My first submission of the vboxguest driver for inclusion into
>> the Linux kernel has lead to some questions about the use of the
>> VBOXGUEST_IOCTL_FLAG to differentiate between 32 and 64 bit
>> ioctls. Under Linux this is not necessary, as the driver already
>> knows if it is serving a 32 bit compat or a regular ioctl.
>> So I've come up with this patch to make VBOXGUEST_IOCTL_FLAG
>> always 0 under Linux. I was hoping the f32bit flag could be
>> used under more platforms so that it would actually be a cleanup,
>> but it seems that Linux is the only platform with a compat_ioctl
>> callback in its file-operations struct.
>> Please let me know if you would be willing to merge this patch
>> into upstream VirtualBox.
> p.s.
> I've only tested this patch with Linux!
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