* RE: ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally a ttached PHYs)
@ 2005-10-21 12:32 Bagalkote, Sreenivas
2005-10-21 12:40 ` Matthew Wilcox
0 siblings, 1 reply; 2+ messages in thread
From: Bagalkote, Sreenivas @ 2005-10-21 12:32 UTC (permalink / raw)
To: 'Jeff Garzik', dougg
Cc: andrew.patterson, Luben Tuikov, Christoph Hellwig, Moore,
Eric Dean, jejb, linux-scsi, Linux Kernel, Linus Torvalds
>Jeff Garzik wrote:
>> Do you know where there are some clear guidelines on the use of
>> pointers in a structure passed to an ioctl to lessen (or bypass)
>> 32<->64 compat ioctl thunking?
>
>Its impossible. If you pass pointers, you need to thunk.
>(Not even passing pointers via sysfs can avoid this.)
>Consider running a 32-bit app (with 32-bit pointers and 32-bit
>ABI) on a 64-bit kernel.
The drivers/scsi/megaraid/megaraid_mm.c simply calls regular ioctl
from within the compat_ioctl, though it does copy to and from the
userland pointers. This is done by adding appropriate padding.
Sincerely,
Sreenivas
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally a ttached PHYs)
2005-10-21 12:32 ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally a ttached PHYs) Bagalkote, Sreenivas
@ 2005-10-21 12:40 ` Matthew Wilcox
0 siblings, 0 replies; 2+ messages in thread
From: Matthew Wilcox @ 2005-10-21 12:40 UTC (permalink / raw)
To: Bagalkote, Sreenivas
Cc: 'Jeff Garzik',
dougg, andrew.patterson, Luben Tuikov, Christoph Hellwig, Moore,
Eric Dean, jejb, linux-scsi, Linux Kernel, Linus Torvalds
On Fri, Oct 21, 2005 at 08:32:25AM -0400, Bagalkote, Sreenivas wrote:
> >Jeff Garzik wrote:
> >> Do you know where there are some clear guidelines on the use of
> >> pointers in a structure passed to an ioctl to lessen (or bypass)
> >> 32<->64 compat ioctl thunking?
> >
> >Its impossible. If you pass pointers, you need to thunk.
> >(Not even passing pointers via sysfs can avoid this.)
> >Consider running a 32-bit app (with 32-bit pointers and 32-bit
> >ABI) on a 64-bit kernel.
>
> The drivers/scsi/megaraid/megaraid_mm.c simply calls regular ioctl
> from within the compat_ioctl, though it does copy to and from the
> userland pointers. This is done by adding appropriate padding.
Yes. This is what is meant by "thunk".
^ permalink raw reply [flat|nested] 2+ messages in thread
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2005-10-21 12:32 ioctls, etc. (was Re: [PATCH 1/4] sas: add flag for locally a ttached PHYs) Bagalkote, Sreenivas
2005-10-21 12:40 ` Matthew Wilcox
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