Re: [ckrm-tech] Re: [PATCH] Process Events Connector

[Evgeniy Polyakov <johnpol@2ka.mipt.ru>]

On Fri, Oct 28, 2005 at 05:57:18PM -0700, Matt Helsley (matthltc@us.ibm.com) wrote:
> On Fri, 2005-10-28 at 16:56 -0700, Matt Helsley wrote:
> > OK, I wasn't as thorough as I had hoped re: 64-bit kernel/32-bit
> > userspace. The uid_t and gid_t types appear to present a problem to the
> > following:
> > 
> > User  <-> Kernel
> > i386  <-> x86_64/IA64
> > sparc <-> sparc64
> > s390  <-> s390x
> > 
> > :(
> > 
> > 	I'll look at this some more and see if I need to resubmit. Until then
> > I'll hold off on my request for inclusion in -mm.
> > 
> > Cheers,
> > 	-Matt Helsley
> 
> 	Userspace can include sys/types.h -- in which case uid_t and gid_t
> match -- or linux/types.h -- in which case they are not guaranteed to
> match. To further complicate things translation is not possible because
> the connector broadcasts the events to multiple 'listener's. A mix of 32
> and 64-bit userspace programs could be listening; guaranteeing
> incompatibility if the structure layouts do not match.
> 
> 	This patch addresses the problem by fixing the size to the largest size
> found in the kernel (and likely the largest size needed). This preserves
> the total size of the event structure while ensuring that the event
> structure layouts match.
> 
> 	Are there better alternative solutions?

Do not know about is it better or not, but you can use
a bit in connector header flags to specify if kernelspace has
64 or 32 bit ABI, so your userspace application could use it's own 
__gid_t/__uid_t which match the kernel.
Since connector header has always the same size, you will not have
problems except usage of own, probably non-standard, types.

> Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
> 
> ---
> 
> Index: linux-2.6.14/include/linux/cn_proc.h
> ===================================================================
> --- linux-2.6.14.orig/include/linux/cn_proc.h
> +++ linux-2.6.14/include/linux/cn_proc.h
> @@ -84,16 +84,16 @@ struct proc_event {
>  
>  		struct id_proc_event {
>  			pid_t process_pid;
>  			pid_t process_tgid;
>  			union {
> -				uid_t ruid; /* current->uid */
> -				gid_t rgid; /* current->gid */
> +				__u32 ruid; /* task uid */
> +				__u32 rgid; /* task gid */
>  			};
>  			union {
> -				uid_t euid;
> -				gid_t egid;
> +				__u32 euid;
> +				__u32 egid;
>  			};
>  		} id;
>  
>  		struct exit_proc_event {
>  			pid_t process_pid;
> 

-- 
	Evgeniy Polyakov