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From: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Organization: IBM Deutschland Entwicklung GmbH
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [patch/rfc] s390: get rid of own uid16 compat system calls
Date: Thu, 27 Jul 2006 03:03:42 +0200
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Cc: linux-kernel@vger.kernel.org, Martin Schwidefsky <schwidefsky@de.ibm.com>
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On Monday 10 July 2006 10:51, Heiko Carstens wrote:
> "Only" thing is that we unfortunately have different sizes for
> __kernel_old_[uid|gid]_t (16 bit on s390, 32 on s390x). I was tempted to
> change these just to find out that there are other users as well:
> 
> include/linux/ncp_fs.h:
>  #define NCP_IOC_GETMOUNTUID _IOW('n', 2, __kernel_old_uid_t)
> include/linux/smb_fs.h:
>  #define SMB_IOC_GETMOUNTUID _IOR('u', 1, __kernel_old_uid_t)
> 
> So, this is no option. Would anybody know of something to get this work?
> Or is this just a stupid idea?

Ok, I don't know exactly what you're talking about, but I have in the
past tried to hack that area as well. It's probably a good idea to
pick up my old patch and work from there, by making these two file systems
understand all possible ways:

#ifdef __KERNEL__
/* anything the user may be passing to us */
#define NCP_IOC_GETMOUNTUID16 _IOW('n', 2, u16)
#define NCP_IOC_GETMOUNTUID32 _IOW('n', 2, u32)
#define NCP_IOC_GETMOUNTUID64 _IOW('n', 2, u64)
#else
/* what the user is _supposed_ to pass */
#define NCP_IOC_GETMOUNTUID _IOW('n', 2, __kernel_old_uid_t) /* 16/32 bit */
#define NCP_IOC_GETMOUNTUID2 _IOW('n', 2, unsigned long) /* 32 or 64 bit */
#endif

int ncp_ioctl(struct inode *inode, struct file *filp, ...)
{
	...
	switch (arg) {
		...
	case NCP_IOC_GETMOUNTUID16:
	case NCP_IOC_GETMOUNTUID32:
	case NCP_IOC_GETMOUNTUID64:
		{
			unsigned long tmp = server->m.mounted_uid;

			if ((file_permission(filp, MAY_READ) != 0)
			    && (current->uid != server->m.mounted_uid))	{
				return -EACCES;
			}
			switch (arg) {
#ifdef CONFIG_UID16
			case NCP_IOC_GETMOUNTUID16:
				SET_UID(tmp, server->m.mounted_uid);
				if (put_user(tmp, (u16 __user *)argp)) 
					return -EFAULT;
#endif
			case NCP_IOC_GETMOUNTUID32:
				if (put_user(tmp, (u32 __user *)argp)) 
					return -EFAULT;
#ifdef CONFIG_64BIT
			case NCP_IOC_GETMOUNTUID64:
				if (put_user(tmp, (u64 __user *)argp)) 
					return -EFAULT;
			}
#endif
			return 0;
		}
	}
	...
}

I'm also posting the two patches I made a long time ago as a reference.

	Arnd <><