Date: Fri, 8 Oct 2004 16:18:37 +0100
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
To: Brian Gerst <bgerst@didntduck.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: how do you call userspace syscalls (e.g. sys_rename) from inside kernel
Message-ID: <20041008151837.GI5551@lkcl.net>
References: <20041008130442.GE5551@lkcl.net> <41669DE0.9050005@didntduck.org>
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On Fri, Oct 08, 2004 at 10:02:08AM -0400, Brian Gerst wrote:
> Luke Kenneth Casson Leighton wrote:
> >could someone kindly advise me on the location of some example code in
> >the kernel which calls one of the userspace system calls from inside the
> >kernel?
> >
> >alternatively if this has never been considered before, please could
> >someone advise me as to how it might be achieved?
> 
> What are you trying to do?  

 call sys_rename, sys_pread, sys_create, sys_mknod, sys_rmdir
 etc. - everything that does file access.

> In most cases needing to use syscalls from 
> within the kernel is an indication of a design flaw.  

 in this case it's an attempt to avoid cutting and pasting
 the entire contents of sys_rename, sys_pread, sys_this,
 sys_that, removing the first couple and last few lines (that
 do copy_from_user) and replacing the arguments with either
 a dentry or a kernel-side char* instead of an __user char*.

 my alternative is to patch every single vfs-related sys_* in fs/*.c to
 be able to "plug in" to these functions.

 l.

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