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Date: Fri, 8 Oct 2004 17:20:25 +0100
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
To: Brice.Goglin@ens-lyon.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: how do you call userspace syscalls (e.g. sys_rename) from inside kernel
Message-ID: <20041008162025.GL5551@lkcl.net>
References: <20041008130442.GE5551@lkcl.net> <41669DE0.9050005@didntduck.org> <20041008151837.GI5551@lkcl.net> <4166AFD0.2020905@ens-lyon.fr>
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On Fri, Oct 08, 2004 at 05:18:40PM +0200, Brice Goglin wrote:
> > call sys_rename, sys_pread, sys_create, sys_mknod, sys_rmdir
> > etc. - everything that does file access.
> 
> If you ever actually call sys_this or sys_that ... from
> the kernel, you'll have to do something like this to avoid
> copy_from/to_user to fail because the target buffer is not
> in kernel space:
> 
> mm_segment_t old_fs;
> old_fs = get_fs();
> set_fs(KERNEL_DS);
> <do you stuff here>
> set_fs(old_fs);
 
 that's it!  that's what i was looking for.  thank you.

 l.
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