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Message-ID: <4166AFD0.2020905@ens-lyon.fr>
Date: Fri, 08 Oct 2004 17:18:40 +0200
From: Brice Goglin <Brice.Goglin@ens-lyon.fr>
Reply-To: Brice.Goglin@ens-lyon.org
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To: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: how do you call userspace syscalls (e.g. sys_rename) from inside
 kernel
References: <20041008130442.GE5551@lkcl.net> <41669DE0.9050005@didntduck.org> <20041008151837.GI5551@lkcl.net>
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>  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);

Just look for set_fs in the kernel source to find examples.
--
Brice Goglin
================================================
Ph.D Student
Laboratoire de l'Informatique et du Parall?lisme
CNRS-ENS Lyon-INRIA-UCB Lyon
France
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