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SubjectRe: Reading a file inside the device driver.
   Date: Wed, 26 Jul 2000 20:09:15 +0100 (BST)
From: Tigran Aivazian <tigran@veritas.com>

> There are games you can play to get around this, but such approaches are
> fragile and complicated, and not what I'd recommend.
ok, then I'd recommend it instead :)

Vinay, have a look at how fs/exec.c:sys_uselib() (uselib(2) system
call) works by using name lookup and then dentry_open() and
file->f_op->read().

sys_uselib doesn't actually try to use f_op->read. For that, you have
to look at kernel_read(); note the magic calls to set_fs(get_ds()) and
setfs(old_fs). This does work, but it's not something which I suspect
we want to encourage wide-spread usage of in the kernel.

In general, it's far better to do file i/o outside the kernel than
inside the kernel, if it is at all possible.

- Ted

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