Use of copy_to_user() and copy_from_user() functions

[Chetan Nanda]

On Mon, Feb 11, 2013 at 5:25 PM, anish singh <anish198519851985 at gmail.com>wrote:

>
>
> On Mon, Feb 11, 2013 at 4:51 PM, पारस <beparas at gmail.com> wrote:
> > Hi All,
> >
> > To read/write data to user-space from kernel-space we use
> copy_from_user()
> > and copy_to_user() functions.
> >
> > What is the use of these function?
> > Why kernel can't directly access user address and read/write on to it?
> what will happen if the user space process gets scheduled out while
> you were using it?
>
> copy_to/from_user should always be called from process context. So even if
a process is scheduled out there is not impact, as when process schedule
back in copying will resume to/from correct page.


> > Can any one explain why kernel can't directly access the user-space
> address.
> >
> > Thanks
> >
> >
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> >
>
>
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