On Tue, Feb 12, 2013 at 9:24 AM, Chetan Nanda <chetannanda@gmail.com> wrote:
On Mon, Feb 11, 2013 at 5:25 PM, anish singh <anish198519851985@gmail.com> wrote:
On Mon, Feb 11, 2013 at 4:51 PM, पारस <beparas@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.
because page fault will be triggered and the user space will be swapped in. That answers the original question.
Can any one explain why kernel can't directly access the user-space address.
Thanks
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