Given a user virtual address and a count I need to be able to get at each
struct page * page that covers it. Then I can kmap() each page in a loop
and generate very safe range (i.e. use __copy_to_user()) inside vread()),
just like file_read_actor() does when called from do_generic_file_read().
So I need something like uvirt_to_page() macro.
Regards,
------
Tigran A. Aivazian | http://www.sco.com
Escalations Research Group | tel: +44-(0)1923-813796
Santa Cruz Operation Ltd | http://www.ocston.org/~tigran
On Tue, 21 Dec 1999, Tigran Aivazian wrote:
> having thought of it for a minute, it is probably not the best design
> though.
>
> I am going to try to change vread() interface to accept kernel addresses
> and make temporary kernel buffers in read_kmem() and see what happens.
>
> Btw, Stephen mentioned kmapping user addresses but I still have not seen
> any working examples of that - the stuff in mm/filemap.c only deals with a
> page at a time...
>
> Regards,
> Tigran.
>
> On Tue, 21 Dec 1999, Tigran Aivazian wrote:
>
> > Hi,
> >
> > I have a question about writing to userspace buffers. Can I do this in
> > read_kmem() (read method of /dev/kmem):
> >
> > if (verify_area(VERIFY_WRITE, buf, count))
> > return -EFAULT;
> >
> > lock_kernel();
> > write to user buf without any worries, even taking spinlocks if needed.
> > unlock_kernel();
> >
> > If I can do this then it is very useful because we could then hold a
> > spinlock in mm/vmalloc.c:vread() which means vmlist can be protected by a
> > simple spinlock which means vmalloc()/vfree()/ioremap() (i.e. really
> > vfree() and get_vm_area()) can be made SMP safe, i.e. without forcing
> > callers to have lock/unlock_kernel().
> >
> > Thank you for your patient explanation :)
> > ------
> > Tigran A. Aivazian | http://www.sco.com
> > Escalations Research Group | tel: +44-(0)1923-813796
> > Santa Cruz Operation Ltd | http://www.ocston.org/~tigran
> >
> >
> >
>
>
>
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