Re: Hopefully a simple question on /proc/pid/mem

Eric W. Biederman
2001-05-01T01:13:53Z

"Stephen C. Tweedie" <sct@redhat.com> writes:

> Hi,
>
> On Mon, Apr 30, 2001 at 03:02:40PM -0400, Benjamin C.R. LaHaise wrote:
> > On Mon, 30 Apr 2001, Alexander Viro wrote:
> >
> > > I wonder what's wrong with reading from /proc/<pid>/mem, though - it's
> > > using the same code as ptrace.
> >
> > We can actually do this cleanly now that we have proper page_dirty
> > semantics for raw io. The original reason for disabling /proc/*/mem was
> > that it left big gaping holes in the mm code in 2.0, and it hasn't been
> > repaired since.
>
> It was mmap of /proc/*/mem which was busted. read/write should be OK.
>
> Hint: think about what happens if you make a shared mapping of a
> private proc/*/mem region...

Now that we have reusable swap cache pages we could make it work
correctly, except for the case of the first write a private mapping of
file. Not that we would want to...

Eric