mdev race conditions

[Mike Frysinger]

On Tuesday 03 June 2008, Denys Vlasenko wrote:
> On Tuesday 03 June 2008 17:17, Mike Frysinger wrote:
> > On Tuesday 03 June 2008, Bernard Blackham wrote:
> > > When I switched from udev+udevd to mdev, booting was much faster and it
> > > shaved a decent amount from the total image size. However, I've
> > > recently noticed device nodes sometimes disappearing on boot.
> >
> > this is a known corner case and will always be there.  it's why the
> > kernel guys have deprecated the hotplug exec mechanism in favor of
> > netlink sockets. the only real solution is a daemon + netlink.  neither
> > of which are desirable in mdev.  everything else is a workaround.  feel
> > free to contribute a mdevd ;).  that plus init/other daemons provided by
> > busybox are good examples of how PIE can be a very very good thing.
>
> Can you chime me in how to build PIE / how it is different from normal
> executable? I guess there are some restrictions and things to do (e.g. have
> to pass -fPIE to gcc)? --

afaik (solar can correct me), just compile all objects with -fPIE and link 
with -pie

a quick test is (1) it still executes ;) and (2) running `file` on the ELF 
should declare it as a shared object rather than executable
-mike
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