Date: Sun, 30 Jan 2011 15:53:41 +0100 From: Juergen Lock <nox@jelal.kn-bremen.de> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org, freebsd-emulation@freebsd.org, Juergen Lock <nox@jelal.kn-bremen.de> Subject: Re: Can vm_mmap()/vm_map_remove() be called with giant held? (linuxolator dvb patches) Message-ID: <20110130145341.GA36312@triton8.kn-bremen.de> In-Reply-To: <20110130103320.GO2518@deviant.kiev.zoral.com.ua> References: <20110129201000.GA10774@triton8.kn-bremen.de> <20110129205105.GI2518@deviant.kiev.zoral.com.ua> <20110129235448.GA15788@triton8.kn-bremen.de> <20110130103320.GO2518@deviant.kiev.zoral.com.ua>
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On Sun, Jan 30, 2011 at 12:33:20PM +0200, Kostik Belousov wrote:
> On Sun, Jan 30, 2011 at 12:54:48AM +0100, Juergen Lock wrote:
> > On Sat, Jan 29, 2011 at 10:51:05PM +0200, Kostik Belousov wrote:
> > > On Sat, Jan 29, 2011 at 09:10:00PM +0100, Juergen Lock wrote:
> > > > Hi!
> > > >
> > > > I was kinda hoping to be able to post a correct patch in public but
> > > > getting an answer to ${Subject} seems to be more difficult than I
> > > > thought... :) So, does anyone here know? copyout_map() and
> > > You do not need Giant locked for vm_map* functions.
> > >
> > The question was more do I need to drop it first before calling them...
> No, you do not need to drop Giant.
>
Ok, thanx!
> [snip]
> > > > + error = ENOMEM;
> > > > + goto out2;
> > > > + }
> > > > + error = copyin((void *) vps.props, l_vp, l_propsiz);
> > > > + if (error)
> > > > + goto out2;
> > > > + for (i = vps.num, l_p = l_vp, p = vp; i--; ++l_p, ++p)
> > > > + linux_to_bsd_dtv_property(l_p, p);
> > > > +
> > > > + error = copyout_map(td, &uvp, propsiz);
> > > > + if (error)
> > > > + goto out2;
> > > > + copyout(vp, (void *) uvp, propsiz);
> > > > +
> > > > + if ((error = fget(td, args->fd, &fp)) != 0) {
> > > > + (void) copyout_unmap(td, uvp, propsiz);
> > > > + goto out2;
> > > > + }
> > > > + vps.props = (void *) uvp;
> > > > + if ((args->cmd & 0xffff) == LINUX_FE_SET_PROPERTY)
> > > > + error = fo_ioctl(fp, FE_SET_PROPERTY, &vps, td->td_ucred, td);
> > > > + else
> > > > + error = fo_ioctl(fp, FE_GET_PROPERTY, &vps, td->td_ucred, td);
> > > > + if (error) {
> > > > + (void) copyout_unmap(td, uvp, propsiz);
> > > > + goto out;
> > > > + }
> > > > + error = copyin((void *) uvp, vp, propsiz);
> > > > + (void) copyout_unmap(td, uvp, propsiz);
> > > No need in space between cast and expression. Bigger issue is that I
> > > do not understand this fragment. You do copyout_map(), and then
> > > immediately call copyout_unmap() for the address range returned
> > > by copyout_map(), or am I missing something ?
> > >
> > The vm allocated by copyout_map() is only needed for the fo_ioctl()
> > call because the struct passed to FE_[GS]ET_PROPERTY describes an
> > array that the drivers then copyin() and (possibly) copyout()
> > themselves. So that array needs to be translated from/to the 32bit
> > Linux version to (possibly) 64bit on the host (linux_to_bsd_dtv_property),
> > and the 64bit version is larger so it doesn't fit in the original
> > place in the userland vm.
> And am I right that the drivers can only take this array from the usermode ?
Yes. And it's a Linux api and Linux code too (running in webcamd)
so I changing it wouldn't make too much sense.
> How is the compatibility for 32/64 bit mode is handled by native
> FE_SET_PROPERTY handlers ?
>
I'm not sure but my impression is this currently isn't handled at all
even on Linux. (And neither on FreeBSD.)
> I could only say that the hack is atrocious. Might be, you indeed have
> no choice there.
> >
I'm not going to disagree there...
(This is actually the second api for this, i.e. FE_[GS]ET_PROPERTY
are an api extension introduced to add dvb-s2 support to the Linux
dvb api, the original proposal was different but wasn't accepted
by the Linux people in charge. The array is an array of `commands'
that are executed by the ioctl, and the unused pointer that's in
there on top of the uint32_t reserved1[3] and that causes the sizes
to differ between 32/64 bits looks like it has been added later too
because without it I think each array element would have been exactly
64 bytes...)
Cheers,
Juergen
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