Date: Wed, 8 Sep 2004 13:49:42 -0400 From: Brian Fundakowski Feldman <green@FreeBSD.org> To: threads@FreeBSD.org Subject: [mistry.7@osu.edu: Re: FreeBSD and wine mmap] Message-ID: <20040908174941.GF928@green.homeunix.org>
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I don't think that any allocated "red zones" should be left empty --
they should be explicitly allocated with no protection so that actually
free memory space can be explicitly searched for. Comments?
----- Forwarded message from Anish Mistry <mistry.7@osu.edu> -----
From: Anish Mistry <mistry.7@osu.edu>
To: Brian Fundakowski Feldman <green@freebsd.org>
Subject: Re: FreeBSD and wine mmap
Date: Sun, 5 Sep 2004 13:15:15 -0400
Cc: freebsd-current@freebsd.org
On Sunday 29 August 2004 12:59 am, you wrote:
> On Tue, Aug 10, 2004 at 01:53:14PM -0400, Anish Mistry wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > On Wednesday 04 August 2004 06:39 pm, you wrote:
> > > On Wed, Aug 04, 2004 at 06:28:02PM -0400, Anish Mistry wrote:
> > > > Ok, so we need something like vm_map_findspace(), but for process
> > > > address mapping? ie. pmap_findspace() that will return an address to
> > > > a large enough free chunk?
> > >
> > > That's a good start, just to get something to work with. How this fits
> > > in with the vm code and whether it is ultimately suitable in the long
> > > run is probably up to Alan Cox. For now, just get something that (a)
> > > doesn't break anything else; and (b) lets Wine behave the way it needs
> > > to.
> > >
> > > AFAIK, there are still pthread issues with Wine, but those can't be
> > > addressed until the mmap issue has a work-around.
> >
> > I've got a small patch that gets by the initial problem about not being
> > to mmap the memory for the libraries, but the addresses that are mmap'ed
> > seem to seem to overlap with memory that the current pthread
> > implementation want to mmap for the "red zone" when wine tries to create
> > a thread. It can't mmap the "red zone" addresses since all those address
> > mapping where gobbled up before the thread launched.
> > I'll try to figure out a way to maybe leave a space for the "red zone"
> > and see if that works.
> > Someone who actually knows what they are doing should probably take a
> > look.
>
> The red pages are implemented by leaving the memory space unallocated;
> I don't like that one bit -- this will cause those spaces to be allocated
> but given no protection, which should provide the crash feature that the
> guard pages are there for, but be less bogus (and it doesn't use more
> "memory," but it will use a few more vm_map_entrys.
>
> Index: lib/libpthread/thread/thr_stack.c
> ===================================================================
> RCS file: /usr/ncvs/src/lib/libpthread/thread/thr_stack.c,v
> retrieving revision 1.8
> diff -u -r1.8 thr_stack.c
> --- lib/libpthread/thread/thr_stack.c 14 Sep 2003 22:39:44 -0000 1.8
> +++ lib/libpthread/thread/thr_stack.c 29 Aug 2004 04:50:28 -0000
> @@ -214,6 +214,17 @@
> stacksize, PROT_READ | PROT_WRITE, MAP_STACK,
> -1, 0)) == MAP_FAILED)
> attr->stackaddr_attr = NULL;
> + if (attr->stackaddr_attr != NULL) {
> + void *red;
> +
> + red = mmap((char *)attr->stackaddr_attr + stacksize,
> + _thr_guard_default, PROT_NONE,
> + MAP_ANON | MAP_FIXED | MAP_PRIVATE, -1, 0);
> + if (red == MAP_FAILED) {
> + (void)munmap(attr->stackaddr_attr, stacksize);
> + attr->stackaddr_attr = NULL;
> + }
> + }
> }
> if (attr->stackaddr_attr != NULL)
> return (0);
This is good. Can this be committed?
--
Anish Mistry
----- End forwarded message -----
--
Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\
<> green@FreeBSD.org \ The Power to Serve! \
Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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