Re: [Qemu-devel] [PATCH] possible mmap regression

["Edgar E. Iglesias" <edgar.iglesias@axis.com>]

On Wed, Feb 20, 2008 at 03:03:39PM +0200, Felipe Contreras wrote:
> Hi Edgar,
> 
> On Feb 16, 2008 11:07 PM, Edgar E. Iglesias <edgar.iglesias@axis.com> wrote:
> >
> > On Tue, Feb 12, 2008 at 09:42:15PM +0200, Felipe Contreras wrote:
> > > Hi,
> > >
> > > I don't know what I'm doing but this seems to fix the weird issue I was having.
> > > http://article.gmane.org/gmane.comp.emulators.qemu/23314
> > >
> > > I've found out that this happens on linux 2.6.23, but not 2.6.24.
> > >
> > > Cheers.
> > >
> > > --
> > > Felipe Contreras
> > > diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> > > index 6292826..3050ad9 100644
> > > --- a/linux-user/mmap.c
> > > +++ b/linux-user/mmap.c
> > > @@ -251,7 +251,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
> > >             especially important if qemu_host_page_size >
> > >             qemu_real_host_page_size */
> > >          p = mmap(g2h(mmap_start),
> > > -                 host_len, prot, flags | MAP_FIXED, fd, host_offset);
> > > +                 host_len, prot, flags, fd, host_offset);
> > >          if (p == MAP_FAILED)
> > >              return -1;
> > >          /* update start so that it points to the file position at 'offset' */
> >
> > Hello,
> >
> > Sorry, but I beleive your patch will break simulations where the targets pagesize is larger than the hosts.
> >
> > Would you mind trying the attach patched and let us know if it helps for you?
> > If not, it would be great if you could provide a small test case that trigs the bug you are seeing so we can debug the problem.
> >
> > Best regards
> > --
> > Edgar E. Iglesias
> > Axis Communications AB
> >
> > diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> > index 6292826..78a8162 100644
> > --- a/linux-user/mmap.c
> > +++ b/linux-user/mmap.c
> > @@ -385,6 +385,9 @@ int target_munmap(abi_ulong start, abi_ulong len)
> >              real_end -= qemu_host_page_size;
> >      }
> >
> > +    if (start < mmap_next_start)
> > +       mmap_next_start = start;
> > +
> >      /* unmap what we can */
> >      if (real_start < real_end) {
> >          ret = munmap(g2h(real_start), real_end - real_start);
> >
> 
> I tried your patch and it still crashes.
> 
> I sent the details before:
> http://article.gmane.org/gmane.comp.emulators.qemu/23314
> http://article.gmane.org/gmane.comp.emulators.qemu/23328
> 
> Basically it was triggered by this change:
> http://repo.or.cz/w/qemu.git?a=commitdiff;h=edbcc0b2eb1d4caee5f293e5c79f81023f3394e2
> 
> And it happens with some recursive Makefiles stuff.

Thanks Felipe,

I was also seeing errors with that commit. Later that same evening I found a few more errors with the mmap code which tried to fix. Would you mind trying that patch too?

You can find it here:
http://lists.gnu.org/archive/html/qemu-devel/2008-02/msg00331.html

Best regards
- 
Edgar E. Iglesias
Axis Communications AB