Date: Tue, 17 Jan 2023 21:46:20 +0100
To: cygwin@cygwin.com
Subject: Re: Cygwin 3.4.3 and 3.5.0... hangs in make, top, procps, ls
 /proc/PID/...
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Precedence: list
From: Corinna Vinschen via Cygwin <cygwin@cygwin.com>
Reply-To: cygwin@cygwin.com
Cc: Corinna Vinschen <corinna-cygwin@cygwin.com>
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Sender: "Cygwin" <cygwin-bounces+archive-cygwin=delorie.com@cygwin.com>

Hi Takashi,

On Jan 16 22:42, Corinna Vinschen via Cygwin wrote:
> On Jan 16 16:18, Corinna Vinschen via Cygwin wrote:
> > Actually, I' running your testcase on two machines in parallel now for
> > quite some time, which only one hunk of 60675f1a7eb2 reverted, i.e.
> > 
> > diff --git a/winsup/cygwin/mm/shared.cc b/winsup/cygwin/mm/shared.cc
> > index 893b20d289b4..6d6d2940b6d4 100644
> > --- a/winsup/cygwin/mm/shared.cc
> > +++ b/winsup/cygwin/mm/shared.cc
> > @@ -140,7 +140,11 @@ open_shared (const WCHAR *name, int n, HANDLE& shared_h, DWORD size,
> >    if (*m == SH_JUSTCREATE || *m == SH_JUSTOPEN)
> >      addr = NULL;
> >    else
> > -    addr = (void *) region_address[*m];
> > +    {
> > +      addr = (void *) region_address[*m];
> > +      VirtualFree (addr, 0, MEM_RELEASE);
> > +    }
> > +
> >  
> >    WCHAR map_buf[MAX_PATH];
> >    WCHAR *mapname = NULL;
> > 
> > So far (and knocking on wood madly while writing this) the mapping
> > problem didn't show up once.  Maybe you'd like to try the same?
> 
> Never mind, I encountered another error.  After a bit more debugging
> I think I understand the problem now, and  I'm just in the process of
> reworking open_shared.  This may take a day or two.  Stay tuned.

I pushed some patches to fix this issue.  Excessive debugging indicated
that the reason cygcheck fails in this way is:

- It's a non-Cygwin process which

- is built with high-entropy ASLR and

- tries to load the Cygwin DLL dynamically and

- therefore suffers from the fact that recent Cygwin code doesn't
  expect that certain memory regions are used by Windows itself.
  Which they are, due to the high-entropy stuff.

The patches are supposed to make the code less rigid in terms of the
addresses of certain memory regions, as well as dropping the
high-entropy VA flag from builds of strace and cygcheck, both of which
are loading the Cygwin DLL dynamically as part of their job.

The test release 3.5.0-0.116.g8d318bf142f7 contains the patches, for
everybody to try.


Thanks,
Corinna

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