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Date: Fri, 5 Jan 2007 11:52:20 -0600
From: Brian Ford <Brian DOT Ford AT FlightSafety DOT com>
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To: cygwin AT cygwin DOT com
Subject: Re: 1.7.0 CVS mmap failure
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On Fri, 5 Jan 2007, Brian Ford wrote:
> On Fri, 5 Jan 2007, Brian Ford wrote:
> > Ok, after further investigation, this is a /3GB boot.ini flag interaction.
> > Unfortunately, this is a critical flag for our application, so all our
> > machines are configured this way.  That is why I failed to realize its
> > significance before.
> >
> > I understand if this is now too much of an obscure case for you to be
> > interested in.  If so, I'll try to look into it soon on my own.  I suspect
> > it must have been related to your MEM_TOP_DOWN change.
>
> One more tidbit before I have time to find the real problem.  Compiling
> the test case with -Wl,large-address-aware makes the test pass on a /3GB
> system.

Here is an interesting strace comparison:

Non-/3GB:
 4978   26688 [main] mmaptest 2284 MapViewNT: 7FFA0000 =
NtMapViewOfSection (h:6EC, addr:0, len:28237, off:0, protect:80, type:0)
[snip]
    60   27113 [main] mmaptest 2284 MapViewNT: 7FFA7000 =
NtMapViewOfSection (h:6E8, addr:7FFA7000, len:36864, off:0, protect:80, type:0)
  126   27239 [main] mmaptest 2284 mmap64: 0x7FFA0000 = mmap()

/3GB not large address aware:
  183   22192 [main] mmaptest 2856 MapViewNT: 7FFF0000 =
NtMapViewOfSection (h:6F0, addr:0, len:28237, off:0, protect:80, type:0)
[snip]
   68   22648 [main] mmaptest 2856 MapViewNT: 0 = NtMapViewOfSection
(h:6EC, addr:7FFF7000, len:36864, off:0, protect:80, type:0)
   44   22692 [main] mmaptest 2856 seterrno_from_win_error:
../../../../cygwin/winsup/cygwin/mmap.cc:1707 windows error 487
   46   22738 [main] mmaptest 2856 geterrno_from_win_error: windows error
487 == errno 22
   41   22779 [main] mmaptest 2856 __set_errno: void
seterrno_from_win_error(const char*, int, DWORD):310 val 22
   79   22858 [main] mmaptest 2856 __set_errno: void* mmap64(void*,
size_t, int, int, int, _off64_t):1251 val 12
--- Process 2856, exception C0000008 at 7C90EB74
13337   36195 [main] mmaptest 2856 mmap64: 0xFFFFFFFF = mmap()

/3GB large address aware:
  191   22246 [main] mmaptest 3420 MapViewNT: AEFA0000 =
NtMapViewOfSection (h:6EC, addr:0, len:28237, off:0, protect:80, type:0)
[snip]
   66   22676 [main] mmaptest 3420 MapViewNT: AEFA7000 =
NtMapViewOfSection (h:6E8, addr:AEFA7000, len:36864, off:0, protect:80,
type:0)
  126   22802 [main] mmaptest 3420 mmap64: 0xAEFA0000 = mmap()

The second MapViewNT call is filling out the padding to a 64k boundary.
It appears in the problem case that the system doesn't like the 0x7FFF7000
address.  Any idea why?

-- 
Brian Ford
Lead Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained crew...



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