[Vm-dev] 64bits Pharo VM for windows

[Ben Coman]

On Thu, Mar 23, 2017 at 7:06 PM, Ben Coman <btc at openinworld.com> wrote:
> Probably not related, but just some things that turned up while I was
> browsing around...
>
> gdb unknown target exception
> http://stackoverflow.com/questions/40923437/gdb-unknown-target-exception
>
> gdb Exception in SetThreadName(unsigned long, char const*) () from
> /usr/bin/cygwin1.dll
> https://www.mail-archive.com/cygwin@cygwin.com/msg149735.html
>
> cygwin gdb Program received signal ?, Unknown signal
> http://stackoverflow.com/questions/40652302/cygwin-gdb-program-received-signal-unknown-signal
>
> Quick reference to Implementation...
> https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/include/setjmp.h
> https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/machine/i386/setjmp.S
> https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/machine/x86_64/setjmp.S
> https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/include/machine/setjmp.h

btw, here is a comparison of i386 versus x86_64 Cygwin longjmp...
https://www.diffchecker.com/iAMuXTMn


> 2015-07-21 Corinna Vinschen <corinna at vinschen.de>
> (setjmp): x86_64 only: Store tls stackptr in Frame now, store MXCSR
> and FPUCW registers in Spare, as MSVCRT does.
> (longjmp): x86_64 only: Restore tls stackptr from Frame now, restore
> MXCSR and FPUCW registers from Spare.
> 2015-06-27 Corinna Vinschen <corinna at vinschen.de>
> * exceptions.cc (_cygtls::call_signal_handler): Drop manipulating
> thread's ss_flags here. It's not safe against longjmp.
> https://github.com/Alexpux/Cygwin/blob/..../winsup/CVSChangeLogs.old/cygwin/ChangeLog-2015
>
>

I've been trawling the web for more candidates.  This is a bit
scattershot and I'm not in a position to experiment on Windows right
now,
but maybe useful hints for someone...

* "setjmp and longjmp (emu.c) and crashes when used in a 64bit windows
environment because setjmp sets the stack register value to 0x10.
Using __builtin_setjump avoids the problem because the stack register
doesn't get messed (doesn't seem to call setjmp3 function of the
C:\Windows\SysWOW64\msvcrt.dll library)."
https://sourceforge.net/p/mingw-w64/bugs/406/

* "The problem turns out to be incorrect relocation by the internal
linker ... only applies to imported symbols."
Maybe why __builtin_setjump reported to work okay ??
https://github.com/golang/go/issues/13672

* probably this doesn't apply to Cygwin non-C++ code. But maybe msvcrt
is written in C++ ?? ... "In portable code, when a non-local goto that
calls longjmp is executed, correct destruction of frame-based objects
might be unreliable."
https://msdn.microsoft.com/en-us/library/yz2ez4as.aspx

* The issue is your jump from longjmp call to setjmp location is
crossing functions on callstack that were created by MCJIT. Those
functions do not have proper stack unwinding information required by
longjmp.
http://lists.llvm.org/pipermail/llvm-dev/2015-April/084889.html

* Perhaps we need to wrap exception handling around calls to functions
in the msvcrt.dll ???
  "Most functions that make use of the stack in 64-bit versions of
Windows must support exception handling even if they make no internal
use of such facilities."
https://www.tortall.net/projects/yasm/manual/html/objfmt-win64-exception.html

* "This is a bug fix needed for 64 bit Windows. QEMU for Windows
currently gets the wrong definition for sigsetjmp. It uses stack
unwinding for longjmp which results in a crash when it is called from
generated code. (1 Mar 2016)"
https://lists.gnu.org/archive/html/qemu-devel/2016-03/msg00000.html

* I'm not sure if I understand it properly, but this seems to imply
that that even pure-C (not C++) applications need to catch exceptions
of OS C++ library ?? .
http://ab-initio.mit.edu/octave-Faddeeva/gnulib/lib/msvc-inval.h

* "The newer runtime libraries of MSVC no longer return error codes
from functions like printf(), close(), dup2(), _get_osfhandle(), when
you pass an invalid format string or invalid file descriptor."
https://lists.gnu.org/archive/html/bug-gnulib/2011-09/msg00239.html

* " With MSVC runtime libraries with the "invalid parameter handler"
concept, Functions like fprintf(), dup2(), or close() crash when the
caller passes an invalid argument.  But POSIX wants error codes (such
as EINVAL or EBADF) instead."
http://ab-initio.mit.edu/octave-Faddeeva/gnulib/lib/msvc-inval.h

* 'The try-except statement is a Microsoft extension to the C ... language"
https://msdn.microsoft.com/en-us/library/s58ftw19.aspx

cheers -ben

<snip>
>> Certainly look ok at the instruction that raised the exception.  Looks like the longjmp is trying to return to somewhere it shouldn't.  Also you've written "snip" at the hot end of the stack.  If that's not a typo, post all of the hot end of the stack.
>>
>> You could look at the returnToInterpreter jmpbuf after the setjmp that initializes it and become familiar with its contents.  Then check when the longjmp occurs that it is t corrupted and the frame that created it still exists on the stack.
<snip>