When kwin is run without execmem access it will SEGV.  This makes things
difficult for people who want to restrict such access to make it more difficult
for their programs to be exploited.

#0  0x00007ffff65615f4 in QTJSC::ExecutablePool::systemAlloc (n=16384) at ../3rdparty/javascriptcore/JavaScriptCore/jit/ExecutableAllocatorPosix.cpp:49
#1  0x00007ffff65e9393 in ExecutablePool (this=<optimized out>, n=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/jit/ExecutableAllocator.h:258
#2  create (n=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/jit/ExecutableAllocator.h:97
#3  ExecutableAllocator (this=0x7fffdddf29c8) at ../3rdparty/javascriptcore/JavaScriptCore/jit/ExecutableAllocator.h:150
#4  QTJSC::JSGlobalData::JSGlobalData (this=0x7fffdddf1800, isShared=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/runtime/JSGlobalData.cpp:146
#5  0x00007ffff65e9b1c in QTJSC::JSGlobalData::create () at ../3rdparty/javascriptcore/JavaScriptCore/runtime/JSGlobalData.cpp:205
#6  0x00007ffff6686821 in QScriptEnginePrivate::QScriptEnginePrivate (this=0x9309d0) at api/qscriptengine.cpp:973
#7  0x00007ffff6687786 in QScriptEngine::QScriptEngine (this=0x7fffffffe5c0) at api/qscriptengine.cpp:1958
#8  0x00007ffff7b9566d in ?? () from /usr/lib/kde4/libkdeinit/libkdeinit4_kwin.so
#9  0x00007ffff7b054e5 in kdemain () from /usr/lib/kde4/libkdeinit/libkdeinit4_kwin.so
#10 0x00007ffff7743ead in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#11 0x00000000004006b1 in _start ()

Above is a backtrace of a kwin SEGV which shows where the problem is.

Is JavaScript really required for KDE operation?  If not can it be an option to
disable it?  If it is required can kwin be made to fallback to interpreting the
code if it can't precompile it?

forwarded 647470 https://bugreports.qt-project.org/browse/QTBUG-32460
thanks

There are actually 2 embedded copies of JavascriptCore in Qt, and one of them allows disabling
the JIT via an env var. Unfortunately not the one used by KWin and libqt4-script.

I've filed a bug upstream about this:
https://bugreports.qt-project.org/browse/QTBUG-32460

It should be a matter of backporting the env var from one javascriptcore to the other (or better yet
get rid of the double-embedded code).

Upstream has replied in [0]:

  This is rather low priority for us right now, but I'd be happy to review a
  patch to fix it.

[0] <https://bugreports.qt-project.org/browse/QTBUG-32460?focusedCommentId=210848&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-210848>

I definetely don't have the time to make a patch for this, so... patches
welcomed :) Preferably directly upstream, as we will ask upstream in the end
if they ACK it.

Upstream has replied in [0]:

  This is rather low priority for us right now, but I'd be happy to review a
  patch to fix it.

[0] <https://bugreports.qt-project.org/browse/QTBUG-32460?focusedCommentId=210848&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-210848>

I definetely don't have the time to make a patch for this, so... patches
welcomed :) Preferably directly upstream, as we will ask upstream in the end
if they ACK it.

-- 
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move huge amounts of money.

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have bothered contacting you. Ultimately I need you to play an
important role in the completion of this business transaction.

Regards,
Mr Alexander Bulyanda