[Bug 13915] Oblivon Script Extender (OBSE) fails to start ("privileged instruction")

[wine-bugs at winehq.org]

http://bugs.winehq.org/show_bug.cgi?id=13915


Nicolas Joyard <joyard.nicolas at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |joyard.nicolas at gmail.com




--- Comment #4 from Nicolas Joyard <joyard.nicolas at gmail.com>  2008-11-01 22:29:07 ---
According to the UESP wiki, the author of OBSE (Ian Patterson) has been
contacted about this issue. Here's his answer, it might be useful to solve this
bug...

--

This appears to be a discrepancy between the Windows implementation of the DLL
dependency handler/loader and the Wine implementation. Unfortunately I don't
have a linux install to test this on, but my first guess would be that calling
CreateProcess with the CREATE_SUSPENDED flag set leaves the new process' loader
critical section locked until the main thread is resumed.

The loader works in a pretty straightforward way:

- create the new process with CREATE_SUSPENDED
- VirtualAllocEx some executable memory in the new process to store enough code
for "jmp LoadLibraryA" and a null-terminated string pointing to our DLL (in a
perfect world we would just point the thread entry point straight at
LoadLibraryA, but this makes some virus scanners explode, literally)
- use CreateRemoteThread to create a thread in the new process pointing to the
injected code, setting the parameter to the thread function to the DLL path in
the new process (conveniently the calling convention and signature of thread
entry points and LoadLibrary are exactly the same)
- wait for the thread to terminate, signifying that the DLL has been loaded
- clean up

This sequence requires that processes not be holding the loader lock
immediately after creation.


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