[Bug 51829] Roblox Player: Long freeze during loading

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51829

Paul Gofman <pgofman at codeweavers.com> changed:

           What    |Removed                     |Added
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                 CC|                            |pgofman at codeweavers.com

--- Comment #1 from Paul Gofman <pgofman at codeweavers.com> ---
I've debugged the issue.

The part of the blamed commit which changed things for Roblox Player is the
change to env.c:create_startup_info(). After the commit the NT path
("\\??\\C:\\...") provided for image name started being converted to DOS path
("C:\\..."). Actually before the commit if the path provided to
RtlCreateUserProcess() in RTL_USER_PROCESS_PARAMETERS was an NT path the
process creation was failing. Things worked in Wine because the higher level
Wine create functions are providing DOS path and the direct use of lower level
creation functions is very rare. Windows instead fails process creation if DOS
path instead of NT path is provided there. So this change is not a bug but an
improvement.

After the start Roblox player process tries to create another instance of
Roblox launcher (the two previous instances of the launcher started before the
Player launch exit soon). That is done by calling RtlCreateUserProcess() with
process parameters previously initialized with RtlCreateProcessParameters()
with NT path for image (which is actually correct on Windows). Before the
blamed commit the new launcher process creation was just failing and somehow
Player is fine with that and goes on without delay. Now when the process
creation succeeds the process start but exits immediately before completing
initialization with intriguing Wine message saying that the executable "is a
dll, not an executable". When the process creation succeeded but process does
not proceed Player gets stuck for 20 seconds waiting for something before
outputting debug messages "WARNING: Infinite yield possible..." and going on.

What is now breaking the process start is the trickery Player does on the newly
launcher process before its initialization completed and before the process is
resumed. Player preserves the contents of the launcher's main exe image
section, unmaps main image sections, allocates anonymous virtual memory at the
same address and puts the data back. That all works fine with Wine except for
when it gets to ntdll/loader.c:build_main_module() and gets
SECTION_IMAGE_INFORMATION for main exe through
NtQueryInformationProcess(ProcessImageInformation) it receives the information
for ntdll.dll instead of main exe which of course has that DLL flag and fails
initialization. That happens because the way of how wineserver's
get_process_info() works. When the image mapping is added for the .exe module
it is put at the head of views list on the server. All the dll mappings are put
at the tail. When process image info is required the first view in the list is
taken and the image info is copied from it. But in the present case the main
exe view was removed before the user part of initialization was finished.

Storing pe_image_info_t directly in the process structure (put there on first
arrival) fixes the issue. The launcher process is created successfully and
stays alive through the tormenting by Player process and the game load proceeds
without delay.

I am going to do some Windows testing and approach a patch for that.

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