[Bug 54015] New: Accessing shared memory from Linux

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=54015

Bug ID: 54015
           Summary: Accessing shared memory from Linux
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: kernel32
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Some Windows games and applications share some internals through shared memory
with external tools. Shared memory is preferred over sockets because it adds no
overhead with no latency.

It's mostly used in driving and flying simulators to provide visual overlays,
data on additional displays, telemetry, rig movement, etc. from external tools.
There's also scientific apps using it for similar purposes or general
inter-process communication.

It's common to use tagged shared memory blocks that external tools can then
access using the already known tag.

Here's an example from a Python application for rFactor 2:

self._rf2_tele = mmap.mmap(0, ctypes.sizeof(rF2Telemetry),
f"$rFactor2SMMP_Telemetry${input_pid}")
  self._rf2_scor = mmap.mmap(0, ctypes.sizeof(rF2Scoring),
f"$rFactor2SMMP_Scoring${input_pid}")
  self._rf2_ext = mmap.mmap(0, ctypes.sizeof(rF2Extended),
f"$rFactor2SMMP_Extended${input_pid}")
  self._rf2_ffb = mmap.mmap(0, ctypes.sizeof(rF2ForceFeedback),
"$rFactor2SMMP_ForceFeedback$")

Allowing these shared memory blocks to be accessed from Linux would allow us to
port some of these tools or even implement or own.

Then these tools could access resources or hardware that isn't available from
inside the Wine prefix. Some of these tools also fail to run on Wine.

Since I guess Wine is already using Linux shared memory mechanism to implement
Windows shared memory, the blocks are already available at /dev/shm but they
use generic names that can't be associated to the tag used on Windows.

Having these shared memory blocks created in the prefix directory with a name
containing the tag used on creation would allow us to use it from our native
applications. Or any other way to find them using the tags used on Windows.

Thanks for your attention.