proton: Copy DLLs provided by the NVIDIA driver into prefix

The upcoming NVIDIA 470 driver series will introduce a DLL (nvngx.dll)
for the support of NVIDIA DLSS in Proton. This change adds logic for
discovering the location of DLL files provided by the NVIDIA driver, and
copies them to C:\Windows\System32\

Reviewed-by: Adam Moss <amoss@nvidia.com>

proton

@@ -15,6 +15,15 @@ import subprocess
 import sys
 import tarfile
 
+from ctypes import CDLL
+from ctypes import POINTER
+from ctypes import Structure
+from ctypes import addressof
+from ctypes import cast
+from ctypes import c_int
+from ctypes import c_char_p
+from ctypes import c_void_p
+
 from filelock import FileLock
 from random import randrange
 
@@ -99,7 +108,7 @@ def merge_user_dir(src, dst):
         else:
             extant_dirs += dst_dir
 
-def try_copy(src, dst, add_write_perm=True, copy_metadata=True):
+def try_copy(src, dst, add_write_perm=True, copy_metadata=True, optional=False):
     try:
         if os.path.isdir(dst):
             dstfile = dst + "/" + os.path.basename(src)
@@ -119,6 +128,12 @@ def try_copy(src, dst, add_write_perm=True, copy_metadata=True):
             new_mode = os.lstat(dstfile).st_mode | stat.S_IWUSR | stat.S_IWGRP
             os.chmod(dstfile, new_mode)
 
+    except FileNotFoundError as e:
+        if optional:
+            log('Error while copying to \"' + dst + '\": ' + e.strerror)
+        else:
+            raise
+
     except PermissionError as e:
         if e.errno == errno.EPERM:
             #be forgiving about permissions errors; if it's a real problem, things will explode later anyway
@@ -162,6 +177,87 @@ def try_get_game_library_dir():
 
     return None
 
+# Function to find the installed location of DLL files for use by Wine/Proton
+# from the NVIDIA Linux driver
+#
+# See https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/issues/71 for
+# background on the chosen method of DLL discovery.
+#
+# On success, returns a str() of the absolute-path to the directory at which DLL
+# files are stored
+#
+# On failure, returns None
+def find_nvidia_wine_dll_dir():
+    try:
+        libdl = CDLL("libdl.so.2")
+    except (OSError):
+        return None
+
+    try:
+        libglx_nvidia = CDLL("libGLX_nvidia.so.0")
+    except OSError:
+        return None
+
+    # from dlinfo(3)
+    #
+    # struct link_map {
+    #     ElfW(Addr) l_addr;  /* Difference between the
+    #                            address in the ELF file and
+    #                            the address in memory */
+    #     char      *l_name;  /* Absolute pathname where
+    #                            object was found */
+    #     ElfW(Dyn) *l_ld;    /* Dynamic section of the
+    #                            shared object */
+    #     struct link_map *l_next, *l_prev;
+    #                         /* Chain of loaded objects */
+    #
+    #     /* Plus additional fields private to the
+    #        implementation */
+    # };
+    RTLD_DI_LINKMAP = 2
+    class link_map(Structure):
+        _fields_ = [("l_addr", c_void_p), ("l_name", c_char_p), ("l_ld", c_void_p)]
+
+    # from dlinfo(3)
+    #
+    # int dlinfo (void *restrict handle, int request, void *restrict info)
+    dlinfo_func = libdl.dlinfo
+    dlinfo_func.argtypes = c_void_p, c_int, c_void_p
+    dlinfo_func.restype = c_int
+
+    # Allocate a link_map object
+    glx_nvidia_info_ptr = POINTER(link_map)()
+
+    # Run dlinfo(3) on the handle to libGLX_nvidia.so.0, storing results at the
+    # address represented by glx_nvidia_info_ptr
+    if dlinfo_func(libglx_nvidia._handle,
+                   RTLD_DI_LINKMAP,
+                   addressof(glx_nvidia_info_ptr)) != 0:
+        return None
+
+    # Grab the contents our of our pointer
+    glx_nvidia_info = cast(glx_nvidia_info_ptr, POINTER(link_map)).contents
+
+    # Decode the path to our library to a str()
+    if glx_nvidia_info.l_name is None:
+        return None
+    try:
+        libglx_nvidia_path = os.fsdecode(glx_nvidia_info.l_name)
+    except UnicodeDecodeError:
+        return None
+
+    # Follow any symlinks to the actual file
+    libglx_nvidia_realpath = os.path.realpath(libglx_nvidia_path)
+
+    # Go to the relative path ./nvidia/wine from our library
+    nvidia_wine_dir = os.path.join(os.path.dirname(libglx_nvidia_realpath), "nvidia", "wine")
+
+    # Check that nvngx.dll exists here, or fail
+    if os.path.exists(os.path.join(nvidia_wine_dir, "nvngx.dll")):
+        return nvidia_wine_dir
+
+    return None
+
 EXT2_IOC_GETFLAGS = 0x80086601
 EXT2_IOC_SETFLAGS = 0x40086602
 
@@ -705,6 +801,15 @@ class CompatData:
                 if os.path.exists(nvapi32_dll):
                     os.unlink(nvapi32_dll)
 
+            # Try to detect known DLLs that ship with the NVIDIA Linux Driver
+            # and add them into the prefix
+            nvidia_wine_dll_dir = find_nvidia_wine_dll_dir()
+            if nvidia_wine_dll_dir:
+                for dll in ["_nvngx.dll", "nvngx.dll"]:
+                    try_copy(nvidia_wine_dll_dir + "/" + dll,
+                             self.prefix_dir + "drive_c/windows/system32/" + dll,
+                             optional=True)
+
             try_copy(g_proton.lib64_dir + "wine/vkd3d-proton/d3d12.dll",
                     self.prefix_dir + "drive_c/windows/system32/d3d12.dll")
             try_copy(g_proton.lib_dir + "wine/vkd3d-proton/d3d12.dll",