Use XDG_DATA_DIRS instead of hardcoding /usr/share

When running nvidia-ctk on a system that uses a custom XDG_DATA_DIRS
environment variable value, the configuration files for `glvnd`,
`vulkan`, and `egl` fail to get passed through from the host to the
container. Reading from XDG_DATA_DIRS instead of hardcoding the default
value allows for finding said files so they can be mounted in the
container.

Signed-off-by: Jared Baur <jaredbaur@fastmail.com>

internal/discover/graphics.go

@@ -59,12 +59,15 @@ func NewGraphicsMountsDiscoverer(logger logger.Interface, driver *root.Driver, n
 		},
 	)
 
+	searchPaths := []string{"/etc"}
+	searchPaths = append(searchPaths, xdgDataDirs()...)
+
 	jsonMounts := NewMounts(
 		logger,
 		lookup.NewFileLocator(
 			lookup.WithLogger(logger),
 			lookup.WithRoot(driver.Root),
-			lookup.WithSearchPaths("/etc", "/usr/share"),
+			lookup.WithSearchPaths(searchPaths...),
 		),
 		driver.Root,
 		[]string{
@@ -295,7 +298,7 @@ func newXorgDiscoverer(logger logger.Interface, driver *root.Driver, nvidiaCTKPa
 		lookup.NewFileLocator(
 			lookup.WithLogger(logger),
 			lookup.WithRoot(driver.Root),
-			lookup.WithSearchPaths("/usr/share"),
+			lookup.WithSearchPaths(xdgDataDirs()...),
 		),
 		driver.Root,
 		[]string{"X11/xorg.conf.d/10-nvidia.conf"},
@@ -371,3 +374,13 @@ func (s selectDeviceByPath) MountIsSelected(Mount) bool {
 func (s selectDeviceByPath) HookIsSelected(Hook) bool {
 	return true
 }
+
+// xdgDataDirs finds the paths as specified in the environment variable XDG_DATA_DIRS.
+// See https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html.
+func xdgDataDirs() []string {
+	if dirs, exists := os.LookupEnv("XDG_DATA_DIRS"); exists && dirs != "" {
+		return root.NormalizeSearchPaths(dirs)
+	}
+
+	return []string{"/usr/local/share", "/usr/share"}
+}

internal/lookup/root/root.go

@@ -38,7 +38,7 @@ func New(logger logger.Interface, path string, librarySearchPaths []string) *Dri
 	return &Driver{
 		logger:             logger,
 		Root:               path,
-		librarySearchPaths: normalizeSearchPaths(librarySearchPaths...),
+		librarySearchPaths: NormalizeSearchPaths(librarySearchPaths...),
 	}
 }
 
@@ -51,12 +51,12 @@ func (r *Driver) Libraries() lookup.Locator {
 	)
 }
 
-// normalizeSearchPaths takes a list of paths and normalized these.
+// NormalizeSearchPaths takes a list of paths and normalized these.
 // Each of the elements in the list is expanded if it is a path list and the
 // resultant list is returned.
 // This allows, for example, for the contents of `PATH` or `LD_LIBRARY_PATH` to
 // be passed as a search path directly.
-func normalizeSearchPaths(paths ...string) []string {
+func NormalizeSearchPaths(paths ...string) []string {
 	var normalized []string
 	for _, path := range paths {
 		normalized = append(normalized, filepath.SplitList(path)...)