1 files changed, 55 insertions, 0 deletions
diff --git a/src/shared/binfmt-util.c b/src/shared/binfmt-util.c
new file mode 100644
index 0000000..a261754
--- /dev/null
+++ b/src/shared/binfmt-util.c
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <sys/vfs.h>
+
+#include "binfmt-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "missing_magic.h"
+#include "stat-util.h"
+
+int binfmt_mounted(void) {
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        fd = RET_NERRNO(open("/proc/sys/fs/binfmt_misc", O_CLOEXEC | O_DIRECTORY | O_PATH));
+        if (fd == -ENOENT)
+                return false;
+        if (fd < 0)
+                return fd;
+
+        r = fd_is_fs_type(fd, BINFMTFS_MAGIC);
+        if (r <= 0)
+                return r;
+
+        return access_fd(fd, W_OK) >= 0;
+}
+
+int disable_binfmt(void) {
+        int r;
+
+        /* Flush out all rules. This is important during shutdown to cover for rules using "F", since those
+         * might pin a file and thus block us from unmounting stuff cleanly.
+         *
+         * We are a bit careful here, since binfmt_misc might still be an autofs which we don't want to
+         * trigger. */
+
+        r = binfmt_mounted();
+        if (r < 0)
+                return log_warning_errno(r, "Failed to determine whether binfmt_misc is mounted: %m");
+        if (r == 0) {
+                log_debug("binfmt_misc is not mounted in read-write mode, not detaching entries.");
+                return 0;
+        }
+
+        r = write_string_file("/proc/sys/fs/binfmt_misc/status", "-1", WRITE_STRING_FILE_DISABLE_BUFFER);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to unregister binfmt_misc entries: %m");
+
+        log_debug("Unregistered all remaining binfmt_misc entries.");
+        return 0;
+}