opt: cygfuse: refactoring

opt/cygfuse/fuse/cygfuse.c

@@ -0,0 +1,166 @@
+/**
+ * @file fuse/cygfuse.c
+ *
+ * @copyright 2015-2018 Bill Zissimopoulos
+ */
+/*
+ * This file is part of WinFsp.
+ *
+ * You can redistribute it and/or modify it under the terms of the GNU
+ * General Public License version 3 as published by the Free Software
+ * Foundation.
+ *
+ * Licensees holding a valid commercial license may use this file in
+ * accordance with the commercial license agreement provided with the
+ * software.
+ */
+
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/cygwin.h>
+
+static void *cygfuse_init_slow(int force);
+static void *cygfuse_init_winfsp();
+
+static pthread_mutex_t cygfuse_mutex = PTHREAD_MUTEX_INITIALIZER;
+static void *cygfuse_handle = 0;
+
+static inline void *cygfuse_init_fast(void)
+{
+    void *handle = cygfuse_handle;
+    __sync_synchronize(); /* memory barrier */
+    if (0 == handle)
+        handle = cygfuse_init_slow(0);
+    return handle;
+}
+
+static void *cygfuse_init_slow(int force)
+{
+    void *handle;
+    pthread_mutex_lock(&cygfuse_mutex);
+    handle = cygfuse_handle;
+    if (force || 0 == handle)
+    {
+        handle = cygfuse_init_winfsp();
+        __sync_synchronize(); /* memory barrier */
+        cygfuse_handle = handle;
+    }
+    pthread_mutex_unlock(&cygfuse_mutex);
+    return handle;
+}
+
+/*
+ * Unfortunately Cygwin fork is very fragile and cannot even correctly
+ * handle dlopen'ed DLL's if they are native (rather than Cygwin ones).
+ *
+ * So we have this very nasty hack where we reset the dlopen'ed handle
+ * immediately after daemonization. This will force cygfuse_init() to
+ * reload the WinFsp DLL and reset all API pointers in the daemonized
+ * process.
+ */
+static inline int cygfuse_daemon(int nochdir, int noclose)
+{
+    if (-1 == daemon(nochdir, noclose))
+        return -1;
+
+    /* force reload of WinFsp DLL to workaround fork() problems */
+    cygfuse_init_slow(1);
+
+    return 0;
+}
+#define daemon                          cygfuse_daemon
+
+#define FSP_FUSE_API                    static
+#define FSP_FUSE_API_NAME(api)          (* pfn_ ## api)
+#define FSP_FUSE_API_CALL(api)          (cygfuse_init_fast(), pfn_ ## api)
+#define FSP_FUSE_SYM(proto, ...)        __attribute__ ((visibility("default"))) proto { __VA_ARGS__ }
+#include <fuse_common.h>
+#include <fuse.h>
+#include <fuse_opt.h>
+
+#if defined(__LP64__)
+#define CYGFUSE_WINFSP_NAME             "winfsp-x64.dll"
+#else
+#define CYGFUSE_WINFSP_NAME             "winfsp-x86.dll"
+#endif
+#define CYGFUSE_WINFSP_PATH             "bin\\" CYGFUSE_WINFSP_NAME
+#define CYGFUSE_GET_API(h, n)           \
+    if (0 == (*(void **)&(pfn_ ## n) = dlsym(h, #n)))\
+        return cygfuse_init_fail();
+
+static void *cygfuse_init_fail();
+static void *cygfuse_init_winfsp()
+{
+    void *h;
+
+    h = dlopen(CYGFUSE_WINFSP_NAME, RTLD_NOW);
+    if (0 == h)
+    {
+        char winpath[260], *psxpath;
+        int regfd, bytes;
+
+        regfd = open("/proc/registry32/HKEY_LOCAL_MACHINE/Software/WinFsp/InstallDir", O_RDONLY);
+        if (-1 == regfd)
+            return cygfuse_init_fail();
+
+        bytes = read(regfd, winpath, sizeof winpath - sizeof CYGFUSE_WINFSP_PATH);
+        close(regfd);
+        if (-1 == bytes || 0 == bytes)
+            return cygfuse_init_fail();
+
+        if ('\0' == winpath[bytes - 1])
+            bytes--;
+        memcpy(winpath + bytes, CYGFUSE_WINFSP_PATH, sizeof CYGFUSE_WINFSP_PATH);
+
+        psxpath = (char *)cygwin_create_path(CCP_WIN_A_TO_POSIX | CCP_PROC_CYGDRIVE, winpath);
+        if (0 == psxpath)
+            return cygfuse_init_fail();
+
+        h = dlopen(psxpath, RTLD_NOW);
+        free(psxpath);
+        if (0 == h)
+            return cygfuse_init_fail();
+    }
+
+    /* winfsp_fuse.h */
+    CYGFUSE_GET_API(h, fsp_fuse_signal_handler);
+
+    /* fuse_common.h */
+    CYGFUSE_GET_API(h, fsp_fuse_version);
+    CYGFUSE_GET_API(h, fsp_fuse_mount);
+    CYGFUSE_GET_API(h, fsp_fuse_unmount);
+    CYGFUSE_GET_API(h, fsp_fuse_parse_cmdline);
+    CYGFUSE_GET_API(h, fsp_fuse_ntstatus_from_errno);
+
+    /* fuse.h */
+    CYGFUSE_GET_API(h, fsp_fuse_main_real);
+    CYGFUSE_GET_API(h, fsp_fuse_is_lib_option);
+    CYGFUSE_GET_API(h, fsp_fuse_new);
+    CYGFUSE_GET_API(h, fsp_fuse_destroy);
+    CYGFUSE_GET_API(h, fsp_fuse_loop);
+    CYGFUSE_GET_API(h, fsp_fuse_loop_mt);
+    CYGFUSE_GET_API(h, fsp_fuse_exit);
+    CYGFUSE_GET_API(h, fsp_fuse_exited);
+    CYGFUSE_GET_API(h, fsp_fuse_get_context);
+
+    /* fuse_opt.h */
+    CYGFUSE_GET_API(h, fsp_fuse_opt_parse);
+    CYGFUSE_GET_API(h, fsp_fuse_opt_add_arg);
+    CYGFUSE_GET_API(h, fsp_fuse_opt_insert_arg);
+    CYGFUSE_GET_API(h, fsp_fuse_opt_free_args);
+    CYGFUSE_GET_API(h, fsp_fuse_opt_add_opt);
+    CYGFUSE_GET_API(h, fsp_fuse_opt_add_opt_escaped);
+    CYGFUSE_GET_API(h, fsp_fuse_opt_match);
+
+    return h;
+}
+
+static void *cygfuse_init_fail()
+{
+    fprintf(stderr, "cygfuse: initialization failed: " CYGFUSE_WINFSP_NAME " not found\n");
+    exit(1);
+    return 0;
+}