[PATCH v2 0/1] MR4023: server: Add cross-platform get_path_from_fd function.

[Marc-Aurel Zent (＠marzent)]

This allows *BSD systems that support kqueue (including macOS) to have working file change notifications when configuring wine `--with-inotify` and linking against https://github.com/libinotify-kqueue/libinotify-kqueue

--
  v2: server: Add cross-platform get_path_from_fd function.

https://gitlab.winehq.org/wine/wine/-/merge_requests/4023

[PATCH v2 1/1] server: Add cross-platform get_path_from_fd function.

[Marc-Aurel Zent]

From: Marc-Aurel Zent

---
 server/change.c | 42 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 35 insertions(+), 7 deletions(-)

diff --git a/server/change.c b/server/change.c
index 7a806abc017..bf22407c7b2 100644
--- a/server/change.c
+++ b/server/change.c
@@ -66,6 +66,12 @@

/* inotify support */

+#ifdef linux
+#define PATH_BUFFER_SIZE 32
+#else
+#define PATH_BUFFER_SIZE PATH_MAX
+#endif
+
 struct inode;

static void free_inode( struct inode *inode );
@@ -721,6 +727,18 @@ static unsigned int filter_from_inode( struct inode *inode, int is_parent )
     return filter;
 }

+static int get_path_from_fd( int fd, char *path )
+{
+#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__)
+    return fcntl( fd, F_GETPATH, path );
+#elif defined(linux)
+    sprintf( path, "/proc/self/fd/%u", fd );
+    return 0;
+#else
+    return -1;
+#endif
+}
+
 static char *inode_get_path( struct inode *inode, int sz )
 {
     struct list *head;
@@ -734,9 +752,15 @@ static char *inode_get_path( struct inode *inode, int sz )
     if (head)
     {
         int unix_fd = get_unix_fd( LIST_ENTRY( head, struct dir, in_entry )->fd );
-        path = malloc ( 32 + sz );
+        path = malloc ( PATH_BUFFER_SIZE + sz );
         if (path)
-            sprintf( path, "/proc/self/fd/%u/", unix_fd );
+        {
+            if (get_path_from_fd( unix_fd, path ))
+            {
+                free( path );
+                return NULL;
+            }
+        }
         return path;
     }

@@ -964,7 +988,7 @@ static int inotify_adjust_changes( struct dir *dir )
     unsigned int filter;
     struct inode *inode;
     struct stat st;
-    char path[32];
+    char path[PATH_BUFFER_SIZE];
     int wd, unix_fd;

if (!inotify_fd)
@@ -990,7 +1014,8 @@ static int inotify_adjust_changes( struct dir *dir )

filter = filter_from_inode( inode, 0 );

-    sprintf( path, "/proc/self/fd/%u", unix_fd );
+    if (get_path_from_fd( unix_fd, path ))
+        return 0;
     wd = inotify_add_dir( path, filter );
     if (wd == -1) return 0;

@@ -1042,7 +1067,7 @@ static int dir_add_to_existing_notify( struct dir *dir )
     struct inode *inode, *parent;
     unsigned int filter = 0;
     struct stat st, st_new;
-    char link[35], *name;
+    char link[PATH_BUFFER_SIZE + 3], *name;
     int wd, unix_fd;

if (!inotify_fd)
@@ -1058,7 +1083,9 @@ static int dir_add_to_existing_notify( struct dir *dir )
         return 0;

/* lookup the parent */
-    sprintf( link, "/proc/self/fd/%u/..", unix_fd );
+    if (get_path_from_fd( unix_fd, link ))
+        return 0;
+    strcat( link, "/.." );
     if (-1 == stat( link, &st ))
         return 0;

@@ -1079,7 +1106,8 @@ static int dir_add_to_existing_notify( struct dir *dir )
     if (!filter)
         return 0;

-    sprintf( link, "/proc/self/fd/%u", unix_fd );
+    if (get_path_from_fd( unix_fd, link ))
+        return 0;
     name = get_basename( link );
     if (!name)
         return 0;

[Marc-Aurel Zent (＠marzent)]

The buffer size should now be back to 32 for Linux (plus whatever will be added).
This might result in paths being constructed bigger than PATH_MAX (especially on non-Linux), but stat should just set ENAMETOOLONG in that case and the existing code handles errors there already.