[pseudo] [PATCH v2] linkat: Fix AT_EMPTY_PATH handling

Currently we don't cover the case where AT_EMPTY_PATH is set for linkat.
Update the code to handle this case in a similar way to the /proc/self
case which is similar.

This is used by some systemd tools which OE might run at rootfs time
such as hwdb generation.

Signed-off-by: Richard Purdie <[email protected]>
---
 ports/unix/guts/linkat.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/ports/unix/guts/linkat.c b/ports/unix/guts/linkat.c
index 60fbf63..3fd708c 100644
--- a/ports/unix/guts/linkat.c
+++ b/ports/unix/guts/linkat.c
@@ -35,13 +35,18 @@
 	}
 #endif
 	oldpath = oldname;
-	if (pseudo_chroot_len && !strncmp(oldpath, pseudo_chroot, pseudo_chroot_len) &&
+	if (oldpath && *oldpath && pseudo_chroot_len && !strncmp(oldpath, pseudo_chroot, pseudo_chroot_len) &&
 		oldpath[pseudo_chroot_len] == '/') {
 		oldpath += pseudo_chroot_len;
 	}
 
 	newpath = pseudo_root_path(__func__, __LINE__, newdirfd, newname, AT_SYMLINK_NOFOLLOW);
 
+	if ((!oldpath || !*oldpath) && (flags & AT_EMPTY_PATH)) {
+		tmpfile_fd = olddirfd;
+		// call actual link
+		rc = real_linkat(olddirfd, "", AT_FDCWD, newpath, flags);
+	} else
 	/* weird special case: if you link /proc/self/fd/N, you're supposed
 	 * to get a link to fd N. Used in conjunction with opening a directory
 	 * with O_TMPFILE in flags, which actually opens an already-deleted