The EFI_FILE_PROTOCOL.SetInfo() member is somewhat under-specified; one of
its modes of operation is renaming/moving the file.
In order to create the destination pathname in canonical format, 2*2=4
cases have to be considered. For the sake of discussion, assume the
current canonical pathname of a VIRTIO_FS_FILE is "/home/user/f1.txt".
Then, consider the following rename/move requests from
EFI_FILE_PROTOCOL.SetInfo():
Destination requested Destination Move into Destination in
by SetInfo() relative? directory? canonical format
--------------------- ----------- ---------- -----------------------
L"\\dir\\f2.txt" no no "/dir/f2.txt"
L"\\dir\\" no yes "/dir/f1.txt"
L"dir\\f2.txt" yes no "/home/user/dir/f2.txt"
L"dir\\" yes yes "/home/user/dir/f1.txt"
Add the VirtioFsComposeRenameDestination() function, for composing the
last column from the current canonical pathname and the SetInfo() input.
The function works on the following principles:
- The prefix of the destination path is "/", if the SetInfo() rename
request is absolute.
Otherwise, the dest prefix is the "current directory" (the most specific
parent directory) of the original pathname (in the above example,
"/home/user").
- The suffix of the destination path is precisely the SetInfo() request
string, if the "move into directory" convenience format -- the trailing
backslash -- is not used. (In the above example, L"\\dir\\f2.txt" and
L"dir\\f2.txt".)
Otherwise, the suffix is the SetInfo() request, plus the original
basename (in the above example, L"\\dir\\f1.txt" and L"dir\\f1.txt").
- The complete destination is created by fusing the dest prefix and the
dest suffix, using the VirtioFsAppendPath() function.
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-43-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
c3f76ef89d