• Todd Kjos's avatar
    binder: use standard functions to allocate fds · 44d8047f
    Todd Kjos authored
    Binder uses internal fs interfaces to allocate and install fds:
    
    __alloc_fd
    __fd_install
    __close_fd
    get_files_struct
    put_files_struct
    
    These were used to support the passing of fds between processes
    as part of a transaction. The actual allocation and installation
    of the fds in the target process was handled by the sending
    process so the standard functions, alloc_fd() and fd_install()
    which assume task==current couldn't be used.
    
    This patch refactors this mechanism so that the fds are
    allocated and installed by the target process allowing the
    standard functions to be used.
    
    The sender now creates a list of fd fixups that contains the
    struct *file and the address to fixup with the new fd once
    it is allocated. This list is processed by the target process
    when the transaction is dequeued.
    
    A new error case is introduced by this change. If an async
    transaction with file descriptors cannot allocate new
    fds in the target (probably due to out of file descriptors),
    the transaction is discarded with a log message. In the old
    implementation this would have been detected in the sender
    context and failed prior to sending.
    Signed-off-by: default avatarTodd Kjos <tkjos@google.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    44d8047f
binder_trace.h 11.3 KB