scripts/gdb: add container_of helper and convenience function

            if hasattr(gdb, 'events') and hasattr(gdb.events, 'new_objfile'):

                gdb.events.new_objfile.connect(self._new_objfile_handler)

        return self._type

long_type = CachedType("long")

def get_long_type():

    global long_type

    return long_type.get_type()

def offset_of(typeobj, field):

    element = gdb.Value(0).cast(typeobj)

    return int(str(element[field].address).split()[0], 16)

def container_of(ptr, typeobj, member):

    return (ptr.cast(get_long_type()) -

            offset_of(typeobj, member)).cast(typeobj)

class ContainerOf(gdb.Function):

    """Return pointer to containing data structure.

$container_of(PTR, "TYPE", "ELEMENT"): Given PTR, return a pointer to the

data structure of the type TYPE in which PTR is the address of ELEMENT.

Note that TYPE and ELEMENT have to be quoted as strings."""

    def __init__(self):

        super(ContainerOf, self).__init__("container_of")

    def invoke(self, ptr, typename, elementname):

        return container_of(ptr, gdb.lookup_type(typename.string()).pointer(),

                            elementname.string())

ContainerOf()

except:

    gdb.write("NOTE: gdb 7.2 or later required for Linux helper scripts to "

              "work.\n")

else:

    import linux.utils