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    Subject[PATCH v7 03/21] scripts/gdb: Add container_of helper and convenience function
    Date
    Provide an internal helper with container_of semantics. As type lookups
    are very slow in gdb-python and we need a type "long" for this, cache
    the reference to this type object. Then export the helper also as a
    convenience function form use at the gdb command line.

    Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
    ---
    scripts/gdb/linux/utils.py | 35 +++++++++++++++++++++++++++++++++++
    scripts/gdb/vmlinux-gdb.py | 2 ++
    2 files changed, 37 insertions(+)

    diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
    index f883611..c9d705b 100644
    --- a/scripts/gdb/linux/utils.py
    +++ b/scripts/gdb/linux/utils.py
    @@ -32,3 +32,38 @@ class CachedType:
    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()
    diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
    index c1d90ce..6495841 100644
    --- a/scripts/gdb/vmlinux-gdb.py
    +++ b/scripts/gdb/vmlinux-gdb.py
    @@ -21,3 +21,5 @@ try:
    except:
    gdb.write("NOTE: gdb 7.2 or later required for Linux helper scripts to "
    "work.\n")
    +else:
    + import linux.utils
    --
    1.8.1.1.298.ge7eed54


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