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    Subject[PATCH v5 03/20] 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/utils.py | 34 ++++++++++++++++++++++++++++++++++
    scripts/gdb/vmlinux-gdb.py | 2 ++
    2 files changed, 36 insertions(+), 0 deletions(-)

    diff --git a/scripts/gdb/utils.py b/scripts/gdb/utils.py
    index fdff85e..d1f6f12 100644
    --- a/scripts/gdb/utils.py
    +++ b/scripts/gdb/utils.py
    @@ -36,3 +36,37 @@ class CachedType:
    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):
    + __doc__ = "Return pointer to containing data structure.\n" \
    + "\n" \
    + "$container_of(PTR, \"TYPE\", \"ELEMENT\"): Given PTR, return a pointer to the\n" \
    + "data structure of the type TYPE in which PTR is the address of ELEMENT.\n" \
    + "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 bcb45cc..8ef76c9 100644
    --- a/scripts/gdb/vmlinux-gdb.py
    +++ b/scripts/gdb/vmlinux-gdb.py
    @@ -20,3 +20,5 @@ from utils import gdb_version
    if gdb_version < "7.1":
    print "NOTE: gdb 7.1 or later required for Linux helper scripts " \
    "to work."
    +else:
    + import utils
    --
    1.7.3.4


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