[PATCH v4 02/13] scripts/gdb: Add container_of helper and convenience function

Jan Kiszka
2013-01-21T17:23:51Z

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 | 41 +++++++++++++++++++++++++++++++++++++++++
scripts/gdb/vmlinux-gdb.py | 2 ++
2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/scripts/gdb/utils.py b/scripts/gdb/utils.py
index 65a2e91..2f6eafb 100644
--- a/scripts/gdb/utils.py
+++ b/scripts/gdb/utils.py
@@ -15,3 +15,44 @@ import gdb
import re

gdb_version = re.sub("^[^0-9]*", "", gdb.VERSION)
+
+long_type = None
+
+def get_type(type_name):
+ t = gdb.lookup_type(type_name)
+ if t == None:
+ raise gdb.GdbError("cannot resolve type '%s'" % type_name)
+ return t
+
+def get_long_type():
+ global long_type
+ if long_type == None:
+ long_type = get_type("long")
+ return long_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