[PATCH] scripts/gdb: Add command to check list consistency

["Thiébaud Weksteen" <thiebaud@weksteen.fr>]

Add a gdb script to verify the consistency of lists.

Signed-off-by: Thiébaud Weksteen <thiebaud@weksteen.fr>
---
 scripts/gdb/linux/lists.py | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 79 insertions(+)
 create mode 100644 scripts/gdb/linux/lists.py

diff --git a/scripts/gdb/linux/lists.py b/scripts/gdb/linux/lists.py
new file mode 100644
index 0000000..d512f62
--- /dev/null
+++ b/scripts/gdb/linux/lists.py
@@ -0,0 +1,78 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  list tools
+#
+# Authors:
+#  Thiebaud Weksteen <thiebaud@weksteen.fr>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+
+from linux import utils
+
+list_head = utils.CachedType("struct list_head")
+
+def check_list(head):
+    nb = 0
+    list_head_ptr_type = list_head.get_type().pointer()
+    c = head.cast(list_head_ptr_type)
+    try:
+        gdb.write("Starting with: {} {}\n".format(c, c.dereference()))
+    except gdb.MemoryError:
+        gdb.write('head is not accessible\n')
+        return
+    while True:
+        p = c['prev']
+        n = c['next']
+        try:
+            if p['next'] != c:
+                gdb.write('prev.next != current: current={current} '
+                          'prev={p} prev.next={pnext}\n'.format(
+                          current=c,
+                          p=p,
+                          pnext=p['next']
+                          ))
+                return
+        except gdb.MemoryError:
+            gdb.write('prev is not accessible: current={current} '
+                      'current.prev={p}\n'.format(
+                      current=c,
+                      p=p
+                      ))
+            return
+        try:
+            if n['prev'] != c:
+                gdb.write('next.prev != current: current={current} '
+                          'next={n}, next.prev={nprev}\n'.format(
+                          current=c,
+                          n=n,
+                          nprev=n['prev']
+                          ))
+                return
+        except gdb.MemoryError:
+            gdb.write('next is not accessible: current={current} '
+                      'current.next={n}\n'.format(
+                      current=c,
+                      n=n
+                      ))
+            return
+        c = n
+        nb += 1
+        if c == head:
+            gdb.write("list is consistent: {} node(s)\n".format(nb))
+            return
+
+class LxChkList(gdb.Command):
+    """Verify a list consistency"""
+
+    def __init__(self):
+        super(LxChkList, self).__init__("lx-check-list", gdb.COMMAND_DATA)
+
+    def invoke(self, arg, from_tty):
+        argv = gdb.string_to_argv(arg)
+        check_list(gdb.parse_and_eval(argv[0]))
+
+LxChkList()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 4848928..ce82bf5 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -28,3 +28,4 @@ else:
     import linux.dmesg
     import linux.tasks
     import linux.cpus
+    import linux.lists
-- 
2.1.0