scripts/gdb: add GDB convenience functions $lx_dentry_name() and $lx_i_dentry()

$lx_dentry_name() generates a full VFS path from a given dentry pointer,
and $lx_i_dentry() returns the dentry pointer associated with the given
inode pointer, if there is one.

Link: https://lkml.kernel.org/r/c9a5ad8efbfbd2cc6559e082734eed7628f43a16.1677631565.git.development@efficientek.com
Signed-off-by: Glenn Washburn <development@efficientek.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Antonio Borneo <antonio.borneo@foss.st.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: crass

scripts/gdb/linux/vfs.py

@@ -13,10 +13,47 @@
 # This work is licensed under the terms of the GNU GPL version 2.
 #
 
+import gdb
+from linux import utils
+
 
 def dentry_name(d):
     parent = d['d_parent']
     if parent == d or parent == 0:
         return ""
     p = dentry_name(d['d_parent']) + "/"
     return p + d['d_iname'].string()
+
+class DentryName(gdb.Function):
+    """Return string of the full path of a dentry.
+
+$lx_dentry_name(PTR): Given PTR to a dentry struct, return a string
+of the full path of the dentry."""
+
+    def __init__(self):
+        super(DentryName, self).__init__("lx_dentry_name")
+
+    def invoke(self, dentry_ptr):
+        return dentry_name(dentry_ptr)
+
+DentryName()
+
+
+dentry_type = utils.CachedType("struct dentry")
+
+class InodeDentry(gdb.Function):
+    """Return dentry pointer for inode.
+
+$lx_i_dentry(PTR): Given PTR to an inode struct, return a pointer to
+the associated dentry struct, if there is one."""
+
+    def __init__(self):
+        super(InodeDentry, self).__init__("lx_i_dentry")
+
+    def invoke(self, inode_ptr):
+        d_u = inode_ptr["i_dentry"]["first"]
+        if d_u == 0:
+            return ""
+        return utils.container_of(d_u, dentry_type.get_type().pointer(), "d_u")
+
+InodeDentry()