scripts/gdb: create linux/vfs.py for VFS related GDB helpers

Patch series "GDB VFS utils".

I've created a couple GDB convenience functions that I found useful when
debugging some VFS issues and figure others might find them useful. For
instance, they are useful in setting conditional breakpoints on VFS
functions where you only care if the dentry path is a certain value. I
took the opportunity to create a new "vfs" python module to give VFS
related utilities a home.


This patch (of 2):

This will allow for more VFS specific GDB helpers to be collected in one
place. Move utils.dentry_name into the vfs modules. Also a local
variable in proc.py was changed from vfs to mnt to prevent a naming
collision with the new vfs module.

[[e-mail]: add SPDX-License-Identifier]
Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/7bb[e-mail]
Signed-off-by: Glenn Washburn <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Antonio Borneo <[e-mail]>
Cc: Jan Kiszka <[e-mail]>
Cc: John Ogness <[e-mail]>
Cc: Kieran Bingham <[e-mail]>
Cc: Petr Mladek <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

scripts/gdb/linux/proc.py

···
+# SPDX-License-Identifier: GPL-2.0
 #
 # gdb helper commands and functions for Linux kernel debugging
 #
···
 from linux import utils
 from linux import tasks
 from linux import lists
+from linux import vfs
 from struct import *
 
 
···
         gdb.write("{:^18} {:^15} {:>9} {} {} options\n".format(
                   "mount", "super_block", "devname", "pathname", "fstype"))
 
-        for vfs in lists.list_for_each_entry(namespace['list'],
+        for mnt in lists.list_for_each_entry(namespace['list'],
                                              mount_ptr_type, "mnt_list"):
-            devname = vfs['mnt_devname'].string()
+            devname = mnt['mnt_devname'].string()
             devname = devname if devname else "none"
 
             pathname = ""
-            parent = vfs
+            parent = mnt
             while True:
                 mntpoint = parent['mnt_mountpoint']
-                pathname = utils.dentry_name(mntpoint) + pathname
+                pathname = vfs.dentry_name(mntpoint) + pathname
                 if (parent == parent['mnt_parent']):
                     break
                 parent = parent['mnt_parent']
···
             if (pathname == ""):
                 pathname = "/"
 
-            superblock = vfs['mnt']['mnt_sb']
+            superblock = mnt['mnt']['mnt_sb']
             fstype = superblock['s_type']['name'].string()
             s_flags = int(superblock['s_flags'])
-            m_flags = int(vfs['mnt']['mnt_flags'])
+            m_flags = int(mnt['mnt']['mnt_flags'])
             rd = "ro" if (s_flags & constants.LX_SB_RDONLY) else "rw"
 
             gdb.write("{} {} {} {} {} {}{}{} 0 0\n".format(
-                      vfs.format_string(), superblock.format_string(), devname,
+                      mnt.format_string(), superblock.format_string(), devname,
                       pathname, fstype, rd, info_opts(FS_INFO, s_flags),
                       info_opts(MNT_INFO, m_flags)))
 

scripts/gdb/linux/utils.py

···
         return gdb.parse_and_eval(expresssion)
     except gdb.error:
         return None
-
-
-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()

scripts/gdb/linux/vfs.py

···
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  VFS tools
+#
+# Copyright (c) 2023 Glenn Washburn
+# Copyright (c) 2016 Linaro Ltd
+#
+# Authors:
+#  Glenn Washburn <[e-mail]>
+#  Kieran Bingham <[e-mail]>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+
+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()

scripts/gdb/vmlinux-gdb.py

···
     import linux.clk
     import linux.genpd
     import linux.device
+    import linux.vfs
     import linux.mm
     import linux.radixtree
     import linux.interrupts