[PATCH 0/2] GDB VFS utils

[PATCH 0/2] GDB VFS utils

[Glenn Washburn]

Hi all,

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.

Glenn

Glenn Washburn (2):
  scripts/gdb: Create linux/vfs.py for VFS related GDB helpers
  scripts/gdb: Add GDB convenience functions $lx_dentry_name() and
    $lx_i_dentry()

 scripts/gdb/linux/proc.py  | 15 +++++-----
 scripts/gdb/linux/utils.py |  8 ------
 scripts/gdb/linux/vfs.py   | 59 ++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 4 files changed, 68 insertions(+), 15 deletions(-)
 create mode 100644 scripts/gdb/linux/vfs.py

-- 
2.30.2

[PATCH 1/2] scripts/gdb: Create linux/vfs.py for VFS related GDB helpers

[Glenn Washburn]

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.

Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 scripts/gdb/linux/proc.py  | 15 ++++++++-------
 scripts/gdb/linux/utils.py |  8 --------
 scripts/gdb/linux/vfs.py   | 22 ++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 4 files changed, 31 insertions(+), 15 deletions(-)
 create mode 100644 scripts/gdb/linux/vfs.py

diff --git a/scripts/gdb/linux/proc.py b/scripts/gdb/linux/proc.py
index 09cd871925a5..f2c9ba62534b 100644
--- a/scripts/gdb/linux/proc.py
+++ b/scripts/gdb/linux/proc.py
@@ -16,6 +16,7 @@ from linux import constants
 from linux import utils
 from linux import tasks
 from linux import lists
+from linux import vfs
 from struct import *
 
 
@@ -170,16 +171,16 @@ values of that process namespace"""
         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']
@@ -187,14 +188,14 @@ values of that process namespace"""
             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)))
 
diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py
index 1553f68716cc..46233e845be3 100644
--- a/scripts/gdb/linux/utils.py
+++ b/scripts/gdb/linux/utils.py
@@ -193,11 +193,3 @@ def gdb_eval_or_none(expresssion):
         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()
diff --git a/scripts/gdb/linux/vfs.py b/scripts/gdb/linux/vfs.py
new file mode 100644
index 000000000000..62d4f9ad7d79
--- /dev/null
+++ b/scripts/gdb/linux/vfs.py
@@ -0,0 +1,22 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  VFS tools
+#
+# Copyright (c) 2023 Glenn Washburn
+# Copyright (c) 2016 Linaro Ltd
+#
+# Authors:
+#  Glenn Washburn <development@efficientek.com>
+#  Kieran Bingham <kieran.bingham@linaro.org>
+#
+# 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()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 3e8d3669f0ce..b5af64dcf4ed 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -37,3 +37,4 @@ else:
     import linux.clk
     import linux.genpd
     import linux.device
+    import linux.vfs
-- 
2.30.2

[PATCH 2/2] scripts/gdb: Add GDB convenience functions $lx_dentry_name() and $lx_i_dentry()

[Glenn Washburn]

$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.

Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 scripts/gdb/linux/vfs.py | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/scripts/gdb/linux/vfs.py b/scripts/gdb/linux/vfs.py
index 62d4f9ad7d79..c77b9ce75f6d 100644
--- a/scripts/gdb/linux/vfs.py
+++ b/scripts/gdb/linux/vfs.py
@@ -13,6 +13,9 @@
 # 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']
@@ -20,3 +23,37 @@ def dentry_name(d):
         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()
-- 
2.30.2

Re: [PATCH 0/2] GDB VFS utils

[Florian Fainelli]

On 2/28/23 16:53, Glenn Washburn wrote:
> Hi all,
> 
> 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.

Andrew, any chance you could pick up those two patches from Glenn:

https://lore.kernel.org/all/7bba4c065a8c2c47f1fc5b03a7278005b04db251.1677631565.git.development@efficientek.com/
https://lore.kernel.org/all/c9a5ad8efbfbd2cc6559e082734eed7628f43a16.1677631565.git.development@efficientek.com/

Thanks!
-- 
Florian

Re: [PATCH 1/2] scripts/gdb: Create linux/vfs.py for VFS related GDB helpers

[Andrew Morton]

On Tue, 28 Feb 2023 18:53:34 -0600 Glenn Washburn <development@efficientek.com> wrote:

> 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.

checkpatch gets unhappy.   Please add this addition?

--- a/scripts/gdb/linux/proc.py~scripts-gdb-create-linux-vfspy-for-vfs-related-gdb-helpers-fix
+++ a/scripts/gdb/linux/proc.py
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
 #
 # gdb helper commands and functions for Linux kernel debugging
 #
_