[PATCHv4 08/12] scripts/gdb: Add mount point list command

From: Kieran Bingham
Date: Wed Mar 30 2016 - 08:03:04 EST


lx-mounts will identify current mount points based on the 'init_task'
namespace by default, as we do not yet have a kernel thread list
implementation to select the current running thread.

Optionally, a user can specify a PID to list from that process'
namespace

Signed-off-by: Kieran Bingham <kieran.bingham@xxxxxxxxxx>

---
Changes from v1:
- Updated to use LX_ constant macros
- Adjusted for new list_for_each_item() function
- Removed unnecessary Null check in vfs['mnt_parent']
- Tested and not needed. It probably occurred in early testing
with a bad iterator

Changes since v2:
- dentry path helper moved to utils module

Changes since v3
- Adjust vfs list_for_each_entry code alignments
---
scripts/gdb/linux/constants.py.in | 21 +++++++++
scripts/gdb/linux/proc.py | 99 +++++++++++++++++++++++++++++++++++++++
2 files changed, 120 insertions(+)

diff --git a/scripts/gdb/linux/constants.py.in b/scripts/gdb/linux/constants.py.in
index 79d9d0092452..57213ad8cf75 100644
--- a/scripts/gdb/linux/constants.py.in
+++ b/scripts/gdb/linux/constants.py.in
@@ -12,7 +12,11 @@
*
*/

+#include <linux/fs.h>
+#include <linux/mount.h>
+
/* We need to stringify expanded macros so that they can be parsed */
+
#define STRING(x) #x
#define XSTRING(x) STRING(x)

@@ -30,3 +34,20 @@
<!-- end-c-headers -->

import gdb
+
+/* linux/fs.h */
+LX_VALUE(MS_RDONLY)
+LX_VALUE(MS_SYNCHRONOUS)
+LX_VALUE(MS_MANDLOCK)
+LX_VALUE(MS_DIRSYNC)
+LX_VALUE(MS_NOATIME)
+LX_VALUE(MS_NODIRATIME)
+
+/* linux/mount.h */
+LX_VALUE(MNT_NOSUID)
+LX_VALUE(MNT_NODEV)
+LX_VALUE(MNT_NOEXEC)
+LX_VALUE(MNT_NOATIME)
+LX_VALUE(MNT_NODIRATIME)
+LX_VALUE(MNT_RELATIME)
+
diff --git a/scripts/gdb/linux/proc.py b/scripts/gdb/linux/proc.py
index d855b2fd9a06..38b1f09d1cd9 100644
--- a/scripts/gdb/linux/proc.py
+++ b/scripts/gdb/linux/proc.py
@@ -12,6 +12,10 @@
#

import gdb
+from linux import constants
+from linux import utils
+from linux import tasks
+from linux import lists


class LxCmdLine(gdb.Command):
@@ -96,3 +100,98 @@ Equivalent to cat /proc/ioports on a running target"""
return show_lx_resources("ioport_resource")

LxIOPorts()
+
+
+# Mount namespace viewer
+# /proc/mounts
+
+def info_opts(lst, opt):
+ opts = ""
+ for key, string in lst.items():
+ if opt & key:
+ opts += string
+ return opts
+
+
+FS_INFO = {constants.LX_MS_SYNCHRONOUS: ",sync",
+ constants.LX_MS_MANDLOCK: ",mand",
+ constants.LX_MS_DIRSYNC: ",dirsync",
+ constants.LX_MS_NOATIME: ",noatime",
+ constants.LX_MS_NODIRATIME: ",nodiratime"}
+
+MNT_INFO = {constants.LX_MNT_NOSUID: ",nosuid",
+ constants.LX_MNT_NODEV: ",nodev",
+ constants.LX_MNT_NOEXEC: ",noexec",
+ constants.LX_MNT_NOATIME: ",noatime",
+ constants.LX_MNT_NODIRATIME: ",nodiratime",
+ constants.LX_MNT_RELATIME: ",relatime"}
+
+mount_type = utils.CachedType("struct mount")
+mount_ptr_type = mount_type.get_type().pointer()
+
+
+class LxMounts(gdb.Command):
+ """Report the VFS mounts of the current process namespace.
+
+Equivalent to cat /proc/mounts on a running target
+An integer value can be supplied to display the mount
+values of that process namespace"""
+
+ def __init__(self):
+ super(LxMounts, self).__init__("lx-mounts", gdb.COMMAND_DATA)
+
+ # Equivalent to proc_namespace.c:show_vfsmnt
+ # However, that has the ability to call into s_op functions
+ # whereas we cannot and must make do with the information we can obtain.
+ def invoke(self, arg, from_tty):
+ argv = gdb.string_to_argv(arg)
+ if len(argv) >= 1:
+ try:
+ pid = int(argv[0])
+ except:
+ raise gdb.GdbError("Provide a PID as integer value")
+ else:
+ pid = 1
+
+ task = tasks.get_task_by_pid(pid)
+ if not task:
+ raise gdb.GdbError("Couldn't find a process with PID {}"
+ .format(pid))
+
+ namespace = task['nsproxy']['mnt_ns']
+ if not namespace:
+ raise gdb.GdbError("No namespace for current process")
+
+ for vfs in lists.list_for_each_entry(namespace['list'],
+ mount_ptr_type, "mnt_list"):
+ devname = vfs['mnt_devname'].string()
+ devname = devname if devname else "none"
+
+ pathname = ""
+ parent = vfs
+ while True:
+ mntpoint = parent['mnt_mountpoint']
+ pathname = utils.dentry_name(mntpoint) + pathname
+ if (parent == parent['mnt_parent']):
+ break
+ parent = parent['mnt_parent']
+
+ if (pathname == ""):
+ pathname = "/"
+
+ superblock = vfs['mnt']['mnt_sb']
+ fstype = superblock['s_type']['name'].string()
+ s_flags = int(superblock['s_flags'])
+ m_flags = int(vfs['mnt']['mnt_flags'])
+ rd = "ro" if (s_flags & constants.LX_MS_RDONLY) else "rw"
+
+ gdb.write(
+ "{} {} {} {}{}{} 0 0\n"
+ .format(devname,
+ pathname,
+ fstype,
+ rd,
+ info_opts(FS_INFO, s_flags),
+ info_opts(MNT_INFO, m_flags)))
+
+LxMounts()
--
2.5.0