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Date: Wed, 20 Jan 2016 12:42:00 +0100
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Kieran Bingham <kieran.bingham@...aro.org>
Cc: linux-kernel@...r.kernel.org, maxime.coquelin@...com,
peter.griffin@...aro.org, lee.jones@...aro.org
Subject: Re: [PATCH 4/5] scripts/gdb: Add mount point list command
Hi Kieran,
just a couple of quick comments:
On 2016-01-20 12:15, Kieran Bingham wrote:
> 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.
current_task? See LxCurrentFunc, could be factored out if usable. Or
what are you looking for?
>
> Optionally, a user can specify a PID to list from that process'
> namespace
>
> This is somewhat limited vs the /proc/mounts file, as that calls into
> vfs hooks through the s_op functions to obtain extra information.
>
> Signed-off-by: Kieran Bingham <kieran.bingham@...aro.org>
> ---
>
>
> In this patch, I'm interested in your opinions on coding styles.
> Would you prefer to see the function helpers, (dentry_name, info_opts) where
> they are, or inside the command as class members? Or perhaps defined in utils?
Need to look into this.
>
> This also shows where I need to take constant information from the kernel.
> In this case, they are simple numerical bitflags, and unlikely to change but
> I didn't want to duplicate their values.
Maybe we can generate python files with the required constants from the
C headers during build? Similar to asm-offsets.c stuff.
>
>
> scripts/gdb/linux/constants.py.in | 21 ++++++++
> scripts/gdb/linux/proc.py | 110 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 131 insertions(+)
>
> diff --git a/scripts/gdb/linux/constants.py.in b/scripts/gdb/linux/constants.py.in
> index d84084ac945b..739a15d2e984 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)
>
> @@ -20,3 +24,20 @@
> <!-- end-c-headers -->
>
> import gdb
> +
> +/* linux/fs.h */
> +LX_MS_RDONLY = MS_RDONLY
> +LX_MS_SYNCHRONOUS = MS_SYNCHRONOUS
> +LX_MS_MANDLOCK = MS_MANDLOCK
> +LX_MS_DIRSYNC = MS_DIRSYNC
> +LX_MS_NOATIME = MS_NOATIME
> +LX_MS_NODIRATIME = MS_NODIRATIME
> +
> +/* linux/mount.h */
> +LX_MNT_NOSUID = MNT_NOSUID
> +LX_MNT_NODEV = MNT_NODEV
> +LX_MNT_NOEXEC = MNT_NOEXEC
> +LX_MNT_NOATIME = MNT_NOATIME
> +LX_MNT_NODIRATIME = MNT_NODIRATIME
> +LX_MNT_RELATIME = MNT_RELATIME
> +
> diff --git a/scripts/gdb/linux/proc.py b/scripts/gdb/linux/proc.py
> index d855b2fd9a06..b79ce2a33a3d 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 +100,109 @@ Equivalent to cat /proc/ioports on a running target"""
> return show_lx_resources("ioport_resource")
>
> LxIOPorts()
> +
> +
> +# Mount namespace viewer
> +# /proc/mounts
> +
> +
> +def dentry_name(d):
> + if d['d_parent'] == d:
> + return ""
> + p = dentry_name(d['d_parent']) + "/"
> + return p + d['d_iname'].string()
> +
> +
> +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.items(mount_ptr_type, "mnt_list", namespace['list']):
> + # There appears to be a null entry at the end of the list...
> + if not vfs['mnt_parent']:
> + break
> +
> + devname = vfs['mnt_devname'].string()
> + devname = devname if devname else "none"
> +
> + pathname = ""
> + parent = vfs
> + while True:
> + mntpoint = parent['mnt_mountpoint']
> + pathname = 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()
>
--
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