add a probe alias $task in trace.py

The $task refers to the current task. In my particular case, I need to trace the number of users for file system associated with the current task. With the probe alias $task, trace.py can easily trace this event ...... trace.py -I 'linux/fs_struct.h' 'mntns_install "users = %d", $task->fs->users' PID TID COMM FUNC - 176566 176566 python2.7 mntns_install users = 2 176566 176566 python2.7 mntns_install users = 2 ...... With $task probe alias, kernel tast_struct fields can be used in trace.py filter or output easily even if they cannot be accessed through input parameters. Signed-off-by: Yonghong Song <[email protected]>
linuxzjs · Jan 25, 2018 · f92fef2 · f92fef2
1 parent 12f4f6e
commit f92fef2
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diff --git a/tools/trace.py b/tools/trace.py
@@ -204,7 +204,8 @@ def _parse_action(self, action):
  "$gid": "(unsigned)(bpf_get_current_uid_gid() >> 32)",
  "$pid": "(unsigned)(bpf_get_current_pid_tgid() & 0xffffffff)",
  "$tgid": "(unsigned)(bpf_get_current_pid_tgid() >> 32)",
- "$cpu": "bpf_get_smp_processor_id()"
+ "$cpu": "bpf_get_smp_processor_id()",
+ "$task" : "((struct task_struct *)bpf_get_current_task())"
  }
 
  def _generate_streq_function(self, string):
@@ -606,6 +607,8 @@ class Tool(object):
  'udpv6_sendmsg(struct sock *sk) (sk->sk_dport == 13568)'
  Trace udpv6 sendmsg calls only if socket's destination port is equal
  to 53 (DNS; 13568 in big endian order)
+trace -I 'linux/fs_struct.h' 'mntns_install "users = %d", $task->fs->users'
+ Trace the number of users accessing the file system of the current task
 """
 
  def __init__(self):

diff --git a/tools/trace_example.txt b/tools/trace_example.txt
@@ -296,4 +296,6 @@ trace -I 'net/sock.h' \\
  'udpv6_sendmsg(struct sock *sk) (sk->sk_dport == 13568)'
  Trace udpv6 sendmsg calls only if socket's destination port is equal
  to 53 (DNS; 13568 in big endian order)
+trace -I 'linux/fs_struct.h' 'mntns_install "users = %d", $task->fs->users'
+ Trace the number of users accessing the file system of the current task
 "