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 $task probe alias, kernel tast_struct fields can be used in trace.py
filter or output easily even if they cannot be accessed through input
parameters.
Signed-off-by: Yonghong Song <yhs@fb.com>
diff --git a/tools/trace.py b/tools/trace.py
index 71688fb..d22b5c4 100755
--- a/tools/trace.py
+++ b/tools/trace.py
@@ -204,7 +204,8 @@
"$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 @@
'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):