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trace_uprobe/sdt: Prevent multiple reference counter for same uprobe 

We assume to have only one reference counter for one uprobe.
Don't allow user to add multiple trace_uprobe entries having
same inode+offset but different reference counter.

Ex,
  # echo "p:sdt_tick/loop2 /home/ravi/tick:0x6e4(0x10036)" > uprobe_events
  # echo "p:sdt_tick/loop2_1 /home/ravi/tick:0x6e4(0xfffff)" >> uprobe_events
  bash: echo: write error: Invalid argument

  # dmesg
  trace_kprobe: Reference counter offset mismatch.

There is one exception though:
When user is trying to replace the old entry with the new
one, we allow this if the new entry does not conflict with
any other existing entries.

Link: http://lkml.kernel.org/r/20180820044250.11659-4-ravi.bangoria@linux.ibm.com

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Ravi Bangoria 2018-08-20 10:12:49 +05:30 committed by Steven Rostedt (VMware)
parent 22bad38286
commit ccea8727dc
1 changed files with 35 additions and 2 deletions
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37
kernel/trace/trace_uprobe.c
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@ -312,6 +312,35 @@ static int unregister_trace_uprobe(struct trace_uprobe *tu)
return 0;
}
/*
* Uprobe with multiple reference counter is not allowed. i.e.
* If inode and offset matches, reference counter offset *must*
* match as well. Though, there is one exception: If user is
* replacing old trace_uprobe with new one(same group/event),
* then we allow same uprobe with new reference counter as far
* as the new one does not conflict with any other existing
* ones.
*/
static struct trace_uprobe *find_old_trace_uprobe(struct trace_uprobe *new)
{
struct trace_uprobe *tmp, *old = NULL;
struct inode *new_inode = d_real_inode(new->path.dentry);
old = find_probe_event(trace_event_name(&new->tp.call),
new->tp.call.class->system);
list_for_each_entry(tmp, &uprobe_list, list) {
if ((old ? old != tmp : true) &&
new_inode == d_real_inode(tmp->path.dentry) &&
new->offset == tmp->offset &&
new->ref_ctr_offset != tmp->ref_ctr_offset) {
pr_warn("Reference counter offset mismatch.");
return ERR_PTR(-EINVAL);
}
}
return old;
}
/* Register a trace_uprobe and probe_event */
static int register_trace_uprobe(struct trace_uprobe *tu)
{
@ -321,8 +350,12 @@ static int register_trace_uprobe(struct trace_uprobe *tu)
mutex_lock(&uprobe_lock);
/* register as an event */
old_tu = find_probe_event(trace_event_name(&tu->tp.call),
tu->tp.call.class->system);
old_tu = find_old_trace_uprobe(tu);
if (IS_ERR(old_tu)) {
ret = PTR_ERR(old_tu);
goto end;
}
if (old_tu) {
/* delete old event */
ret = unregister_trace_uprobe(old_tu);