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Commit ccea8727 authored by Ravi Bangoria's avatar Ravi Bangoria Committed by Steven Rostedt (VMware)
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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: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: default avatarSong Liu <songliubraving@fb.com>
Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Tested-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarRavi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 22bad382

kernel/trace/trace_uprobe.c

+35 −2
Original line number Diff line number Diff line
@@ -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);