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Date: Tue, 21 Aug 2018 13:46:22 -0700 From: Song Liu <liu.song.a23@...il.com> To: Ravi Bangoria <ravi.bangoria@...ux.ibm.com> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Oleg Nesterov <oleg@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, mhiramat@...nel.org, Peter Zijlstra <peterz@...radead.org>, mingo@...hat.com, acme@...nel.org, alexander.shishkin@...ux.intel.com, jolsa@...hat.com, namhyung@...nel.org, open list <linux-kernel@...r.kernel.org>, ananth@...ux.vnet.ibm.com, Alexis Berlemont <alexis.berlemont@...il.com>, naveen.n.rao@...ux.vnet.ibm.com, linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org, linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com Subject: Re: [PATCH v9 3/4] trace_uprobe/sdt: Prevent multiple reference counter for same uprobe On Sun, Aug 19, 2018 at 9:42 PM, Ravi Bangoria <ravi.bangoria@...ux.ibm.com> wrote: > 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. > > Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com> > Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com> > Reviewed-by: Song Liu <songliubraving@...com> Reviewed-and-tested-by: Song Liu <songliubraving@...com> > Reviewed-by: Oleg Nesterov <oleg@...hat.com> > --- > kernel/trace/trace_uprobe.c | 37 +++++++++++++++++++++++++++++++++++-- > 1 file changed, 35 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c > index a7ef6c4ca16e..21d9fffaa096 100644 > --- a/kernel/trace/trace_uprobe.c > +++ b/kernel/trace/trace_uprobe.c > @@ -324,6 +324,35 @@ 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) > { > @@ -333,8 +362,12 @@ 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); > -- > 2.14.4 >
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