Messages in this thread | | | Date | Mon, 27 Nov 2017 18:09:11 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH 4/6] hw_breakpoint: Factor out __modify_user_hw_breakpoint function |
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On Mon, Nov 27, 2017 at 05:46:39PM +0100, Peter Zijlstra wrote: > On Mon, Nov 27, 2017 at 05:21:31PM +0100, Jiri Olsa wrote: > > +static int __modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) > > +{ > > + u64 old_addr = bp->attr.bp_addr; > > + u64 old_len = bp->attr.bp_len; > > + int old_type = bp->attr.bp_type; > > + bool modify = attr->bp_type != old_type; > > + int err = 0; > > + > > + bp->attr.bp_addr = attr->bp_addr; > > + bp->attr.bp_type = attr->bp_type; > > + bp->attr.bp_len = attr->bp_len; > > + > > + err = validate_hw_breakpoint(bp); > > + if (!err && modify) > > + err = modify_bp_slot(bp, old_type); > > + > > + if (err) { > > + bp->attr.bp_addr = old_addr; > > + bp->attr.bp_type = old_type; > > + bp->attr.bp_len = old_len; > > + return err; > > + } > > + > > + bp->attr.disabled = attr->disabled; > > + return 0; > > +} > > I think this function is failing to check if anything else in the attr > changes. > > For example, someone could have added PERF_SAMPLE_BRANCH_STACK. That's > something you'll fail to create breakpoints with, but this modification > would 'accept'. >
hum, I dont think so.. the only things you're allowed to change are bp_addr, bp_type and bp_len.. we put new values in those fields and keep the rest untouched.. apart from 'disabled' bit
jirka
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