>
> On Tue, 18 Nov 2014 14:01:06 +0000, Kan Liang wrote:
> >> On Fri, 14 Nov 2014 08:44:12 -0500, kan liang wrote:
> >> > + /* LBR only affects the user callchain */
> >> > + if (i != chain_nr) {
> >> > + struct branch_stack *lbr_stack = sample-
> >> >branch_stack;
> >> > + int lbr_nr = lbr_stack->nr;
> >> > + /*
> >> > + * LBR callstack can only get user call chain.
> >> > + * The mix_chain_nr is kernel call chain
> >> > + * number plus LBR user call chain number.
> >> > + * i is kernel call chain number,
> >> > + * 1 is PERF_CONTEXT_USER,
> >> > + * lbr_nr + 1 is the user call chain number.
> >> > + * For details, please refer to the comments
> >> > + * in callchain__printf
> >> > + */
> >> > + int mix_chain_nr = i + 1 + lbr_nr + 1;
> >> > +
> >> > + if (mix_chain_nr > PERF_MAX_STACK_DEPTH) {
> >> > + pr_warning("corrupted callchain.
> >> skipping...\n");
> >> > + return 0;
> >> > + }
> >>
> >> I'm not sure whether this is really a corrupted callchain. If a
> >> single chain is greater than the max it should be corrupted, but
> >> we're now summing up with other values..
> >>
> >> What about checking callchain_nr and lbr_nr separately or mix_nr with
> >> 2*max?
> >
> > The lbr_nr max is 16. I will change it to max+16.
>
> Shouldn't it be 18 (16 + 1 + 1) at least?
In the new patch, I use PERF_MAX_BRANCH_DEPTH from Andi's patch. It's
127. It should be enough.
+ if (mix_chain_nr > PERF_MAX_STACK_DEPTH +
PERF_MAX_BRANCH_DEPTH) {
+ pr_warning("corrupted callchain. skipping...\n");
+ return 0;
+ }
Thanks,
Kan
>
> Thanks,
> Namhyung
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