| Message ID | 1504901592-10357-1-git-send-email-wei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 08/09/2017 22:13, Wei Huang wrote: > Currently pmu.c sets num_counters to MIN(num_gp_counters, num_gp_events). > This is to prevent the out-of-bound access to gp_events[] array in > check_counters_many(). However it also means that check_counters_many() > can NOT stress all gp counters if num_gp_counters > num_gp_events. This > small patch changes the value of num_counters back to num_gp_counters and > prevents the out-of-bound problem by using the mod function in the array > access. > > Signed-off-by: Wei Huang <wei@redhat.com> > --- > x86/pmu.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/x86/pmu.c b/x86/pmu.c > index a0238dc..b56b61e 100644 > --- a/x86/pmu.c > +++ b/x86/pmu.c > @@ -275,7 +275,8 @@ static void check_counters_many(void) > > cnt[n].count = 0; > cnt[n].ctr = MSR_IA32_PERFCTR0 + n; > - cnt[n].config = EVNTSEL_OS | EVNTSEL_USR | gp_events[i].unit_sel; > + cnt[n].config = EVNTSEL_OS | EVNTSEL_USR | > + gp_events[i % ARRAY_SIZE(gp_events)].unit_sel; > n++; > } > for (i = 0; i < edx.split.num_counters_fixed; i++) { > @@ -397,8 +398,6 @@ int main(int ac, char **av) > printf("Fixed counter width: %d\n", edx.split.bit_width_fixed); > > num_counters = eax.split.num_counters; > - if (num_counters > ARRAY_SIZE(gp_events)) > - num_counters = ARRAY_SIZE(gp_events); > > apic_write(APIC_LVTPC, PC_VECTOR); > > Clever! I applied the patch. Paolo
diff --git a/x86/pmu.c b/x86/pmu.c index a0238dc..b56b61e 100644 --- a/x86/pmu.c +++ b/x86/pmu.c @@ -275,7 +275,8 @@ static void check_counters_many(void) cnt[n].count = 0; cnt[n].ctr = MSR_IA32_PERFCTR0 + n; - cnt[n].config = EVNTSEL_OS | EVNTSEL_USR | gp_events[i].unit_sel; + cnt[n].config = EVNTSEL_OS | EVNTSEL_USR | + gp_events[i % ARRAY_SIZE(gp_events)].unit_sel; n++; } for (i = 0; i < edx.split.num_counters_fixed; i++) { @@ -397,8 +398,6 @@ int main(int ac, char **av) printf("Fixed counter width: %d\n", edx.split.bit_width_fixed); num_counters = eax.split.num_counters; - if (num_counters > ARRAY_SIZE(gp_events)) - num_counters = ARRAY_SIZE(gp_events); apic_write(APIC_LVTPC, PC_VECTOR);
Currently pmu.c sets num_counters to MIN(num_gp_counters, num_gp_events). This is to prevent the out-of-bound access to gp_events[] array in check_counters_many(). However it also means that check_counters_many() can NOT stress all gp counters if num_gp_counters > num_gp_events. This small patch changes the value of num_counters back to num_gp_counters and prevents the out-of-bound problem by using the mod function in the array access. Signed-off-by: Wei Huang <wei@redhat.com> --- x86/pmu.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)