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Subject[RFC][PATCH 8/8] perf/x86: Add sanity checks to x86_schedule_events()

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/events/core.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)

--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -855,17 +855,30 @@ int x86_schedule_events(struct cpu_hw_ev
struct event_constraint *c;
unsigned long used_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
struct perf_event *e;
- int i, wmin, wmax, unsched = 0;
+ int n0, i, wmin, wmax, unsched = 0;
struct hw_perf_event *hwc;

bitmap_zero(used_mask, X86_PMC_IDX_MAX);

+ /*
+ * Compute the number of events already present; see x86_pmu_add(),
+ * validate_group() and x86_pmu_commit_txn(). For the former two
+ * cpuc->n_events hasn't been updated yet, while for the latter
+ * cpuc->n_txn contains the number of events added in the current
+ * transaction.
+ */
+ n0 = cpuc->n_events;
+ if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
+ n0 -= cpuc->n_txn;
+
if (x86_pmu.start_scheduling)
x86_pmu.start_scheduling(cpuc);

for (i = 0, wmin = X86_PMC_IDX_MAX, wmax = 0; i < n; i++) {
c = cpuc->event_constraint[i];

+ WARN_ON_ONCE((c && i >= n0) || (!c && i < n0));
+
/*
* Request constraints for new events; or for those events that
* have a dynamic constraint due to the HT workaround -- for
@@ -945,11 +958,7 @@ int x86_schedule_events(struct cpu_hw_ev
x86_pmu.commit_scheduling(cpuc, i, assign[i]);
}
} else {
- i = cpuc->n_events;
- if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
- i -= cpuc->n_txn;
-
- for (; i < n; i++) {
+ for (i = n0; i < n; i++) {
e = cpuc->event_list[i];

/*

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