3 files changed, 63 insertions, 41 deletions

diff --git a/arch/sh/include/asm/hw_breakpoint.h b/arch/sh/include/asm/hw_breakpoint.h
index 199d17b765f2..361a0f57bdeb 100644
--- a/arch/sh/include/asm/hw_breakpoint.h
+++ b/arch/sh/include/asm/hw_breakpoint.h
@@ -48,10 +48,7 @@ struct pmu;
 /* Maximum number of UBC channels */
 #define HBP_NUM		2
 
-static inline int hw_breakpoint_slots(int type)
-{
-	return HBP_NUM;
-}
+#define hw_breakpoint_slots(type) (HBP_NUM)
 
 /* arch/sh/kernel/hw_breakpoint.c */
 extern int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw);
diff --git a/arch/x86/include/asm/hw_breakpoint.h b/arch/x86/include/asm/hw_breakpoint.h
index a1f0e90d0818..0bc931cd0698 100644
--- a/arch/x86/include/asm/hw_breakpoint.h
+++ b/arch/x86/include/asm/hw_breakpoint.h
@@ -44,10 +44,7 @@ struct arch_hw_breakpoint {
 /* Total number of available HW breakpoint registers */
 #define HBP_NUM 4
 
-static inline int hw_breakpoint_slots(int type)
-{
-	return HBP_NUM;
-}
+#define hw_breakpoint_slots(type) (HBP_NUM)
 
 struct perf_event_attr;
 struct perf_event;
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 7df46b276452..9fb66d358d81 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -40,13 +40,16 @@ struct bp_cpuinfo {
 	/* Number of pinned cpu breakpoints in a cpu */
 	unsigned int	cpu_pinned;
 	/* tsk_pinned[n] is the number of tasks having n+1 breakpoints */
+#ifdef hw_breakpoint_slots
+	unsigned int	tsk_pinned[hw_breakpoint_slots(0)];
+#else
 	unsigned int	*tsk_pinned;
+#endif
 	/* Number of non-pinned cpu/task breakpoints in a cpu */
 	unsigned int	flexible; /* XXX: placeholder, see fetch_this_slot() */
 };
 
 static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]);
-static int nr_slots[TYPE_MAX] __ro_after_init;
 
 static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type)
 {
@@ -73,6 +76,54 @@ struct bp_busy_slots {
 /* Serialize accesses to the above constraints */
 static DEFINE_MUTEX(nr_bp_mutex);
 
+#ifdef hw_breakpoint_slots
+/*
+ * Number of breakpoint slots is constant, and the same for all types.
+ */
+static_assert(hw_breakpoint_slots(TYPE_INST) == hw_breakpoint_slots(TYPE_DATA));
+static inline int hw_breakpoint_slots_cached(int type)	{ return hw_breakpoint_slots(type); }
+static inline int init_breakpoint_slots(void)		{ return 0; }
+#else
+/*
+ * Dynamic number of breakpoint slots.
+ */
+static int __nr_bp_slots[TYPE_MAX] __ro_after_init;
+
+static inline int hw_breakpoint_slots_cached(int type)
+{
+	return __nr_bp_slots[type];
+}
+
+static __init int init_breakpoint_slots(void)
+{
+	int i, cpu, err_cpu;
+
+	for (i = 0; i < TYPE_MAX; i++)
+		__nr_bp_slots[i] = hw_breakpoint_slots(i);
+
+	for_each_possible_cpu(cpu) {
+		for (i = 0; i < TYPE_MAX; i++) {
+			struct bp_cpuinfo *info = get_bp_info(cpu, i);
+
+			info->tsk_pinned = kcalloc(__nr_bp_slots[i], sizeof(int), GFP_KERNEL);
+			if (!info->tsk_pinned)
+				goto err;
+		}
+	}
+
+	return 0;
+err:
+	for_each_possible_cpu(err_cpu) {
+		for (i = 0; i < TYPE_MAX; i++)
+			kfree(get_bp_info(err_cpu, i)->tsk_pinned);
+		if (err_cpu == cpu)
+			break;
+	}
+
+	return -ENOMEM;
+}
+#endif
+
 __weak int hw_breakpoint_weight(struct perf_event *bp)
 {
 	return 1;
@@ -95,7 +146,7 @@ static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
 	unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
 	int i;
 
-	for (i = nr_slots[type] - 1; i >= 0; i--) {
+	for (i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) {
 		if (tsk_pinned[i] > 0)
 			return i + 1;
 	}
@@ -312,7 +363,7 @@ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
 	fetch_this_slot(&slots, weight);
 
 	/* Flexible counters need to keep at least one slot */
-	if (slots.pinned + (!!slots.flexible) > nr_slots[type])
+	if (slots.pinned + (!!slots.flexible) > hw_breakpoint_slots_cached(type))
 		return -ENOSPC;
 
 	ret = arch_reserve_bp_slot(bp);
@@ -632,7 +683,7 @@ bool hw_breakpoint_is_used(void)
 			if (info->cpu_pinned)
 				return true;
 
-			for (int slot = 0; slot < nr_slots[type]; ++slot) {
+			for (int slot = 0; slot < hw_breakpoint_slots_cached(type); ++slot) {
 				if (info->tsk_pinned[slot])
 					return true;
 			}
@@ -716,42 +767,19 @@ static struct pmu perf_breakpoint = {
 
 int __init init_hw_breakpoint(void)
 {
-	int cpu, err_cpu;
-	int i, ret;
-
-	for (i = 0; i < TYPE_MAX; i++)
-		nr_slots[i] = hw_breakpoint_slots(i);
-
-	for_each_possible_cpu(cpu) {
-		for (i = 0; i < TYPE_MAX; i++) {
-			struct bp_cpuinfo *info = get_bp_info(cpu, i);
-
-			info->tsk_pinned = kcalloc(nr_slots[i], sizeof(int),
-							GFP_KERNEL);
-			if (!info->tsk_pinned) {
-				ret = -ENOMEM;
-				goto err;
-			}
-		}
-	}
+	int ret;
 
 	ret = rhltable_init(&task_bps_ht, &task_bps_ht_params);
 	if (ret)
-		goto err;
+		return ret;
+
+	ret = init_breakpoint_slots();
+	if (ret)
+		return ret;
 
 	constraints_initialized = true;
 
 	perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
 
 	return register_die_notifier(&hw_breakpoint_exceptions_nb);
-
-err:
-	for_each_possible_cpu(err_cpu) {
-		for (i = 0; i < TYPE_MAX; i++)
-			kfree(get_bp_info(err_cpu, i)->tsk_pinned);
-		if (err_cpu == cpu)
-			break;
-	}
-
-	return ret;
 }