libpmc: enable pmu_utils on arm64

This allows supported libpmc to query/select from the pmu-events table,
which may have a more complete set of events than what we define
manually. A future update to these definitions should greatly improve
this support. The alias table is empty for now, until this future import
is complete.

Add the Foundation's copyright for recent work on this file.

Reviewed by:	ray (slightly earlier version)
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D30603

lib/libpmc/libpmc_pmu_util.c

@@ -2,6 +2,10 @@
  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
  *
  * Copyright (c) 2018, Matthew Macy
+ * Copyright (c) 2021, The FreeBSD Foundation
+ *
+ * Portions of this software were developed by Mitchell Horne
+ * under sponsorship from the FreeBSD Foundation.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -139,6 +143,24 @@ pmu_alias_get(const char *name)
 	return (name);
 }
 
+#elif defined(__aarch64__)
+
+static struct pmu_alias pmu_armv8_alias_table[] = {
+	{NULL, NULL},
+};
+
+static const char *
+pmu_alias_get(const char *name)
+{
+	struct pmu_alias *pa;
+
+	for (pa = pmu_armv8_alias_table; pa->pa_alias != NULL; pa++)
+		if (strcasecmp(name, pa->pa_alias) == 0)
+			return (pa->pa_name);
+
+	return (name);
+}
+
 #else
 
 static const char *
@@ -549,6 +571,28 @@ pmc_pmu_pmcallocate(const char *event_name, struct pmc_op_pmcallocate *pm)
 		return (pmc_pmu_amd_pmcallocate(event_name, pm, &ped));
 }
 
+#elif defined(__aarch64__)
+
+int
+pmc_pmu_pmcallocate(const char *event_name, struct pmc_op_pmcallocate *pm)
+{
+	const struct pmu_event *pe;
+	int idx = -1;
+
+	event_name = pmu_alias_get(event_name);
+	if ((pe = pmu_event_get(NULL, event_name, &idx)) == NULL)
+		return (ENOENT);
+	if (pe->event == NULL)
+		return (ENOENT);
+
+	assert(idx >= 0);
+	pm->pm_md.pm_md_flags |= PM_MD_RAW_EVENT;
+	pm->pm_class = PMC_CLASS_ARMV8;
+	pm->pm_caps |= (PMC_CAP_READ | PMC_CAP_WRITE);
+
+	return (0);
+}
+
 #else
 
 int