+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2024-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#define _LGPL_SOURCE
+#include "common/getenv.h"
+#include "common/logging.h"
+#include "common/populate.h"
+
+enum populate_policy {
+ POPULATE_UNSET,
+
+ POPULATE_NONE,
+ POPULATE_CPU_POSSIBLE,
+
+ POPULATE_UNKNOWN,
+};
+
+static enum populate_policy map_populate_policy = POPULATE_UNSET;
+
+static void init_map_populate_policy(void)
+{
+ const char *populate_env_str;
+
+ if (map_populate_policy != POPULATE_UNSET)
+ return;
+
+ populate_env_str = lttng_ust_getenv("LTTNG_UST_MAP_POPULATE_POLICY");
+ if (!populate_env_str) {
+ map_populate_policy = POPULATE_NONE;
+ return;
+ }
+ if (!strcmp(populate_env_str, "none")) {
+ map_populate_policy = POPULATE_NONE;
+ } else if (!strcmp(populate_env_str, "cpu_possible")) {
+ map_populate_policy = POPULATE_CPU_POSSIBLE;
+ } else {
+ /*
+ * populate_env_str is an untrusted environment variable
+ * input (can be provided to setuid/setgid binaries), so
+ * don't even try to print it.
+ */
+ WARN("Unknown policy for LTTNG_UST_MAP_POPULATE_POLICY environment variable.");
+ map_populate_policy = POPULATE_UNKNOWN;
+ }
+}
+
+/*
+ * Return the shared page populate policy for global pages. Returns true
+ * if shared memory pages should be pre-populated, false otherwise.
+ */
+bool lttng_ust_map_populate_is_enabled(void)
+{
+ init_map_populate_policy();
+
+ switch (map_populate_policy) {
+ case POPULATE_UNKNOWN: /* Fall-through */
+ case POPULATE_NONE:
+ return false;
+ case POPULATE_CPU_POSSIBLE:
+ return true;
+ default:
+ abort();
+ }
+ return false;
+}
+
+/*
+ * Return the shared page populate policy based on the @cpu number
+ * provided as input. Returns true if shared memory pages should be
+ * pre-populated, false otherwise.
+ *
+ * The @cpu argument is currently unused except for negative value
+ * validation. It is present to eventually match cpu affinity or cpu
+ * online masks if those features are added in the future.
+ */
+bool lttng_ust_map_populate_cpu_is_enabled(int cpu)
+{
+ /* Reject invalid cpu number. */
+ if (cpu < 0)
+ return false;
+
+ return lttng_ust_map_populate_is_enabled();
+}
projects / lttng-ust.git / commitdiff
