Handout

arch/core.cc

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+#include "core.h"
+
+#include "apic.h"
+#include "lapic.h"
+
+/*! \brief Initial size of CPU core stacks
+ *
+ * Used during startup in `boot/startup.asm`
+ */
+extern "C" const unsigned long CPU_CORE_STACK_SIZE = 4096;
+
+/*! \brief Reserved memory for CPU core stacks
+ */
+alignas(
+    16) static unsigned char cpu_core_stack[Core::MAX * CPU_CORE_STACK_SIZE];
+
+/*! \brief Pointer to stack memory
+ *
+ * Incremented during startup of each core (bootstrap and application
+ * processors) in `boot/startup.asm`
+ */
+unsigned char* cpu_core_stack_pointer = cpu_core_stack;
+
+namespace Core {
+
+static unsigned cores = 0;  ///< Number of available CPU cores
+static volatile unsigned
+    core_id[255];  ///< Lookup table for CPU core IDs with LAPIC ID as index
+
+static unsigned online_cores = 0;    ///< Number of currently online CPU cores
+static bool online_core[Core::MAX];  ///< Lookup table for online CPU cores with
+                                     ///< CPU core ID as index
+
+void init() {
+  // Increment number of online CPU cores
+  if (__atomic_fetch_add(&online_cores, 1, __ATOMIC_RELAXED) == 0) {
+    // Fill Lookup table
+    for (unsigned i = 0; i < Core::MAX; i++) {
+      uint8_t lapic_id = APIC::getLAPICID(i);
+      if (lapic_id < APIC::INVALID_ID) {  // ignore invalid LAPICs
+        core_id[lapic_id] = i;
+        cores++;
+      }
+    }
+  }
+
+  // Get CPU ID
+  uint8_t cpu = getID();
+
+  // initialize local APIC with logical APIC ID
+  LAPIC::init(APIC::getLogicalAPICID(cpu));
+
+  // set current CPU online
+  online_core[cpu] = true;
+}
+
+void exit() {
+  // CPU core offline
+  online_core[getID()] = false;
+  __atomic_fetch_sub(&online_cores, 1, __ATOMIC_RELAXED);
+}
+
+unsigned getID() { return core_id[LAPIC::getID()]; }
+
+unsigned count() { return cores; }
+
+unsigned countOnline() { return online_cores; }
+
+bool isOnline(uint8_t core_id) {
+  return core_id > Core::MAX ? false : online_core[core_id];
+}
+
+}  // namespace Core