percpu,drivers: Add cpu self reference to percpu

Adding a self reference to the percpu allows
checking what CPU some code is currently
running on. We use this in pb_set_handler
to ensure it runs on the bsp.

Author: sparchatus

common/cpu.c

@@ -49,6 +49,7 @@ static void init_cpu(cpu_t *cpu, unsigned int id, bool is_bsp, bool enabled) {
 
     cpu->percpu = get_percpu_page(id);
     BUG_ON(!cpu->percpu);
+    cpu->percpu->cpu = cpu;
 
     cpu->lock = SPINLOCK_INIT;
     list_init(&cpu->task_queue);

drivers/power_button.c

@@ -24,6 +24,9 @@ static void default_handler(void *notused) {
 }
 
 void pb_set_handler(pb_handler_t handler, void *context) {
+    // check that we are on the bsp. Assumes that there is no task migration
+    ASSERT(is_cpu_bsp(get_this_cpu()));
+
     unsigned long flags = interrupts_disable_save();
     pb_handler = handler;
     pb_context = context;

include/cpu.h

@@ -67,6 +67,10 @@ extern void wait_for_all_cpus(void);
 
 /* Static declarations */
 
+static inline cpu_t * get_this_cpu() {
+    return PERCPU_GET(cpu);
+}
+
 static inline bool is_cpu_bsp(cpu_t *cpu) {
     return cpu->flags.bsp;
 }

include/percpu.h

@@ -31,6 +31,7 @@
 #include <list.h>
 #include <page.h>
 
+struct cpu;
 struct percpu {
     list_head_t list;
 
@@ -60,6 +61,7 @@ struct percpu {
     unsigned long usermode_private;
     volatile unsigned long apic_ticks;
     bool apic_timer_enabled;
+    struct cpu *cpu;
 } __aligned(PAGE_SIZE);
 typedef struct percpu percpu_t;