kernel: add function to query CPU clock cycle count

arch/x86_64/cpu_ctrl.S

@@ -38,3 +38,13 @@ wrmsr:
 	wrmsr
 
 	ret
+
+
+	.global get_cycles
+	.type get_cycles, @function
+
+get_cycles:
+	rdtsc
+	shl $32, %rdx
+	orq %rdx, %rax
+	ret

include/socks/compiler.h

@@ -35,4 +35,7 @@ void write_once(volatile T *ptr, T value)
 #undef __aligned
 #define __aligned(x) __attribute__((__aligned__(x)))
 
+#undef __weak
+#define __weak __attribute__((__weak__))
+
 #endif

include/socks/cpu.h

@@ -1,7 +1,9 @@
 #ifndef SOCKS_CPU_H_
 #define SOCKS_CPU_H_
 
+#include <socks/types.h>
 #include <socks/machine/cpu.h>
+#include <stdint.h>
 #include <socks/sched.h>
 
 #ifdef __cplusplus
@@ -33,6 +35,8 @@ extern void put_cpu(struct cpu_data *cpu);
 extern void cpu_set_available(unsigned int cpu_id);
 extern void cpu_set_online(unsigned int cpu_id);
 
+extern cycles_t get_cycles(void);
+
 #define irq_enable() ml_int_enable()
 #define irq_disable() ml_int_disable()
 

include/socks/types.h

@@ -4,5 +4,6 @@
 #include <stdint.h>
 
 typedef uintptr_t phys_addr_t;
+typedef uint64_t cycles_t;
 
 #endif

kernel/cpu.c

@@ -69,3 +69,8 @@ unsigned int cpu_get_highest_available(void)
 {
 	return bitmap_highest_set(cpu_available, CPU_MAX);
 }
+
+cycles_t __weak get_cycles(void)
+{
+	return 0;
+}