new: vma反向映射

kernel/arch/x86_64/current.h

@@ -0,0 +1,20 @@
+#pragma once
+#include <common/glib.h>
+
+#pragma GCC push_options
+#pragma GCC optimize("O0")
+struct process_control_block;
+// 获取当前的pcb
+static __always_inline struct process_control_block *get_current_pcb()
+{
+	struct process_control_block *current = NULL;
+	// 利用了当前pcb和栈空间总大小为32k大小对齐，将rsp低15位清空，即可获得pcb的起始地址
+	barrier();
+	__asm__ __volatile__("andq %%rsp, %0   \n\t"
+						 : "=r"(current)
+						 : "0"(~32767UL));
+	barrier();
+	return current;
+};
+#define current_pcb get_current_pcb()
+#pragma GCC pop_options