20211024

20211024

1.用局部变量struct 存储全局变量，很有可能造成栈溢出，出现fatal error 。更好的办法是取其指针，struct temp = &（context ［0］）
2把线性地址映射到物理地址的数据结构称为页表，页表存放在主存中，并在启用分页单元之前必须由内核对页表进行适当的初始化
3.段有四个特权级别，页有两个
4.内核中thread_info数据结构与处理器相关【即与硬件相关】：
如x86处理器：

struct thread_info {
	struct task_struct	*task;		/* main task structure */
	struct exec_domain	*exec_domain;	/* execution domain */
	__u32			flags;		/* low level flags */
	__u32			status;		/* thread synchronous flags */
	__u32			cpu;		/* current CPU */
	int			preempt_count;	/* 0 => preemptable,
						   <0 => BUG */
	mm_segment_t		addr_limit;
	struct restart_block    restart_block;
	void __user		*sysenter_return;
#ifdef CONFIG_X86_32
	unsigned long           previous_esp;   /* ESP of the previous stack in
						   case of nested (IRQ) stacks
						*/
	__u8			supervisor_stack[0];
#endif
	int			uaccess_err;
};

如arm处理器：

struct thread_info {
	unsigned long		flags;		/* low level flags */
	int			preempt_count;	/* 0 => preemptable, <0 => bug */
	mm_segment_t		addr_limit;	/* address limit */
	struct task_struct	*task;		/* main task structure */
	struct exec_domain	*exec_domain;	/* execution domain */
	__u32			cpu;		/* cpu */
	__u32			cpu_domain;	/* cpu domain */
	struct cpu_context_save	cpu_context;	/* cpu context */
	__u32			syscall;	/* syscall number */
	__u8			used_cp[16];	/* thread used copro */
	unsigned long		tp_value;
	struct crunch_state	crunchstate;
	union fp_state		fpstate __attribute__((aligned(8)));
	union vfp_state		vfpstate;
#ifdef CONFIG_ARM_THUMBEE
	unsigned long		thumbee_state;	/* ThumbEE Handler Base register */
#endif
	struct restart_block	restart_block;
};